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THE JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
Copyright © 1997 by The American Society for Pharmacology and Experimental Therapeutics
JPET 283:274 –280, 1997
Vol. 283, No. 1
Printed in U.S.A.
Inhibition of Prostaglandin Synthesis and Effects of Ethanol
and Pentobarbital in Humans
WALLACE B. PICKWORTH, REGINALD V. FANT and JACK E. HENNINGFIELD
National Institute on Drug Abuse, Intramural Research Program, Addiction Research Center, Baltimore, Maryland (W.B.P., R.V.F.), The Johns
Hopkins University School of Medicine, Baltimore, Maryland (J.E.H.), and Pinney Associates, Bethesda, Maryland (J.E.H.)
Accepted for publication June 23, 1997
Alcohol consumption is widespread and results in significant mortality. In the United States, ethanol ingestion is
implicated in traffic accidents and hospital admissions and is
the primary cause of death for 100,000 citizens each year
(McGinnis and Foege, 1993). The profound public health
implications of ethanol consumption have spurred a variety
of pharmacological approaches to diminish the effects of
acute ethanol administration or to reduce the appeal of ethanol to the dependent patient. For example, the opiate antagonist naltrexone decreased craving for ethanol, ethanolinduced euphoria and ethanol consumption in dependent
subjects (for a review, see O’Brien et al., 1996). Selective
serotonin reuptake inhibitors, such as fluoxetine, appear to
attenuate ethanol craving and self-administration in depressed and nondepressed heavy drinkers (Gorelick and
Paredes, 1992; Naranjo et al., 1994) Ondansetron, a 5-hydroxytryptamine3 receptor antagonist, exaggerated the subjective effects of intoxication but did not influence the effects
of ethanol on measures of performance (Swift et al., 1996).
Some animal studies suggest that certain calcium channel
blockers suppress ethanol intake (De Beun et al., 1996).
Received for publication March 4, 1997.
taining indomethacin or placebo. One hour later, they swallowed capsules that contained pentobarbital or placebo and a
large drink (500 ml) of tonic water that contained ethanol or
placebo (tonic water with 2 ml of ethanol floated on top). Both
ethanol and pentobarbital affected subjective ratings, performance measures and heart rate. However, indomethacin pretreatment had no influence on drug-induced changes to ethanol and pentobarbital. The results of this study illustrate the
relationship between depressant drugs and human performance, but they do not support the hypothesis that inhibition of
prostaglandin synthesis diminishes the effects of ethanol and
pentobarbital in humans.
PGSIs have been shown to antagonize some of the effects of
ethanol in animal studies. For example, indomethacin reduced excitatory (George and Collins, 1979; Ritz et al., 1981)
and depressant (George et al., 1982) effects of ethanol in
rodents. Gender and the genetic sensitivity of the animal
strain to ethanol influenced the interaction between indomethacin and ethanol (George et al., 1983, 1986). Indomethacin also reduced responding for ethanol in a self-administration paradigm (George, 1989). Pretreatment with PGSIs
(e.g., aspirin, indomethacin) inhibited the rate-depressant
effects of ethanol in operant responding (George and Meisch,
1990). The BAL indicated that the effects were due to diminished sensitivity to ethanol and not the result of pharmacokinetic differences in ethanol metabolism. In a test of central
nervous system depressant activity, there was a high correlation between the PGSI potency and inhibition of the ethanol response (Elmer and George, 1991). Prostaglandins mediated the rate depressant and narcosis induced by ethanol
(Elmer and George, 1996). Prostaglandin E1 and prostanoid
precursor fatty acids modulated ethanol withdrawal behavior in mice, an effect that was inhibited by PGSI administration (Segarnick et al., 1985). Aspirin pretreatment reduced
ethanol withdrawal severity in a mouse model of binge drink-
ABBREVIATIONS: PGSI, prostaglandin synthesis inhibitor; PAB, (Walter Reed) Performance Assessment Battery; DSST, digit symbol substitution;
ARCI, Addiction Research Center Inventory; BAL, blood alcohol level; ANOVA, analysis of variance; hsd, honestly significant difference; MBG,
morphine-benzedrine group (ARCI subscale); PCAG, pentobarbital-chlorpromazine-alcohol group (ARCI subscale); LSD, lysergic acid diethylamide (ARCI subscale); A, alcohol (ARCI subscale).
