Illnerovd et al., 1985), and it has been speculated that
postmortem serum levels of melatonin approximate
its antemortem levels (Sturner et al., 1990). Melato-
nin is biosynthesized through the serotonin pathway
(Fig. 1), and increases in the levels of neurotransmitters
are known to occur during excitement and stress, but it
is not established whether these physiological states have
any influence in altering the melatonin levels in the
circulation. Therefore, some uncertainty exists about
changes in melatonin levels during panic situations in
relation to normal physiological conditions.

Stanley and Brown (1988) studied the postmortem
levels of melatonin in the pineal glands of suicide
victims and compared them to the melatonin levels in
acontrol group matched for suddenness and violence
of deaths. After segregating the values by the time of
day in which death occurred, they found that the
melatonin content was significantly lower in the pi-
neal glands of suicide victims than in their corre-
sponding “controls,” which may be related to the low
melatonin levels observed in acutely depressed pa-
tients (Beck-Friis et al., 1985).

Most published concentrations of circulating me-
latonin are presented as serum or plasma values, but
no detailed information is available on the whole
blood level of this neurohormone. Development of a
suitable analytical method for whole blood and other
tissues appears to be warranted, and melatonin distri-
bution in whole blood components is also needed.
Such information could be applied to the interpreta-
tion of results obtained from postmortem blood
samples, particularly when cleaner samples (e.g., plasma
and serum) are not available.

CONCLUSIONS

Melatonin appears to be beneficial in alleviating
perceived jet lag effects when taken in the usual 2-3
mg dosage after arrival at a stable light-dark cycle
environment. Timing of ingestion (before normal
bedtime at destination) is important. Melatonin taken
during a transmeridian flight may further destabilize
the individual’s circadian rhythm; side effects, such as
sleepiness, make its use inadvisable for on-duty flight
crews. While melatonin use by flight crews after
transmeridian flight is not proscribed, care should be
taken to avoid entering duty status with any residual
effects. A 24-hour interval between ingestion and
flying should allow circulating melatonin concentra-
tions to return to normal levels. Melatonin use by air

10

traffic controllers and other aviation personnel whose
duties involve shift work should be self-regulated by
similar considerations. Off duty use to improve sleep
at the end of a shift change may prove to be practical,
but its use should be discontinued in ample time to
prevent residual effects during duty hours. Medical
certification of airmen who are high-dose or long-
term melatonin users may require careful evaluation.
The watchword here is “caution,” at least until both
the efficacy and the clinical relationships of exog-
enous melatonin with the human endocrine system
are better defined.

Current analytical methods are adequate to deter-
mine even the low daytime levels of melatonin in
serum/plasma and urine. Where cost and usage per-
mit, GC-MS appears to be the preferred technique
because ofits extreme sensitivity and specificity. Other
well-validated methods (HPLC and RIA) may be
better suited for infrequent use. Care should be taken
in interpreting some of the early literature values for
melatonin obtained before the development of ad-
equately validated analytical methods.

Utilization of melatonin quantitation in the pineal
body as a means of determining time-of-day in which
aircraft accident victims expired may have a specific
but limited utility. Most air crashes are well docu-
mented chronologically, but for the occasional unob-
served accident in an isolated location, the knowledge
of approximate time-of-day might assist the investiga-
tor in defining the possible contributions of weather
and visibility existing at that time. Determination of
melatonin levels in serum or urine provides even less
specific information. A high concentration in either
one raises the question of whether that level is caused
by ingested or endogenously produced melatonin.
Certainly, finding high levels of melatonin in the
blood of a daytime crash victim would suggest pos-
sible ingestion, and such levels would require very
careful medicolegal interpretations.

Despite extensive research, there are still unan-
swered questions about the influence of ingested me-
latonin on certain physiological and psychological
conditions, particularly when used in combination
with other medications. There are also unresolved
differences of opinion among investigators related to
the efficacy and safety of melatonin self-treatment for
some popularized user expectations. Clearly, much
remains to be determined before precise clinical guide-
lines can be formulated for melatonin use in the
aviation environment.


AEROMEDICAL ASPECTS OF MELATONIN—AN OVERVIEW

INTRODUCTION

Confronted with the widespread use of melatonin
for the self-treatment of sleep disorders and other
alleged health benefits, scientists have voiced their
concerns by urging the National Institutes of Health
to support clinical trials to determine its efficacy and
long-term safety. The extent of melatonin use was
illustrated by the 20 million new U.S. consumers in
1995 and by an estimated U.S. retail market of $200
million to $350 million annually (Lamberg, 1996;
Rawls, 1996). The increasing use of melatonin to
promote sleep and to minimize jet lag effects stems
from enthusiastic and sometimes extravagant claims
in the media and in popular books, while the inability
to patent this endogenously-produced neurohormone
has tended to limit the amount of support and incen-
tive for pharmaceutical research. Since this substance
occurs naturally in some foods, it can be sold in the
U.S. as a dietary supplement without premarket ap-
proval from the Food and Drug Administration, in
contrast to its formal banning of sale by some Euro-
pean governments (Moody, 1996). Indeed, this is one
of the few biologically-active chemicals on which
basic animal research has been more extensive than
clinical research (Redman et al., 1983; Tamarkin et
al., 1985; Pang et al., 1990; Lerchl and Schlatt, 1992;
Lamberg, 1996).

Saper (1996), of the Harvard Medical School, felt
that individuals taking melatonin risk potentially
dangerous long term effects, which have not been
adequately studied. This author relates melatonin
self-treatment to a similar fad involving “food supple-
ment” tryptophan several years ago, where a batch of
the unregulated amino acid contained a contaminant
that caused neuromuscular damage. Since melatonin
is not approved as a therapeutic agent, there is no
standardization of dosage and no certification of the
quality of commercial preparations.

