Pharmacokinetics of diazepam in disordered liver function

Pharmacokinetic of antiepileptic drugs in patients with hepatic or renal impairment

Many factors influence choice of antiepileptic drugs (AEDs), including efficacy of the drug for the indication (epilepsy, neuropathic pain, affective disorder, migraine), tolerability, and toxicity. The first-generation AEDs and some newer AEDs are predominately eliminated by hepatic metabolism. Other recent AEDs are eliminated by renal excretion of unchanged drug or a combination of hepatic metabolism and renal excretion. The effect of renal and hepatic disease on the dosing will depend on the fraction of the AED eliminated by hepatic and/or renal excretion, the metabolic isozymes involved, as well as the extent of protein binding, if therapeutic drug monitoring is used. For drugs that are eliminated by renal excretion, methods of estimating creatinine clearance can be used to determine dose adjustments. For drugs eliminated by hepatic metabolism, there are no specific markers of liver function that can be used to provide guidance in dosage adjustments. Based on studies with probe drugs, the hepatic metabolic enzymes are differentially affected depending on the cause and severity of hepatic disease, which can aid in predicting dose adjustment when clinical data are not available. Several AEDs are also associated with laboratory markers of mild hepatic dysfunction and, rarely, more severe hepatic injury. In contrast, the risk of renal injury from AEDs is generally low. In general, co-morbid hepatic or renal diseases influence the decision for the selection of an AED. For some patients dosing changes to their existing AEDs may be appropriate. For others, a change to another AED may be a better option.

Drug-Induced Liver Disease and Drug Use Considerations in Liver Disease

Chronic liver disease encompasses a large number of hepatic disorders. One of the most important etiologies of liver disease is drug-induced liver disease, which is the leading cause of liver failure in patients referred for liver transplantation in the United States. Drug-induced liver disease can present in all forms of acute and chronic liver disease with highly variable clinical presentations. There is no effective treatment for most drug-induced liver disease and the recognition and prevention of drug-induced liver disease remain the most important management strategy. Drug dosing in patients with liver disease represents an even more challenging task to clinicians, as there is only scant information on biomarkers that can be used to predict the pharmacokinetic changes of drugs in patients with underlying liver disease. Several factors contribute to alterations in drugs metabolism and clearance in cirrhotic patients, including the severity of the liver disease and the metabolic pathways of each individual drug. Only general guidelines on dosage adjustment in patients with hepatic impairment are available. When drugs with extensive hepatic metabolism are required in patients with preexisting liver disease, benefit of therapeutic effect must be evaluated against the risk of toxicity, and the drugs must be initiated with extreme caution with appropriate dosage reduction.

Dose adjustment in patients with liver disease

Unfortunately, there is no endogenous marker for hepatic clearance that can be used as a guide for drug dosing. In order to predict the kinetic behaviour of drugs in cirrhotic patients, agents can be grouped according to their extent of hepatic extraction. For drugs with a high hepatic extraction (low bioavailability in healthy subjects), bioavailability increases and hepatic clearance decreases in cirrhotic patients. If such drugs are administered orally to cirrhotic patients, their initial dose has to be reduced according to hepatic extraction. Furthermore, their maintenance dose has to be adapted irrespective of the route of administration, if possible, according to kinetic studies in cirrhotic patients. For drugs with a low hepatic extraction, bioavailability is not affected by liver disease, but hepatic clearance may be affected. For such drugs, only the maintenance dose has to be reduced, according to the estimated decrease in hepatic drug metabolism. For drugs with an intermediate hepatic extraction, initial oral doses should be chosen in the low range of normal in cirrhotic patients and maintenance doses should be reduced as for high extraction drugs. In cholestatic patients, the clearance of drugs with predominant biliary elimination may be impaired. Guidelines for dose reduction in cholestasis exist for many antineoplastic drugs, but are mostly lacking for other drugs with biliary elimination. Dose adaptation of such drugs in cholestatic patients is, therefore, difficult and has to be performed according to pharmacological effect and/or toxicity. Importantly, the dose of drugs with predominant renal elimination may also have to be adapted in patients with liver disease. Cirrhotic patients often have impaired renal function, despite a normal serum creatinine level. In cirrhotic patients, creatinine clearance should, therefore, be measured or estimated to gain a guideline for the dosing of drugs with predominant renal elimination. Since the creatinine clearance tends to overestimate glomerular filtration in cirrhotic patients, the dose of a given drug may still be too high after adaptation to creatinine clearance. Therefore, the clinical monitoring of pharmacological effects and toxicity of such drugs is important. Besides the mentioned kinetic changes, the dynamics of some drugs is also altered in cirrhotic patients. Examples include opiates, benzodiazepines, NSAIDs and diuretics. Such drugs may exhibit unusual adverse effects that clinicians should be aware of for their safe use. However, it is important to realise that the recommendations for dose adaptation remain general and cannot replace accurate clinical monitoring of patients with liver disease treated with critical drugs.