274
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ABSTRACT
Results from animal research suggest that pretreatment with
prostaglandin synthesis inhibitors (PGSIs) may inhibit physiological and behavioral effects of moderate ethanol ingestion.
We examined the effects of ethanol and pentobarbital in humans with and without pretreatment with indomethacin, a potent PGSI. Ten male subjects with histories of recreational use
of ethanol and sedative/hypnotics participated in this inpatient
study. The effects of indomethacin alone (0.66 mg/kg), indomethacin (0, 0.17, 0.33, 0.66 and 1.33 mg/kg) in combination
with ethanol (0 and 1 g/kg) and indomethacin (0 and 0.66
mg/kg) in combination with pentobarbital (0, 1.33 and 4 mg/kg)
were tested. On test days, subjects swallowed capsules con-
1997
Indomethacin, Ethanol and Pentobarbital
Methods
Subjects
Ten male subjects with histories of recreational use of ethanol and
sedative/hypnotics within the past 2 years volunteered for this inpatient study. The subjects’ average age was 33.7 years (range, 26 – 42
years) and weighed an average of 74.6 kg (range, 60 –110 kg). None
of the subjects were addicted to a drug other than nicotine, and they
had never been diagnosed as an alcoholic or treated for alcoholism.
Nine subjects reported current cigarette smoking (mean number
cigarettes per day, 21.9). All of the subjects reported lifetime use of
alcohol and either barbiturates or other tranquilizers. Mean current
alcohol use was reported as being ;12 standard drinks per week.
Subjects with histories of active hepatitis, pancreatic disease, cardiovascular disease, seizures, Parkinson’s disease, ulcers, or allergies to the study drugs were not eligible to participate. Each subject
signed a consent form that had been approved by the local institutional review board and met U.S. Department of Health and Human
Services guidelines for the protection of human research subjects.
For the duration of the experiment, subjects resided on a clinical
research unit. They ate a usual hospital diet, but they were not
allowed to consume caffeine-containing foods. On the morning of the
study days, they were asked to eat a light “cereal and toast” breakfast. Subjects who completed the protocol were paid an average of
$600.
Study Design and Drug Administration
During their first 5 days on the research unit, subjects were
familiarized with the cognitive and psychomotor tasks of the study.
Training sessions were repeated several times to permit acquisition
and stabilization on performance tests.
This was a double-blind crossover study. Each subject was tested
on 11 occasions; study days were separated by $48 hr. The treat-
ment conditions are summarized in table 1. On test days, subjects
swallowed capsules containing indomethacin (0.17, 0.33, 0.66 or 1.33
mg/kg) or placebo with a large glass of water (480 ml). One hour
later, they swallowed capsules that contained pentobarbital (1.33 or
4 mg/kg) or placebo and a large drink (500 ml) of tonic water that
contained ethanol (1 g/kg) or placebo (tonic water with 2 ml of
ethanol floated on top) that was consumed in 15 min. The order of
presentation of the drug conditions was randomized across subjects
with the restriction that the low dose of pentobarbital always preceded the higher dose.
The dose of ethanol (1 g/kg) and doses of pentobarbital (1.33 and 4
mg/kg) were selected because they reliably produced impairment on
performance tests used in previous studies (Pickworth et al., 1997;
Pickworth et al., in press). Dose-response relationships on the interaction of PGSIs and ethanol in animal studies indicate that many
PGSIs, including indomethacin, have an inverted U shape (Elmer
and George, 1991). This indicates that only a limited range of doses
are effective. For that reason, the dose of indomethacin in the
present study was extended from 0.17 to 1.33 mg/kg. The usual
therapeutic range of single doses of indomethacin is 0.35 to 0.7
mg/kg.
Dependent Measures
Physiological, subjective and performance measures were collected before the first capsules (9:00 A.M.); 1 hr after the capsules, but
before the drink and the second capsules (10:30 A.M.), and 30, 60, 90
120 and 240 min after the drink and the second capsules.
Physiological measures. At each measurement time, BAL, diastolic and systolic blood pressures, heart rate, respiratory rate and
oral and skin temperatures were recorded.