Although the Federal Aviation Administration
(FAA) offers no formal guidance to pilots or to their
medical practitioners, the use of melatonin is cau-
tioned (Aerospace Medical Association, 1996). Col-
lectively, the lay press implies a fairly active interest in
the use of melatonin by aviation workers and air
travelers, but surveys of such use by pilots and passen-

gers have not been documented. Two anonymous
surveys conducted during the early 1997 Aircraft
Cabin Safety Workshops for Flight Attendants at the
FAA’s Civil Aeromedical Institute in Oklahoma City,
Oklahoma, revealed a fairly low actual use of melato-
nin during the preceding 3 months (3 of 40; 2 of 22).
However, a seasoned business traveler, K. E. Grubbs,
Jr., Editor-in-Chief of World Trade, is quoted in its
May 1997 edition: “...As we pass the melatonin, hope
for more and cheaper supersonic passenger planes,
and pray for closer-to-home international airports, we
should ponder for a moment...” Perhaps the editor
speaks for a large segment of the traveling population
who have compelling reasons to feel that melatonin
use is an option in grueling travel settings.

Since melatonin usage by aviation professionals
can reasonably be expected to follow general popula-
tion trends, it is prudent to consider the related safety
and side-effects, including any residual attention defi-
cits in persons charged with aviation safety. There-
fore, issues of jet lag, shift work, and medical
certification are emphasized under clinical perspec-
tives of this article. Melatonin’s biochemical pharma-
cology, analytical methods, and postmortem
toxicology are also provided as background informa-
tion potentially needed by clinicians and aircraft
accident investigators. The more general aspects of its
use in humans are discussed in several extensive review
articles available in the literature (Miles and Philbrick,
1987; Arendt, 1988; Claustratetal., 1990; Webb and Puig-
Domingo, 1995; Lamberg, 1996; Brzezinski, 1997).

CHEMISTRY, BIOSYNTHESIS, AND
METABOLISM

Lerner et al. (1958) first isolated a few micrograms
of N-acetyl-5-methoxytryptamine from kilogram
quantities of bovine pineal glands and named it mela-
tonin because of its biological activity on the melano-
cytes in frog skin. It is a pale yellow solid, melting at
116-118°C (Budavari, 1989) and has been synthe-
sized from 5-methoxyindole (Szmuszkovicz et al.,
1960). Melatonin was originally thought to be
biosynthesized only in the pineal gland, but subsequent


Petrie K, Dawson AG, Thompson L, Brook R (1993). A
double-blind trial of melatonin as a treatment for
jet lag in international cabin crew. Biol Psychiatry
33:526-30.

Pierpaoli W, Maestroni GJM (1987). Melatonin: A
principal neuroimmunoregulatory and anti-stress
hormone: Its anti-aging effects. Immunology Let-
ters 16:355-62.

Pierpaoli W, Regelson W, Colman C (1995). The mela-
tonin miracle: Nature’s age-reversing, disease-fight-
ing, sex-enhancing hormone. New York, NY:
Simon & Schuster.

Plebani M, Masiero M, Burlina AP, Chiozza ML,
Scanarini M, Burlina A (1990). Measurement of
melatonin in blood by radioimmunoassay: Ana-
lytical considerations and clinical usefulness. Childs
Nerv Syst 6:220-1.

Poeggeler B, Saarela S, Reiter RJ, Tan D, Chen L,
Manchester L, Barlow-Walden LR (1994). Mela-
tonin—A highly potent endogenous radical scav-
enger and electron donor: New aspects of the
oxidation chemistry of this indole accessed in
vitro. Ann NY Acad Sci 738:419-20.

Rawls R (1996). Melatonin and DHEA: Hormones at
your own risk, Chemical & Engineering News 74:27.

Raynaud F, Pévet P (1991). Determination of 5-
methoxyindoles in pineal gland and plasma samples
by high-performance liquid chromatography with
electrochemical detection. J Chromatogr

564:103-13.

Redfern PH (1992). Can pharmacological agents be
used effectively in the alleviation of jet-lag? Drugs
43:146-53.

Redman J, Armstrong S, Ng KT (1983). Free-running
activity rhythms in the rat: Entrainment by mela-
tonin. Science 219:1089-91.

Reiter RJ (1995a). The pineal gland and melatonin in
relation to aging: A summary of the theories and of
the data. Experimental Gerontology 30:199-212.

Reiter RJ (1995b). The role of the neurohormone mela-
tonin asa buffer against macromolecular oxidative
damage. Neurochem Int 27:453-60.

Rojdmark S, Wikner J, Adner N, Andersson DEH,
Wetterberg L (1993). Inhibition of melatonin
secretion by ethanol in man. Metabolism

42:1047-51.

Sagara Y, Okatani Y, Yamanaka S, Kiriyama T (1988).
Determination of plasma 5-hydroxytryptophan,
5-hydroxytryptamine, 5-hydroxyindoleacetic acid,
tryptophan and melatonin by high-performance
liquid chromatography with electrochemical de-
tection. J Chromatogr 431:170-6.

Saper C (1996). Why we sleep (or can’t). Harvard
Mahoney Neuroscience Institute Letter 5:1-3.

Sasaki M, Kurosaki Y, Mori A, Endo S (1986). Patterns
of sleep-wakefulness before and after transmeridian
flight in commercial airline pilots. Aviat Space
Environ Med [Suppl] 57:B29-B42.

Schroeder DJ, Goulden DR (1983). A bibliography of
shift work research: 1950-1982. Washington, DC:
U.S. Department of Transportation, Federal Avia-
tion Administration, 1983 Sep. Report No.: FAA-
AM-83-17. Available from: National Technical
Information Service, Springfield, VA 22161; or-
dering no. ADA135644.

Sieghart W, Ronca E, Drexler G, Karall S (1987).
Improved radioimmunoassay of melatonin in se-
rum. Clin Chem 33:604-5.

Skene DJ, Leone RM, Young IM, Silman RE (1983).
The assessment of a plasma melatonin assay using
gas chromatography negative ion chemical ioniza-
tion mass spectrometry. Biomed Mass Spectroscopy
10:655-9.

