Sedative effects of PK 9084 and PK 8165, alone and in combination with chlordiazepoxide

1 The sedative effects in rats of two phenylquinolines, PK 9084 and PK 8165 (5-50 mg/kg), were examined in a holeboard: both when given alone and when given in conjunction with chlordiazepoxide (5 mg/kg). 2 Both phenylquinolines produced significant dose-related decreases in locomotor activity and rearing, with an ED50 about twice that for chlordiazepoxide. 3 When the phenylquinolines were combined with chlordiazepoxide the degree of sedation was equal to that seen with either drug given alone, whichever produced the greater sedation; the sedative effects of the two drugs were never additive. 4 PK 9084 (10 and 50 mg kg) significantly reduced rectal temperature, as did chlordiazepoxide (5 mg/kg), but there was no addition nor interaction of their effects. 5 Both phenylquinolines also reduced exploratory head-dipping, as did chlordiazepoxide, but in combination they antagonized each other's effects. 6 The classification of the phenylquinolines as non-sedative anxiolytics, acting as agonists at the benzodiazepine receptors needs revision.     

Effect of metiamide, a histamine H2-receptor antagonist on reserpine-induced gastric ulcers and acid secretion

The effect of metiamide on reserpine-induced gastric ulcers and on gastric secretion during 6 h after ip administration was investigated in conscious intact rats and in rats with chronic gastric fistula. Reserpine, 3 mg/kg ip increased substantially the concentration of gastric acid in the first 4 h. Metiamide given every 3 h in a low dose (0.01 mumol/kg) intensified reserpine-induced gastric ulcers and also significantly increased the reserpine-induced acid concentration and output. In larger doses, (50-100 mumol/kg) metiamide considerably diminished gastric ulcer development and decreased gastric acid concentration. Given every 2 h metiamide in doses of 50-100 mumol/kg almost completely abolished gastric ulcer formation and markedly reduced the secretion of gastric acid in reserpinized rats. Anti-ulcer effect of metiamide was stronger than its antisecretory action, suggesting also the antiulcer action of metiamide other than inhibition of acid secretion. The results suggest that in conscious rats histamine H2-receptors are involved in reserpine-induced gastric ulcer development and gastric acid secretion. The antiulcer effect of metiamide may in part depend on its antisecretory action.     

Gastric cytoprotective, antisecretory and antiulcer activities of (E)-4-oxo-4-(3,4,5-trimethoxyphenyl)-2-butenoic acid (RU 38086)

As a result of trials of a large series of compounds, RU 38086 (E)-4-oxo-4-(3,4,5-trimethoxyphenyl)-2-butenoic acid) was selected because of its cytoprotective, antisecretory and antiulcer properties. In pylorus-ligated rats, RU 38086 dose-dependently decreased the total acid output, at 2.5, 5 and 10 mg/kg orally and at 10 and 50 mg/kg intraduodenally. In the perfused rat stomach, 1.2 mg/kg RU 38086 in situ inhibited acid secretion stimulated by histamine or pentagastrin but was inactive against carbachol. In the same test 5 mg/kg intravenously did not antagonize pentagastrin-induced acid secretion. In the cat Heidenhain pouch, 0.6 mg/kg RU 38086 was also antisecretory, reducing the acid concentration when in contact with the mucosa of the pouch. In ulcers induced in rats by ligature of the pylorus plus acetylsalicylic acid, RU 38086 at 2.5 and 5 mg/kg demonstrated much more striking activity after oral than after intraduodenal administration. It also had antiulcer activity against stress ulcers (restraint plus cold), starting at a dose of 5 mg/kg orally. RU 38086 had marked gastric cytoprotective activity in rats against the necrotizing effects of ethanol from the low dose of 0.3 mg/kg orally. This cytoprotective activity was not significantly affected by indomethacin pre-treatment. At 4 and 20 mg/kg orally, RU 38086 strongly increased prostaglandin E2 levels in gastric juice of pylorus-ligated rats and in stomach tissue of normal rats. These data indicate that RU 38086 is an orally effective cytoprotective, antisecretory and antiulcer agent.     