Subjective measures. At each of the time points, subjective
effects of the drugs were assessed by means of computer-delivered
questions from a shortened form of the ARCI (Haertzen, 1966; Jasinski, 1977). The questions formed the following subscales: MBG,
which measures euphoria; PCAG, which measures apathetic sedation; and LSD, which measures drug-induced dysphoria. Six computer-delivered visual-analog scales rated subjective responses to “like
drug,” “good effects,” “bad effects,” “drug strength,” “tired” and
“drunk”. The 100-mm scale used the phrases “not at all” and “extremely” to define the scale’s extremes. Subjects placed a cursor
along the line to rate their level of endorsement using computer
keystrokes.
Performance measures. Subjects completed several tests of cognitive and psychomotor performance. Two tests (serial arithmetic
and six-letter search) from the PAB (Snyder et al., 1989; Thorne et
al., 1985) were used. In the serial arithmetic task, two digits appeared sequentially on the computer screen for 250 msec, with each
followed by a plus or minus sign. The subject mentally performed the
indicated operation. If the answer was a two-digit number (e.g., 15),
TABLE 1
Experimental drug conditions
Condition
Indomethacin
Drink
mg/kg
1
2
3
4
5
6
7
8
9
10
11
P
P
0.17
0.33
0.66
1.33
0.66
P
0.66
P
0.66
Pentobarbital
mg/kg
P
E
E
E
E
E
P
P
P
P
P
P
P
P
P
P
P
P
1.33
1.33
4.0
4.0
The indomethacin dose was administered 1 hr before administration of the
drink or pentobarbital dose. P, placebo (lactose capsules or tonic water for drink);
E, ethanol (1 g/kg).
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ing (Hale et al., 1992). Overall, these animal studies suggest
that some of the effects of ethanol in the brain are due to an
increase in prostaglandin synthesis or release and that PGSIs diminish these effects.
However, interactions between PGSIs and ethanol in human experiments have yielded mixed results. Aspirin (Strakosch et al., 1980) and indomethacin (Barnett et al., 1980)
prevented the alcohol-induced flush in some patients taking
chlorpropamide. Minocha et al. (1986) reported that combinations of indomethacin and ethanol impaired visual memory more than either drug alone, but indomethacin prevented
ethanol-induced impairment in auditory/verbal memory. In a
systematic study of the interactions between ethanol and
acetaminophen, Pickworth et al. (1991) reported that over a
wide dose range, this PGSI did not inhibit physiological and
subjective effects of moderate ethanol ingestion. That research was extended in the present study in which an intoxicating ethanol dose and a more potent PGSI, indomethacin,
were tested in a larger group of volunteer subjects. In addition, doses of pentobarbital were added to the research design because ethanol and pentobarbital have similar pharmacological profiles in that their effects may be mediated
through modulation of g-aminobutyric acid activity at the
chloride channel (for a review, see Tabakoff and Hoffman,
1996). Furthermore, there is cross-tolerance between barbiturates and ethanol, and the abstinence syndrome from ethanol can be diminished by administration of barbiturates
(Jaffe, 1970). However, the role of prostaglandins in ethanol
and pentobarbital tolerance and withdrawal has not been
defined.
275
276
Pickworth et al.
Data Analysis
Because the purpose of the present study was to examine the
effects of indomethacin on either ethanol or pentobarbital, the data
from the two drugs were examined separately. Table 1 summarizes
the drug conditions used in each of the two ANOVAs. On the measure of “drug liking,” data provided by one subject were eliminated
from the analysis due to the subject’s misunderstanding of the question.
To examine the interactions between indomethacin and ethanol,
data from all dependent measures, except card sorting, were subjected to two-way repeated measures ANOVA (Winer et al., 1991).
The two factors of each ANOVA were drug condition (seven levels:
conditions 1–7 from table 1) and time (seven levels: each of the seven
time points described in Dependent Measures). Where there were
significant drug condition 3 time interactions (P , .05), post hoc
comparisons were made using Tukey’s hsd test. To assess the sensitivity of each measure to ethanol, comparisons were made between
the placebo-placebo condition (condition 1) and the placebo-ethanol
condition (condition 2). For measures that were shown to be sensitive
to ethanol’s effects, comparisons were made between the condition in
which pretreatment contained placebo (condition 2) and the four
conditions in which active doses of indomethacin were followed by
ethanol (conditions 3– 6).
