Clinical importance of the interaction of diazepam and cimetidine

Drug Interactions with Antiulcer Agents: Considerations in the Treatment of Acid-Peptic Disease

All of the antiulcer agents have been implicated in drug interactions. These agents generally influence the absorption, metabolism, or elimination of other medications. However, these interactions can lead to alterations in pharmacodynamic response. The mechanisms by which antiulcer agents produce drug interactions differ among the agents. It is beyond the scope of this article to review all of the drug interactions that have been reported with antiulcer agents. However, it is the intent to provide the reader with a detailed understanding of the mechanisms by which antiulcer agents may interact with other medications and to provide insight into factors that may influence the potential magnitude or clinical consequences of these interactions. An understanding of antiulcer drug interactions will aid pharmacists in assisting clinicians with drug selection and/or monitoring of drug interactions. Specifically, pharmacists can assist with the identification of potential antiulcer drug interactions and develop strategies designed to minimize adverse consequences of these interactions.

Understanding the pharmacokinetics of anxiolytic drugs

INTRODUCTION

Anxiety disorders are considered the most common mental disorders and they can increase the risk for comorbid mood and substance use disorders, significantly contributing to the global burden of disease. For this reason, anxiolytics are the most prescribed psychoactive drugs, particularly in the Western world.

AREAS COVERED

This review aims to analyze pharmacokinetic profile, plasma level variations so as the metabolism, interactions and possible relation to clinical effect of several drugs which are used primarily as anxiolytics. The drugs analyzed include benzodiazepines, anticonvulsants (pregabalin, gabapentin), buspirone, β-blockers and antihistamines (hydroxyzine). Regarding the most frequently used anxiolytic benzodiazepines, data on alprazolam, bromazepam, chlordesmethyldiazepam, chlordiazepoxide, clotiazepam, diazepam, etizolam, lorazepam, oxazepam, prazepam and clonazepam have been detailed.

EXPERT OPINION

There is a need for a more balanced assessment of the benefits and risks associated with benzodiazepine use, particularly considering pharmacokinetic profile of the drugs to ensure that patients, who would truly benefit from these agents, are not denied appropriate treatment. An optimal pharmacological approach involving an integrative pharmacokinetic and pharmacodynamic optimization strategy would ensure better treatment and personalization of anxiety disorders. So it would be desirable for the development of new anxiolytic drug(s) that are more selective, fast acting and free from the unwanted effects associated with the traditional benzodiazepines as tolerance or dependence.

Maintenance time of sedative effects after an intravenous infusion of diazepam: a guide for endoscopy using diazepam

AIM

To examine whether the sedative effects assessed by psychomotor tests would depend on the cytochrome P450 (CYP) 2C19 genotypes after an infusion regimen of diazepam commonly used for gastrointestinal endoscopy in Japan.

METHODS

Fifteen healthy Japanese volunteers consisting of three different CYP2C19 genotype groups underwent a critical flicker fusion test, an eye movement analysis and a postural sway test as a test for physical sedative effects, and a visual analog scale (VAS) symptom assessment method as a test for mental sedative effects during the 336 h period after the intravenous infusion of diazepam (5 mg).

RESULTS

The physical sedative effects assessed by the critical flicker test continued for 1 h (t values of 5 min, 30 min and 60 min later: 4.35, 5.00 and 3.19, respectively) and those by the moving radial area of a postural sway test continued for 3 h (t values of 5 h, 30 h, 60 min and 3 h later: -4.05, -3.42, -2.17 and -2.58, respectively), which changed significantly compared with the baseline level before infusion (P<0.05). On the other hand, the mental sedative effects by the VAS method improved within 1 h. The CYP2C19 genotype-dependent differences in the postinfusion sedative effects were not observed in any of the four psychomotor function tests.

CONCLUSION

With the psychomotor tests, the objective sedative effects of diazepam continued for 1 h to 3 h irrespective of CYP2C19 genotype status and the subjective sedative symptoms improved within 1 h. Up to 3 h of clinical care appears to be required after the infusion of diazepam, although patients feel subjectively improved.

Voriconazole and fluconazole increase the exposure to oral diazepam

OBJECTIVE

We assessed the effect of voriconazole and fluconazole on the pharmacokinetics and pharmacodynamics of diazepam.

METHODS

Twelve healthy volunteers took 5 mg of oral diazepam in a randomised order on three study sessions: without pretreatment, after oral voriconazole 400 mg twice daily on the first day and 200 mg twice daily on the second day, or after oral fluconazole 400 mg on the first day and 200 mg on the second day. Plasma concentrations of diazepam and N-desmethyldiazepam were determined for up to 48 h. Pharmacodynamic variables were measured for 12 h.

RESULTS

In the voriconazole phase, the area under the plasma concentration time curve (AUC 0-infinity) of diazepam was increased (geometric mean ratio) 2.2-fold (p < 0.05; 90% confidence interval [CI] 1.56 to 2.82). This was associated with the prolongation of the mean elimination half-life (t(1/2)) from 31 h to 61 h (p < 0.01) after voriconazole. In the fluconazole phase, the AUC 0-infinity of diazepam was increased 2.5-fold (p < 0.01; 90% CI 1.94 to 3.40), and the t(1/2) was prolonged from 31 h to 73 h (p < 0.001). The peak plasma concentration of diazepam was practically unchanged by voriconazole and fluconazole. The pharmacodynamics of diazepam were changed only modestly.

CONCLUSION

Both voriconazole and fluconazole considerably increase the exposure to diazepam. Recurrent administration of diazepam increases the risk of clinically significant interactions during voriconazole or fluconazole treatment, because the elimination of diazepam is impaired significantly.

Pharmacokinetic and Pharmacodynamic Interactions Between Zolpidem and Caffeine

The kinetic and dynamic interaction of caffeine and zolpidem was evaluated in a double-blind, single-dose, six-way crossover study of 7.5 mg zolpidem (Z) or placebo (P) combined with low-dose caffeine (250 mg), high-dose caffeine (500 mg), or placebo. Caffeine coadministration modestly increased maximum plasma concentration (C(max)) and area under the plasma concentration-time curve of zolpidem by 30-40%, whereas zolpidem did not significantly affect the pharmacokinetics of caffeine or its metabolites. Compared to P+P, Z+P significantly increased sedation, impaired digit-symbol substitution test performance, slowed tapping speed and reaction time, increased EEG relative beta amplitude, and impaired delayed recall. Caffeine partially, but not completely, reversed most pharmacodynamic effects of zolpidem. Thus, caffeine only incompletely reverses zolpidem's sedative and performance-impairing effects, and cannot be considered as an antidote to benzodiazepine agonists.

