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FAA-AM-82-19 

EFFECTS OF SOME MOTION SICKNESS SUPPRESSANTS ON TRACKING 

PERFORMANCE DURING ANGULAR ACCELERATIONS 

David J. Schroeder, William E. Collins, Gary w. Elam* 

Aviation Psychology Laboratory 

FAA Civil Aeromedical Institute 

Oklahoma City, Oklahoma 73125 

and *Medical Building, 601 West 4th, Odessa, Texas 79760 

OCTOBER 1982 

Document is available to the public through the 

National Technical Information Service 

Springfield, Virginia 22161 

Prepared for 

U.S. DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

Office of Aviation Medicine 

Washington, D.C. 20591 
NOTICE 

This document is disseminated under the sponsorship of the 

Department of Transportation in the interest of information 

exchange. The United States Government assumes no liability 

for its contents or use thereof. 
1. Report No. 2 . Government Accession No . 

FAA-AM-82- 19 

4. Title and Subtitle 

EFFECTS OF SOME MOTION SICKNESS SUPPRESSANTS ON 

TRACKING PERFORMANCE DURING ANGULAR ACCELERATIONS 

Technical Report Documentation Page 

3. Recip ient's Catalog No . 

5 . Repo rt Date 

OCTOBER 1982 

6. Performing Organization Code 

1-::-----:-:-----------------------------f B. Performing Organization Report No . 7 · Authorls) David J. Schroeder, William E. Collins, 

and Gary W. Elam 

9. Performing Organization Name and Address 

FAA Civil Aeromedical Institute 

P.O. Box 25082 

Oklahoma City, Oklahoma 73125 

10 . Work Un it No . (TRAIS) 

11 . Contract or Grant No . 

13. Type of Report and Period Covered 

~~------------------------------------------------------~ 12: Sponsoring Agency Name and Address 

Office of Aviation Medicine 

Federal Aviation Administration 

800 Independence Avenue, S.W. 

Washington, D.C. 20591 

15. Supplementary Notes 

14. Sponsoring Agency Code 

Work was performed under tasks AM-D-77/78-PSY-62 and AM-A-82-PSY-86. 

16. Abstract 

Student pilots sometimes experience motion sickness early in their flight 

training and drug remedies may be prescribed for dual flights. Moreover, 

prescriptions are not required for some motion sickness preventives. In 

addition, business associates or spouses often accompany private pilots on 

flying trips; some of these passengers, who may be required to pilot the 

aircraft in an emergency, use antimotion sickness drugs. While the basic 

efficacy of such drugs is rooted in the reduction of motion sickness symptoms, 

adverse side effects are important practical considerations of their usage in 

aviation. The two studies reported here examined the influence of three 

established antimotion sickness drugs on tracking performance in static 

(stationary) and dynamic (angular acceleration) conditions and on visual 

fixation ability during motion. In Study I, 40 young men were randomly assigned 

in equal numbers to either a control (lactose placebo), dimenhydrinate (50 mg), 

promethazine hydrochloride (25 mg), or mixture (25 mg promethazine plus 10 mg 

d-amphetamine) group. Study II used 30 new subjects equally divided into 

control, dimenhydrinate (100 mg), and promethazine (50 mg) groups. Following 

practice, tests were conducted prior to 1, 2, and 4 hours after drug ingestion. 

The depressant drugs had little effect on static tracking, but impaired dynamic 

tracking performance and reduced ability to maintain visual fixation on a 

localizer/glide slope instrument due to increased ocular nystagmus. The mixture 

of promethazine and d-amphetamine produced none of these deleterious effects. 

17. KeyWords 

Performance 

Motion Sickness 

Drugs 

Visual-Vestibular Interactions 

Medical Certification Policy 

19. Security Classif. (of this report) 

Unclassified 

18. Distribution Statement 

Document is available to the public 

through the National Technical 

Information Service, Springfield, 

Virginia, 22161 

20. Security Classif. (of this page) 21. No. of Pages 22. Pri ce 

Unclassified 17 

Form DOT F 1700.7 <B-72l Reproduction of completed page authorized 
ACKNOWLEDGMENT 

We gratefully acknowledge the assistance of Greg Constant, Cynthia Mitchell, 

Cissy Lennon, Debbie Taylor, Linda VanBuskirk, and Linda Foreman. 
EFFECTS OF SOME MOTION SICKNESS SUPPRESSANTS ON TRACKING 

PERFORMANCE DURING ANGULAR ACCELERATIONS 

Introduction. 

