Pharmacokinetic and clinical observations on prolonged administration of flunitrazepam

Pharmacological Augmentation in Unipolar Depression: A Guide to the Guidelines

BACKGROUND

Pharmacological augmentation is a recommended strategy for patients with treatment-resistant depression. A range of guidelines provide advice on treatment selection, prescription, monitoring and discontinuation, but variation in the content and quality of guidelines may limit the provision of objective, evidence-based care. This is of importance given the side effect burden and poorer long-term outcomes associated with polypharmacy and treatment-resistant depression. This review provides a definitive overview of pharmacological augmentation recommendations by assessing the quality of guidelines for depression and comparing the recommendations made.

METHODS

A systematic literature search identified current treatment guidelines for depression published in English. Guidelines were quality assessed using the Appraisal of Guidelines for Research and Evaluation II tool. Data relating to the prescription of pharmacological augmenters were extracted from those developed with sufficient rigor, and the included recommendations compared.

RESULTS

Total of 1696 records were identified, 19 guidelines were assessed for quality, and 10 were included. Guidelines differed in their quality, the stage at which augmentation was recommended, the agents included, and the evidence base cited. Lithium and atypical antipsychotics were recommended by all 10, though the specific advice was not consistent. Of the 15 augmenters identified, no others were universally recommended.

CONCLUSIONS

This review provides a comprehensive overview of current pharmacological augmentation recommendations for major depression and will support clinicians in selecting appropriate treatment guidance. Although some variation can be accounted for by date of guideline publication, and limited evidence from clinical trials, there is a clear need for greater consistency across guidelines to ensure patients receive consistent evidence-based care.

Benzodiazepines Drive Alteration of Chromatin at the Integrated HIV-1 LTR

Antiretroviral therapy (ART) lowers human immunodeficiency virus type 1 (HIV-1) viral load to undetectable levels, but does not eliminate the latent reservoir. One of the factors controlling the latent reservoir is transcriptional silencing of the integrated HIV-1 long terminal repeat (LTR). The molecular mechanisms that control HIV-1 transcription are not completely understood. We have previously shown that RUNX1, a host transcription factor, may play a role in the establishment and maintenance of HIV-1 latency. Prior work has demonstrated that inhibition of RUNX1 by the benzodiazepine (BDZ) Ro5-3335 synergizes with suberanilohydroxamic acid (SAHA) to activate HIV-1 transcription. In this current work, we examine the effect of RUNX1 inhibition on the chromatin state of the integrated HIV-1 LTR. Using chromatin immunoprecipitation (ChIP), we found that Ro5-3335 significantly increased the occupancy of STAT5 at the HIV-1 LTR. We also screened other BDZs for their ability to regulate HIV-1 transcription and demonstrate their ability to increase transcription and alter chromatin at the LTR without negatively affecting Tat activity. These findings shed further light on the mechanism by which RUNX proteins control HIV-1 transcription and suggest that BDZ compounds might be useful in activating HIV-1 transcription through STAT5 recruitment to the HIV-1 LTR.

Concentrations of scheduled prescription drugs in blood of impaired drivers: considerations for interpreting the results