To examine the interactions between indomethacin and pentobarbital, data from all dependent measures, except card sorting, were
subjected to two-way repeated measures ANOVA. The two factors of
each ANOVA were drug condition (six levels: conditions 1 and 7–11
from table 1) and time (seven levels). Where there were significant
drug condition 3 time interactions (P , .05), post hoc comparisons
were made using Tukey’s hsd test. To assess the sensitivity of each
measure to pentobarbital, comparisons were made between the placebo-placebo condition (condition 1) and the two conditions in which
placebo was followed by active pentobarbital (1.33 or 4 mg/kg; conditions 8 and 10 from table 1, respectively). For measures that were
shown to be sensitive to pentobarbital’s effects, comparisons were
made between effects of each pentobarbital dose with and without
indomethacin pretreatment (i.e., comparisons were made between
conditions 8 vs. 9 and 10 vs. 11).
Data from the card-sorting tasks were analyzed using two threeway repeated measures ANOVAs. The three factors of the ANOVAs
were condition (six or seven levels for pentobarbital and ethanol,
respectively), time (seven levels) and task difficulty (four levels: two-,
four- and eight-pile sort and motor control). Post hoc comparisons
were made using Tukey’s hsd test as described above.
For all measures, to assess the effects of indomethacin (0.66 mg/
kg) alone across the entire session, comparisons were made between
the placebo-placebo condition (condition 1) and the indomethacinplacebo condition (condition 7) at each time point. Also, to assess
differences between indomethacin doses alone, comparisons were
made on the data collected from a single time point (1 hr after the
first capsule) between placebo (condition 2) and all active indomethacin doses (0.17, 0.33, 0.66 and 1.33 mg/kg; conditions 3– 6, respectively).
Results
Table 2 shows the results of the two-way repeated measures ANOVAs for both ethanol and pentobarbital. The table
illustrates the drug condition 3 time interaction F values,
their significance level and whether the measure was sensitive to either ethanol or pentobarbital as described in Data
Analysis. Post hoc analyses on measures in which there was
a significant drug condition 3 time interaction on the
ANOVA for either ethanol or pentobarbital showed that indomethacin alone had no effect on any subjective, physiological or performance measures [i.e., there were no significant
differences between the placebo-placebo condition (condition
1) and the indomethacin-placebo condition (condition 7) at
any time point during the session]. Furthermore, subjective,
physiological or performance measures were not significantly
altered 1 hr after administration of any dose of indomethacin
(conditions 3– 6) compared with placebo (condition 2).
Ethanol. Drug condition time interaction effects were
noted on a variety of subjective (fig. 1), physiological (fig. 2)
and performance (figs. 3 and 4) measures. Significant drug
condition 3 time interactions were shown on visual-analog
scale measures of “drug strength,” “drunk,” “liking,” “good
effects,” “bad effects” and “tired.” On each of these visualanalog scale measures, significant differences were found
between the placebo-placebo combination (condition 1) and
the placebo-ethanol combination (condition 2), demonstrating that these measures were sensitive to ethanol’s effects.
On each measure, significant score elevations in condition 2
over condition 1 levels were shown as soon as the 30-min
postdrinking time point and lasted throughout the session,
with the exceptions of “bad effects,” which became elevated at
the 90-min time point, and “tired,” which was only significantly increased at the 240-min time point. Significant drug
condition 3 time interactions were also shown on the PCAG
scales of the ARCI. Scores on the PCAG scale were significantly elevated after ethanol (condition 2) over scores after
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the correct response was the unit digit (e.g., 5). If the answer was a
negative number (e.g., 22), 10 was added to the answer, and the
resulting single positive digit was entered (e.g., 8). In the six-letter
search task, subjects answered with a single keystroke (“Y” or “N”) if
each of the six letters displayed at the top of the computer screen
were contained in the random string of 24 letters concomitantly
displayed below.