An overview of psychiatric issues in liver disease for the consultation-liaison psychiatrist

Liver disease is a common cause of morbidity and mortality in the United States and elsewhere. Arising from infectious, hereditary, or toxin-induced sources, the detection of liver disease often requires a high index of suspicion. Clinical presentations are highly variable and are often accompanied by neuropsychiatric symptoms. This fact, along with an increased incidence of liver disease among patients with primary psychiatric disorders and the presence of varied drug use, complicates the tasks of providing care to patients with liver disease. To assist the consultation-liaison psychiatrist, the authors present the first of a two-part series focused on psychiatric issues in liver disease.

Antiepileptic drugs and liver disease

Antiepileptic drugs (AEDs) are no longer restricted to the treatment of epilepsy. These are widely used in a broad spectrum of psychiatric and neurological disorders. Liver plays a major role in the metabolism of a majority of these drugs. Hepatotoxicity is rare, but a real concern when initiating therapy. Likewise, liver disease can adversely affect the biotransformation of some of these drugs. This manuscript addresses the significance of elevated liver enzymes associated with AED use, the role of therapeutic drug monitoring, pharmacokinetics during liver disease and potential risk of hepatotoxicity.

The role of diazepam in the treatment of nerve agent poisoning in a civilian population

The main site of action of diazepam, as with other benzodiazepines, is at the GABA(A) receptor, although it has been suggested that some of the potentially beneficial actions of diazepam in nerve agent poisoning are mediated through other means. It is likely that convulsions may have long-term sequelae in the central nervous system, because of damage by anoxia and/or excitotoxicity. Numerous pharmacodynamic studies of the action of diazepam in animals experimentally poisoned with nerve agents have been undertaken. In nearly all of these, diazepam has been studied in combination with other antidotes, such as atropine and/or pyridinium oximes, sometimes in combination with pyridostigmine pretreatment. These studies show that diazepam is an efficacious anticonvulsant in nerve agent poisoning. There is considerable experimental evidence to support the hypothesis that diazepam (and other anticonvulsants) may prevent structural damage to the central nervous system as evidenced by neuropathological changes such as neuronal necrosis at autopsy. In instances of nerve agent poisoning during terrorist use in Japan, diazepam seems to have been an effective anticonvulsant. Consequently, the use of diazepam is an important part of the treatment regimen of nerve agent poisoning, the aim being to prevent convulsions or reduce their duration. Diazepam should be given to patients poisoned with nerve agents whenever convulsions or muscle fasciculation are present. In severe poisoning, diazepam administration should be considered even before these complications occur. Diazepam is also useful as an anxiolytic in those exposed to nerve agents.