We report the concentrations of scheduled prescription drugs in blood samples from people arrested in Sweden for driving under the influence of drugs (DUID). The investigation covered a 2 year period 2004 (N = 7052 cases) and 2005 (N = 7759 cases) and was prompted by recent legislation stipulating zero-concentration limits in blood for controlled substances. However, prescription drugs are exempt from the zero-limit law provided that the medication was being used in accordance with a doctor's prescription. The blood concentrations of various psychoactive substances were compared with the limits of quantitation of the analytic method used and the so-called therapeutic concentration range according to various reference books and tabulations. Diazepam [N = 1950 (26%)] and nordazepam [N = 2168 (28%)] were the therapeutic agents most frequently identified in these forensic blood samples along with other benzodiazepines such as alprazolam [N = 430 (5.6%)], flunitrazepam [N = 308 (4.0%)], and nitrazepam [N = 222 (2.9%)]. The newer hypnotics, exemplified by zolpidem [N = 148 (1.9%)] and zopiclone [N = 111 (1.5%)], were also high on the list of psychoactive substances identified. Interpreting the concentration of a prescription drug in blood in relation to whether the person had taken an overdose or was abusing the substance in question is not always easy. The age, gender, degree of obesity, and ethnicity of the person concerned; the pharmacokinetic profile of the drug; polymorphism of drug-metabolizing enzymes as well as liver and kidney function and blood hematocrit need to be considered. Among preanalytic factors, stability of the drug in blood after sampling, the type of tubes and preservatives used, the dosage form and route of administration deserve consideration. When therapeutic drug monitoring concentrations are compared with forensic toxicology results, then the plasma-to-whole blood distribution ratio of the drug also needs to be considered. In blood samples from DUID suspects, the concentrations of many commonly used sedatives and hypnotics exceeded the accepted therapeutic limits, which gives an indication of the abuse potential of these types of medications.

The role of cytochrome P450 2C19 activity in flunitrazepam metabolism in vivo

Flunitrazepam, a hypnotic benzodiazepine, is widely prescribed around the world for the treatment of insomnia and as a preanesthetic. In vitro studies have shown that the metabolism of flunitrazepam to desmethylflunitrazepam and 3-hydroxyflunitrazepam is mediated in part by the polymorphic enzyme CYP2C19. The objective was to examine the role of CYP2C19 activity in determining flunitrazepam kinetics in vivo. Sixteen healthy volunteers (14 genotypic extensive metabolizers and 2 poor metabolizers) were recruited who had a wide range of CYP2C19 activity (0.50-28.8), as determined by the omeprazole/ 5-hydroxyomeprazole ratio (OMR) at 3 hours following administration of omeprazole, 20 mg orally. Each subject received flunitrazepam, 1 mg orally. Blood samples were collected immediately before and up to 48 hours after drug administration and were assayed by HPLC for flunitrazepam and its metabolites, 7-aminoflunitrazepam, desmethylflunitrazepam, and 3-hydroxyflunitrazepam. Spearman correlations were determined for OMR and pharmacokinetic parameters. With increasing OMR (decreasing CYP2C19 activity), the ratio of flunitrazepam to both desmethylflunitrazepam and 3-hydroxyflunitrazepam AUCs increased ( r = 0.55, p = 0.03 and r = 0.65, p = 0.01, respectively). However, variation in CYP2C19 activity did not significantly affect the AUCs of flunitrazepam or its metabolites. The authors conclude that CYP2C19 contributes to the metabolism of flunitrazepam to desmethylflunitrazepam and 3-hydroxyflunitrazepam in vivo, but these data suggest that its role is minor and that differences in CYP2C19 activity do not likely substantially influence its clinical effects.

Simultaneous determination of flunitrazepam and its metabolites in plasma and urine by HPLC/DAD after solid phase extraction

A high performance liquid chromatography (HPLC) assay was developed for the determination of flunitrazepam (FNZ) and its metabolites in urine and plasma. The analytes and the internal standard (triazolam, TRZ) were extracted by Sep-Pak C18 SPE-cartridge and separated utilizing a 5 microm ChromSpher C8 glass column with a gradient mobile phase containing methanol and 0.125% (v/v) of isopropylamine in water. Diode array detection (DAD) was carried out at a monitoring wavelength of 240 nm and a reference wavelength of 550 nm. Standard curves were linear from their quantitation limits until 200 ng ml(-1) urine or 250 ng ml(-1) plasma for 7-amino-desmethyl-flunitrazepam (ADF), 7-amino-flunitrazepam (AF), 7-acetamino-flunitrazepam (ACF) and until 400 ng ml(-1) urine or 500 ng ml(-1) plasma for FNZ, 1-desmethyl-flunitrazepam (DF), and 3-hydroxyl-flunitrazepam (HF). The intraday and interday coefficients of variation ranged from 2.04 to 9.07% and from 2.64 to 14.10%, respectively in urine and from 5.13 to 8.60% and from 7.27 to 10.46%, respectively in plasma. The developed method is used in forensic toxicology and is also applicable to pharmacokinetic studies in man.

