Exhibit 99.1

PRESS RELEASEFor Immediate Release

# ORPHAN MEDICAL
ANNOUNCES STRONG POSITIVEXYREM® CLINICAL RESULTS-Landmark Trial
Demonstrates Significant Improvement inExcessive Daytime Sleepiness Associated with
Narcolepsy-

MINNEAPOLISMay 19, 2004ORPHAN
MEDICAL, INC. (Nasdaq: ORPH) announced that it has received strong positive data across
both primary and secondary endpoints from its Phase III(b) clinical trial known as
SXB-15. The trial evaluated improvement in the excessive daytime sleepiness (EDS) of
patients with narcolepsy when a dose of 4.5, 6.0 or 9.0 grams of Xyrem®(sodium
oxybate) oral solution was added to the unchanged stimulant therapy. This double-blind,
placebo-controlled, randomized trial assessed 228 patients over an eight week treatment
period in 40 sleep centers in North America and eight in Europe.

Narcolepsy is a chronic,
debilitating neurological disease characterized by symptoms of excessive daytime
sleepiness, cataplexy (sudden loss of muscle tone) and fragmented nighttime sleep.
Excessive daytime sleepiness is experienced by all narcolepsy patients and is usually
treated with stimulants during the day to help keep patients awake. Xyrem is currently
the only approved medication for the treatment of cataplexy.

Bill Houghton, M.D., Chief Medical
& Scientific Officer, Orphan Medical, said, This was a positive trial across
all measures. The results are all the more striking given that Xyrem was used in addition
to stimulants commonly prescribed to treat EDS. We are very pleased with the results of
this trial and look forward to analyzing the data further over the next few weeks.

Trial ResultsPrimary endpoints of
the trial were changes in the Epworth Sleepiness Score (ESS) and Clinical Global
Impressions of Change (CGIc). The ESS results were statistically significant at the 6.0
gram (p < 0.001) and 9.0 gram (p < 0.001) doses. A statistically significant
response (p = 0.001) was seen at all Xyrem dose levels in the CGIc using a responder
analysis that classified responders as patients who were much improved or
very much improved as assessed by the treating physician.

Secondary endpoints included changes
in the Maintenance of Wakefulness Test (MWT), polysomnography recordings, as well as
reductions in inadvertent daytime naps, nighttime awakenings and the number of cataplexy
attacks.

MWT is an objective test used to
measure the degree of EDS. The 9.0 gram Xyrem dose showed a particularly dramatic MWT
response with a statistically significant (p < 0.001) increase of more than 10 minutes
from the baseline measure of 7.6 minutes. The 4.5 and 6.0 gram doses showed minor
improvements that did not reach statistical significance. Inadvertent daytime naps were
significantly reduced at both the 6.0 gram (p < 0.001) and 9.0 gram (p = 0.002) dose
levels.

Polysomnography is used to record
the brains electrical activity in order to measure the stages of a patients
sleep. The polysomnography results indicated that Xyrem increased the duration of Stage 3
and Stage 4 sleep, which are referred to as slow wave sleep and are believed to be the
physiologically restorative components of sleep. Xyrem extended total Stage 3 and 4 sleep
by 24



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minutes per night at the 6.0 gram
dose (p < 0.001) and by over 50 minutes per night at the 9.0 gram dose (p < 0.001).
The increase in slow wave sleep was accommodated by dose related increases in total sleep
time and by dose related decreases in Stage 1 and REM sleep. Furthermore, nighttime
awakenings per week were significantly reduced at both the 6.0 gram dose (p < 0.001)
and the 9.0 gram dose (p = 0.004).

Jed Black, M.D., Medical Director,
Stanford University Sleep Disorders Clinic, and an investigator in the SXB-15 trial,
commented, An increase of three to four minutes in MWT is important, but an
increase of over 10 minutes is remarkable especially when it represents an incremental
improvement beyond stimulant therapy. The effect on Stage 3 and 4 sleep is also
substantial. The reduction in the number of awakenings at night and in time spent awake
during the night is compelling. Clearly, based on this and previous trials, Xyrem should
have an important and primary role in addressing the fragmented sleep and the
debilitating daytime symptoms of narcolepsy patients.

The trial reaffirmed the efficacy of
Xyrem at the 6.0 gram (p= 0.002) and 9.0 gram (p< 0.001) doses in
reducing cataplexy attacks, which had been demonstrated in prior Xyrem trials. Moreover,
the 4.5 gram dose in this trial showed efficacy (p = 0.021) in reducing cataplexy over
the eight-week treatment period.