Student pilots sometimes experience motion sickness to varying degrees 

early in their training and the use of drug remedies is not prohibited when 

prescribed for dual flights. Moreover, prescriptions are not required for 

some motion sickness preventives. In addition, spouses or business 

executives often accompany private pilots on flying trips; some of these 

passengers, who may be required to pilot the aircraft in an emergency, use 

antimotion sickness drugs. 

The recommended use of drugs to suppress motion sickness involves a 

prior assessment of undesirable side effects. In most cases, the side 

effects that are considered are those such as drowsiness, dry mouth, blurred 

vision, irritability, talkativeness, etc. (8). In some cases, performance 

data under drug conditions are available, but almost invariably such data 

are based on performance in static (stationary) environments. There are 

data, however, that indicate that moderate doses of two types of depressant 

drugs, alcohol and secobarbital sodium, may have no demonstrable effect on 

the performance of a tracking task in a static environment but may produce 

significant impairment of both performance and visual fixation ability in a 

dynamic (angular acceleration) environment (1,4,9,10). Since motion 

sickness suppressants are specifically used in dynamic environments, the 

possible deleterious effects of such prescriptions on performance and visual 

acuity during motion are important considerations in a variety of 

applications for transportation systems. Thus, the present study was 

designed to compare the effects of several drugs used as motion sickness 

preventives on performance at an eye-hand coordination task (tracking) under 

both stationary conditions and conditions involving whole-body angular 

motion and concomitant nystagmic eye movements. 

Method. 

Subjects. In the first of two experiments, 40 male college students 

served as subjects; none had any previous laboratory experience involving 

vestibular stimulation. These students were assigned to one of four groups 

of 10 subjects each: (i) control (lactose placebo), (ii) 50 mg 

dimenhydrinate, (iii) 25 mg promethazine hydrochloride, and (iv) a mixture 

group (25 mg promethazine hydrochloride plus 10 mg d-amphetamine). The 

latter combination of drugs was included because it has been cited as one of 

the most effective antimotion sickness drugs in laboratory studies (13). A 

second experimental series involved higher drug dosages administered to 30 

new subjects who were placed in three groups of 10 each: (i) control 

(lactose placebo), (ii) 100 mg dimenhydrinate, and (iii) 50 mg promethazine 

hydrochloride. 

1 
Apparatus. A modified Stille-Werner RS-3 rotation device provided the 

angular stimulation, viz, a triangular waveform stimulus with a 48-s period 

and a peak turning velocity of 120°/s in both the clockwise and 

counterclockwise directions. Subjects were seated in the device with their 

heads secured in a headrest positioned so as to place the lateral pair of 

semicircular canals approximately in the plane of stimulation. 

An aircraft localizer-glide slope indicator located directly in front 

of the subject provided the visual stimulus for the one-degree-of-freedom 

tracking task. While the room was in total darkness during the trial, the 

indicator was illuminated at a level comparable to that recommended for 

aircraft instruments during night flight, viz, one fL. The vertical needle 

of the indicator was driven to the left and right of center by a sinusoidal 

forcing function with a 14-s period. Movements of the needle were thus in 

the same approximate plane as the eye movements arising from the rotary 

stimulation. The subject was instructed to make compensatory movements of a 

joystick in order to maintain the needle in the center or null position. 

Deviations from the null position were considered as errors and a voltage 

proportional to these deviations was electronically integrated over 1-s 

intervals and recorded. Further details concerning the operation of the 

tracking task are presented elsewhere (3). 

To monitor and record eye movements during vestibular stimulation, 

electrodes were taped beside the outer canthus of each eye. An electrode 

placed on the forehead served as a ground. The eye movement signals passed 

through a series of slip rings located at the base of the rotation device 

and were then recorded on a Beckman Type T electroencephalograph located in 

an adjoining room. Calibration of these ocular movements was accomplished 

by having the subject sweep his eyes between two small flashing lights on 

the front of the rotator. 