Skene DJ, Aldhous ME, Arendt J (1989). Melatonin,
jet-lag and the sleep-wake cycle. In: J. Horne, ed.
Sleep ’88: Transient insomnia, shift-work and jet-
lag, Symposium 1. New York, NY: Gustav Fischer
Verlag, pp. 39-41.

Stanley M, Brown GM (1988). Melatonin levels are
reduced in the pineal glands of suicide victims.
Psychopharmacology Bulletin 24:484-8.

Strughold, H (1952). Physiological day-night cycle in
global flights. Aviation Med 23:464-73.

Sturner WQ, Lynch HJ, Deng MH, Gleason RE,
Wurtman RJ (1990). Melatonin concentrations

in the sudden infant death syndrome. Forensic Sci
Int 45:171-80.

Szmuszkovicz J, Anthony WC, Heinzelman RV (1960).

Synthesis of N-acetyl-5-methoxytryptamine. J Org
Chem 25:857-9.

Tamarkin L, Baird CJ, Almeida OFX (1985). Melato-
nin: A coordinating signal for mammalian repro-
duction. Science 227:714-20.


air-evacuated casualties. Certainly, the advent of
commercial jet aircraft has made it possible to trans-
port passengers across multiple time zones to areas
where the day-night cycle is different from the cycle
that existed at takeoff. This rapid travel has lead to “jet
lag,” which is generally described as transient insom-
nia, degraded performance, and a general lack of well
being. Jet lag is attributed to lack of sleep and to
disturbed 24-hour rhythmic functions. It is usually
more severe in eastward flights, where the night period
occurs before the subject’s normal bedtime, than on
westward flights, where the day period is extended and
sleep is delayed. Arendt and Marks (1983) first sug-
gested that melatonin might hasten the resyn-
chronization of human 24-hour rhythms after time
zone changes. Arendt and co-workers (1986, 1987)
performed a double-blind study on 17 human sub-
jects who flew from London to San Francisco, re-
mained 14 days in San Francisco, and returned to
London. Daily doses of 3 mg of melatonin were taken
at 1800 hours local time for 3 days before the return
(eastward) flight and for 4 days after returning. Jet lag
was considered to be significantly less severe in the
melatonin-treated group, with improvements in sleep
quality, decreased sleep latency, and more rapid
resynchronization of endogenous melatonin and cor-
tisol rhythms.

Subsequently, Petrie et al. (1989) reported a study
of 20 subjects flown from Auckland, New Zealand, to
London (eastward) and returning after a 3-week inter-
val. All subjects took 5 mg of melatonin daily (or a
placebo) between 1000 and 1200 hours for 3 days
before the flight, once during the flight, and daily
between 2200 and 2400 hours (destination time) for
3 days after arrival. Effects were determined by visual
analog ratings of jet lag and tiredness, by a profile
from a moods states questionnaire for the measure-
ment of vigor-activity and fatigue-inertia, and by a
retrospective rating of jet lag on Day 10 after arrival.
Subjects taking melatonin reported less jet lag and
took less time to recover than the controls from the
shifts across 12 time zones in both directions.

A double-blind study with 61 subjects, flying from
the UK to Australia/New Zealand and return, indi-
cated that melatonin treatment significantly improved
self-rated jet lag (Skene et al., 1989). On the eastward
flight, subjects took 5 mg of melatonin daily at a local
time corresponding to 0200 hours at the destination
time zone for 2 days before arrival, then daily for 4
days after arrival at local bedtime. On the return flight

(westward), 5 mg of melatonin or a placebo was taken
daily at the local bedtime for 4 days after arrival.
Evening tiredness was only significantly increased
after the 4 days of administration, suggesting an effect
on timing mechanisms of fatigue instead of the phar-
macological hypnotic effect. Infrequent side effects
included drowsiness, headache, and nausea.

A simplified protocol was used by Claustrat et al.
(1992) fora study wherein 40 volunteers were selected
for their sensitivity to eastward jet lag. With no pre-
departure treatment, each subject took 8 mg of mela-
tonin (or placebo) at 2200 hours on the day of the
nocturnal flight (USA to France) and for 3 consecu-
tive days between 2200 and 2300 hours in France.
Thirty self-rating questionnaires, completed on Day 7
after return, rated melatonin treatment (n = 15) at the
median of efficiency scores (visual analogue scale) of
73, whereas the median of 48 was observed with the
placebo-treated subjects (n = 15). Two cases of side
effects were related to the melatonin’s hypnotic activ-
ity. A single case of tachycardia and 2 cases of “heavy
head” were considered to be of minor consequence.

Unlike passengers, international aircrews are com-
monly required to travel through a number of time
zones without time to adapt to the new environment
before continuing to the next sector. The resulting
circadian desynchronization can result in performance
decrements and could possibly compromise the safety
of airline operations. The crews work during flight,
making them less able than the passengers to alter
their sleep and rest patterns. Melatonin administra-
tion to aircrews prior to their arrival at home might
simply add a confusing cue to an already disturbed
circadian rhythm (Petrie et al., 1993). Harm et al.
(1993) measured salivary melatonin in airline flight
attendants on a 4-day trip over 10 time zones and
found that subjects had disturbed melatonin secretion
for 7-8 days in connection with each transmeridian
flight. Petrie et al. (1993) evaluated the timing of
melatonin dosage in 52 members of an Air New
Zealand cabin crew on a 9-day duty schedule flying
from Auckland to Los Angeles to London and return-
ing by the same route. In the study, Group | received
5 mg of melatonin on each of 3 days prior to returning
to New Zealand (0700-0800 Los Angeles time) and
on each of 5 days at home (2200-2400 New Zealand
time). Group 2 received placebo during the preflight
and flight periods and were given melatonin only after
arrival in New Zealand. Group 3 received only pla-
cebo. The group receiving melatonin only following