Diazepam in the treatment of organophosphorus ester pesticide poisoning

Although the main site of action of diazepam, as with other benzodiazepines, is at the gamma-aminobutyric acid A (GABAA) receptor, the degree to which the beneficial actions of diazepam in organophosphorus (OP) ester pesticide poisoning are mediated through the GABAA receptor has been a matter of controversy. Although in most series of OP intoxications, convulsions have been relatively uncommon, it is probable that convulsions produce long-term sequelae in the central nervous system by causing structural damage. Animal studies have demonstrated that diazepam prevents and treats convulsions produced by OPs and may prevent the late effects caused by damage to the central nervous system induced by such convulsions. Consequently, the use of diazepam is an important part of the treatment regimen of severe OP poisoning as it prevents, or at least reduces the duration of, convulsions. In addition, case reports suggest that diazepam will also ameliorate muscle fasciculation, a subjectively unpleasant feature of OP pesticide poisoning. There are no data, either experimental or clinical, demonstrating any clear effect of diazepam alone on lethality in OP poisoning. In fact, in one study of large animals, diazepam, given alone, increased lethality. In animals experimentally poisoned with OPs, combined treatment with atropine and diazepam significantly lowered lethality compared with atropine treatment alone, indicating a clear beneficial effect. There are numerous case reports of the use of diazepam, generally as an adjunct to other more specific OP antidotes such as atropine and/or pyridinium oximes. Based on this evidence and pharmacodynamic studies in experimental animals, diazepam should be given to patients poisoned with OPs whenever convulsions or pronounced muscle fasciculation are present. In severe poisoning, diazepam administration should be considered even before these complications develop. Although diazepam has a large therapeutic index, there appears to be no place for its routine use in OP poisoning. Diazepam should be given intravenously to patients treated in hospital for OP poisoning, although the intramuscular route is used to administer diazepam outside hospital, such as on the battlefield, when an auto-injector is employed. It should be recognised, however, that absorption by the intramuscular route is poor.

Effects of liver disease on the pharmacokinetics of intravenous and oral chlordesmethyldiazepam

We studied the pharmacokinetics of a single 0.5-mg i.v. dose of chlordesmethyldiazepam in 8 patients with liver disease and in 12 age-matched healthy controls. The kinetics were also studied of a single 1-mg oral dose in the patients with liver disease. After i.v. administration the kinetics of total chlordesmethyldiazepam in patients with liver disease differed from those in controls: elimination half-life was almost twice that in controls (395 and 204 h), as a consequence of a marked reduction in total clearance (0.13 and 0.25 ng.ml-1.h-1), whereas the apparent volume of distribution was similar in patients and controls (4.7 and 3.9 l/kg-1). The free fraction of the drug in patients was higher (5.5%) than in controls (2.9%). Correction for differences in protein binding revealed clearance in the patients was one-fifth (1.8 and 10.5 ng ml-1.kg-1) and volume of distribution one-half (65.0 and 118.4 l.kg-1) that in controls. The systemic availability of oral chlordesmethyldiazepam was high (110%) in spite of a relatively slow absorption rate. These results indicate a need for caution in the administration of chlordesmethyldiazepam to patients with liver disease.