Procedure. The basic experimental paradigm was nearly identical to 

that used in previous studies concerning the effects of alcohol and of 

secobarbital on performance (1,10). The subjects were tested on five 

separate occasions during a single day. A practice session was used to 

acquaint the subject with the task and with the sensations arising from the 

stimulation. This was followed by a predrug session and three postdrug 

sessions conducted 1, 2, and 4 hours after the subjects ingested their 

respective capsules. The capsules were administered using a double-blind 

procedure. Subjects were not allowed to smoke or to drink beverages 

containing caffeine, except during a 2-h lunch period which preceded the 

final session. Each experimental testing session consisted of (i) 1 1/2 min 

of static tracking (30-s warmup; 1-min scored) prior to the start of 

motion, and (ii) dynamic tracking during five periods of angular 

accelerations (first period for warmup). Prior to each session, subjects 

rated 15 adjectives (active, drowsy, dull, sluggish, tired, sleepy, bored, 

lazy, leisurely, nonchalant, energetic, vigorous, fatigued, happy, and 

annoyed) from the 80-item Composite Mood Adjective Check List (CMACL) 

developed by Malstrom (7). Each rating was on a 9-point scale ranging from 

2 
"not at all" descriptive through "moderately" to "definitely" descriptive of 

the subject's current feelings. Three mood scores were calculated, viz, 

fatigue, vigor, and sleepy (7). 

Scoring. Tracking error was measured in 1-s intervals for both the 

static and dynamic conditions. Error scores were accumulated and averaged 

across groups for the last min of static tracking and for the first min 

(following warmup) of dynamic tracking. For the same period of dynamic 

tracking, the amount of slow-phase eye displacement was measured and the 

frequency of nystagmic eye movements was calculated; mean values were then 

determined and used as measures of nystagmic output. Scores on each of the 

two measures of nystagmus were used in separate statistical analyses. 

Additional scoring of tracking error and nystagmus included the three 

dynamic periods following warmup to assess other effects of time on task. 

All these data were treated by analysis of variance techniques followed by 

Tukey's Honestly Significant Difference (HSD) tests. 

For some graphic presentations, "change" scores were computed. For 

each group and each measure, the mean score for the predrug session was 

plotted as "zero" and the percentage of increase or decrease in scores 

during subsequent sessions was plotted as "percent increase" or "percent 

decrease" from the predrug level. 

Results. 

TRACKING 

Within Groups Comparisons. Although error scores for the placebo and 

mixture groups (see Figure 1) generally declined across sessions, the 

decline during static tracking in Study I was significant only for the 

placebo group; all three postingestion sessions were lower (better 

performance) than the preingestion session (p < .01 - .001). For the same 

duration of dynamic tracking (1 min), the placebo group scored significantly 

better (p < .05) during the 2-h postingestion session than during the 

preingestion level while the mixture group had significantly (p < .05) less 

error during the 1-h and 2-h postingestion session in comparison with 

predrug performance. For both static and dynamic tracking, the 

dimenhydrinate and promethazine groups showed no significant change across 

sessions. 

In Study II, no significant change across sessions occurred for any 

group in static tracking (see Figure 2). Dynamic tracking scores showed 

significant effects only for the dimenhydrinate group, viz, the 2-h 

postingestion session had significantly more error than-either of the two 

preceding sessions (p < .05 in both cases). Higher error scores for the 

promethazine group during the last two sessions approached but did not reach 

significance due primarily to increased variance. 

3 
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Pre Post I 2 4 Pre Post I 2 4 

TEST SESSIONS 

FIGURE 1. Changes in tracking performance in Study I under static 

(stationary) and dynamic (angular acceleration) conditions. 

Drug dosages were SO mg dimenhydrinate, 2S mg promethazine 

hydrochloride, and a mixture of 2S mg promethazine hydrochloride 

plus 10 mg dextroamphetamine. 

Between Groups Comparisons. Analyses of variance yielded no overall 

differences for static tracking in Study I but simple effects tests showed 

significantly (p < .OS) less error for the placebo vs. the promethazine 

group 2-h postdrug, while the placebo vs. dimenhydrinate difference for the 

same session fell just short of significance. The analyses for dynamic 

tracking yielded several significant effects. Scores for the mixture group 

were (i) better (p < .01) than those for dimenhydrinate subjects during the 

1-h postingestion session, (ii) better (p < .001) than both the 

dimenhydrinate and promethazine groups during the 2-h session, and 

(iii)-better (p < .OS) than promethazine scores during the final session. 

In addition, placebo scores were better (p < .001) than both dimenhydrinate 

and promethazine during the 2-h session and were better (p < .OS) than 

promethazine during the final session. 

In Study II, differences between groups in static tracking scores were 

relatively slight and no statistically reliable differences were found. 