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studies have shown that it is also produced in the
retina, Harderian glands, and gastrointestinal tract
(Huether, 1994), The rhythmic nature of the synthe-
sis and secretion of pineal melatonin are controlled by
the light-dark environment, acting through the hypo-
thalamic suprachiasmatic nuclei (SCN). These light-
dark signals are transmitted by a neural pathway from
the retina, through the SCN, preganglionic neurones
of the upper thoracic spinal cord, and postganglionic
sympathetic fibers from the superior cervical ganglia,
to the pineal gland (Webb and Puig-Domingo, 1995).
Thus, the pineal melatonin synthesis is inhibited by
light and stimulated by darkness, and it is indepen-
dent of sleep (Deacon et al., 1993; Miyauchi, 1993;
Webb and Puig-Domingo, 1995). The gastrointesti-
nal tract contributions to circulating melatonin are
more likely to be affected by food intake (tryptophan
availability) and nutritional state (Huether, 1994).
As shown in Fig. 1, starting from the amino acid
tryptophan, melatonin biosynthesis occurs in four
basic steps (Miles and Philbrick, 1987; Claustrat et
al., 1990). The major regulating step in the synthesis
is the N-acetyltransferase-mediated conversion of se-
rotonin to N-acetylserotonin, the step inhibited by
light and stimulated by darkness, thereby creating a
marked rhythm in the pineal output. It is generally
conceded that the direct secretion into blood is the
major route for the transport of endogenous melato-
nin to its targets. There does not appear to be any
storage site, so the circulating melatonin levels essen-
tially parallel pineal activity. Studies of pinealectomized
animals indicate that the extrapineal sources of mela-
tonin synthesis may be able to maintain the relatively
low daytime levels in circulation, but the expected
nighttime elevations are much lower (Huether, 1994).
Melatonin is rapidly metabolized in the liver to 6-
hydroxymelatonin, which is then conjugated as 60-
70% sulfate and 20-30% glucuronide (Webb and
Puig-Domingo, 1995). Circulating plasma melato-
nin has a relatively short half-life, with about 90%
being cleared during a single hepatic passage (Huether,
1994). A small fraction is biotransformed into N7-
acetyl-5-methoxykynurenamine in the brain (Hirata
et al., 1974). These metabolic routes are outlined in
Fig. 2. The 24-hour urinary excretion of conjugated
6-hydroxymelatonin (6-sulfatoxymelatonin) has been
correlated with the corresponding 24-hour plasma
melatonin profile (Arendt et al, 1985; Markey et al.,
1985; Bojkowski et al., 1987), thus providing a non-
invasive method for measuring pineal function in

normal subjects. However, the metabolic clearance
rate of plasma melatonin in persons with liver dys-
function is much reduced (Iguchi et al., 1982a).

PHARMACOLOGY

Normal melatonin secretion patterns display a dis-
tinct circadian rhythm resulting in very low daytime
serum concentrations (10 pg/ml) and nocturnal levels
that can range from 30 to 120 pg/ml (Iguchi et al.,
1982b; Bojkowski et al., 1987; Miles and Philbrick,
1987; Claustrat et al., 1990). Salivary melatonin lev-
els range from 27 to 32% of the corresponding plasma
levels (Miles et al., 1987). Secretion patterns also
display seasonal phase delays with the evening melato-
nin rise in winter being delayed approximately 1.5
hours relative to that in the summer (IIllnerovd et al.,
1985; Arendt, 1988). Pineal melatonin secretion is
highest in young children, decreases in adults, and
continues to decrease with age, where little melatonin
secretion can be observed. Iguchi et al. (1982b) found
an approximately linear correlation for daytime serum
levels from 10 pg/ml down to 2 pg/ml in 81 human
subjects from 1 to 92 years old. During the same
study, they compared nighttime peak serum melato-
nin levels for two age groups (26 and 84 years) and
found 83 and 12 pg/ml, respectively.

The relationship between circulating melatonin
levels and light-dark cycles led to research directed
toward the therapeutic administration of melatonin
to treat certain sleep disorders (James et al., 1990;
Waldhauser et al., 1990; Dollins et al., 1994; Jan and
Espezel, 1995). Early studies varied considerably in
the dosage of the hormone and its time of administra-
tion, factors now known to be critical in the interpre-
tation of the observed response (Lewy and Sack,
1993). High oral dosages (100 mg) of crystalline
melatonin have been well tolerated in humans
(Cagnacci et al., 1991). Doses as large as 300 mg/day
for 30 days were given to subjects in one study of
pituitary-ovarian function (Voordouw et al., 1992).
Pharmacokinetic studies reveal that serum melatonin
levels return to the basal level within 4 hours after a 2-
mg oral dose and have a mean elimination half-life of
0.54 to 0.67 hour (Dollins et al., 1994; Aldous et al.,
1985). After an 80-mg dose, the level increased from
17 pg/ml (basal level) to 25800 pg/ml within 1 hour
and decreased to 203 pg/ml in 10 hours (Waldhauser
et al., 1990). While large differences in its

interindividual absorption exist, representative examples


Tan D, Péeggeler B, Reiter RJ, Chen L, Chen S,
Manchester LC, Barlow-Walden LR (1993). The
pineal hormone melatonin inhibits DNA-adduct
formation induced by the chemical carcinogen
safrole in vivo. Cancer Letters 70:65-71.

Tan D, Reiter RJ, Chen L, Poeggeler B, Manchester LC,
Barlow-Walden LR (1994). Both physiological
and pharmacological levels of melatonin reduce
DNA adduct formation induced by the carcino-
gen safrole. Carcinogenesis 15:215-8.

Terzolo M, Piovesan A, Osella G, Torta M, Buniva T,
Paccotti P, Wierdis T, Angeli A (1991). Exog-
enous melatonin enhances the TRH-induced pro-
lactin release in normally cycling women: A sex-

specific effect. Gynecol Endocrinol 5:83-94.

Tetsuo M, Markey SP, Colburn RW, Kopin IJ (1981).
Quantitative analysis of 6-hydroxymelatonin in
human urine by gas chromatography-negative
chemical ionization mass spectrometry. Anal
Biochem 110:208-15.