Antidepressant-drug interactions are potentially but rarely clinically significant

The salient pharmacologic features of the selective serotonin reuptake inhibitors (SSRIs) discovered in the late 1980s included an in vitro ability to inhibit various cytochrome P450 enzymes (CYPs). Differences in potency among the SSRIs for CYP inhibition formed the basis of a marketing focus based largely on predictions of in vivo pharmacokinetic drug interactions from in vitro data, conclusions derived from case reports, and the extrapolation of the results of pharmacokinetic studies conducted in healthy volunteers to patients. Subsequently introduced antidepressants have undergone a similar post hoc scrutiny for potential drug-drug interactions. Concern for the untoward consequences of drug interactions led the FDA to publish guidance for the pharmaceutical industry in 1997 recommending that in vitro metabolic studies be conducted early in the drug development process to evaluate inhibitory properties toward the major CYPs. However, the prevalence of clinically significant enzyme inhibition interactions occurring during antidepressant treatment remains poorly defined despite millions of exposures. Although lack of evidence does not equate to evidence of absence, sparse epidemiological and post-marketing surveillance data do not substantiate a conclusion that widespread morbidity results from antidepressant-induced drug interactions. This commentary discusses points of uncertainty and controversy in the field of drug interactions, notes areas where inadequate data exist, and suggests explanations for a low prevalence of serious interactions. The conclusion is drawn that drug interactions from CYP inhibition caused by the newer antidepressants are potentially, but rarely, clinically significant.

Clinical significance of the cytochrome P450 2C19 genetic polymorphism

Cytochrome P450 2C19 (CYP2C19) is the main (or partial) cause for large differences in the pharmacokinetics of a number of clinically important drugs. On the basis of their ability to metabolise (S)-mephenytoin or other CYP2C19 substrates, individuals can be classified as extensive metabolisers (EMs) or poor metabolisers (PMs). Eight variant alleles (CYP2C19*2 to CYP2C19*8) that predict PMs have been identified. The distribution of EM and PM genotypes and phenotypes shows wide interethnic differences. Nongenetic factors such as enzyme inhibition and induction, old age and liver cirrhosis can also modulate CYP2C19 activity. In EMs, approximately 80% of doses of the proton pump inhibitors (PPIs) omeprazole, lansoprazole and pantoprazole seem to be cleared by CYP2C19, whereas CYP3A is more important in PMs. Five-fold higher exposure to these drugs is observed in PMs than in EMs of CYP2C19, and further increases occur during inhibition of CYP3A-catalysed alternative metabolic pathways in PMs. As a result, PMs of CYP2C19 experience more effective acid suppression and better healing of duodenal and gastric ulcers during treatment with omeprazole and lansoprazole compared with EMs. The pharmacoeconomic value of CYP2C19 genotyping remains unclear. Our calculations suggest that genotyping for CYP2C19 could save approximately 5000 US dollars for every 100 Asians tested, but none for Caucasian patients. Nevertheless, genotyping for the common alleles of CYP2C19 before initiating PPIs for the treatment of reflux disease and H. pylori infection is a cost effective tool to determine appropriate duration of treatment and dosage regimens. Altered CYP2C19 activity does not seem to increase the risk for adverse drug reactions/interactions of PPIs. Phenytoin plasma concentrations and toxicity have been shown to increase in patients taking inhibitors of CYP2C19 or who have variant alleles and, because of its narrow therapeutic range, genotyping of CYP2C19 in addition to CYP2C9 may be needed to optimise the dosage of phenytoin. Increased risk of toxicity of tricyclic antidepressants is likely in patients whose CYP2C19 and/or CYP2D6 activities are diminished. CYP2C19 is a major enzyme in proguanil activation to cycloguanil, but there are no clinical data that suggest that PMs of CYP2C19 are at a greater risk for failure of malaria prophylaxis or treatment. Diazepam clearance is clearly diminished in PMs or when inhibitors of CYP2C19 are coprescribed, but the clinical consequences are generally minimal. Finally, many studies have attempted to identify relationships between CYP2C19 genotype and phenotype and susceptibility to xenobiotic-induced disease, but none of these are compelling.

Drug interaction studies with esomeprazole, the (S)-isomer of omeprazole

Esomeprazole, the (S)-isomer of omeprazole, is the first proton pump inhibitor (PPI) developed as a single isomer for the treatment of patients with acid related diseases. Because of the extensive use of PPIs, the documentation of the potential for drug interactions with esomeprazole is of great importance. Altered absorption or metabolism are 2 of the major mechanisms for drug-drug interactions. Since intragastric pH will increase with esomeprazole treatment, it can be hypothesised that the absorption of drugs with pH-sensitive absorption (e.g. digoxin and ketoconazole) may be affected. Esomeprazole does not seem to have any potential to interact with drugs that are metabolised by cytochrome P450 (CYP) 1 A2, 2A6, 2C9, 2D6 or 2E1. In drug interaction studies with diazepam, phenytoin and (R)-warfarin, it was shown that esomeprazole has the potential to interact with CYP2C19. The slightly altered metabolism of cisapride was also suggested to be the result of inhibition of a minor metabolic pathway for cisapride mediated by CYP2C19. Esomeprazole did not interact with the CYP3A4 substrates clarithromycin (2 studies) or quinidine. Since the slightly increased area under the concentration-time curve (AUC) of cisapride could be explained as an inhibition of CYP2C19, the data on these 3 CYP3A4 substrates indicate that esomeprazole does not have the potential to inhibit this enzyme. The minor effects reported for diazepam, phenytoin, (R)-warfarin, and cisapride are unlikely to be of clinical relevance. Clarithromycin interacts with the metabolism of esomeprazole resulting in a doubling of the AUC of esomeprazole. The increased plasma concentrations of esomeprazole are unlikely to have any safety implications. It can be concluded that the potential for drug-drug interactions with esomeprazole is low, and similar to that reported for omeprazole.