Abuse liability of flunitrazepam

Flunitrazepam is among the most frequently prescribed hypnotics in many countries. Although it was never marketed in the United States, flunitrazepam, in recent years, has been smuggled into the country, and reports of abuse--including alleged use of the drug to facilitate "date rape"--have attracted a great deal of scrutiny. It has been suggested that flunitrazepam may have greater liability for abuse than other benzodiazepines; such suggestions are supported by surveys of opioid abusers, many of whom report a distinct preference for flunitrazepam over other benzodiazepines. Experimental studies of animals and normal human subjects indicate that, although flunitrazepam has high efficacy and is very potent, it is pharmacologically similar to most other benzodiazepines. Although the studies are limited in number and scope, the data show no apparent differences between flunitrazepam and other benzodiazepines in ability to produce drug-taking or drug-seeking behavior, in capacity to produce physiologic dependence, nor in the characteristics of withdrawal after administration of an antagonist or discontinuation of treatment. Similar to other benzodiazepines, flunitrazepam produces dose-dependent effects on psychomotor performance and recall. Flunitrazepam does not seem to be involved in medical emergencies more often than other benzodiazepines, and there is no indication that flunitrazepam is more toxic than other benzodiazepines when taken in overdose by drug abusers or other individuals. Survey research among typical patient populations suggests that flunitrazepam is characteristic of benzodiazepines in that it is used appropriately and conservatively, with low liability for abuse. Thus the reported preference for flunitrazepam among opioid abusers seems to be the only way in which flunitrazepam is distinguished from other benzodiazepines; it is unclear what characteristics of the drug may be responsible for this reported preference. The evidence considered in this review indicates that abuse of flunitrazepam in this special population is not associated with any distinctive threats to the health of the general public.

Sudden death and benzodiazepines

A study of 16 deaths associated with toxic concentrations of benzodiazepines during the period of 5 years leading up to July 1994 is presented. Cases where other drugs, including ethanol, had contributed to the death were excluded. All cases were subject to a full macroscopic and microscopic examination by pathologists, and all cases were subject to a full toxicological work-up. Preexisting natural disease was a feature of 11 cases. In the remaining five cases, death was caused solely by benzodiazepines. There were 14 suicides. Nitrazepam and temazepam were the most prevalent drugs detected, followed by oxazepam and flunitrazepam. Minimum toxic femoral blood concentrations of 7-aminonitrazepam, 7-aminoflunitrazepam, and oxazepam were estimated as 0.5, 0.2, and 2 mg/L, respectively. Relating these deaths to prescription rates in Victoria suggest that flunitrazepam may be inherently more toxic if misused than other benzodiazepines currently available on the Australian market.

A comparison of the physical dependence inducing properties of flunitrazepam and diazepam

Dogs dosed chronically (4-7 weeks) with oral flunitrazepam (7.6 mg/kg/day) or diazepam (24-36 mg/kg/day) administered in 4 equally divided doses had dose-related flumazenil precipitated benzodiazepine abstinence scale scores (BPAS) of comparable intensities despite the fact that plasma levels of flunitrazepam and its metabolites were much lower than nordiazepam levels in the diazepam-dependent dog. Both groups of dependent dogs had clonic and tonic-clonic seizures after oral and IV flumazenil. Precipitated abstinence signs persisted longer in the diazepam than in the flunitrazepam-dependent dogs. Differences in the pharmacokinetics of the drugs of dependence, their metabolites, and their interactions at receptor sites offer a partial explanation for the high level of dependence seen in the flunitrazepam dog. The finding that the estimated plasma free concentration of flunitrazepam and its metabolites is equal to or greater than that of diazepam and its metabolites together with the fact that flunitrazepam has a higher affinity for the benzodiazepine receptor than either diazepam, nordiazepam or oxazepam can explain why the intensity of the precipitated abstinence syndrome is comparable in flunitrazepam- and diazepam-dependent dogs. Although the flumazenil-induced precipitated abstinence syndromes observed in flunitrazepam- and diazepam-dependent dogs differed qualitatively they did not differ quantitatively. It is therefore concluded from these data that the doses of flunitrazepam and diazepam, chosen for producing comparable degrees of weight loss during dose escalation, did not differ in the degree of physical dependence that they produced in the dog.