The sedative effects of CL 218,872, like those of chlordiazepoxide,are reversed by benzodiazepine antagonists

The effects of CL 218,872, initially classified as a non-sedative anxiolytic, were investigated and compared with those of chlordiazepoxide in the holeboard. The ability of two drugs that antagonise the effects of benzodiazepines, CGS 8216 and Ro 15-1788, to reverse the effects of CL 218,872 and chlordiazepoxide were also investigated, to see whether their effects might be mediated via benzodiazepine receptors. CL 218,872 (10 mg/kg) was found to be significantly sedative in both mice and rats (i.e., both locomotor activity and head-dipping were significantly decreased). In mice, the effects of CL 218,872 and of chlordiazepoxide were very similar over a range of doses, except that the stimulatory effect seen with low doses of chlordiazepoxide on head-dipping just failed to reach significance with CL 218,872. This study is in agreement with recently published results from different tests showing that sedative effects can be obtained with doses of CL 218,872 that are low and not much higher than those leading to anxiolysis. The sedative effects of both CL 218,872 (10 mg/kg) and chlordiazepoxide (20 mg/kg) were significantly reversed by RO 15-1788 (10 and 20 mg/kg) and CGS 8216 (10 mg/kg), suggesting that their effects are mediated via benzodiazepine receptors. The increase in head-dipping seen with chlordiazepoxide (2.5 mg/kg) was also reversed by RO 15-1788 and CGS 8216.     

Benzodiazepines and barbiturates: turnover changes in central 5-hydroxytryptamine pathways

The effect of chlordiazepoxide, diazepam and phenobarbitone on 5-hydroxytryptamine turnover in the cortex cerebri as compared to the rest of the brain was studied in rats using biochemical determinations of 5-hydroxytryptamine. As an index for a change in turnover, differences in 5-hydroxytryptamine depletion following tryptophan hydroxylase inhibition with α-propyldopacetamide were observed. Chlordiazepoxide (25–50 mg/kg) and diazepam (25 mg/kg) reduced the turnover of 5-hydroxytryptamine in the cortex cerebri, whereas no change was found in the rest of the brain. Lower doses of chlordiazepoxide (5–10 mg/kg) were ineffective. Phenobarbitone (100 mg/kg) reduced the turnover of 5-hydroxytryptamine both in the cortex cerebri and in the rest of the brain. Lower doses were without effect. The doses of the various drugs which yielded an effect on the depletion of 5-hydroxytryptamine caused pronounced sedation.It is suggested that chlordiazepoxide and diazepam in sedative doses decrease the turnover of 5-hydroxytryptamine in the 5-hydroxytryptamine pathway to the cortex cerebri whereas phenobarbitone causes a generalized decrease in turnover in the brain 5-hydroxytryptamine neurons. The hypothesis is given that the reduced activity in 5-hydroxytryptamine pathways may be part of the neurochemical mechanisms mediating some of the pharmacological actions of the benzodiazepines and the barbiturates, e.g. the reduction of stage 4 slow wave sleep.     

Effects of FRG-8701 on gastric acid secretion, gastric mucosal lesions by necrotizing agents and experimental gastric or duodenal ulcer in rats

Effects of FRG-8701, a new histamine H2-receptor antagonist, on gastric acid secretion, necrotizing agents-induced gastric lesions and acute gastric or duodenal ulcer in rats were studied. In lumen-perfused rats, intravenous injection of FRG-8701 reduced gastric acid secretion, and its antisecretory effect was almost equipotent to that of famotidine but the duration of action was substantially longer. In pylorus-ligated rats, the antisecretory effect of intraduodenal FRG-8701 administration was about 7 times more potent than that of cimetidine. FRG-8701 effectively inhibited macroscopic gastric hemorrhagic lesions induced by various kinds of necrotizing agents. Intraperitoneal injection was effective in preventing the lesions as well as oral treatment. The oral ED50 values for these lesions ranged from 1.1 to 9.4 mg/kg. On the other hand, famotidine failed to reduce these lesions, and the cytoprotective effect of cimetidine was observed only in high doses compared with the doses for antisecretory activity. In addition, the cytoprotective effect of FRG-8701 was not affected by the treatment of indomethacin or N-ethylmaleimide. FRG-8701 showed antiulcer activity against stress and indomethacin gastric ulcer and mepirizole duodenal ulcer. Its antiulcer effect was 5-15 times more potent than that of cimetidine. These results indicate that FRG-8701 is a new antiulcer drug that exerts a potent cytoprotective effect in addition to its gastric antisecretory activity.     