Selection of drugs to treat gastro-oesophageal reflux disease: the role of drug interactions

Gastro-oesophageal reflux disease is probably the most common acid-peptic disease in Western countries, and the successful treatment of mild to moderate disease with pharmacotherapy has become commonplace. A large number of effective drugs are now available, and so the decision-making process for physicians increasingly relies on considerations other than pure efficacy. Cost, adverse effects and drug interactions have therefore become important, particularly in the most vulnerable patients - children, the elderly and patients who are ill and are taking medications that may influence the efficacy of antireflux therapy. Important drug interactions with antacids include the prevention of the absorption of antibacterials such as tetracycline, azithromycin and quinolones. H2 antagonists, proton pump inhibitors and prokinetic agents undergo metabolism by the cytochrome P450 (CYP) system present in the liver and gastrointestinal tract. Cimetidine is an inhibitor of CYP3A and it may cause significant interactions with drugs of narrow therapeutic range and low bioavailability that are metabolised by these enzymes. The gastroparietal proton pump inhibitors lansoprazole, omeprazole and pantoprazole are all primarily metabolised by a genetically polymorphic enzyme, CYP2C19, that is absent from approximately 3% of Caucasians and 20% of Asians. These drugs may also interact with CYP3A, but to a lesser extent. Interactions with prokinetic agents carry the greatest potential for harm. Metoclopramide is a dopamine antagonist that may cause extrapyramidal effects when administered alone at high concentrations, or when coadministered with antipsychotic agents such as haloperidol or phenothiazines. Cisapride is clearly able to prolong the electrocardiographic QT interval and cause lethal ventricular arrhythmias when its metabolism is slowed by interaction with inhibitors of CYP3A, such as erythromycin, ketoconazole or itraconazole.

Pharmacologic considerations in the treatment of neonatal septicemia and its complications

This article focuses on the pharmacologic properties of drugs commonly used in the treatment of neonatal septicemia and its complications. Rational therapy demands an awareness of not only the pharmacology of individual drugs but also the interactions and anticipated fate of such drugs in the rapidly changing physiologic environment of the neonate. Further research in the area of equine neonatal pharmacology should greatly assist our understanding of the impact of the disease state on the unique physiology of the newborn and should allow us to better predict the ultimate fate of drugs commonly used for such purposes. Careful dosing and close monitoring of pharmacologic effects are critical for a successful outcome. In the future, newer therapeutic strategies that are safe and efficacious may provide a means to circumvent many of the problems currently encountered with treating the septicemic newborn foal.

Metabolism of anxiolytics and hypnotics: benzodiazepines, buspirone, zoplicone, and zolpidem

1. The benzodiazepines are among the most frequently prescribed of all drugs and have been used for their anxiolytic, anticonvulsant, and sedative/hypnotic properties. Since absorption rates, volumes of distribution, and elimination rates differ greatly among the benzodiazepine derivatives, each benzodiazepine has a unique plasma concentration curve. Although the time to peak plasma levels provides a rough guide, it is not equivalent to the time to clinical onset of effect. The importance of alpha and beta half-lives in the actions of benzodiazepines is discussed. 2. The role of cytochrome P450 isozymes in the metabolism of benzodiazepines and in potential pharmacokinetic interactions between the benzodiazepines and other coadministered drugs is discussed. 3. Buspirone, an anxiolytic with minimal sedative effects, undergoes extensive metabolism, with hydroxylation and dealkylation being the major pathways. Pharmacokinetic interactions of buspirone with other coadministered drugs seem to be minimal. 4. Zopiclone and zolpidem are used primarily as hypnotics. Both are extensively metabolized; N-demethylation, N-oxidation, and decarboxylation of zopiclone occur, and zolpidem undergoes oxidation of methyl groups and hydroxylation of a position on the imidazolepyridine ring system. Zopiclone has a chiral centre, and demonstrates stereoselective pharmacokinetics. Metabolic drug-drug interactions have been reported with zopiclone and erythromycin, trimipramine, and carbamazepine. Reports to date indicate minimal interactions of zolpidem with coadministered drugs; however, it has been reported to affect the Cmax and clearance of chlorpromazepine and to decrease metabolism of the antiviral agent ritonavin. Since CYP3A4 has been reported to play an important role in metabolism of zolpidem, possible interactions with drugs which are substrates and/or inhibitors of that CYP isozyme should be considered.

Drug-drug interactions in pediatric psychopharmacology

Serious consequences caused by drug-drug interactions continue to plague contemporary pharmacotherapy. The possibility of a drug-drug interaction should be suspected anytime a new or unexpected effect occurs that complicates the clinical management of a patient in the setting where the patient is receiving more than one drug. In this article, the authors address the mechanisms of pharmacokinetic-based drug-drug interactions focusing on important interactions that may occur with the common medications a pediatrician may prescribe to the child receiving psychoactive medication(s) prescribed by a child psychiatrist.

Pharmacokinetic interactions between acute alcohol ingestion and single doses of benzodiazepines, and tricyclic and tetracyclic antidepressants -- an update

Recent reports of interactions between alcohol and benzodiazepines, tricyclic and tetracyclic antidepressants during their acute concomitant use are reviewed. Acute ingestion of alcohol (ethanol) with tranquilizers or hypnotics is responsible for several pharmacokinetic interactions that can have significant clinical implications. In general, metabolism of these drugs is delayed when combined with alcohol but some reports have suggested otherwise. The amount of alcohol consumed, the presence or absence of liver disease, and differences in the dosage and administration of these drugs may account for the observed discrepancies. In recent years, the cytochrome P450 (P450 or CYP) isoenzyme that catalyses the metabolism of these drugs has also been identified. However, since changes in the pharmacogenetic metabolism of benzodiazepines and tricyclic and tetracyclic antidepressants are mainly governed by CYP2C19 and CYP2D6, caution is needed when used together with alcohol.

A kinetic and dynamic study of oral alprazolam with and without erythromycin in humans: in vivo evidence for the involvement of CYP3A4 in alprazolam metabolism

OBJECTIVE

To assess the possible involvement of CYP3A4 in the metabolism of alprazolam in vivo.

METHOD

Twelve healthy male volunteers were randomly allocated to one of the two different treatment sequences, placebo-erythromycin or erythromycin-placebo, with an at least 6-week washout period between the two trial phases. Each volunteer received 400 mg erythromycin or matched placebo given orally three times a day for 10 days and an oral dose (0.8 mg) of alprazolam on the posttreatment day 8. Plasma concentration of alprazolam was measured up to 48 hours after the administration, and psychomotor function was assessed at each time of blood samplings with use of the Digit Symbol Substitution Test, visual analog scale, and Udvalg for kliniske undersøgelser side effect rating scale.