Assessment of liver metabolic function. Clinical implications

Inter- and intraindividual variability in pharmacokinetics of most drugs is largely determined by variable liver function as described by parameters of hepatic blood flow and metabolic capacity. These parameters may be altered as a result of disease affecting the liver, genetic differences in metabolising enzymes, and various types of drug interactions, including enzyme induction, enzyme inhibition or down-regulation. With the now known large number of drug metabolising enzymes, their differential substrate specificity, and their differential induction or inhibition, each test substance of liver function should be used as a probe for its specific metabolising enzyme. Thus, the concept of model test-substances providing general information about liver function has severe limitations. To test the metabolic activity of several enzymes, either several test substances may be given (cocktail approach) or several metabolites of a single test substance may be analysed (metabolic fingerprint approach). The enzyme-specific analysis of liver function results in a preference for analysis of the metabolites rather than analysis of the clearance of the parent test substance. There are specific methods to quantify the activity of cytochrome P450 enzymes such as CYP1A2, CYP2C9, CYP2C19MEPH, CYP2D6, CYP2E1, and CYP3A, and phase II enzymes, such as glutathione S-transferases, glucuronyl-transferases or N-acetyltransferases, in vivo. Interactions based on competitive or noncompetitive inhibition should be analysed specifically for the cytochrome P450 enzyme involved. At least 5 different types of cytochrome P450 enzyme induction may result in major variability of hepatic function; this may be quantified by biochemical parameters, clearance methods, or highly enzyme-specific methods such as Western blot analysis or molecular biological techniques such as mRNA quantification in blood and tissues. Therapeutic drug monitoring is already implicitly used for quantification of the enzyme activities relevant for a specific drug. Selective impairment of hepatic enzymes due to gene mutations may have an effect on the pharmacokinetics of certain drugs similar to that caused by cirrhosis. Assessment of this heritable source of variability in liver function is possible by in vivo or ex vivo enzymological methods. For genetically polymorphic enzymes and carrier proteins involved in drug disposition, molecular genetic methods using a patient's blood sample may be used for classification of the individual into: (i) the impaired or poor metaboliser (homozygous deficient); (ii) the extensive (homozygous active) metaboliser group; and (iii) the moderately extensive metaboliser (heterozygous) group. For hepatic blood flow determinations, galactose or sorbitol given at relatively low doses may be much better indicators than the indocyanine green.(ABSTRACT TRUNCATED AT 400 WORDS)

Benzodiazepine poisoning. Clinical and pharmacological considerations and treatment

Benzodiazepines are among the most frequently prescribed drugs worldwide. This popularity is based not only on their efficacy but also on their remarkable safety. Pure benzodiazepine overdoses usually induce a mild to moderate central nervous system depression; deep coma requiring assisted ventilation is rare, and should prompt a search for other toxic substances. The severity of the CNS depression is influenced by the dose, the age of the patient and his or her clinical status prior to the ingestion, and the coingestion of other CNS depressants. In severe overdoses, benzodiazepines can occasionally induce cardiovascular and pulmonary toxicity, but deaths resulting from pure benzodiazepine overdoses are rare. Quantitative determinations of benzodiazepines are not useful in the clinical management of intoxicated patients since there is no correlation between serum concentrations and pharmacological and toxicological effects. Benzodiazepine overdoses occurring during pregnancy rarely induce serious morbidity in mothers or fetuses, although large doses administered near delivery can induce respiratory depression in neonates. The teratogenic potential of benzodiazepines remains controversial, but is probably small if it exists at all. There is clear evidence that the prolonged use of even therapeutic doses of benzodiazepines will lead to dependence. The risk of developing significant withdrawal symptoms is related to dosage and duration of treatment. Prevention of gastrointestinal absorption should be initiated in all intentional benzodiazepine overdoses. Forced diuresis and dialysis techniques are not indicated since they will not significantly accelerate the elimination of these agents. Intravenous administration of flumazenil, a pure benzodiazepine antagonist, effectively reverses benzodiazepine-induced CNS depression.

Psychopharmacology in patients with hepatic and gastrointestinal disease

Psychotropic drugs often need to be prescribed to patients who also have pre-existing gastrointestinal (GI) and/or hepatic disease. This paper addresses the effect of GI and hepatic disease on the pharmacokinetics of psychotropic drugs, the effect of psychotropic drugs on pre-existing GI and hepatic diseases, the adverse GI and hepatic effects of psychotropic medications, the effects of GI medications on mental status, and the potential drug interactions between commonly prescribed GI medications and psychotropic drugs. Drug selection and dosage modification based on these considerations should allow safe and effective psychotropic treatment for patients with pre-existing GI and/or hepatic disease.