Inter- and intraindividual variability in the concentration-effect (sedation) relationship of flunitrazepam

1. The relationship between plasma flunitrazepam concentrations and the degree of sedation was evaluated in 20 healthy subjects receiving two single oral doses of 1 mg flunitrazepam on two different occasions (1 week apart). The degree of sedation was rated blindly during the two treatment sessions in parallel with blood sampling (48 h). 2. A strong correlation between the concentrations of flunitrazepam in plasma and the degree of sedation was found according to the sigmoid Emax model. The plasma drug concentration producing 50% of maximal effect (EC50) was found to be 7.0 and 6.5 ng ml-1 on the two occasions, respectively. The variability in EC50 between subjects was larger (C.V. 39%) than the variability within subjects (C.V. 27%). 3. The steepness of the concentration-response curve as reflected in the slope factor(s) showed a virtual 'all or none' response to flunitrazepam with s values ranging from 3 to 30 with a mean of about 14. 4. The results in young healthy subjects suggest that the present dosage recommendations for temporary insomnia (1-2 mg) may be inappropriate; the dose can probably be reduced to 0.5 mg in some patients to achieve moderate sedation.

Daytime wakefulness following a bedtime oral dose of zolpidem 20 mg, flunitrazepam 2 mg and placebo

1. The effects of zolpidem 20 mg, flunitrazepam 2 mg and placebo, administered at bed time, were studied in 12 healthy young male volunteers. 2. The assessments included, at awakening, subjective ratings of overnight sleep, cognitive function, psychomotor performance (digit symbol substitution, choice reaction time, flicker fusion threshold), subjective ratings of alertness, and plasma assay of residual drug concentration. Daytime sleep propensity during the day after dosing was evaluated with the multiple sleep latency test. 3. Compared with placebo, both active drugs improved subjective assessment of the ease of getting to sleep. At awakening, under flunitrazepam treatment, the reduction of performance, on memory and psychomotor tests, paralleled an increased subjective rating of sleepiness, but zolpidem treatment left subjects unimpaired compared with placebo. Similarly, daytime sleep propensity was enhanced throughout the following day under flunitrazepam treatment, but not under zolpidem treatment. Plasma assay for residual drug concentration at awakening found significant amounts of flunitrazepam and marginal amounts of zolpidem. 4. Results indicate that zolpidem 20 mg is devoid of residual effects in a range of tasks that were sensitive enough to demonstrate a prolonged wakefulness impairment following flunitrzepam 2 mg in healthy volunteers.

Pharmacokinetics of temazepam compared with other benzodiazepine hypnotics--some clinical consequences

When the various benzodiazepine hypnotics are studied, large differences are seen with regard to their pharmacokinetic properties and metabolism in man. Some are eliminated from the body at a relatively slow rate (e.g. nitrazepam), others are metabolized rather rapidly (temazepam, triazolam). Some benzodiazepine hypnotics have major active metabolites that are slowly eliminated (flurazepam, quazepam), while others have non-active metabolites (temazepam, lormetazepam). In hypnotic treatment, the duration of drug action should be restricted to the duration of the night, hence a compound with a relatively short elimination half-life may represent a more rational choice. An overview is given of the pharmacokinetics of the currently available benzodiazepine hypnotics with emphasis on temazepam and other hydroxylated benzodiazepines.