RESULTS

Erythromycin significantly (p < 0.001) increased the area under the plasma concentration-time curves (200 +/- 43 versus 322 +/- 49 ng . hr/ml from 0 to 48 hours and 229 +/- 52 versus 566 +/- 161 ng . hr/ml from 0 hour to infinity), decreased the apparent oral clearance (1.02 +/- 0.31 versus 0.41 +/- 0.12 ml/min/kg), and prolonged the elimination half-life (16.0 +/- 4.5 versus 40.3 +/- 14.4 hours) of alprazolam. However, any psychomotor function variables did not differ significantly between the erythromycin and placebo trial phases.

CONCLUSION

This study suggests that erythromycin, an inhibitor of CYP3A4, inhibits the metabolism of alprazolam, providing an in vivo evidence for the involvement of CYP3A4 in its metabolism. However, the kinetic change of alprazolam by erythromycin does not result in the pharmacodynamic change of this triazolobenzodiazepine, at least after single dosing.

Comparison of the interaction potential of a new proton pump inhibitor, E3810, versus omeprazole with diazepam in extensive and poor metabolizers of S-mephenytoin 4'-hydroxylation

OBJECTIVE

To compare the interaction potential of E3810, [(+/-)-sodium 2-[[4-(3-methoxpropoxy)-3-methylpyridin-2-yl]methylsulfinyl] -1H-benzimidazole] a new proton pump inhibitor, and omeprazole with diazepam in relation to S-mephenytoin 4'-hydroxylation status.

STUDY DESIGN

Fifteen healthy male volunteers consisting of six poor metabolizers and nine extensive metabolizers of S-mephenytoin 4'-hydroxylation participated in the study, where two poor and three extensive metabolizers each as a group were randomly allocated to one of the three different treatment sequences with a 3-week washout period among the three trial phases. Each volunteer received an oral once-daily dose of E3810 (20 mg), omeprazole (20 mg), or placebo for 23 days and an intravenous dose (0.1 mg/kg) of diazepam on posttreatment day 8. Plasma concentrations of diazepam and demethyldiazepam were measured up to 16 days after the administration of diazepam.

RESULTS

Diazepam was more slowly metabolized in the poor metabolizers than in the extensive metabolizers. No significant effects of E3810 and omeprazole on any kinetic parameters of diazepam were observed in the poor metabolizers. In the extensive metabolizers, omeprazole significantly decreased the mean clearance of diazepam and increased its half-life, area under the plasma concentration-time curve, and mean residence time compared with E3810 and placebo (p < 0.05 or 0.01), whereas no changes in these kinetic parameters were observed during the treatment with E3810. Omeprazole significantly increased the mean area under the plasma concentration-time curve (0-16 days) of demethyldiazepam in the extensive metabolizers compared with placebo (p < 0.01), whereas E3810 significantly increased it in the poor metabolizers compared with omeprazole or placebo (p < 0.05).

CONCLUSION

The results indicate that E3810 as a substrate goes less toward S-mephenytoin 4'-hydroxylase (CYP2C19) and has a much weaker, if any, potential to interact with diazepam compared with omeprazole.

Drug interactions with intravenous and local anaesthetics

Relatively few clinically significant drug interactions with anaesthetics have been documented in the literature. The following should be stressed since these interactions are not readily predictable or are potentially fatal. Pethidine should never be administered to patients who have received monamine oxidase inhibiting drugs within the last fortnight, since a fatal hyperpyrexia and/or hypertension may result. Thiopentone induction seems to make the heart more susceptible to arrhythmias caused by adrenergic drugs, and may cause severe arterial hypotension in patients treated with diazoxide. Midazolam orally should possibly be avoided as premedication in patients treated with erythromycin since anaesthetic concentrations of midazolam may result. Patients for whom bupivacaine analgesia is planned could preferentially be premedicated with other drugs than diazepam, which causes the serum level of bupivacaine to increase. Bradycardia and hypotension not attributable to sympathetic blockade have been reported following bupivacaine extradurally in verapamil-treated patients. Sulfonamides and the ester group of local anaesthetics, such as prilocaine in combination, may result in severe methaemoglobinaemia in infants. Epinephrine added to local anaesthetics may cause local vasodilation if administered to patients concurrently being treated with cyclic antidepressants, and the combination imposes the risk of severe hypertension and arrhythmias.

Interaction of H2-receptor antagonists and benzodiazepine sedation. A double-blind placebo-controlled investigation of the effects of cimetidine and ranitidine on recovery after intravenous midazolam

H2-receptor antagonists differentially inhibit cytochrome P450 and this may affect the rate at which benzodiazepines are metabolised. However, it is not known whether this delayed clearance results in prolonged psychomotor impairment. In a randomised double-blind trial 28 healthy volunteers received two single doses of midazolam (0.07 mg.kg-1) at an interval of one week during which they took cimetidine 400 mg, ranitidine 150 mg or placebo, each twice daily. Recovery from the benzodiazepine was monitored on each occasion over a 12 h period using a battery of psychometric tests. There was wide individual variation in performance; however, an overall measure of impairment indicated a significant difference at 2.5 h (p < 0.05), the cimetidine group having a high impairment score. This decrement appeared to be in cognitive and psychomotor functions and was not reflected in the subjective assessment.

Pharmacology of gastric acid inhibition

Gastric acid secretion is precisely regulated by neural (acetylcholine), hormonal (gastrin), and paracrine (histamine; somatostatin) mechanisms. The stimulatory effect of acetylcholine and gastrin is mediated via increase in cytosolic calcium, whereas that of histamine is mediated via activation of adenylate cyclase and generation of cAMP. Potentiation between histamine and either gastrin or acetylcholine may reflect postreceptor interaction between the distinct pathways and/or the ability of gastrin and acetylcholine to release histamine from mucosal ECL cells. The prime inhibitor of acid secretion is somatostatin. Its inhibitory paracrine effect is mediated predominantly by receptors coupled via guanine nucleotide binding proteins to inhibition of adenylate cyclase activity. All the pathways converge on and modulate the activity of the luminal enzyme, H+,K(+)-ATPase, the proton pump of the parietal cell. Precise information on the mechanisms involved in gastric acid secretion and the identification of specific receptor subtypes has led to the development of potent drugs capable of inhibiting acid secretion. These include competitive antagonists that interact with stimulatory receptors (e.g. muscarinic M1-receptor antagonists and histamine H2-receptor antagonists) as well as non-competitive inhibitors of H+,K(+)-ATPase (e.g. omeprazole). The histamine H2-receptor antagonists (cimetidine, ranitidine, famotidine, nizatidine and roxatidine acetate) continue as first-line therapy for peptic ulcer disease and are effective in preventing relapse. Although they are generally well tolerated, histamine H2-receptor antagonists may cause untoward CNS, cardiac and endocrine effects, as well as interfering with the absorption, metabolism and elimination of various drugs. The dominance of the histamine H2-receptor antagonists is now being challenged by omeprazole. Omeprazole reaches the parietal cell via the bloodstream, diffuses through the cytoplasm and becomes activated and trapped as a sulfenamide in the acidic canaliculus of the parietal cell. Here, it covalently binds to H+,K(+)-ATPase, the hydrogen pump of the parietal cell, thereby irreversibly blocking acid secretion in response to all modes of stimulation. The main potential drawback to its use is its extreme potency which sometimes leads to virtual anacidity, gastrin cell hyperplasia, hypergastrinaemia and, in rats, to the development of carcinoid tumours. The cholinergic receptor on the parietal cell has recently been identified as an M3 subtype and that on postganglionic intramural neurones of the submucosal plexus as an M1 subtype.(ABSTRACT TRUNCATED AT 400 WORDS)