Effects of 3-hydroxymethyl-2-methylimidazo [2, 1-b] benzothiazole (NIK-228) on gastric acid secretion and various experimental peptic ulcers in rats

We examined the antisecretory and antiulcer activities of NIK-228 in rats. Male Wistar rats (200 to 250 g) were used under 24 to 48 hr fasted (without water) conditions. NIK-228 and famotidine were administered orally 1 hr before pylorus ligation, stress or each ulceration inducer. Both NIK-228 (10 to 100 mg/kg) and famotidine (0.3 to 3 mg/kg) dose-dependently inhibited gastric secretion in pylorus ligated rats. Water-immersion stress-, indomethacin- or pylorus ligation (Shay)-induced gastric ulcers were dose-dependently inhibited by NIK-228 (10 to 100 mg/kg), but only water-immersion stress and indomethacin induced ulcers were dose-dependently inhibited by famotidine (0.03 to 3 mg/kg). Ethanol- and 0.6 N HCl-induced gastric lesions were remarkably inhibited by NIK-228 (ED50 = 2.7 and 5.6 mg/kg), but tended to be inhibited also by famotidine (0.3 to 3 mg/kg). Cysteamine-induced duodenal ulcer was inhibited significantly by NIK-228 (30, 100 mg/kg) or famotidine (3 mg/kg). NIK-228 may produce its antiulcer effects via antisecretory and cytoprotective effects. These results suggest that NIK-228 has antisecretory and antiulcer activities.     

Further behavioural evidence for the selective sedative action of zolpidem

Small doses of benzodiazepines stimulate behavioural output in experimental animals in a variety of situations. Zolpidem, which displaces benzodiazepines from their binding sites, however, has been shown to exert preferential sedative activity. In order to investigate whether small doses of zolpidem would also have stimulant effects, the actions of zolpidem and chlordiazepoxide were compared in three procedures which are sensitive to the behavioural-facilitating effects of benzodiazepines in rats. A small dose of chlordiazepoxide (3.0 mg/kg) increased locomotion in an open field whereas a large dose (30 mg/kg) suppressed this behaviour. Zolpidem (0.3-3.0 mg/kg) only decreased locomotion. The effects of both chlordiazepoxide and zolpidem were antagonised by flumazenil. Chlordiazepoxide (2.5-10 mg/kg) increased the intake of food in rats habituated to a daily feeding schedule but similar doses of zolpidem neither increased nor decreased the intake of food. Rates of punished operant responding were increased by chlordiazepoxide (3.0-30 mg/kg) but zolpidem (1.0-4.0 mg/kg) produced no such anti-punishment effect and suppressed responding at the large dose. These results show that zolpidem does not increase behavioural output in situations which are sensitive to the stimulant effects of benzodiazepines and further emphasize the selective sedative activity of this drug.     

Development of differential tolerance to the sedative and anti-stress effects of benzodiazepines

Differential degree of tolerance has been reported to develop for anticonvulsant, sedative and skeletal muscle relaxant effects of benzodiazepines (BZDs). Acute treatment with BZDs reportedly reduces the formation of gastric stress ulcers and attenuates stress-induced immunosuppression. The present study investigates whether tolerance develops to these antistress effects of BZDs by using diazepam and chlordiazepoxide as representative drugs. A single dose of diazepam (5 mg/kg, i.p.) or chlordiazepoxide (20 mg/kg, i.p.) produced a significant reduction in locomotor activity, a measure of sedative effect and antagonized the effect of restraint stress (RS) on gastric mucosal lesions and anti-sheep red blood cell (SRBC) antibody titre. With chronic treatment (X 7 d), there was a marked tolerance to the sedative effect of both the studied BZD drugs, while much less tolerance developed to their ulcer protective action. However, no tolerance was observed to the attenuating effect of diazepam and chlordiazepoxide on RS-induced immunosuppression. Thus, the results of the present study indicate that different mechanisms may be involved in the development of tolerance to the sedative, antiulcer and immunomodulatory effects of BZDs.     