Sedation for gastroscopy: a comparative study of midazolam and Diazemuls in patients with and without cirrhosis

A double-blind controlled study comparing the effects of intravenous Diazemuls (0.15 mg kg-1) with midazolam (0.07 mg kg-1) in patients with normal liver function and with cirrhosis and portal hypertension is described. The clinical effect of the two drugs was assessed by serial tests of psychomotor function before and at varying intervals after administration. Using this dosage regime, midazolam caused significantly greater impairment in psychomotor function in both cirrhotic and non cirrhotic subjects, and the time taken for recovery of normal function was also significantly prolonged. Patients with cirrhosis showed a significantly prolonged recovery time following administration of either benzodiazepine compared with the controls. Administration of midazolam in a lower dose might reduce the degree of sedation and shorten the recovery time, but this could also lead to a loss of some of the amnesic effect. Caution is recommended in the administration of benzodiazepines to patients with cirrhosis.

Effect of cirrhosis and renal failure on the kinetics of clotiazepam

The kinetics of a single 5-mg oral dose of the thienodiazepine clotiazepam was evaluated in a series of patients with biopsy-proven cirrhosis, and in patients with renal insufficiency requiring maintenance hemodialysis, compared to healthy matched controls. Clotiazepam volume of distribution (Vz) was significantly smaller in cirrhotic patients than in controls (1.83 vs 2.57 l/kg), and total clearance was likewise reduced (2.15 vs 3.15 ml/min/kg). Elimination half-life was similar between groups (10.0 vs. 10.2 h). There were no significant differences between renal failure and control patients in clotiazepam Vz, oral clearance, or elimination half-life. Thus cirrhosis is associated with reduced clearance of clotiazepam, probably due to impairment of its microsomal oxidation. However clotiazepam disposition is not significantly altered in dialysis-dependent renal insufficiency patients.

Comparative pharmacokinetics and cardiovascular effects of tiapamil in healthy volunteers and patients with hepatic cirrhosis

Tiapamil 70 mg was administered i.v. to 8 healthy male volunteers and 8 patients (7 males, 1 female) with biopsy proven hepatic cirrhosis. Two of the patients also received 600 mg p.o. Serial plasma and urine samples were collected and the parent drug in plasma and urine and desmethyl-tiapamil in urine were assayed by a specific HPLC method. The plasma and urine data for the parent drug after i.v. and p.o. dosing were simultaneously fitted to linear p.o. and i.v. two compartment models with exit from and input into the central compartment. Absorption was assumed to be a first order process. In the volunteers the mean pharmacokinetic parameters were: 101 l for the steady-state volume of distribution 750 ml X min-1 for nonrenal clearance, 195 ml X min-1 for renal clearance and 1.7 h for the half-life of the terminal disposition phase. The urinary recoveries of the parent drug and desmethyltiapamil averaged 21.4 and 0.8% of the dose, respectively. In the patients the steady-state volume of distribution, the amount of unchanged drug in urine and the half-life of the terminal disposition phase were significantly increased (171 l, 29.0% of the dose, 3.5 h, respectively). Decreased plasma protein binding in the patients accounted for the larger steady-state volume of distribution. The nonrenal clearance of 519 ml X min-1, tended to be smaller in the patients than in the volunteers. Together with the increased urinary recovery of tiapamil in the patients this indicates a moderately impaired elimination capacity in the cirrhotics.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of an experimental liver cirrhosis upon the metabolism of diazepam and imipramine hydrochloride in the rat

When either diazepam or imipramine hydrochloride was administered orally to rats with thioacetamide-induced hepatic cirrhosis, the biliary and faecal elimination of metabolites was significantly decreased compared with that in normal animals. However, renal excretion of metabolites of diazepam or imipramine was increased in the liver-damaged rats. Experiments in vitro showed that liver homogenates from cirrhotic rats metabolized diazepam or imipramine hydrochloride in qualitatively and quantitatively similar ways to those from normal rats. Clearance of radioactivity from the blood following i.v. administration of either diazepam or imipramine hydrochloride was prolonged in animals with experimental cirrhosis.