Clinical relevance of cimetidine drug interactions

The excellent efficacy and tolerability profiles of H2-antagonists have established these agents as the leading class of antiulcer drugs. Attention has been focused on drug interactions with H2-antagonists as a means of product differentiation and because many patients are receiving multiple drug therapy. The main mechanism of most drug interactions involving cimetidine appears to be inhibition of the hepatic microsomal enzyme cytochrome P450, an effect which may be related to the different structures of H2-antagonists. Ranitidine appears to have less affinity than cimetidine for this system. There have been many published case reports and studies of drug interactions with cimetidine, but many of these have provided pharmacokinetic data only, with little information concerning the clinical significance of these findings. Nevertheless, the coadministration of cimetidine with drugs that have a narrow therapeutic margin (such as theophylline) may potentially result in clinically significant adverse effects. The monitoring of serum concentrations of drugs coadministered with cimetidine may reduce the risk of adverse events but does not abolish the problem. However, for most patients, concomitant administration of cimetidine with drugs possessing a wide therapeutic margin is unlikely to pose a significant problem.

The pharmacokinetics and pharmacodynamics of sublingual and oral alprazolam in the post-prandial state

We gave 12 healthy male volunteers 1 mg of alprazolam or placebo on three occasions after a standard breakfast in a double-blind, randomized, single-dose, three-way crossover study. The three trials were: (a) oral alprazolam and sublingual placebo; (b) oral placebo and sublingual alprazolam; (c) placebo by both routes. Plasma alprazolam concentrations during 24 h after each dose were measured by electron-capture gas-liquid chromatography. Peak plasma concentrations were reached later after sublingual than oral dosage (2.8 vs 1.8 h, P less than 0.01). Other kinetic variables were not significantly different: peak plasma concentration, 11.3 vs 12.0 ng.ml-1; elimination half-life, 12.5 vs 11.7 h; and total area under the plasma concentration versus time curve, 197 vs 186 h.ng.ml-1. Pharmacodynamic measures showed that sublingual and oral alprazolam both produced sedation, fatigue, impaired digit symbol substitution, slowing of reaction time, and impairment of the acquisition and recall of information. These changes were initially observed at 0.5 h after dosage and lasted up to 8 h. In general the two routes were significantly different from placebo but not from each other.

Effect of orally administered misoprostol and cimetidine on the steady state pharmacokinetics of diazepam and nordiazepam in human volunteers

The effects of misoprostol and cimetidine on diazepam pharmacokinetics were evaluated in order to determine whether the kinetic variables for diazepam and nordiazepam alone differ with the repeated oral administration of misoprostol and cimetidine to healthy adult volunteers. The trial was conducted as an open crossover study in 12 normal subjects, divided into two groups with all subjects receiving both regimens. Total study duration was 5 weeks. An initial clinical assessment, including blood biochemistry and assessment of subject oxidation status was carried out on study day 1. On this day, subjects began taking diazepam (10 mg) orally for one week, with pharmacokinetic studies performed at day 8, when steady state levels of diazepam were reached. This was followed by one week with active drug, misoprostol to Group I and cimetidine to Group II, with pharmacokinetic studies performed at the end of a 1-week treatment. After a 2-week wash-out period, both groups took for one week, the alternate drug, i.e. cimetidine plus diazepam to Group I and misoprostol plus diazepam to Group II. On days 8, 15 and 36, subjects were admitted to the hospital for 12 h, during which time a clinical examination was carried out and blood samples were taken at time zero and at 4, 8, 12, 24, and 36 h post-dosing for the measurement of serum diazepam and nordiazepam. The main parameters measured and evaluated were diazepam and nordiazepam pharmacokinetics at steady state (days 8, 15 and 36). These were areas under the curve in the dose intervals (AUC0-24h), maximum plasma concentrations (Cmax), time to peak concentrations (Tmax), elimination half-life (t1/2), elimination constant (Kel), distribution volume (Vd), total body clearance (ClB) and clearance after oral administration (Cloral). The results demonstrated that plasma diazepam and nordiazepam concentrations had a significant increase after steady states have been reached with the simultaneous administration of 800 mg of cimetidine daily for one week. The simultaneous administration of 800 micrograms of misoprostol did not cause any significant change in diazepam and nordiazepam plasma levels after steady states had been reached. Comparing the pharmacokinetic parameters of Groups A and B as well as within groups on days 8, 15 and 36, a significant increase in plasma diazepam and nordiazepam levels was detected. This was due to a cimetidine-induced impairment in microsomal oxidation of diazepam and nordiazepam, which caused a decrease in total metabolic clearance and increased mean steady state plasma concentrations. A more prolonged half-life was observed for both groups taking cimetidine as well as an increase of mean maximum plasma concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)

Psychologic factors associated with peptic ulcer disease

Peptic ulcer disease provides an excellent model for the study of mind-body interactions in the pathogenesis and course of an illness. Early psychodynamic explanations of the role of personality factors in the evolution of peptic ulcer disease have been supplemented in recent years by more scientifically based studies on the role of stress and coping ability. Multiple psychosocial variables have confounded the outcome of many of these studies. Yet, a clear need and guidelines exist for the comprehensive medical and psychosocial evaluation and treatment of patients with peptic ulcer disease. Concomitant psychiatric assessment and management, including psychotherapeutic and psychopharmacologic approaches, for those patients with refractory symptoms or ongoing psychiatric symptoms carried out in close collaboration with primary caregivers will significantly decrease overall morbidity and mortality.