Valcavi R, Dieguez C, Azzarito C, Edwards CA, Dotti
C, Page MD, Portioli I, Scanlon MF (1987).
Effect of oral administration of melatonin on GH
responses to GRF 1-44 in normal subjects. Clin
Endocrinol 26:453-8.

15

Vieira R, Miguez J, Lema M, Aldegunde M (1992).
Pineal and plasma melatonin as determined by
high-performance liquid chromatography with
electrochemical detection. Anal Biochem

205:300-5.

Vitale AA, Ferrari CC, Aldana H, Affanni JM (1996).
Highly sensitive method for the determination of
melatonin by normal-phase high-performance liq-
uid chromatography with fluorometric detection.

J Chromatogr B (Biomed Appl) 681:381-4.

Voordouw BCG, Euser R, Verdonk RER, Alberda BT,
DeJong FH, Drogendijk AC, Fauser BCJM, Cohen
M (1992). Melatonin and melatonin-progestin
combinations alter pituitary-ovarian function in
women and can inhibit ovulation. J Clin Endocrinol
Metab 74:108-17.

Waldhauser F, Saletu B, Trinchard-Lugan I (1990).
Sleep laboratory investigations on hypnotic proper-
ties of melatonin. Psychopharmacology 100:222-6.

Webb SM, Puig-Domingo M (1995). Role of mela-
tonin in health and disease. Clin Endocrinol
42:221-34.

EUS. GOVERNMENT PRINTING OFFICE: 2001 660-082/20015


of dose/1-hour serum levels are 0.1mg/50 pg/ml, 0.3
mg/120 pg/ml, 1 mg/400 pg/ml, 2 mg/1900 pg/ml,
10 mg/6300 pg/ml, and 80 mg/25800 pg/ml (Dollins
et al., 1994; Aldous et al., 1985; Waldhauser et al.,
1990). Unlike the sustained blood levels observed
from endogenous release, oral doses produce a rapid
increase in blood concentration followed by a rapid
decrease.

Experimental sleep laboratory investigations indi-
cate that melatonin exerts some sedative and hypnotic
effects by accelerating sleep initiation and improving
sleep maintenance, without hangover problems on
the following morning (Waldhauser et al., 1990).
When 2 tol0 mg doses were given at bedtime to
children suffering from chronic sleep disorders, re-
searchers reported that melatonin administration fully
or partially corrected the sleep-wake cycle (Jan and
Espezel, 1995). However, similar doses given to adult
patients with insomnia proved ineffective (James et
al., 1990). Daytime administration of 0.1 to 0.3 mg
generated peak serum melatonin concentrations within
the normal nocturnal ranges of untreated people.
These and higher doses produce measurable hypnotic
effects, independent of the circadian time signal syn-
chronizing action. The development of a parenteral
sustained release pharmaceutical preparation produc-
ing an extended plasma melatonin plateau at physi-
ological levels may define whether it acts primarily as
a hypnotic or actually speeds up resynchronization of
circadian rhythms (Claustrat et al., 1992). A submu-
cosal patch as described by Bénés et al. (1993) can
simulate the rise, plateau, and decrease of endogenous
plasma melatonin, providing a near-physiological
delivery system for future research.

Animal studies continue to reveal melatonin effects
worthy of further study in their applications to hu-
mans. Melatonin treatment appears to decrease brain
serotonin release leading to hypotension and brady-
cardia in rats (Chuang et al., 1993). It has also been
shown to exaggerate the development of collagen-
induced arthritis in mice (Hansson et al., 1992) and
to reduce in vitro insulin secretion from rat pancreas
(Atkins et al., 1973). Indications of melatonin’s func-
tion as a neuroimmunoregulatory and anti-stress hor-
mone in mice were noted in a study by Pierpaoli and
Maestroni (1987). Recent studies by Reppert at the
Harvard Medical School (cited by Barinaga, 1997)
indicate that melatonin’s principal action may be the
suppression of SCN neuron activity. Different recep-
tors in mouse brain have been identified for melatonin’s

SCN-inhibition and phase-shifting activities. Since
the resultant phase shifts are short (< 1 hr), it appears
that melatonin’s sleep-inducing effects are caused by
its SCN-suppression activity.

CLINICAL PERSPECTIVES

The medical practitioner must interpret melatonin
use in the context of varied user expectations. Some
users have been inspired by the claims that melatonin
is a “magic bullet” that reverses the aging process,
helps in the treatment of cancer, improves sex, acti-
vates the body’s immune response, and cures sleep
disorders (Pierpaoli and Maestroni 1987; Hearn, 1995;
Pierpaoli et al., 1995; Dille 1996; Lamberg 1996).
Although this hormone is ostensibly the most potent
known hydroxyl radical scavenger (Poeggeler et al.,
1994; Reiter, 1995a, b), and a prominent theory
attributes the rate of aging to accumulated free radical
damage especially in DNA, such dramatic protection
has only been demonstrated in rodents (Tan et al.,
1993, 1994). Its anti-cancer activity is based on labo-
ratory reports of the inhibition of mitosis in tumor
growth and, conversely, on the metastasis-enhancing
effects of pinealectomy (Miles and Philbrick, 1987).
Clinical studies have been mostly on patients with
advanced cancer, where melatonin was given in large
(20 to 40 mg/day) doses in combination with radio-
therapy or chemotherapy. Some of the preliminary
results have been encouraging, but confirmation is
needed with larger groups observed over a longer
period of time (Brzezinski, 1997). Similarly, claims
for improved sex, enhanced immune response, or a
cure-all for sleep disorders have not been scientifically
validated through clinical trials in humans. Whether
or not these claims prove valid, the indiscriminate use
of melatonin poses a fundamental safety issue in air
travel, based on its known sedative/hypnotic effects.
Therefore, specific clinical studies and issues related
to jet lag, shift work, and airman medical certification
are discussed in the following subsections.