Binding and disposition of sulfisoxazole in alcoholic cirrhosis

The disposition of sulfisoxazole was studied in six male patients hospitalized with biopsy-proven Laennec's alcoholic cirrhosis and six normal, healthy volunteers. Four of the patients were restudied at a time their liver disease had improved clinically. On the average, compared to the normal group, the metabolism of sulfisoxazole (clearance values with respect to unbound concentration values) appears to be unaltered for the cirrhotic patients. For patients with alcoholic cirrhosis having normal renal function for age and weight, the renal elimination of sulfisoxazole was normal. For those subjects with decreased renal function, the renal clearance of sulfisoxazole appeared to be disproportionately decreased, as evidenced by a lower-than-normal sulfisoxazole renal clearance-to-creatinine clearance values. The apparent steady-state volume of distribution of unbound sulfisoxazole was not altered in cirrhotic patients when compared to normal subjects, while the apparent volume of distribution of total drug increased by more than what could be expected from protein binding changes alone. The elimination rate constant did not differ from values found in normals. These data suggest that the total binding capacity of sulfisoxazole in cirrhotic patients is not different from that of normal subjects.

The influence of age and multimorbidity on the pharmacokinetics and metabolism of spironolactone

The pharmacokinetics of the metabolites of spironolactone (canrenone and fluorigenic metabolites) were investigated in 10 geriatric female patients with multimorbidity after a multiple daily oral administration of 100 mg spironolactone under steady state conditions. The concentration determinations were carried out simultaneously with a specific HPLC method and a less specific fluorimetric method. On comparison of the pharmacokinetic parameters with the respective values of a control group of younger healthy female subjects, the serum concentrations in the elderly patients were found to be twice as high. In addition, a statistically significant positive correlation with age was found in the patients for the kinetic parameters investigated. A positive correlation existed between erythrocyte count and the pharmacokinetic parameters of canrenone, especially with the area under the concentration/time curve. No such association was detectable, however, for the total fraction of fluorigenic metabolites (including canrenone). The results of our investigation indicate that, in addition to the known high binding of canrenone to plasma proteins, there is also possibly a (restrictive) binding to erythrocytes.

Plasma concentrations of benzodiazepines--a review of clinical findings and implications

Methods for benzodiazepine analysis are briefly discussed and the pharmacokinetics of the benzodiazepines reviewed. Studies of the relationship between plasma concentration and anxiolytic response have produced conflicting results. Routine monitoring in anxiety states is not warranted. Some specific indications for monitoring are in elderly patients; in cases of suspected non-compliance; in patients with renal and hepatic disease. The relationship between plasma concentration and ECG changes following benzodiazepine overdose showed that monitoring was of little value in these cases.

Serum protein binding of diazepam in maternal and foetal serum during pregnancy

1 The serum binding capacity for diazepam was significantly lower in pregnancy and there was a linear correlation with gestational age. 2 The binding of diazepam was not correlated to albumin during pregnancy. 3 In cord sera there was a significantly reduced binding capacity for diazepam with albumin levels of less than 40 g/l.

Drugs as indicators of hepatic function

It is well recognized that liver disease may influence the disposition of many drugs. Conversely, it has been suggested that knowledge of the disposition of a model drug might provide an index of certain aspects of hepatic function. This review discusses the physiology of drug disposition and indicates how recent progress in understanding the determinants of drug disposition has provided useful indices of individual aspects of hepatic function. Topics which are discussed are the interpretation of pharmacokinetic parameters as indices of hepatic function, including half-life clearance, and intrinsic clearance. Utilizing the "intact hepatocyte hypothesis" as an operational model, an approach is described that uses the pharmacokinetic disposition of high and low intrinsic clearance drugs following p.o. and i.v. administration to provide quantitative estimates of hepatic function, flow to functioning hepatocytes, and the extent of portasystemic shunting through the liver. Thus, the theoretical basis for quantitation of certain aspects of hepatic function are available. It remains to be determined whether these indices will provide clinically useful measures to follow the natural history of hepatic disease.