Dynamic tracking scores for the placebo group were better (p < .OS) than 

those for the two drug groups during the 2-h postingestion session. 

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Post I 2 4 

TEST 

DYNAMIC TRACKING 

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SESSIONS 

FIGURE 2. Changes in tracking performance in Study II under static 

(stationary) and dynamic (angular acceleration) conditions. 

Drug dosages were 100 mg dimenhydrinate and SO mg promethazine 

hydrochloride. Plotting procedures were as in Figure 1. 

NYSTAGMUS WHILE TRACKING 

Within Groups Comparisons. In Study I, all postdrug sessions for both 

measures of nystagmus showed less output for the placebo and mixture groups, 

and (with one minor exception) increased output for the dimenhydrinate and 

promethazine groups when compared to predrug levels (see Figure 3). 

However, analysis of variance for repeated measures yielded significant 

sessions effects for measures of both slow-phase (p < .001) and frequency of 

eye movements (p < .01) only for the mixture group. Simple effects tests 

indicated significantly less slow-phase output for mixture subjects during 

all three postdrug sessions (p < .OS - .001) in comparison with the predrug 

session, and a lower frequency of nystagmus (p < .01) during the 2-h 

postdrug trial. 

In Study II, analyses of variance within each group yielded significant 

sessions effects (p < .01 - .001) for both measures of nystagmus for the 

s 

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HOURS AFTER INGESTION 

FIGURE 3. Slow-phase displacement and the frequency of nystagmus obtained 

in Study I while subjects were tracking in the dynamic condition. 

Drug dosages were 50 mg dimenhydrinate, 25 mg promethazine 

hydrochloride, and a mixture of 25 mg promethazine hydrochloride 

plus 10 mg dextroamphetamine. Measures for the pretrial (before 

ingestion of the drug or placebo capsule) were set at 0. 

Measures for the postingestion sessions were converted to 

percentages of increase or decrease from the preingestion 

baseline. 

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Pre 2 4 

HOURS AFTER INGESTION 

FIGURE 4. Slow-phase displacement and the frequency of nystagmus obtained 

in Study II while subjects were tracking in the dynamic 

condition. Drug dosages were 100 mg dimenhydrinate and SO mg 

promethazine hydrochloride. Plotting procedures were as in 

Figure 3. 

7 
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PRE 2 4 PR E 2 4 

HOURS AFTER INGESTION 

FIGURE 5. Tracking error, slow-phase nystagmus displacement, and fast-phase frequency of 

nystagmus, across the 48-s stimulus periods in each session of Study I. Scores 

for each measure for the first 48-s stimulus of the first session (preingestion) 

were set at 0; all subsequent scores across stimulus periods and sessions for 

each measure were plotted as percentages of increase or decrease from that 0 I 

baseline. 

8 
_FIGURE 6. Tracking error, slow-phase nystagmus displacement, and fast-phase frequency of 

nystagmus across the three 48-s stimulus periods in each session of Study II. 

Plotting procedures were as in Figure 5. 

9 
placebo and the promethazine groups (see Figure 4). The direction of the 

effects were opposite, however, in that the placebo group showed a steady 

decline across postdrug sessions while the promethazine group had higher 

scores for all but one of the postdrug sessions. Dimenhydrinate resulted in 

no significant effects, although increased nystagmus characterized the 1-h 

and 2-h postdrug sessions for both measures. For slow-phase measures, 

simple effects tests showed that the outputs for both the 2-h and the 4-h 

postdrug sessions for placebo were less than the predrug session (p < .01), 

and the 4-h postdrug session for promethazine had higher scores than both 

the predrug and first postdrug session (p < .OS). For the frequency of eye 

movements, (i) both the 2-h and 4-h postdrug sessions had less output than 

the predrug session (p < .001) for placebo, (ii) the 4-h session output was 

greater than the predrug (p < .01) and the 1-h (p < .001) sessions for 

promethazine, and (iii) the 2-h postdrug output was greater (p < .OS) than 

the 4-h postdrug output for dimenhydrinate. 

Between Groups Comparisons. Overall analyses of variance for the two 

eye movement measures yielded three significant F-r atios in Study I; one 

for slow-phase scores (p < .001 between groups) and two for the ocular 

frequency (p < .01 between groups and p < .OS for the groups x sessions 

interactions). HSD tests for slow-phase scores yielded significantly less 

nystagmus for the mixture group than for the dimenhydrinate and the 

promethazine conditions during all three postdrug sessions (p < .OS - .001). 