In the computer-delivered DSST, a digit appeared on the computer
screen, and the subject reproduced the geometric pattern associated
with the digit using three keystrokes on the numeric keypad (Heishman et al., 1988). The dependent measures in the DSST and PAB
tasks were the number of correct responses, percent correct and
response time. An incentive of $0.01 for each correct response was
given on these tasks.
In the circular lights task (Heishman et al., 1990), subjects rapidly
pushed lighted buttons on a wall-mounted panel that consisted of 33
button lights. As the one illuminated button was pushed, another
lighted. The dependent measure was the number of illuminated
buttons pushed during the 1-min task. Subjects were given $0.01 for
each correct button press as an incentive.
In the 1-min rotary pursuit task, subjects attempted to keep a
wand with a photoelectric cell directly above a rotating (30 rpm)
lighted target. The dependent measures were the time on target and
the number of times the tracking was lost. An incentive of $0.01 was
paid for each second on target.
In a hand-steadiness test, subjects inserted a stylus (diameter, 1
mm) into a series of eight holes with diameters ranging from 15 to 2
mm and held the stylus without touching the side for 15 sec per hole.
The dependent measures were the number of seconds without touching a side and the total number of times the subject touched a side.
For each second without a side touch, the subjects were awarded
$0.01.
Subjects completed a series of four card-sorting tasks of increasing
difficulty (Berry et al., 1965) that are sensitive to the effects of
ethanol and pentobarbital [Pickworth et al., 1997]. A well-shuffled
deck of 32 playing cards was sorted into two (color), four (suit) and
eight piles (suit and type, face or number). As a motor control, cards
were placed one at a time into two piles without regard to color or
suit. The dependent measures for the card tasks were time to sort,
number of mistakes and dropped cards.
Vol. 283
1997
Indomethacin, Ethanol and Pentobarbital
277
TABLE 2
Results of two ANOVAs showing drug condition 3 time
interactions and direction of pentobarbital and ethanol effects
Measure
6.3c
6.2c
3.7c
7.6c
1.9b
1.5a
N.S.
1.8b
1.9b
N.S.
N.S.
4.6c
N.S.
N.S.
1.9b
40.0c
Pentobarbital
F(30, 270)
1
1
1
1
1
1
8.1c
2.4c
5.7c
7.3c
N.S.
2.4c
1
1
1
1
1
1
2.1c
1.6a
3.8c
1
1
1
N.S.
N.S.
2.1c
N.S.
N.S.
N.S.
N.S.
4.8c
2
5.3c
2
1.6a
4.7c
2
N.S.
8.5c
2
1.6a
2.0b
1.6a
2.3c
2
2
2
1
1
N.S.
N.S.
N.S.
N.S.
2
2.0c
1.9b
N.S.
2.1c
2
2
1.8b
2.3c
2.2c
1.9b
2
2
2
1
1.9b
1.9b
N.S.
1.6a
2
2
5.1c
5.0c
2.1b
3.3c
2
2
2
1
1
Fig. 1. Mean subject ratings of drug liking and drug strength on
100-mm visual-analog scales before and after administration of test
drugs. ‚, E and M, Pretreatment (260 min) with placebo capsules. Œ,
F and f, Pretreatment with 0.66 mg/kg indomethacin. This pretreatment was followed by administration (0 min) of either placebo (‚, Œ), 1
g/kg ethanol (E, F) or 4 mg/kg pentobarbital (M, f).
Numbers indicate the interaction F value and significance level (a P , .05;
b
P , .01; c P , .001) from ANOVAs that measured the effects of ethanol
(conditions 1–7, table 1) and pentobarbital (conditions 1, and 7–11). Arrows
indicate the direction of a significant change from baseline due to ethanol (1 g/kg)
or pentobarbital, (4 mg/kg) (Tukey’s hsd).
placebo (condition 1). Post hoc analyses showed no differences between the placebo-ethanol combination (condition 2)
and the conditions in which the four active doses of indomethacin were combined with ethanol (conditions 3–6). Significant drug condition 3 time interactions were also shown
on the LSD scale of the ARCI. However, scores on the LSD
scale were not sensitive to the effects of ethanol (i.e., no
difference between conditions 1 and 2).