Zopiclone produces effects on human performance similar to flurazepam, lormetazepam and triazolam

The cognitive function and psychomotor performance of 10 healthy male volunteers were measured following single oral doses of: zopiclone (7.5 mg), flurazepam (15 mg), lormetazepam (1 mg), triazolam (0.25 mg) and placebo. The performance tests selected (stroop task, five choice serial reaction time, memory span, logical reasoning, mood and saccadic eye movement analysis) were thought to reflect aspects of normal daily activity. The tests demonstrated a clear reduction of performance for all active treatments. No drug emerged as the most potent sedative overall, as each of the tests was affected to a different degree by each drug. Drug effects were not qualitatively different between active treatments so that zopiclone was indistinguishable from the three benzodiazepines with which it was compared.

Pharmacokinetics of flunitrazepam in rats studied by a radioreceptor assay

In rat the kinetics of flunitrazepam (FNZ) was evaluated by a radioreceptor assay (RRA) after i.v. administration of 1 mg/kg and after oral administration of 1 and 3 mg/kg. The i.v. kinetics is biexponential and the g.i. absorption is very rapid (with a plasma peak at 0.25 hour) with a good bioavailability (69%); the apparent distribution volume is high, 4.8 L/kg; the half-life is equal to 3.5 hours; the elimination constant is equal to 0.8 h-1; the urinary excretion of FNZ-equivalent is negligible; the plasma total clearance is equal to 3.9 (L/kg)h-1. The concentrations of FNZ-equivalents after oral administration of 1 mg/kg show a peak at the 2-nd hour with a very high concentration in the following organs (in decreasing order): brain, kidneys, heart, liver; after 8 hours no FNZ-equivalents are present in these organs except in the brain, which shows detectable concentrations at the 32-nd hour. The peak concentrations of FNZ-equivalent in brain, kidneys and heart are higher than the corresponding peak concentration in plasma.

Trace analysis of benzodiazepine drugs in blood using deactivated amberlite XAD-7 porous polymer beads and silica capillary column gas chromatography with electron-capture detection

A general method for the trace analysis of benzodiazepine drugs and their major metabolites at single dose therapeutic levels in 0.2 ml blood samples is described. The method involves solvent extraction of blood with toluene, isolation of the analytes using deactivated Amberlite XAD-7 porous polymer beads, and analysis of the cleaned-up extracts by capillary column gas chromatography with electron-capture detection. The clean-up technique eliminates lipids and other interfering material, enabling routine analysis of blood extracts to be carried out with no significant deterioration in column or detector performance over a period of many months. The use of fused-silica capillary columns coated with SE-52 and the correct choice of chromatographic conditions permits underivatised benzodiazepines of widely differing volatilities and polarites to be analysed. Data for 26 benzodiazepines and metabolites are presented.

Pharmacokinetic and clinical studies with a benzodiazepine radioreceptor assay

Since the presence of benzodiazepine (BD) receptors was demonstrated in mammalian brain tissue, simple, sensitive and rapid techniques have been established to use BD-receptor preparations for specific radioreceptor assays (RRA). The RRA allows in vitro estimations of receptor affinity and concentration of BD in biological material, e.g. the time course of total BD binding activity in plasma (parent compound and active metabolites) may be evaluated. Several studies in volunteers with short and long-acting BD used as sedatives and hypnotics including diazepam (DZP), flunitrazepam (FNZ), flurazepam (FZP), lormetazepam (LMZ), oxazepam, temazepam and triazolam indicate that pharmacokinetic data (e.g. elimination half-lives of receptor active compounds) concur with the results obtained from other methods, if active metabolites are taken into account. For the evaluation of BD long-term and hangover effects in two placebo controlled double-blind studies (placebo vs. 1 mg and 2 mg LMZ, 2 mg FNZ, 30 mg FZP, 10 mg DZP) BD-binding equivalents and pharmaco-EEG recordings, subjective state, psychomotor as well as cognitive function were determined by standardized methods up to 154 hours following drug administration. Compared to placebo a distinct long-lasting increase in the relative power in beta-frequencies (12.5-30 Hz) and an impairment of psychomotor performance could be evidenced up to 12 h following FNZ and FZP intake. These effects correspond to the BD-binding activity in plasma. These findings indicate that BD-receptor preparations as used for the RRA are valuable tools to investigate binding affinities and pharmacokinetic properties of BD. Plasma levels of RRA active material may reflect a better correspondence to some clinical effects of BD than levels of the parent compound alone.