Cytochrome P-450 monooxygenases and interactions of psychotropic drugs

The authors review drug biotransformation. Phase I reactions are preconjugation processes that take place through cytochrome P-450--a hepatic mixed function oxidase (MFO) enzyme system with multiple isozymes to metabolize foreign substances. Phase II reactions are conjugation processes of the substrates. Based on the characteristics of the cytochrome P-450 microsomal enzyme systems, the authors explain the clinical phenomena of induction and inhibition of these enzymes when psychotropic agents interact. This article describes both MFO inducers (barbiturates) and inhibitors (cimeditine, fluoxetine and neuroleptic drugs). With this information, clinicians can enhance the ability to monitor drug interactions of psychotropic agents.

A guide to benzodiazepine selection. Part I: Pharmacological aspects

Since absorption rates, volumes of distribution and elimination rates differ greatly among the benzodiazepine derivatives, each benzodiazepine has a unique plasma concentration curve. Although the time to peak plasma levels provides a rough guide, it is not equivalent to the time to clinical onset of effect. Two half-lives can be described: the alpha half-life, the rate of decline in plasma concentrations due to the process of drug redistribution from the central to the peripheral compartment, and the beta half-life, the rate of decline due to the process of drug elimination due to metabolism. The frequent classification of benzodiazepines into long, intermediate, and short-"acting" categories based on their terminal beta half-lives is unfounded; the duration of action is much more dependent on the alpha half-life. Benzodiazepines with short beta half-lives are commonly thought to be preferable because they accumulate less. However, with repeated use, sedation and cognitive neuromotor impairment usually diminish progressively despite stable or even rising benzodiazepine plasma concentrations, whereas anxiolytic effects generally persist over time.

Effect of omeprazole and cimetidine on plasma diazepam levels

The effects of steady state dosing with omeprazole and cimetidine on plasma diazepam levels have been studied in 12 healthy males. Single doses of diazepam (0.1 mg.kg-1 i.v.) were administered after one week of treatment with omeprazole 20 mg once daily, cimetidine 400 mg b.d. or placebo, and the treatment was continued for a further 5 days. Blood was collected for 120 h after the dose of diazepam for the measurement of diazepam and its major metabolite desmethyl diazepam. The mean clearance of diazepam was decreased by 27% and 38% and its half-life was increased by 36% and 39% after omeprazole and cimetidine, respectively. Neither drug had any apparent effect on the volume of distribution of diazepam. Desmethyldiazepam appeared more slowly after both omeprazole and cimetidine. It is concluded that the decrease in diazepam clearance was associated with inhibition of hepatic metabolism both by omeprazole and cimetidine. However, since diazepam has a wide therapeutic range, it is unlikely that concomitant treatment with therapeutically recommended doses of either omeprazole or cimetidine will result in a clinically significant interaction with diazepam.

The neuropsychiatric effects of aspartame in normal volunteers

Ten healthy volunteers with no history of aspartame intolerance (6 men and 4 women, aged 21-36 years) received a single dose of aspartame (15 mg/kg body weight in capsules) or matching placebo in a randomized, double-blind crossover study. Eleven blood samples collected over 24 hours were analyzed for plasma glucose and amino acid concentrations. The following variables were evaluated at 1, 2, 4, 8, and 24 hours post-dosage: changes in mood measured on visual analog scales, cognitive function determined by digit-symbol substitution test (DSST) and arithmetic test scores, and reaction time measured with a brake-pedal reaction timer. Memory was tested at 2 and 24 hours after dosage based on recall of standardized 16-item word lists. No significant differences between aspartame and placebo were found in measures of sedation, hunger, headache, reaction-time, cognition, or memory at any time during the study. Plasma phenylalanine levels were significantly higher following aspartame (P less than .01) than with placebo between 1 and 6 hours postdosage, reaching a maximum difference of +3.36 mumols/dl at 2 hours. Plasma glucose concentrations were not significantly different between aspartame and placebo. The results of this study suggest that following a single 15 mg/kg dose of aspartame, no detectable effects are observed in a group of healthy volunteers with no history of aspartame intolerance, despite significant increases in plasma phenylalanine concentrations.

Effect of the benzodiazepines diazepam, des-N-methyldiazepam and midazolam on corticosteroid biosynthesis in bovine adrenocortical cells in vitro; location of site of action

Diazepam and midazolam inhibited cortisol and aldosterone synthesis in bovine adrenal cells in vitro. The biologically active metabolite des-N-methyldiazepam did not. Midazolam was a more potent inhibitor (IC50: 6 micrograms/ml) than diazepam (IC50: 13 micrograms/ml) in ACTH-stimulated cells. Both compounds inhibited steroidogenesis at several points in the biosynthetic chain; the greatest effects were on 17 alpha hydroxylation and 21 hydroxylation. Diazepam had a relatively greater effect on 17 alpha hydroxylation; midazolam on 21 hydroxylation. Both were less potent inhibitors of 11 beta hydroxylation and had little apparent effect on side chain cleavage. Thus microsomal hydroxylation is more vulnerable to benzodiazepines than mitochondrial hydroxylation. It is suggested that the drugs act by competing with steroid mixed function oxidases for cytochrome P-450. The plasma concentrations required for these effects are high in relation to therapeutic levels but may be achieved, for example, during acute infusions or when they are used in combination with imidazole drugs such as cimetidine.

Benzodiazepines in the treatment of alcoholism

This chapter comprises three sections that cover the main aspects of benzodiazepines and alcohol: (1) the basic pharmacology of benzodiazepines; (2) use of benzodiazepines in the treatment of withdrawal; and (3) the use of benzodiazepines in treating alcoholics. The basic studies suggest that a major site of action of alcohol may be the GABA/benzodiazepine receptor complex and that compensatory alterations in this complex may underly withdrawal. In the section on alcohol withdrawal, interactions between the GABA/benzodiazepine receptor complex, sympathetic nervous system, and hypothalamic-pituitary-adrenal axis are discussed. Use of benzodiazepines in the treatment of the alcohol withdrawal syndrome are reviewed, including the possibility that the benzodiazepines may prevent withdrawal-induced "kindling." Lastly, we review indications for, and efficacy of, benzodiazepines in long-term treatment of patients with alcoholism. Benzodiazepines are not indicated for the treatment of alcoholism. Furthermore, they have very few indications in alcoholics and their dependency-producing potency has to be appreciated when they are used in patients with alcoholism.