HSD tests for the frequency of eye movements yielded effects only for the 

1-h and 2-h postdrug sessions, viz, less eye movement for the mixture group 

than for dimenhydrinate (p < .osr-in the former session, and again less 

nystagmus for the mixture condition than for each of the other three 

conditions (p < .OS - .001) during the second postdrug hour. 

Overall analyses of variance in Study II yielded significant F-ratios 

for groups and for the groups x sessions interactions for both the 

slow-phase (p < .01 in both cases) and frequency (p < .001 in both cases) 

measures. HSD tests showed, for both measures of nystagmus, more eye 

movement for promethazine (p < .01 in all cases) than for the placebo 

condition during both the 2-h and 4-h postdrug sessions. The 4-h postdrug 

sessions also yielded significantly more eye movement for promethazine than 

for dimenhyrinate (p < .OS for slow-phase; p < .01 for frequency). In 

addition, the frequency of eye movements was greater for dimenhydrinate than 

for the placebo (p < .01) during the second postdrug session. 

Effects of Longer Durations of Angular Stimulation. Tracking error and 

nystagmus measures were also tabulated for each of the three scored 48-s 

periods of angular acceleration following warmup. "Change" scores were 

computed on a percentage basis using the mean score for the first period of 

the first session as 100 percent; each subsequent 48-s period for a given 

condition was plotted in terms of "Percent Change" from the base (Figures S 

and 6). 

10 
In both studies, postingestion tracking scores tended to increase 

across each block of three 48-s periods regardless of drug or placebo, with 

the two depressant drugs, dimenhydrinate and promethazine, showing the 

largest average increases in tracking error. Nystagmus measures yielded 

similar but less consistent results. There was invariably less nystagmus 

(both slow and fast phases) during the third 48-s period of each session for 

the placebo and mixture groups in Study I, but the third period uniformly 

had more nystagmus than the first period for the placebo group in Study II. 

Promethazine tended to produce increased nystagmus during third-period 

stimulation, with the effects more pronounced in Study II (Figure 6). 

Results for dimenhydrinate were less consistent; both Study II measures for 

the third period showed more nystagmus than the first period but the 

opposite effect was evident for the frequency measures in Study I. 

Statistical analyses yielded significant period effects during tracking 

(increased error) for both doses of promethazine (p < .05) and for the 

double dose of dimenhydrinate (p < .05). In Study I, the placebo and 

mixture groups showed significant period effects (p < .05 - .01) for both 

measures of nystagmus (less output) and dimenhydrinate yielded a significant 

(p < .05) fast phase effect (less output). There were significant period 

effects for all three groups in Study II for both measures of nystagmus 

(p -( , .05 - .01). 

MOOD SCORES 

Within Groups Comparisons. The three mood factors in Study I showed no 

significant differences across sessions for placebo or dimenhydrinate 

subjects (see Table I). For the promethazine group, scores for the last 

session were higher (p < .01) than the predrug session for both the fatigue 

and sleepy mood factors. For the mixture group, (i) the high sleepy score 

on the final session differed (p < .05) from the low score for the 2-h 

session, and (ii) the fatigue factor was higher for the final session than 

for each of the preceding sessions (p < .05 - p < .01). 

In Study II, analyses for each of the three mood factors yielded no 

sessional differences for the placebo group. Two hours after taking the 

drug, dimenhydrinate subjects had higher (p < .05) sleepy scores than they 

did during the 1-h postdrug session and reported more fatigue (p < .05) and 

less vigor (p < .01) than during the predrug session; their vigor scores 

remained significantly depressed (p < .01) during the final session. 

Promethazine subjects also showed mood changes but they were shifted toward 

the final session. Specifically, for promethazine subjects (i) fatigue 

scores were significantly higher than the predrug level, 2-h (p < .05) and 

4-h (p < .001) postingestion; scores for the 4-h session were also higher 

(p < .01) than the first postdrug session; (ii) vigor scores were lower 

(p < .05) during the final session than they were prior to drug-taking; 

(iii) sleepy scores peaked during the final session and were higher than 

both the predrug (p < .001) and the first postdrug (p < .01) sessions. 