Jet Lag

It is not surprising that melatonin, with its prom-
ising ability to shift circadian rhythms, might be
considered for the treatment of diurnal rhythm dis-
ruptions caused by travel through time zones.
Strughold (1952) described this phenomenon in terms
of the physiological readiness of rapidly-transported
military troops and in the treatment adjustment for


DOTIEAAIAN-28/10 Aeromedical Aspects of
Office of Aviation Medicine

Washington, D.C. 20591 Melatonin—An Overview

Donald C. Sanders

Arvind K. Chaturvedi

Jerry R. Hordinsky

Civil Aeromedical Institute
Federal Aviation Administration

Oklahoma City, OK 73125

March 1998

Final Report

This document is available to the public
through the National Technical Information
Service, Springfield, Virginia 22161.

@

U.S. Department
of Transportation

Federal Aviation
Administration


(Valcavi et al., 1987; Terzolo et al., 1991; Webb and
Puig-Domingo, 1995). In a study of healthy young
women over a period of four months, a 300-mg daily
dose of melatonin reportedly did suppress luteinizing
hormone at mid-cycle and demonstrated some ovula-
tory inhibition (Brzezinski, 1997). This is a very high
dose and lesser doses are more likely to be selected for
self-administration. Several disease states —Klinefelters
syndrome, Turners syndrome, psoriasis vulgaris, spina
bifida occulta, and sarcoidosis — have been associated
with disrupted melatonin profiles, both in terms of
rhythm and magnitude (Miles and Philbrick, 1987).
Although individuals with these disorders may not
make up a significant portion of the airman applicant
pool, the effects of exogenous melatonin in these
disease states could be presumed to differ from healthy
subjects. Therefore, from a practitioner’s perspective,
caution and special endocrinological evaluation may
be warranted in the high-dose users or in the low-dose,
long-term users.

Melatonin findings in neuropsychiatric conditions
are also of interest. In a review, Webb and Puig-
Domingo (1995) reported 3 studies that (i) indicated
increases in the cortisol/melatonin ratio and disturbed
melatonin rhythms in depressed individuals (Claustrat
etal., 1984), (ii) observed very low melatonin levels in
chronic schizophrenics (Ferrier et al., 1982), and (iii)
proposed low nighttime levels of melatonin as a trait
marker for major depressive disorders (Beck-Friis et
al., 1985). However, high doses of melatonin wors-
ened moderate to severe clinical depression (Carman
et al., 1976), leading to the discontinuation of the
treatment. Ethanol ingestion has also been shown to
inhibit nocturnal melatonin secretion (Rojdmark et
al., 1993), and it has been suggested that urinary
melatonin can be used as a marker of alcohol abuse
(Murialdo et al., 1991).

Finally, one must reemphasize that melatonin’s
interactions with many clinical conditions and with
prevalent medications (inclusive of those certifiable
within the airman population) are scarcely docu-
mented. Also, the effects of chronic melatonin use
have not been adequately studied, and additional
research is needed in these areas if competent clinical
evaluations are to be performed. These observations
are strongly supported by the National Institutes of
Health (Lamberg, 1996) and the National Institute
on Aging (Rawls, 1996).

ANALYTICAL METHODS

Melatonin analytical methods vary from techniques
that measure nanogram quantities in the entire pineal
body to picogram concentrations in plasma and urine.
Current studies on human pineal function depend
heavily on plasma and urine measurements. After
accounting for variations in early analytical values due
to developing methodology, normal daytime human
plasma melatonin levels are now considered to be less
than 20 pg/ml with nighttime peak levels of 40-80 pg/
ml (Arendt, 1986). Analytical techniques in current
use are radioimmunoassay (RIA), high-performance
liquid chromatography (HPLC), and gas chromatog-
raphy-mass spectrometry (GC-MS).

RIA methods have undergone many refinements in
recent years, making this technique reliable, sensitive,
and specific. A modified extraction procedure coupled
with a commercial RIA kit was used to analyze mela-
tonin in 0.1 to 5.0 ml of serum with 96-104% recov-
ery (Sieghart et al., 1987). Sturner et al. (1990) used
a single chloroform extraction of body fluids with an
RIA procedure to study melatonin concentrations in
Sudden Infant Death Syndrome. A significant degree
of interference from calcium heparin has been re-
ported in a study of anticoagulants and extraction
techniques by Plebani and co-workers (1990). A di-
rect saliva RIA method using '%I-2-iodomelatonin
was described by English et al. (1993). An enzyme-
linked immunosorbent assay (ELISA) was evaluated
in comparison with a routinely-used RIA method
(Chegini et al., 1995). This ELISA method utilized a
smaller serum volume (0.1 ml) and was technically
simpler, but required a 10-fold concentration step to
detect the low daytime melatonin levels. Both RIA
and ELISA methods were easily able to detect melato-
nin in concentrations less than 10 pg/ml of suitable
samples.

Compared to RIA methods, HPLC techniques
offer a non-bioassay for melatonin and have been used
to validate the specificity of RIA analyses. More re-
cently, HPLC was used for the quantitative analyses
of melatonin in tissue extracts (Peniston-Bird et al.,
1993). Early HPLC methods utilized an electrochemi-
cal detector with its concomitant limitations on the
mobile phase composition, but they possessed the
advantage of shorter analysis time without requiring
radioactive reagents (Mefford and Barchas, 1980;
Sagara et al., 1988; Raynaud and Pévet, 1991; Vieira


the flight (Group 2) showed significantly lower visual
analogue ratings of jet lag, compared with the “early”
melatonin or placebo group (Group 1 or 3). In these
aircrews, melatonin taken prior to returning home
resulted in worse adjustment. These authors suggest
that melatonin administration before arrival does not
re-entrain the disrupted circadian rhythm. In a less
formal study, a research group in Italy confirmed that
prior treatment was unnecessary and that a single 5-
mg melatonin dose on the evening of arrival was
adequate to prevent the classic symptoms of jet lag
(Lino et al., 1993).