Ranitidine versus cimetidine. A comparison of their potential to cause clinically important drug interactions

The literature on H2-antagonist drug interactions is now extensive. The whole subject is so complicated as to make things difficult for the potential prescriber. However, it is possible to reduce most of the information contained in the literature to a few simple messages. Firstly, H2-antagonists bind to cytochrome P450 and may inhibit the metabolism of drugs eliminated by the mixed function oxygenase system. In this respect, cimetidine has a marked effect which, in most studies, has reached statistical significance. Ranitidine, on the other hand, has a much weaker effect which, even if demonstrable, is statistically non-significant. The potential benefit of ranitidine, however, has to be weighed against the relative costs of the 2 drugs. Secondly, H2-antagonists inhibit gastric acid production and may alter the rate of gastric emptying, and hence the rate of drug absorption. They may also have some effect on portal vein and hepatic artery flow. However, these effects are small and probably not clinically relevant. Thirdly, pharmacodynamic effects of H2-antagonist-drug interactions are difficult to demonstrate in planned studies, and although they are reported from time to time, adverse reactions of consequence are relatively uncommon. Fourthly, the prescriber needs to be aware that cimetidine may produce higher plasma concentrations of some drugs which have a fairly narrow therapeutic range, and this may be clinically important. Examples of drugs for which it may be undesirable to inadvertently increase plasma concentrations include warfarin, theophylline and phenytoin. Finally, for most drugs metabolised by the liver, the risk of an important interaction is small. However, if such an interaction is noted it may be helpful to refer to the other reported cases, and a number of references are included here.

Triazolam kinetics: interaction with cimetidine, propranolol, and the combination

Nineteen healthy volunteers received a single 0.5-mg oral dose of triazolam on four occasions under the following conditions: (1) triazolam alone; (2) triazolam with cimetidine, 300 mg four times daily; (3) triazolam with propranolol, 40 mg four times daily; (4) triazolam with both cimetidine and propranolol. Triazolam kinetics were determined from multiple plasma concentrations measured during 24 hours after each dose. Compared with control, peak plasma triazolam concentration (Cmax) was significantly increased by cimetidine (5.4 versus 3.9 ng/mL), total area under the plasma concentration curve (AUC) increased (21.3 versus 16.1 ng/mL X hr), and oral clearance decreased (485 versus 668 mL/min). However triazolam half-life was not increased. During propranolol alone, triazolam Cmax (4.1 ng/mL), AUC (14.3 ng/mL X hr), and clearance (759 mL/min) did not differ significantly from control, whereas kinetic variables for triazolam with cimetidine plus propranolol were similar to those with cimetidine alone. Plasma free fraction for triazolam (17 to 18% unbound) did not differ significantly among the four treatment conditions. Mean steady-state plasma cimetidine concentrations during trials 2 and 4 were similar (1.04 versus .98 micrograms/mL), whereas plasma propranolol was significantly higher during cimetidine plus propranolol than with propranolol alone (47 versus 29 ng/ml, P less than .001). Thus cimetidine coadministration significantly inhibits triazolam clearance, causing increased triazolam AUC and Cmax, but without a prolongation in half-life. Propranolol itself does not impair triazolam clearance, nor does propranolol potentiate the inhibitory effect of cimetidine alone.

Interaction of roxatidine acetate with antacids, food and other drugs

The inhibition of hepatic mixed-function oxidase microsomal enzymes by cimetidine can lead to clinically important drug interactions. The metabolism of antipyrine is used as an index of hepatic enzymatic activity. The pharmacokinetic profiles of salivary antipyrine obtained following treatment with roxatidine acetate 75 mg or placebo twice a day for 7 days showed similar characteristics with no difference in the areas under the plasma concentration-time curves. In addition, roxatidine acetate 75 mg daily did not modify the clearance of propranolol, diazepam, desmethyldiazepam or controlled release theophylline preparations. Furthermore, there was no interference in the bioavailability of roxatidine acetate 150 mg daily when administered alone or in combination with a meal or antacids.

Therapeutic approach in patients with concomitant disease/drug--drug interactions (roxatidine acetate)

Possible mechanisms of drug interactions with H2-antagonists are outlined. The mode of action of roxatidine acetate on hepatic microsomal enzymes is contrasted with those of cimetidine and ranitidine, and their differing structure-activity relationships are discussed. In the light of the mechanisms of drug interactions with H2-antagonists, clinical studies with roxatidine acetate are contrasted with published interaction data of cimetidine and ranitidine. The therapeutic consequences of these data are considered.

Comparison of the effectiveness of midazolam and diazepam in lipid emulsion as sedation during upper gastrointestinal endoscopy

In a study of 101 patients undergoing upper gastrointestinal endoscopy, 90% of patients had complete amnesia for the procedure after intravenous midazolam (average dose 10 mg), but only 61% had complete amnesia after intravenous diazepam in lipid emulsion (average dose 18.4 mg) (P = 0.0006). However, when assessed by two different tests, recovery within the first hour was significantly more rapid after diazepam (P less than 0.0001). Prolonged sedation (over 20 hours after injection) was reported occasionally by patients who had received either drug. Thus, as with patients who have been sedated with diazepam, those who have been sedated with midazolam should also be advised to avoid driving or operating machinery for at least 24 hours after injection.

Effect of gradual withdrawal on the rebound sleep disorder after discontinuation of triazolam

Sixty volunteers with insomnia participated in a randomized, double-blind, controlled clinical trial. After an initial six nights of placebo, 30 subjects (the abrupt-withdrawal group) received 0.5 mg of triazolam nightly for 7 to 10 nights, after which they received placebo. The other 30 subjects (the tapered-dosage group) received the same initial placebo treatment, then triazolam at 0.5 mg for seven nights, at 0.25 mg for two nights, and at 0.125 mg for two nights, and then placebo. As compared with the initial placebo period, the triazolam period significantly reduced the interval before the onset of sleep (sleep latency), and it prolonged sleep duration, reduced the number of awakenings, and improved the self-rated soundness of sleep in all cohorts. In the abrupt-withdrawal group, plasma levels of triazolam were undetectable the morning after the first night of placebo substitution, and subjects reported prolongation of sleep latency (57 minutes longer than base line), reduction in sleep duration (1.4 hours less than base line), and increased awakenings (1.2 per night above base line). The symptoms of rebound sleep disorder lasted one or possibly two nights, and there was a reversion toward base line on subsequent placebo nights. In the tapered-dosage group, however, plasma triazolam levels fell gradually to zero, and rebound symptoms were decreased or eliminated. Thus, rebound sleep disorder following abrupt discontinuation of triazolam can be attenuated by a regimen of tapering.