11 
Tahle I. Means (M) and Standard Deviations (SD) for Self-Reported Fatigue, Vigor, and Sleepy Score

STUDY I 

Single Dose 

Factor Session Measure Placebo Dimenh::z:drinate Mixture Promethazine Placebo 

Fatigue Pre M 35.7 30.8 28.0 28.5 28.3 

SD 10.4 17.4 9.2 9.0 8.6 

Post 1-h M 31.7 35.9 28.0 34.7 31.4 

SD 9.9 14.5 9.4 12.6 9.3 

Post 2-h M 38.8 41.2 25.6 36.7 33.1 

SD 9.9 13.3 10.2 8.5 9.4 

Post 4-h M 36.2 34.0 38.8 42.2 35 .6 

SD 12.4 12.6 14.5 9.5 9.2 

1-' Vigor Pre M 12 . 0 14 . 2 15 . 3 15.4 13 . 4 

N SD 4.9 6. 3 4.1 6.9 5.7 

Post 1-h M 12.3 12.4 16.2 15.4 13.7 

SD 6.1 6.1 5.9 7.8 5.2 

Post 2-h M 11.5 11.0 17 . 3 14.0 13.9 

SD 6 . 5 5.3 5.3 5.6 4.6 

Post 4-h M 14 . 1 14 . 1 13.2 13.4 14.4 

SD 5.5 4.8 6.4 6.8 5.3 

Sleepy Pre M 16 . 9 14.1 13.1 12.2 11.5 

SD 5.0 8.4 5. 8 6.3 7.2 

Post 1-h M 13.7 16.0 13.1 16.0 13 . 8 

SD 5.0 7.6 5.2 9.0 6 . 1 

Post 2-h M 17.7 19.2 11.2 15.6 15.9 

SD 5.9 8.8 5.3 6.5 5.2 

Post 4·-h M 16.1 15.3 18 . 9 22.0 15.6 

SD 6.2 8.0 8 . 8 4.7 6 . 4 
Between Groups Comparisons. Statistical comparisons of Study I scores 

between groups for each mood factor led to no significant differences for 

the fatigue ratings. The mean sleepy score during the final sessions for 

the promethazine group was the highest obta~ned for that factor and differed 

significantly (p < .OS) from that of the placebo group. Only one other 

difference was significant between groups, viz, the higher vigor score for 

the mixture group vs. the reduced score for the dimenhydrinate groups 

(p.( •• OS) during the 2-h postingestion session. 

In Study II, comparisons of difference scores showed the dimenhydrinate 

group to be significantly lower in vigor than the placebo group (p ( .OS) 

during each of the last two sessions; the mean vigor score for the final 

session was also lower (p < .OS) than that of placebo. Scores for the 

fatigue and sleepy factors yielded an identical pattern of significant 

effects; for both mood factors, promethazine scores were significantly 

higher (p ( .OS in all cases) than both placebo and dimenhydrinate during 

the final session. 

Discussion. 

Tracking and Nystagmus. The patterns of results obtained in this study 

both for tracking and for nystagmus during dynamic tracking are highly 

similar to those obtained in previous reports dealing with effects of 

alcohol (1,4,9), and of secobarbital and d-amphetamine (2,10), on the same 

measures. Specifically, subjects given placebos show, over several test 

sessions, (i) some decrease or no change in static tracking error, (ii) some 

improvement in dynamic tracking scores, and (iii) some reduction in the 

amount of nystagmus during dynamic tracking. 

On the other hand, with due consideration given for the action times of 

the various drugs, subjects given substances that are primarily depressants 

(alcohol, secobarbital, dramamine, and phenergan) show (i) no improvement in 

static tracking performance or less improvement than placebo subjects, 

(ii).impairment of dynamic tracking, and (iii) increases in the amount of 

nystagmus (less control of eye movements) during dynamic tracking. 

Conversely, d-amphetamine (either alone (10) or as it was administered in 

the present study with promethazine) produced opposite effects in subjects, 

viz, (i) improved static tracking scores, (ii) improved dynamic tracking 

performance, and (iii) marked reductions in nystagmus (better ocular 

control) during dynamic tracking. 

The improvement across sessions in tracking scores and in (reduced) 

nystagmus for control subjects appears to reflect positive effects of 

practice. The introduction of d-amphetamine (alone or in the combination 

used in this study) appears not to interfere with this learning process. 

However, each of the depressant drugs tested so far has produced an opposite 

pattern of results, viz, during the period of peak effectiveness of the 

drugs (and depending upon the dosage), clear impairment both of dynamic 

tracking performance and of visual fixation ability has occurred. 