Diurnal variations in plasma diazepam concentrations associated with reciprocal changes in free fraction

1 The characteristics and mechanism of fluctuations in diazepam and N-desmethyldiazepam concentrations and diazepam free fraction were studied in six volunteers, who received diazepam (10 mg, i.v. over 20 min) and in five chronic diazepam users. 2 Within a day total diazepam and N-desmethyldiazepam concentrations varied significantly (P less than 0.001) and were lower than predicted between 23.00 and 08.00 h and higher by 09.00 h. In contrast, diazepam free fraction also varied significantly (P less than 0.001) and was highest between 23.00 and 08.00 h and lower by 09.00 h. Coincident increases in total diazepam concentrations (P less than 0.005) and decreases in diazepam free fraction were associated with food intake (P less than 0.05). 3 The coincident diurnal variations in diazepam and N-desmethyldiazepam concentrations and the negative correlation between total diazepam concentration and diazepam free fraction (r = 0.73, P less than 0.001) suggest that the mechanism of the fluctuations is intravascular and tissue redistribution rather than effect on drug biotransformation. 4 These variations may introduce large between and within investigator experimental differences in the determination of kinetic parameters. Free drug concentration varies over the day, and within day variations in clinical effect may be observed.

A radioreceptor assay for benzodiazepines

A simple, rapid and sensitive radioreceptor assay for determining benzodiazepines in serum is based on the displacement by the drug of specific [3H]diazepam binding to a membrane fraction from rat brain. The limit of detection of the more active benzodiazepines is about 0.5 ng. Diazepam, nitrazepam, clobazam and HR 458 have been assayed in human serum after a single oral clinical dose. The results can be used for determining pharmacokinetic parameters. The technique measures not only the parent benzodiazepine but also clinically active metabolites.

Barbital and diazepam plasma levels during treatment of delirium tremens

Plasma concentrations of barbital and diazepam were measured daily during a double-blind study of the efficacy of the two drugs in the treatment of delirium tremens and less severe clinical states. Treatment was estimated as satisfactory in the majority of cases; the present study deals with the satisfactory groups only. Both in the barbital group and in the diazepam group the same plasma level was seen in different clinical states. This result is discussed in relation to the theories about the aetiology of delirium tremens, and it is concluded that the data fits best with the assumption that delirium tremens is released from a withdrawal state, but once established, the delirious state is not interrupted by the drugs. The barbital concentrations were rather high, many at a level where non-alcoholics would show pronounced intoxication symptoms not seen in the present material. The diazepam concentrations on the other hand were low, often below a level where a cerebral effect is measurable in normal subjects. On this basis it is concluded, that the two drugs have different modes of action. Barbital may act by its cross-dependence properties with alcohol and thus diminish the withdrawal reaction, whereas diazepam may act by its anti-anxiety effect, but not in the doses here applied, by cross-dependence properties with alcohol. Finally, this hypothesis is discussed in relation to clinical experience in the treatment of delirium tremens.

[Clinical pharmacokinetics of diazepam and its biologically active metabolites (author's transl)]

The pharmacokinetics of diazepam and its biologically active metabolites desmethyldiazepam and oxazepam is critically evaluated from a clinically relevant point of view. The slow elimination of diazepam is dependent on the degree of plasma protein binding, the duration of the medication, the age and the liver function of the patient. While the normal half-life (T1/2(beta)) varies between 1 and 2 days, it can be increased to up to 80--100 h in subjects over 60 years of age. In patients with liver disease T1/2(beta) is about doubled, which is caused by a reduction (factor 2) of the normal hepatic clearance of 26 ml/min. After subchronic treatment with diazepam the elimination rate is reduced about 20--70% in healthy subjects, but liver patients exhibit only a slightly further prolongation in T1/2(beta). The major metabolite desmethyldiazepam has a T1/2(beta) of 51 h and a Cl of 11 ml/min and accumulates after multiple doses of diazepam since its elimination is much slower than that of its parent compound. The elimination of this drug is also impaired (factor 2) in patients with liver disease. In contrast to these findings oxazepam is excreted as glucuronide in the urine relatively fast and independently of the liver function with a T1/2(beta) of 5.5 h and a Cl of 130 ml/min.