The trial also assessed the daytime
functioning of narcolepsy patients using the Functional Outcomes Sleep Questionnaire
(FOSQ), a validated tool to evaluate this important measure. FOSQ global scores were
statistically significant at the 6.0 gram (p = 0.040) and 9.0 gram (p < 0.001) doses.
The FOSQ is composed of five factorial scores, four of which were statistically
significant at the 9.0 gram dose (p = 0.001).

No new or unexpected adverse events
were seen in the SXB-15 trial and the safety profile was similar to that of previous
Xyrem trials and commercial use. The most common adverse events included nausea,
dizziness and vomiting, and were dose related. Disorientation at night, sleepwalking and
enuresis, or bedwetting, occurred infrequently, but more often at the 9.0 gram dose.

Additional data from the SXB-15
trial will be presented at the upcoming Associated Professional Sleep Societies meeting
in Philadelphia, June 6-10.

Xyrem Update and Next StepsJohn H.
Bullion, the Companys CEO, stated, These impressive SXB-15 results are
convincing evidence that Xyrem has a broader application for the treatment of narcolepsy.
With its current cataplexy labeling, Xyrem prescribing continues to grow steadily: 2,962
Xyrem prescriptions were filled in the past six weeks. Our plan is to expand the Xyrem
label beyond cataplexy. We expect to obtain results of our second Phase III(b) trial,
EXCEEDS, later in the third quarter and intend to file a Supplemental New Drug
Application (sNDA) incorporating the results of both trials with the U.S. Food and Drug
Administration (FDA) by the end of the year.

We also believe Xyrem has
therapeutic potential beyond narcolepsy, added Bullion. We will begin patient
enrollment this summer in a proof-of-principle trial to assess Xyrem as a treatment for
fibromyalgia syndrome and we are pursuing a number of Phase IV studies. Finally, our
program to develop an extended-release once-nightly Xyrem formulation is on schedule.



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Conference CallThe Company also
announced that Orphan Medical management will host a live Webcast to review the results
of SXB-15 and provide an update on continuing Xyrem development efforts on Thursday, May
20, at 10:00 a.m. Eastern Time.

To access the Webcast, go to the
investor section of the Orphan Medical Web site at http://www.orphan.com and click on the
Webcast icon. A replay of the Webcast will be available at the same address for two weeks.

Background InformationNarcolepsy is
a chronic, debilitating neurological disease. Cataplexy, a sudden loss of muscle tone, is
usually triggered by strong emotions such as laughter, anger, or surprise. As such,
patients often selectively isolate themselves from interaction with others resulting in a
dramatic effect on a patients quality of life. Narcolepsy afflicts approximately
100,000 to 140,000 Americans with about 50,000 to 75,000 patients receiving some form of
treatment for their symptoms. An estimated sixty to ninety percent of those with
narcolepsy suffer from cataplexy. All patients with narcolepsy suffer from excessive
daytime sleepiness.

Fibromyalgia is a chronic condition
that is estimated to affect as many as four million individuals in the United States and
represents a market opportunity in excess of a billion dollars per year. The disease is
characterized by widespread muscle pain and stiffness and affects women three times more
often than men. Other symptoms include persistent fatigue, headaches, cognitive or memory
impairment, morning stiffness and non-restorative sleep.

Orphan Medical acquires, develops,
and markets pharmaceuticals of high medical value for inadequately treated and uncommon
CNS diseases treated by specialist physicians. The lead product for the company is Xyrem,
which is the first and only approved treatment for cataplexy associated with narcolepsy.
Xyrem is also being assessed as a treatment for the full range of narcolepsy symptoms
including excessive daytime sleepiness. Orphan Medicals pipeline includes
development stage products for fibromyalgia and pain. Orphan Medicals Internet Web
site address is www.orphan.com

|CONTACT: | Tim McGrath (CFO)David Folkens (Corporate Communications) | (952) 513-6900(952) 513-6994
|-------- | --------------------------------------------------------- | ----------------------------

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The information in this press
release may contain forward-looking statements within the meaning of the Private
Securities Litigation Reform Act of 1995. A number of factors could cause actual results
to differ materially from the Companys assumptions and expectations. These are set
forth in the cautionary statements included in Orphan Medicals most recent Form
10-Q or Form 10-K filed with the Securities and Exchange Commission. (These documents can
be accessed through the Orphan Medical Web site at http://www.orphan.com). All
forward-looking statements are qualified by, and should be considered in conjunction
with, such cautionary statements.

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