Effects of a gastric antisecretory-cytoprotectant 2-methyl-8-(phenylmethoxy)imidazo[1,2-a]pyridine-3-acetonitrile (Sch 28 080) on cysteamine, reserpine and stress ulcers in rats

Prostaglandin E2 and carbenoxolone, putative cytoprotective agents, were tested in cysteamine, reserpine and stress ulcers in rats. In cysteamine-induced duodenal ulcer, PGE2 was inactive at 0.1 and 0.5 mg/kg p.o.; carbenoxolone at 100 mg/kg p.o. decreased the incidence but not the severity of the ulcer. PGE2 at 5.0 mg/kg p.o. and carbenoxolone at 300 mg/kg p.o. showed moderate effects, but the dosage also inhibited cysteamine-stimulated acid secretion. PGE2 (0.1 and 0.3 mg/kg p.o.) was inactive and carbenoxolone (100 and 300 mg/kg p.o.) further aggravated the gastric ulceration caused by reserpine or cold-restraint stress. In contrast, atropine (3 and 10 mg/kg p.o.) and cimetidine (30, 100 and 300 mg/kg p.o.) were active in all three ulcer models. But the results with cimetidine in stress ulcer were somewhat variable. 2-methyl-8-(phenylmethoxy) imidazo [1,2-a] pyridine-3-acetonitrile (Sch 28 080), a novel structure with both cytoprotective and antisecretory activity, was highly efficacious in cysteamine, reserpine and stress ulcers (1-30 mg/kg p.o.), which was presumably adequately accounted for by its potent antisecretory activity. It is concluded that cysteamine, reserpine and stress ulcers may not be appropriate models for testing the potential antiulcer effect of primarily cytoprotective compounds.     

Recovery from lorazepam tolerance and the effects of a benzodiazepine antagonist (RO 15-1788) on the development of tolerance

After 3 days of dosing rats with lorazepam (0.25 mg/kg), tolerance developed to its sedative effects. Recovery from this tolerance was rapid. No differences could be detected in undrugged behaviour 24 h after the last dose and no differences in response to a probe injection could be found when 2 drug-free days intervened between the chronic treatment and test dose. RO 15-1788 (1–4 mg/kg) antagonised the sedative effects of acute lorazepam (0.5 and 0.25 mg/kg), but chronic treatment with these doses concomitantly with lorazepam did not prevent the development of tolerance. However, 4 mg/kg RO 15-1788 administered for 5 days at the same time as lorazepam (0.5 mg/kg) and again 45 min later attenuated the development of tolerance. Plasma concentrations after acute and chronic treatment did not differ for 0.25 mg/kg lorazepam, but they were lower following chronic treatment with 0.5 mg/kg. Therefore the development of behavioural tolerance in rats to the sedative effects of benzodiazepines probably involves changes in benzodiazepine receptors, in addition to a pharmacokinetic contribution after treatment with high doses.Wellcome Trust Senior Lecturer     

The pharmacological profile of chlordesmethyldiazepam and other benzodiazepines

The pharmacological profile of chlordesmethyldiazepam was studied in mice and compared with that of other benzodiazepines (diazepam, lorazepam, clonazepam, nitrazepam, oxazepam, flunitrazepam, medazepam and chlordiazepoxide). All the drugs were administered perorally and their anticonvulsive activity (antagonism towards pentetrazole-induced clonic convulsions), anxiolytic action (the four-plate test), myorelaxant activity (the rota-rod test), sedative effect (inhibition of the locomotor activity) and neurotoxic effect (abolition of the righting reflex) were estimated. Chlordesmethyldiazepam revealed an anticonvulsive action (ED50 = 0.11 mg/kg), anxiolytic activity (MED = 2 mg/kg), myorelaxant action (ED50 = 17.5 mg/kg), sedative effect (ED50 = 34 mg/kg) and neurotoxic action (NTD50 = 190 mg/kg). Considering the potency of action (ED50) in respective tests and the therapeutic indices (NTD50/ED50 ratio), chlordesmethyldiazepam in respect of its profile resembles most lorazepam and diazepam.     

Effects of chlordiazepoxide, nicotine and d-amphetamine in the rat potentiated startle model of anxiety

The effects of acute administration of chlordiazepoxide (2.5 and 5.0mg/kg, i.p.), nicotine (0.05, 0.1 and 0.4mg/kg, s.c.) and d- amphetamine (0.5 and 1.0mg/kg, i.p.) on rat potentiated startle were investigated. Chlordiazepoxide, 2.5 and 5.0mg/kg, attenuated potentiation of startle, indicating an anxiolytic profile, although the effect of the higher dose was less marked and was accompanied by a reduction in overall startle response, probably reflecting drug-induced sedation. Nicotine at doses of 0.05 and 0.4mg/kg had no significant effects in this test. However, 0.1mg/kg nicotine eliminated potentiation of startle (in two separate experiments), an action comparable to that of 2.5mg/kg chlordiazepoxide. d-Amphetamine at doses of 0.5 and 1.0mg/kg did not significantly influence potentiation of startle. The results suggest that nicotine has an anxiolytic profile in the potentiated startle paradigm which is not due to its psychostimulant properties.     