The efficacy of melatonin in preventing sleep loss
and cognitive degradation after travel across 8 time
zones was recently tested in a military study of U.S.
Army personnel (29 male aircrew) deployed on a
training mission to the Middle East (Comperatore et
al., 1996). Melatonin was given orally in dosages of 10
mg/day for 3 days pre-travel, once during travel, and
for 5 days after arrival. The melatonin-treated subjects
exhibited fewer post-deployment errors in both dual-
vigilance and reaction time tasks than their placebo-
treated counterparts and were able to extend their
sleep periods under noisy crowded conditions. In this
and other studies, it is difficult to unequivocally
determine whether the indicated improvements in
overcoming jet lag effects are due to melatonin’s
hypnotic activity or chronobiotic property. Redfern
(1992) suggests that we are probably asking too much
of any “jet lag pill” to expect resynchronization, at the
same rate, of all physiological functions to new time
cues following phase shift and that a single pharmaco-
logical entity capable of this re-entrainment is still in
the future.

Shift Work

Many of the problems manifested in jet lag are also
present in shift work. The diurnal nature of humans
makes it harder to remain alert at night and to sleep in
the daytime, when the reversed light-dark periods
provide cues that conflict with normal behavior pat-
terns. The slow and uneven adjustment of the human
internal circadian rhythm to a change in work sched-
ule is limited by the amount to which it can adjust on
adaily basis. This adjustment is also directional—that
is, it is easier to postpone the sleep-wake cycle than to
advance the cycle (Moline et al., 1992).

The demands of the aviation environment require
round-the-clock activity of both pilots and support
personnel. Pilots with evening departures need to

sleep during the day at a time usually out of phase with
their biological clocks. Maintenance workers and air
traffic control specialists frequently work rapidly-
rotating shifts (Schroeder and Goulden, 1983; Melton
and Bartanowicz, 1986; Della Rocco and Cruz, 1995;
1996). Individuals employ a variety of sleep strategies
to cope with the disturbances of their circadian rhythms
(Sasaki et al., 1986), and concern has been expressed
about melatonin’s use by shift workers, citing its
residual effects on mood, interest, and efficiency
(Lieberman et al., 1984; Dille, 1996).

Ina study of 17 volunteer police officers working 7
successive night shifts, 5 mg of melatonin, taken at the
desired bedtime, increased rated sleep quality and
duration relative to baseline and placebo conditions
(Folkhard et al., 1993). The data also suggested in-
creased alertness, especially in the early morning, but
there was no evidence that melatonin treatment had
resulted in a phase delay of the alertness rhythm.
Midshift performance showed a reduced memory
scanning speed and an increased perception of mental
workload relative to baseline and placebo conditions,
suggesting that melatonin’s effects on performance
may need careful evaluation. Josephine Arendt, a co-
author in that 1993 study and pioneer researcher on
melatonin, is cited by Lamberg (1996) as saying, “But
we would not dream of giving melatonin to shift
workers except in experimental conditions. Timing is
critical. Taking melatonin at the wrong time may
disrupt biological rhythms. Melatonin-induced sleepi-
ness may impair driving or job performance.” Thus, it
would appear that the use of melatonin by shift
workers to speed adjustments to new schedules will
require further evaluation.

Medical Certification

The aeromedical practitioner charged with assess-
ing the implications of melatonin use must keep in
mind the related current societal applications and
clinical observations, including any effects of exog-
enous melatonin on the endocrine system. Melatonin
secretion does not change during a woman’s normal
menstrual cycle (Brzezinski, 1997), nor did a dose of
10 mg of melatonin to female subjects change the
menstrual characteristics (Kirby et al., 1997). Acute
oral doses of melatonin have been associated with
stimulation of prolactin levels and some increase in
growth hormone levels, but no significant effects on
follicle stimulating hormone, luteinizing hormone,
thyroid stimulating hormone, and testosterone


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Technical Report Documentation Page

T. Report No. 2, Government Accession No. 3, Recipients Catalog No,
DOT/FAA/AM-98/10
4 Tite and Subte 5, Report Date
Aeromedical Aspects of Melatonin—An Overview March 1998
6. Performing Organization Code
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Sanders, D.C., Chaturvedi, A.K., and Hordinsky, J.R.
9, Performing Organization Name and Address 10. Work Unit No, (TRAIS)
FAA Civil Aeromedical Institute
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15. Supplemental Notes
This work was accomplished under the approved task AM-B-97-TOX-202.

16. Abstract

Melatonin, a pineal hormone present in the blood of humans and other species, has a distinct diurnal variation in its biosynthesis
and, therefore, in its concentration. This variation has suggested the possibility of a regulatory function in day/night-dependent
physiological processes, such as sleep, and has led scientists to explore the effects of administered melatonin on the modulation of
circadian rhythms. For the self-treatment of sleep disorders and other benefits, melatonin usage has been extolled to the extent that
20 million new consumers were added to the U.S. retail market in 1995. Its principal aeromedical application has been in the
experimental treatment of jet lag effects. For aircraft passengers, melatonin administration at destination-bedtime appears to improve
sleep quality and to decrease the time required to reestablish normal circadian rhythms. For international aircrews, who travel
through multiple time zones without time to adapt to new environments, taking melatonin prior to arriving home may further
impair already disturbed circadian rhythms. Its use to adjust to shiftwork changes by air traffic controllers, aircraft maintenance
workers, and support personnel is even more controversial. Limited studies suggest that giving this hormone to shift workers should
be done only under controlled conditions and that taking it at the wrong time may actually impair job performance. Because of its
possible interaction with certain medications and the changes in its concentrations observed in some clinical conditions, the
practitioner must exercise caution during the medical certification of airmen. The variations in the concentration of melatonin can
be effectively determined by radioimmunoassay, high-performance liquid chromatography, and gas chromatography-mass
spectroscopy analytical techniques. These techniques are capable of measuring the human daytime (10 pg/ml) and nighttime (30-
120 pg/ml) melatonin in plasma/serum. Melatonin measurements in victims of accidental deaths may allow forensic scientists and
accident investigators to utilize the relationship between its concentration and the time of day when death occurred. The most
accurate estimations of the time of death result from analysis of melatonin content of the whole pineal body, whereas less accurate
estimates are obtained from serum and urine analyses—pineal levels of melatonin are unlikely to be altered by exogenous melatonin,
but its blood and urine levels would change. Its high blood levels in a daytime crash victim would suggest exogenous
supplementation. The possible interfering effects of postmortem biochemical processes on melatonin concentrations in whole blood
and in other tissues are not well understood, and there is a need for the continuing research into melatonin’s chronobiological
properties to define its proper applications and limitations. The indiscriminate use of melatonin by aviation professionals may pose
unacceptable safety risks for air travel.