13 
Performance during static tracking may be misleading regarding the 

deleterious influence of those drugs since improvement has occurred 

following alcohol ingestion (4) and since control subjects sometimes do not 

show improvement (as in Study II of this report). Parenthetically, in 

addition to data on motion sickness prevention, Wood and Graybiel (14) 

reported the absence of any significant changes in (static) visual acuity, 

balance, reaction time, and decision-making behavior following 

administration of either dimenhydrinate or promethazine. But the negative 

performance effects of the depressants have been consistent in the motion 

environment and suggest strongly that, for many practical situations, 

knowledge regarding the influence of drugs on various types of performance 

requires an assessment of motion effects. 

The deleterious effects on dynamic tracking performance, which have 

been consistently obtained with depressant drugs, have been accompanied by a 

loss of ability to maintain adequate visual fixation during vestibular 

stimulation. The impairment of visual acuity arising from the inability to 

suppress vestibular nystagmus by visual means seems to be a primary proximal 

cause of the increased tracking errors (3,6,10). 

The addition of d-amphetamine to promethazine obviated the undesirable 

ocular and performance consequences of the depressant. This positive effect 

is of particular significance since the combination of these substances is 

so highly effective as a motion sickness preventive. In fact, the addition 

of d-amphetamine (or ephedrin) to depressants such as promethazine 

hydrochloride or scopolamine, two drugs which are themselves reasonably 

effective in preventing motion sickness, tends to improve their 

effectiveness in this regard (5,12,13). Thus, these combined drug 

treatments have the advantages of greater protection against motion sickness 

and (at least with the d-amphetamine plus promethazine mixture, and probably 

with the other analeptic/depressant combinations noted above) abolition of 

ordinary undesirable side effects such as drowsiness, plus protection 

against some practical but less well-known consequences associated with 

performance and visual fixation during motion. 

Effects of Longer Durations of Angular Stimulation. Over the three 

consecutive 48-s periods of angular stimulation, it is clear that tracking 

error tended to increase with time on task (even though overall performance 

might have generally improved from session to session, as with the placebo 

and mixture groups). The between-period increases in error occurred 

irrespective of drug or placebo conditio?s, but were more pronounced for 

dimenhydrinate and promethazine. It is difficult to assess the effects on 

nystagmus of prolonging the angular stimulation since the pattern of 

significant findings was not necessarily in the same direction (even for the 

placebo conditions) across the two studies. Thus, while it may be 

reasonable to conclude that tracking error increases with time-on-task 

(within the limits of this study) and probably increases more under a 

depressant drug, effects on nystagmus are less clear. 

14 
Mood Ratings. The presence or absence of the various drugs and dosages 

was reflected to some degree by the mood scores. Effects were particularly 

evident in Study II where decreased vigor and increased fatigue and 

sleepiness were associated with the times of action for dimenhydrinate and 

promethazine. At the lower dosages (Study I) the fatigue and sleepy scores 

showed significant effects associated with the final session and, 

interestingly, they involved more fatigue and sleepiness for the . 

promethazine and the mixture groups. The latter group may have been 

demonstrating a wearing-off of the d-amphetamine while the promethazine was 

still active, a rebound depressive effect of the d-amphetamine, or both. 

While the mood scores showed some drug effects consistent with known 

symptoms, (i) they did not appear to relate meaningfully to static tracking 

scores in either Study I or Study II, and (ii) they generally showed 

inconsistent relationships in both studies (particularly for the final 

session) with respect to dynamic tracking scores· and measures of nystagmus; 

an exception was the nystagmus measures for promethazine in Study II. The 

latter result suggests that the mood-altering effects of the drugs may have 

properties and a time course that differ somewhat from the effects on 

tracking skill and the ability to use the visual fixation mechanism to 

inhibit vestibular nystagmus or, that at these dosage levels, the direction 

of attention to a task can override some of the depressant subjective 

characteristics of those drugs. 

15 
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1971. Effects of alcohol ingestion 

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2. Collins, w. E., D. J. Schroeder, and G. w. Elam, 1975. Effects of 

d-amphetamine and of secobarbital on optokinetic and rotation-induced 

nystagmus. Aviat. Space Environ. Med. 46: 357-364. 

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drugs: A new effective remedy revealed. 

16 

Evaluation of antimotion sickness 

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17 

>}U.S. Government Printing Office 1982 - 394-726/343