Effects of TU-199, a novel H+, K(+)-ATPase inhibitor, on gastric acid secretion and gastroduodenal ulcers in rats.

We studied the effects of TU-199, a novel H+, K(+)-ATPase inhibitor, on gastric acid secretion and gastroduodenal lesions in rats in comparison with those of omeprazole. TU-199 inhibited hog gastric H+, K(+)-ATPase activity and its potency was almost equal to that of omeprazole (IC50 = 6.2 and 4.2 microM, respectively). In vivo, TU-199 inhibited basal gastric acid secretion in pylorus-ligated rats in a dose-dependent manner (ED50 = 4.2 mg/kg p.o.). In gastric fistula rats. TU-199 (2.5 and 5 mg/kg i.d.) also inhibited gastric acid secretion stimulated by histamine, carbachol or tetragastrin. Furthermore, TU-199 prevented the formation of water-immersion restraint stress-, pylorus ligation- and indomethacin-induced gastric lesions, and mepirizole-induced duodenal ulcer in rats. These antisecretory and antiulcer effects of TU-199 were 2-4 times more potent than those of omeprazole. The results demonstrate that TU-199 potently inhibits the acid secretion and formation of ulcers in various experimental rat models via an inhibition of H+, K(+)-ATPase. These findings suggest that TU-199 may have a beneficial effect against peptic ulcer disease in humans.     

Synthesis of novel 2-[2-(substituted amino)phenethyl]-1 H-benzimidazoles; 3,4-dihydro and 1,2,3,4,-tetrahydropyrimido[1,6-a]-benzimidazoles as potential antiulcer agents

In an effort to establish new antiulcer agents a series of 2-(2-substituted amino)-1 H-benzimidazoles 8, 9, 14; 1,3-disubstituted-3,4-dihydropyrimido[1,6-a]benzimidazoles 4, 7, 11, 12; 3-substituted-3,4-dihydropyrimido[1,6-a]benzimidazol-1 (2H)-thiones (or (2H)-ones) 10, 17 and 3-substituted-1,2,3,4-tetrahydropyrimido[1,6-a]benzimidazoles 15 were synthesized. Representative members were selected to evaluate their gastric antisecretory activity using an in vivo pylorus ligated rat method. Omeprazole was used as reference. The results indicated that the test compounds exhibit gastric antisecretory activity. The percent inhibition+/-SEM at the indicated dose level was demonstrated as omeprazole (59%+/-0.16 at 3 mg/kg) > 15a (53%+/-1.39 at 3 mg/kg) > 7a (51%+/-1.04 at 1 mg/kg) > 10a (50%+/-1.36 at 3 mg/kg).     

Antiulcer activity of the calcium antagonist propyl-methylenedioxyindene--I. Effect on cold/restraint stress-induced ulcers in rats

1. Propyl-methylenedioxyindene (pr-MDI) is an intracellularly acting calcium antagonist with H2-receptor blocking properties. Stimulus-secretion coupling is inhibited by much lower concentrations of pr-MDI than is excitation-contraction coupling. 2. Since the processes leading to gastric ulceration are calcium-dependent, the aim of this study was to determine if pr-MDI could provide useful antiulcer activity at doses below those required to produce cardiovascular effects. 3. The antiulcer activity of pr-MDI (10-30 mg/kg) was examined in the cold (4 degree C)/restraint (3 hr) stress-induced ulcer model in male rats, and compared with the effects of the H2-blocker cimetidine (10-30 mg/kg) and the calcium channel blocker verapamil (11-32 mg/kg). The drugs were administered intraperitoneally 10 min prior to the cold/restraint stress. 4. All three drugs significantly reduced the number of ulcers and the cumulative length of ulcerated stomach surface in a roughly dose-dependent and equivalent manner. However, whereas the antiulcer doses of verapamil were extremely high, those of pr-MDI were one-sixth to one-half of its antiarrhythmic ED50 in rodents.     