Hepatotoxicity in patients with liver disease

The biochemical and physiological disturbances caused by liver disease may enhance the toxicity of drugs. Besides alterations in liver blood flow and drug binding, a decreased rate of drug metabolism is an important phenomenon. Studies with phenazone, a model drug, demonstrates that the rate of microsomal drug metabolism is related to the degree of metabolic hepatic impairment. Individual dosage adjustments in patients with liver disease are complicated for many drugs, because of the counteracting influences of a decreased hepatic blood clearance and an increased free fraction of drug which may enhance drug metabolism and drug action. Moreover, many drugs owe part of their pharmacological action to active metabolites formed in the liver. Finally, little is known about altered receptor sensitivity in patients with liver disease. Non-predictable hepatotoxic reactions appear not to occur more frequently in patients with liver disease than in other patients. However, hepatotoxicity may be masked by the liver disease or by the intake of ethanol.

Plasma nitrazepam concentrations after an acute intake and their correlation to sedation and serum growth hormone levels

Concentrations of nitrazepam in plasma were determined by gas chromatography in healthy volunteers after an acute peroral administration of nitrazepam (5 and 10 mg). Placebo tablets were also used, and an assessement of subjective drug effects was made during each medication. In addition serum growth hormone levels were determined. The peak plasma nitrazepam concentration was achieved at 120 minutes (46.9 +/- 3.2 ng/ml, mean +/- S.E.M.) after 5 mg of nitrazepam and at 180 minutes (82.8 +/- 10.5 ng/ml) after the dose of 10 mg. The half-life of nitrazepam in plasma ranged from 16.5 to 48.3 (mean 28.8) hours. A significant positive correlation was seen between the subjective sedative effects and the magnitude of the peak nitrazepam concentrations in plasma. This drug effect was highly significant when the plasma levels of nitrazepam were rising. The subjective sedative effects were more prominent after 10 mg than after 5 mg dose of nitrazepam. The plasma nitrazepam concentration was not significantly correlated with the subjective sedative effect the next morning, 12 hours after the drug intake. Serum growth hormone levels rose significantly during the study both after 5 mg and 10 mg nitrazepam doses (peak levels 16.3 +/- 4.0 and 12.7 +/- 3.1 ng/ml) and were significantly higher than after placebo administration (3.7 +/- 0.7 ng/ml).

Neuropsychologic effects of diazepam related to single dose kinetics and liver function

The neurophysiologic and neuropsychologic effects and their relation to the kinetics of diazepam (DZ) were studied in 10 patients with impaired liver function of various degrees and in three normal subjects after 10 mg DZ i.v. The plasma concentration data were treated according to a two-compartment open model. Neurophysiologic effect measurements were obtained from galvanic skin response, continuous reaction times (CRT), heart rate, and averaged evoked potentials; neuropsychologic measurements were obtained from trail making A + B, hidden pattern, word fluency, and subtraction tests; in addition, clinical effects were rated by Beechers Mood Scale and Spielbergers Anxiety Scale. Except for trail making A and word fluency all tests discriminated well between the experimental conditions with or without diazepam. No difference from normal in the response to acute diazepam administration could be detected in patients with reduced liver function. A linear correlation between prolongation in CRT and DZ log plasma concentration was demonstrated in the entire, heterogenous patient material. In the clinical ratings only items of a predominantly sedative and autonomic significance responded to the diazepam injection, while predominantly anxiolytic items did not.