Significant drug condition 3 time interactions were shown
on physiological measures of heart rate, skin temperature
and BAL. Post hoc analyses showed that both heart rate and
BAL were significantly increased in the active drink condition (condition 2) above placebo drink levels (condition 1). In
the condition in which ethanol administration was preceded
by placebo, peak BALs were reached within 30 min after
drinking; mean BAL at this time was 115 mg%. No significant differences were found between the placebo-ethanol
combination (condition 2) and the four conditions in which
the four active doses of indomethacin were combined with
Fig. 2. Mean heart rate before and after administration of test drugs.
‚, E and M, Pretreatment (260 min) with placebo capsules. Œ, F and
f, Pretreatment with 0.66 mg/kg indomethacin. This pretreatment was
followed by administration (0 min) of either placebo (‚, Œ), 1 g/kg
ethanol (E, F) or 4 mg/kg pentobarbital (M, f).
ethanol (conditions 3–6) on either heart rate or BAL measures.
Significant drug condition 3 time interactions were shown
on performance measures, including circular lights, rotary
pursuit (number of times off target and amount of time spent
on target), serial math task and DSST. No significant effects
of ethanol were found on the hand-steadiness task. Post hoc
analyses showed that in general, performance was impaired
in the placebo-ethanol condition (condition 2) compared with
the placebo-placebo condition (condition 1). As on subjective
and physiological measures, no significant differences were
found between the placebo-ethanol combination (condition 2)
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Subjective
Visual-analog scales
Strength
Drunk
Drug liking
Good effects
Bad effects
Tired
ARCI
MBG
LSD
PCAG
Physiological
Systolic blood pressure
Diastolic blood pressure
Heart rate
Respiration rate
Oral temperature
Skin temperature
BAL
Performance
Circular lights
Rotary pursuit
Number times off
Time on target
Six-letter search
Attempts
Correct
% Correct
Response time
Serial math
Attempts
Correct
% Correct
Response time
DSST
Attempts
Correct
% Correct
Response time
Ethanol
F(36, 324)
278
Pickworth et al.
Vol. 283
Fig. 3. Mean performance scores before and after administration of
test drugs. ‚, E and M, Pretreatment (260 min) with placebo capsules.
Œ, F and f, Pretreatment with 0.66 mg/kg indomethacin. This pretreatment was followed by administration (0 min) of either placebo (‚, Œ), 1
g/kg ethanol (E, F) or 4 mg/kg pentobarbital (M, f).
and the four conditions in which an active dose of indomethacin preceded ethanol (conditions 3–6). On the card-sorting
task, the three-way ANOVA yielded a condition 3 time 3
task interaction that neared significance [F(108, 972) 5 1.23,
P 5 .063]. In general, times to sort cards were longer on the
more difficult tasks (i.e., sorting into eight piles) after active
ethanol dosing than after placebo dosing. Indomethacin pretreatment did not affect ethanol-induced card sorting performance impairment.
Pentobarbital. The effects of pentobarbital on subjective
measures were similar to those seen after ethanol (fig. 1).
Significant drug condition 3 time interactions were shown on
all visual-analog scale scores except “tired.” In each case, post
hoc analyses showed that scores were significantly higher in
the placebo-pentobarbital 4 mg/kg condition (condition 10)
than in the placebo-placebo condition (condition 1). The placebo-pentobarbital 1.33 mg/kg condition (condition 8) was not
significantly different from the placebo-placebo condition
(condition 1). Significant drug condition 3 time interactions
were shown on the MBG and PCAG scales of the ARCI. Post
hoc analyses showed that scores on the MBG and PCAG
scales were higher in the placebo-pentobarbital 4 mg/kg condition (condition 10) than in the placebo-placebo condition
(condition 1). Post hoc analyses showed no significant effects
of indomethacin on pentobarbital’s effects; there were no
differences between the placebo-pentobarbital 1.33 mg/kg
(condition 8) and indomethacin-pentobarbital 1.33 mg/kg
combinations (condition 9), nor were there any differences
between the placebo-pentobarbital 4 mg/kg (condition 10)
and indomethacin-pentobarbital 4 mg/kg combinations (condition 11). Significant drug condition 3 time interactions
were also shown on the LSD scale of the ARCI. However,
scores on the LSD scale were not sensitive to the effects of
pentobarbital (i.e., no difference between condition 1 and
condition 8 or 10).