Facilitation of stimulatory effect of chlordiazepoxide-amphetamine combination by subacute administration of chlordiazepoxide in mice

Spontaneous locomotor activity was tested in CD-1 mice receiving subacutely (for 4 days) chlordiazepoxide (10 mg/kg) and then treated with d-amphetamine (0.5 or 1 mg/kg) and various doses of chlordiazepoxide (2.5, 5 or 10 mg/kg) separately or in combination. Chlordiazepoxide pretreatment enhanced the stimulatory effect of the chlordiazepoxide-amphetamine combination.     

Effects of topical application of KT1-32 on transmucosal potential difference and acid secretion in the rat stomach

Effects of intragastric application of azuletil sodium (KT1-32), a novel antiulcer drug, on transmucosal potential difference (PD) and acid secretion were investigated in the rat stomach. The stomach was mounted on a Lucite chamber and perfused with saline before and after exposure to KT1-32 for 10 min. KT1-32 (3-30 mg/kg) produced an elevation of PD in a dose-dependent manner with a rise of the luminal pH. The increased PD response caused by KT1-32 (10 mg/kg) persisted after removal of the agent from the stomach, but this PD generating effect was significantly mitigated by pretreatment with omeprazole (60 mg/kg, i.p.). KT1-32 raised PD under basal conditions, but did not significantly affect the reduced PD response caused by 30% ethanol. In addition, topical application of KT1-32 significantly reduced acid secretion caused by histamine (4 mg/kg/hr, i.v.) and carbachol (20 micrograms/kg/hr, i.v.). In the in vitro study, KT1-32 at 3.9 x 10(-4) M showed 50% inhibition of the H/K ATPase activity prepared from the hog gastric mucosa. These results suggest that KT1-32 exerts locally antisecretory and PD generating effects. The latter may be accounted for by the antisecretory action, which is probably related to the H/K ATPase inhibition.     

Gastric antisecretory and antiulcer/cytoprotective effects of 2-cyano-3-(ethylthio-3-methylthio)-2-propenoic acid methyl ester

AY-28,200 (2-cyano-3-(ethylthio-3-methylthio)-2-propenoic acid methyl ester), a new gastric antisecretory/antiulcer agent, inhibited basal and pentagastrin-stimulated gastric acid secretion in the conscious rat (ED50 = 7.6 and 1.9 mg/kg i.g., respectively). For inhibition of basal secretion, peak activity was attained in 5 to 6 h after dosing and was maintained for more than 10 h, with no gastric antisecretory activity occurring at 24 h. The K+ stimulated H+-K+ ATPase activity from rabbit gastric microsomes was inhibited by AY-28,200 (IC50 = 22 mumol/l). AY-28,200 inhibited ethanol-induced gastric lesions, at 3 mg/kg p.o. AY-28,200's cytoprotective effects against ethanol lasted for more than 4 h. AY-28,200 blocked acetylsalicylic acid and stress-induced gastric ulcers but was inactive against indomethacin-induced gastric ulcers. These results suggest that AY-28,200 is a parietal cell proton pump inhibitor with cytoprotective properties, and may produce its cytoprotective effect by stimulating the formation of endogenous prostaglandins.     

Determination of sedative and amnestic doses of lorazepam in children

An open-label, dose-escalation study was conducted to determine doses of lorazepam required to induce anterograde amnesia and sedation in children without producing excessive toxicity. Oncology patients 4 to 17 years of age undergoing lumbar puncture or bone marrow aspiration were eligible; a patient could be entered in the study for a second procedure at a different lorazepam dose. A single oral dose of lorazepam was administered 45-60 minutes before the procedure. Starting with 0.02 mg/kg, the same dose was given to three patients; if no dose-limiting effects occurred, dose was increased by 0.01 mg/kg. Before the procedure the patient was shown a toy that he or she was later asked to identify. Immediately after the procedure (usually 60-75 minutes after the lorazepam dose), sedation was assessed on a scale of 0 (alert) to 4 (coma), and the clinician performing the procedure was asked to subjectively evaluate sedation. Patients were rated for amnesia 24 hours after the procedure; a scale of 0 (recalls procedure and toy without prompting) to 4 (recalls nothing since procedure) was used. Twenty patients received 28 doses of lorazepam. The study was terminated when two patients who received 0.10 mg/kg had excessive ataxia. Sedation was subjectively considered adequate for 24 of the procedures. Sedation and amnesia scores were not well correlated with increased dose. Amnesia occurred in some patients with doses as low as 0.03 mg/kg. In children undergoing lumbar puncture or bone marrow aspiration, premedication with oral lorazepam 0.02-0.09 mg/kg generally produced adequate sedation for the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)