Pharmacokinetics of benzodiazepines: metabolic pathways and plasma level profiles

Large differences exist among the various benzodiazepines with regard to their pharmacokinetic properties and metabolism in man. Some are eliminated from the body at a relatively slow rate, e.g. desmethyldiazepam, and others are metabolized rapidly, e.g. midazolam, triazolam. Several benzodiazepines have major active metabolites that are slowly eliminated, e.g. medazepam, halazepam , quazepam and, consequently, should be considered as potentially long-acting. Such differences may be very important clinically because pharmacokinetic data will help to optimize drug therapy with respect to the choice of the proper drug and drug preparation, as well as with the choice of a proper dose and dosage regimen. The therapeutic objectives of drug therapy differ quite considerably for the various clinical indications of benzodiazepines. In anti-anxiety and anti-epileptic therapy, prolonged or continuous treatment is pursued, so that compounds with relatively long or intermediate elimination half-lives of parent drug or active metabolites are of advantage. In hypnotic treatment, on the other hand, the duration of drug action should be restricted to the duration of the night, hence a compound with a short elimination half-life may be preferred. An overview is given of the pharmacokinetics of the major benzodiazepines currently available and of some interesting new ones that are still in the development stage.

A radioreceptor assay to study the affinity of benzodiazepines and their receptor binding activity in human plasma including their active metabolites

1 A radioreceptor assay has been established to measure the receptor affinities of numerous benzodiazepines in clinical use. 2 The time course of receptor binding activity was studied by this method in the plasma of eight healthy subjects randomly treated with 1 mg lormetazepam (Noctamid, 2 mg flunitrazepam (Rohypnol, and 10 mg diazepam (Valium, and placebo on a cross-over basis. Blood samples were collected up to 154 h after treatment. 3 Receptor affinities of numerous benzodiazepines on vitro show good correlation with therapeutic human doses (r = 0.96) and may be predictive of drug potency in man. 4 Mean peak plasma levels of lormetazepam binding equivalents were 4.8 +/- 1 ng/ml at 2 h after lormetazepam, 7.2 +/- 1.8 ng/ml at 8 h after flunitrazepam, and 17.9 +/- 2.7 ng/ml at 15 h after diazepam. Plasma elimination half-lives of benzodiazepine binding equivalents were 9.3, 23 and 63 h, respectively. 5 Slow elimination of benzodiazepine binding equivalents following flunitrazepam and diazepam may be due to persistent active metabolites.

Residual effects of repeated doses of 0.5 and 1 mg flunitrazepam

9 normal subjects were tested on a large battery of tests the morning after a hypnotic dose of flunitrazepam (0.5 mg and 1 mg) and a placebo. Each drug was given for 8 nights and assessments were made 10 and 13 h later on days 1, 4 and 8. Self-ratings of sleep were made every morning. The tests comprised mood and bodily symptom self-ratings, taping rate, visual reaction time, symbol copying and substitution tests, critical flicker fusion threshold, digit span and cancellation test. The EEG was recorded under eyes open and eyes closed conditions and analysed using broad waveband filters. Subjectively, the 0.5 mg dose was associated with increased alertness, contentment and calmness, the 1 mg dose with minimal decrease in alertness and contentment. Sleep onset was accelerated by flunitrazepam initially but effects on quality of sleep were not major due to subject selection. The 1 mg dose occasionally impaired performance on tapping, symbol copying and substitution and critical flicker fusion. The 0.5 mg dose marginally impaired symbol substitution and improved symbol copying. The EEG showed definite dose-related effects which tended to increase over the 8 nights of ingestion of the drug. It is concluded that whereas the 1 mg dose may sometimes be associated with definite residual effects the next day, the 0.5 mg dose possesses positive qualities in producing useful subjective effects the next day without appreciable impairment of psychological performance.