Significant drug condition 3 time interactions were shown
on measures of heart rate (fig. 2). Both active doses of pentobarbital combined with placebo (conditions 8 and 10) decreased heart rate below placebo-placebo levels (condition 1).
The active dose of indomethacin combined with pentobarbital
4 mg (condition 11) tended to decrease heart rate (maximum
decrease, 6.2 bpm) more than the placebo-pentobarbital 4
mg/kg combination (condition 10) (maximum decrease, 2.6
bpm); however, these differences were not statistically significant.
Drug condition 3 time interactions were shown on all
performance tasks measured with the exception of the handsteadiness task (fig. 3). For each measure, performance was
slowed and accuracy was decreased in the placebo-pentobarbital 4 mg/kg condition (condition 10) below levels seen in the
placebo-placebo condition (condition 1). In general, however,
indomethacin had little or no effect on pentobarbital-induced
performance decrements. As illustrated in fig. 4, a significant
drug condition 3 time 3 task interaction effect was shown on
the card-sorting task [F(90, 810) 5 1.76, P , .001]. The 4
mg/kg dose of pentobarbital (condition 10) significantly increased sort times in the two-, four- and eight-pile sorts with
mean increases of up to 8.5, 17.4 and 20.2 sec in these three
tasks, respectively, over placebo times (condition 1). No significant effects of pentobarbital were seen on the motor control task. As on other performance tasks, indomethacin had
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Fig. 4. Mean time to sort cards into piles before and after administration of test drugs. ‚, E and M, Pretreatment(260 min) with placebo
capsules. Œ, F and f, Pretreatment with 0.66 mg/kg indomethacin.
This pretreatment was followed by administration (0 min) of either
placebo (‚, Œ), 1 g/kg ethanol (E, F) or 4 mg/kg pentobarbital (M, f).
Subjects sorted cards into two, four or eight piles according to color,
suit and denomination as described in Methods. Cards were sorted into
two piles without regard to color as a motor control.
1997
Indomethacin, Ethanol and Pentobarbital
no significant effect on pentobarbital-induced card-sorting
performance impairment.
Discussion
0.625 g/kg over 2 hr did not cause significant changes in
performance (Pickworth et al., 1991). Gengo et al. (1990)
reported that the threshold for effects of ethanol on performance depended on the task: ;40 mg% for a driving
simulator and ;60 mg% for the DSST. Others have reported that levels of ;50 mg% are near threshold for the
detection of performance impairment (de Wit et al., 1987).
A series of card-sorting tasks (Berry et al., 1965) was
among the performance measures of the present study. In a
previous study (Pickworth et al., 1997), pentobarbital and
ethanol impaired card-sorting speed. The advantage of this
series of tasks is that they impose increasing levels of
cognitive load, but the motor component of the performance stays relatively constant. In the present study,
neither pentobarbital nor ethanol diminished card-sorting
rate in the motor control task (no cognitive component) and
in the easy two-pile sort task. However, as the task difficulty increased in the four- and eight-pile sorting tasks,
both drugs significantly slowed the response. These data
illustrate an intuitive but seldom demonstrated point; as
task complexity increases, the effects of drugs become
more apparent. The high dose of pentobarbital in the
present study (4 mg/kg) did not cause significant impairment on the motor control task; however, in another study
(Pickworth et al., 1997), a higher dose (5.7 mg/kg) did
cause impairment in the motor control sorting task. Taken
together, these indicate that pentobarbital affected the
cognitive component of the task at doses lower than those
needed to influence the motor component.
In summary, the results of the present study and those of
a previous study (Pickworth et al., 1991) do not support the
hypothesis that prostaglandin-dependent processes mediate
the subjective or performance effects of ethanol or pentobarbital in humans. Although there are several reports that
PGSIs modify the effects of ethanol in rodents (for a review,
see George, 1989), pretreatment with indomethacin, a potent
PGSI over a wide dose range, failed to alter subjective, physiological or performance effects of ethanol and pentobarbital.