Pharmacokinetic interactions of cimetidine 1987

The number of studies on drug interactions with cimetidine has increased at a rapid rate over the past 5 years, with many of the interactions being solely pharmacokinetic in origin. Very few studies have investigated the clinical relevance of such pharmacokinetic interactions by measuring pharmacodynamic responses or clinical endpoints. Apart from pharmacokinetic studies, invariably conducted in young, healthy subjects, there have been a large number of in vitro and in vivo animal studies, case reports, clinical observations and general reviews on the subject, which is tending to develop an industry of its own accord. Nevertheless, where specific mechanisms have been considered, these have undoubtedly increased our knowledge on the way in which humans eliminate xenobiotics. There is now sufficient information to predict the likelihood of a pharmacokinetic drug-drug interaction with cimetidine and to make specific clinical recommendations. Pharmacokinetic drug interactions with cimetidine occur at the sites of gastrointestinal absorption and elimination including metabolism and excretion. Cimetidine has been found to reduce the plasma concentrations of ketoconazole, indomethacin and chlorpromazine by reducing their absorption. In the case of ketoconazole the interaction was clinically important. Cimetidine does not inhibit conjugation mechanisms including glucuronidation, sulphation and acetylation, or deacetylation or ethanol dehydrogenation. It binds to the haem portion of cytochrome P-450 and is thus an inhibitor of phase I drug metabolism (i.e. hydroxylation, dealkylation). Although generally recognised as a nonspecific inhibitor of this type of metabolism, cimetidine does demonstrate some degree of specificity. To date, theophylline 8-oxidation, tolbutamide hydroxylation, ibuprofen hydroxylation, misonidazole demethylation, carbamazepine epoxidation, mexiletine oxidation and steroid hydroxylation have not been shown to be inhibited by cimetidine in humans but the metabolism of at least 30 other drugs is affected. Recent evidence indicates negligible effects of cimetidine on liver blood flow. Cimetidine reduces the renal clearance of drugs which are organic cations, by competing for active tubular secretion in the proximal tubule of the kidney, reducing the renal clearances of procainamide, ranitidine, triamterene, metformin, flecainide and the active metabolite N-acetylprocainamide. This previously unrecognised form of drug interaction with cimetidine may be clinically important for both parent drug, and metabolites which may be active.(ABSTRACT TRUNCATED AT 400 WORDS)

Determinants of benzodiazepine brain uptake: lipophilicity versus binding affinity

Factors influencing brain uptake of benzodiazepine derivatives were evaluated in adult Sprague Dawley rats (n = 8-10 per drug). Animals received single intraperitoneal doses of alprazolam, triazolam, lorazepam, flunitrazepam, diazepam, midazolam, desmethyldiazepam, or clobazam. Concentrations of each drug (and metabolites) in whole brain and serum 1 h after dosage were determined by gas chromatography. Serum free fraction was measured by equilibrium dialysis. In vitro binding affinity (apparent Ki) of each compound was estimated based on displacement of tritiated flunitrazepam in washed membrane preparations from rat cerebral cortex. Lipid solubility of each benzodiazepine was estimated using the reverse-phase liquid chromatographic (HPLC) retention index at physiologic pH. There was no significant relation between brain:total serum concentration ratio and either HPLC retention (r = 0.18) or binding Ki (r = -0.34). Correction of uptake ratios for free as opposed to total serum concentration yielded a highly significant correlation with HPLC retention (r = 0.78, P less than 0.005). However, even the corrected ratio was not correlated with binding Ki (r = -0.22). Thus a benzodiazepine's capacity to diffuse from systemic blood into brain tissue is much more closely associated with the physicochemical property of lipid solubility than with specific affinity. Unbound rather than total serum or plasma concentration most accurately reflects the quantity of drug available for diffusion.

Actual versus reported benzodiazepine usage by medical outpatients

Benzodiazepines are widely prescribed, and in 1979 almost 10% of the adult population was taking them. Prior studies of outpatient usage of benzodiazepines have relied on survey or prescription data, which may be confounded by noncompliance. To determine the actual use of benzodiazepines, plasma benzodiazepine concentrations were measured in 225 consecutive outpatients from a university cardiology outpatient service. Self reports indicated that the great majority of the patients (191) were taking at least one medicine, and 70 reported being on a psychotropic drug. Seventy-seven patients reported taking benzodiazepines, the majority being on bromazepam (20), diazepam (26) or oxazepam (19). In 25 of those 77 patients, the reported drug could not be detected in plasma. Conversely, in 10 of the 225 patients, benzodiazepines which were not reported were detected (diazepam or flurazepam). Of those taking benzodiazepines, many had a low concentration, suggesting intermittent rather than regular use. Thus, many patients for whom benzodiazepines are prescribed take them irregularly, and a small group uses them without reporting their prescription. These findings have implications for the clinical presentation of illness and for the possibility of drug interactions.

Benzodiazepine hypnotic metabolism: drug interactions and clinical implications

Benzodiazepines are the drugs of choice when initiating hypnotic therapy. Though the mechanism of benzodiazepine action in the central nervous system is similar for all drugs in this class, differences in absorption and pathway of elimination are associated with differences in observed clinical effect. After single-dose administration, onset of hypnotic effect is most closely related to rate of drug absorption and duration of effect is more closely associated with extent of drug distribution. Relative affinity of the individual benzodiazepine for the specific central nervous system binding site may also determine duration of action. During multiple-dose chronic therapy, route of metabolic biotransformation and elimination half-life assume more importance. An increased incidence of adverse drug effects due to high doses of accumulating benzodiazepines may be seen in the elderly and patients with central nervous system deficits or chronic liver disease. Benzodiazepine metabolic biotransformation and clearance is broken into three groups. Group 1--oxidative biotransformation; Group 2--high clearance drugs; Group 3--drug conjugation. Groups 1 and 2 are implicated in a number of drug-disease and drug-drug interactions. Group 3 drugs have little change in patients with liver disease or when administered with inhibitors of drug biotransformation. Clinical implications of these metabolic interactions are variable, but inhibition of Group 1 and 2 benzodiazepine clearance has been associated with increased sedation and psychomotor impairment.