17, Key Words 18. Distibution Statement

Melatonin, Biochemical Pharmacology, Analytical Document is available to the public through the

Methods, Postmortem Toxicology, Jet Lag, Shift Work, National Technical Information Service,

Medical Certification, Aircraft Accident Investigation Springfield, Virginia 22161

19. Security Class. (ofthis repor) 20. Security Classi (of his page) 21. No, of Pages 22, Price
Unclassified Unclassified 18

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized



NOTICE

This document is disseminated under the sponsorship of
the U.S. Department of Transportation in the interest of
information exchange. The United States Government
assumes no liability for the contents or use thereof.


et al., 1992). Later studies, using fluorescence detec-
tion, allowed a more robust methodology with a
simple methanol-water (Peniston-Bird et al., 1993) or
ethyl acetate (Vitale et al., 1996) mobile phase, giving
relatively rapid separation and column regeneration.
HPLC’s principal disadvantage is that larger volumes
of sample are required when measuring low daytime
concentrations. Depending on the specific method,
detection limits are about 2-20 pg/ml in plasma with
0.2-2.0 ml sample sizes and 7 pg/ml in urine with an
8.0 ml sample size.

Originally, melatonin values obtained by GC-MS
served primarily as standards for the validation of
other methods. Until recently, the extensive sample
workup, low throughput, and expense of the assay
have limited GC-MS use for routine analytical appli-
cations. Extraction methods varied, but the conver-
sion of melatonin to the fluorinated derivative using
pentafluoropropionic anhydride is widely employed
for gas chromatographic separation (Kennaway et al.,
1977; Greiner and Chan, 1978; Lewy and Markey,
1978; Tetsuo etal., 1981; Skene etal., 1983; Fourtillan
et al., 1994). A 150-fold increase in the sensitivity of
GC-MS for electron-capturing derivatives was pro-
vided by the technique of negative chemical ioniza-
tion (Lewy and Markey, 1978). This technique utilizes
a deuterated internal standard and detects melatonin
as low as 1 pg/ml in plasma. Skene et al. (1983)
simplified the extraction and derivatization proce-
dures suitable for analysis using the double focusing
magnetic mass spectrometer. Melatonin was mea-
sured at 0.5 pg/ml levels in plasma using the gas
chromatography/negative ion chemical ionization
mass spectrometry procedure with methane as the
reagent gas (Fourtillan et al., 1994). This highly sensi-
tive assay used a simple liquid-liquid extraction proce-
dure and allowed a laboratory throughput of 50 samples/
day. GC-MS techniques have also been described for the
quantitation of the 6-hydroxymelatonin conjugates in
urine (Fellenberg et al., 1980; Tetsuo et al., 1981).

In general, GC-MS appears to be the analytical
technique of choice based on its high sensitivity and
small sample size requirement. The specificity of GC-
MS methods has also resolved the somewhat ambigu-
ous data that surrounded the early measurements of
melatonin in biomatrices and should further improve
the understanding of pineal function. However, the
applicability of these methods has not been fully
established in the analysis of postmortem whole blood
and other tissue specimens.

POSTMORTEM TOXICOLOGY

In forensic toxicology, postmortem levels of drugs
and their metabolites are used to determine the ante-
mortem or perimortem physical state of victims. The
significance of postmortem analysis for melatonin has
not been definitively established. While melatonin is
endogenously produced, it has a strong potential to be
deliberately ingested, and this will present problems
in the interpretation of the postmortem analytical
results. One possible application of postmortem analy-
sis has been suggested by Mikami et al. (1994), who
investigated the quantitation of melatonin in cadavers
as a means of estimating the time of death. These
authors relate the melatonin content of the pineal
body to the hourly segment of the day in which death
occurred. In selected cadavers, where time of death
was known, they measured melatonin concentrations
in the pineal body (75 samples), serum (27 samples),
and urine (14 samples). Postmortem time intervals for
the collection of these specimens varied from 3.5 to 48
hours. After determining that melatonin in human
cerebral cortex decreases to approximately one-third
of its initial concentration in 24 hours and remains at
that level for 7 days, the investigators extrapolated the
original values to represent a 0.5-hour postmortem
interval. They proposed the following criteria for the
estimation of time of death in relation to melatonin
concentration in (ng/pineal body)/time of death: (0-
0.5)/1100-1500; (0.5-1)/0500-1900; (1-2)/inconclu-
sive; (2-5)/1000-0100; (5-15)/1800-0900; (>15)/
1900-0500. Attempts to correlate serum and urinary
melatonin levels with time of death were less precise.
Serum melatonin levels in excess of 100 pg/ml were
related to death between 2200 and 0100 hours and
urinary concentrations over 35 pg/ml were related to
death in the 1800-0600 hour period. These authors
feel that the serum and urinary criteria can be used
without any adjustment to estimate time of death,
since they and earlier workers (Sturner et al., 1990)
found no significant change in the concentration of
melatonin in serum or urine as a function of the
postmortem interval.

In the literature, no technique could be found that
can differentiate endogenous melatonin from ingested
melatonin. The amount of melatonin in the pineal
gland is unlikely to be affected by ingested melatonin,
but the level in circulation would be increased. It is
known that serum melatonin levels vary with age,
time of the day, and season (Iguchi et al., 1982b;


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