From a practical standpoint, the results of the present study
indicate that indomethacin (and other PGSIs) does not prevent subjective and performance effects of ethanol. This suggests that PGSIs are ineffective as treatments for acute alcohol or pentobarbital intoxication.
Although the present study did not yield significant interactions between indomethacin and ethanol and pentobarbital, there are limitations in the experimental design that
might influence the overall interpretation. The interaction
between indomethacin and ethanol was tested using a
single dose of ethanol; the interaction between pentobarbital and indomethacin was tested using a single dose of
indomethacin. It is possible that an extension of the dose
range may have yielded significant interactions. The battery of performance tests used in the present study may
not have captured the interaction between indomethacin
and ethanol and pentobarbital. For example, some studies
in animals that have demonstrated an interaction (George,
1989; George and Meisch, 1990) have used measures of
operant behavior and self- administration. Furthermore,
there was no direct measure of prostaglandin synthesis
inhibition or prostaglandin levels in the present study.
Downloaded from jpet.aspetjournals.org at ASPET Journals on August 11, 2017
A major objective of this study was to determine whether
inhibition of prostaglandin synthesis would alter the subjective, physiological and performance effects of ethanol and
pentobarbital. In a previous clinical study, acetaminophen
pretreatment did not reduce the subjective or cardiovascular
effects of ethanol (Pickworth et al., 1991). The design of the
present study offered several improvements. First, indomethacin, a more potent PGSI than acetaminophen, was
used over a wide range of doses. Ethanol was administered at
a higher dose (1 g/kg) over 15 min to maximize the intoxication and performance impairment. A more comprehensive
battery of cognitive and psychomotor tests was used to determine the effects of the experimental drugs over a wide
range of cognitive and motor functions. The interaction between indomethacin and pentobarbital was added to the
design because there is evidence to indicate that both ethanol
and pentobarbital exert their pharmacological effects
through modulation of g-aminobutyric acid activity at the
chloride channel (Tabakoff and Hoffman, 1996). Finally, the
power of the present study was increased by raising the
sample size from six to 10. Despite these experimental
changes, there was no evidence indicating that indomethacin
pretreatment altered the effects of ethanol or pentobarbital.
Although there are encouraging results from preclinical experiments, the results of the present study and a previous
study (Pickworth et al., 1991) do not support the use of PGSIs
to diminish the acute effects of ethanol ingestion.
Indomethacin is a potent inhibitor of brain PG synthesis.
At 30 min after oral administration, doses as low as 1 mg/kg
(IC50 , 1 mM/kg) completely inhibited the ex vivo production
of prostaglandin E2 in mouse brain (Ferrari et al., 1990). Of
the six PGSIs tested (indomethacin, zomepirac, naproxen,
ibuprofen, acetaminophen and aspirin), indomethacin was
the most potent in the inhibition of prostaglandin E2 synthesis and analgesia. These results and those of Elmer and
George (1991), in which indomethacin was the most potent in
a series of PGSIs in the inhibition of the ethanol responses in
rodents, led to the selection of indomethacin for the present
study. Indomethacin pretreatment did not significantly
change the BAL profiles attained after the administration of
ethanol. These results are similar to those obtained in rats by
George and Meisch (1990), in which PGSIs, including indomethacin, did not affect the pharmacokinetics of ethanol.
Roine et al. (1990) reported that pretreatment with aspirin (1
g) increased BAL of subsequently administered ethanol (0.3
g/kg) by 30% and increased performance impairment. The
authors attributed the increase in BAL to aspirin-induced
inhibition of gastric alcohol dehydrogenase. The results of
this study do not indicate that indomethacin significantly
affects ethanol metabolism; however, the larger doses of ethanol used in this study may account for the differences between BALs obtained in this study and those obtained by
Roine et al. (1990).
As in other studies (Pickworth et al., 1997; Pickworth et al.,
in press), ethanol decreased speed and accuracy on the computer-delivered PAB and DSST tests and on the circular
lights score. However, ethanol in divided doses that totaled
279
280
Pickworth et al.
Acknowledgments
The authors gratefully acknowledge the technical assistance of
Edward Bunker and Janeen Nichels and the research nursing efforts
of Nelda Snidow, R.N. Dr. Gregory Elmer made helpful suggestions
regarding the experimental design.
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