Impact of benzodiazepines on posaconazole serum concentrations. A population-based pharmacokinetic study on drug interaction

OBJECTIVES

Posaconazole is broadly used for antifungal prophylaxis and therapy. Current data suggest a concentration-dependent effect. Unlike other triazoles, cytochrome P450 is not a relevant route of biotransformation for posaconazole but glucuronidation, which might lead to a different spectrum of drug interactions. For benzodiazepines, the major metabolic pathway involves oxidation, but some, including lorazepam and temazepam, undergo conjugation to glucuronic acid.

RESEARCH DESIGN AND METHODS

Since 2006 serum levels of posaconazole are determined regularly in all hospitalized patients with intake of this triazole. Here we investigate posaconazole concentration at steady state in relation to the concomitant medication of benzodiazepines.

RESULTS

While similar posaconazole concentrations were determined in samples obtained from patients receiving temazepam when compared to samples without any benzodiazepine, a relevant reduction of posaconazole concentration could be observed in patients with concomitant intake of lorazepam. This difference in posaconazole concentration with or without concomittant intake of lorazepam, was consistently significant for analyses of all samples (median 336 ng/ml vs. 585 ng/ml, p 0.001), for the average concentrations (569 ng/ml vs. 276 ng/ml, p 0.039), and for patients receiving a total daily dose of 800 mg posaconazole (292 ng/ml vs. 537 ng/ml, p 0.003). There was also a similar, but not significant trend for patients with a prophylactic dosage of 200 mg posaconazole three times daily (689 ng/ml vs. 512 ng/ml, p 0.186).

CONCLUSIONS

In this retrospective study, analyzing blood samples from daily clinical practice of patients in various clinical settings and with different indications for antifungal therapy, concomitant medication of lorazepam was associated with decreased posaconazole concentrations. Therefore, lorazepam but not temazepam might induce posaconazole clearance by glucuronidation.

Impact of melatonin, zaleplon, zopiclone, and temazepam on psychomotor performance

INTRODUCTION

Modern military operations may require pharmaceutical methods to sustain alertness and facilitate sleep in order to maintain operational readiness. In operations with very limited sleep windows, hypnotics with very short half-lives (e.g., zaleplon, t(1/2) 1 h) are of interest, while with longer sleep opportunities, longer acting agents (e.g., zopiclone, temazepam (t(1/2) 4-6 hours) may be used. This study was designed to compare the effect of a single dose of zaleplon, zopiclone, temazepam, and melatonin on psychomotor performance and to quantify the post-ingestion time required for return to normal performance.

METHOD

There were 23 subjects (9 men, 14 women), 21-53 yr of age, assessed for psychomotor performance on 2 test batteries (4 tasks) that included a sleepiness questionnaire. Psychomotor testing was conducted prior to, and for 7 h after, ingestion of a single dose of each of placebo, zaleplon 10 mg, zopiclone 7.5 mg, temazepam 15 mg, and time-released melatonin 6 mg. The experimental design was a double-blind cross-over with counter-balanced treatment order.

RESULTS

Zaleplon, zopiclone, and temazepam impaired performance on all four tasks: serial reaction time (SRT), logical reasoning (LRT), serial subtraction (SST), and multitask (MT). Melatonin did not impair performance on any task. The time to recovery of normal performance for SRT during the zaleplon, zopiclone and temazepam conditions were 3.25, 6.25, and 5.25 h respectively; for LRT were 3.25, >6.25, and 4.25 h; for SST were 2.25, >6.25, and 4.25 h, and for MT were 2.25, 4.25, and 3.25 h. The recovery time to baseline subjective sleepiness levels for zaleplon, zopiclone, temazepam, and melatonin were 4.25, >6.25, 5.25, and >4.25 h, respectively.

CONCLUSIONS

In spite of a prolonged period of perceived sleepiness, melatonin was superior to zaleplon in causing no impact on performance. The remaining drugs listed in increasing order of performance impact duration are zaleplon, temazepam, and zopiclone.

[Comparative kinetics of 3-hydroxyphenazepam and its metabolism during transdermal and intravenous administration]

The kinetics of excretion of 2-(14)C-3-hydroxyphenazepam and its metabolites were studied upon a single transdermal and intravenous administration in mice. The main fraction of the total radioactivity (approximately 80%) was eliminated within approximately 84 h upon intravenous injection and within approximately 360 h after transdermal introduction. In the latter case, the ratio of lipophilic and hydrophilic metabolites is modified as well: the former fraction increases by a factor of 1.75, while the latter decreases by a factor of 1.2 as compared to the case of intravenous drug administration.

Mechanism of increased dissolution of diazepam and temazepam from polyethylene glycol 6000 solid dispersions

Solid dispersion literature, describing the mechanism of dissolution of drug-polyethylene glycol dispersions, still shows some gaps; (A). only few studies include experiments evaluating solid solution formation and the particle size of the drug in the dispersion particles, two factors that can have a profound effect on the dissolution. (B). Solid dispersion preparation involves a recrystallisation process (which is known to be highly sensitive to the recrystallisation conditions) of polyethylene glycol and possibly also of the drug. Therefore, it is of extreme importance that all experiments are performed on dispersion aliquots, which can be believed to be physico-chemical identical. This is not always the case. (C). Polyethylene glycol 6000 (PEG6000) crystallises forming lamellae with chains either fully extended or folded once or twice depending on the crystallisation conditions. Recently, a high resolution differential scanning calorimetry (DSC)-method, capable of evaluating qualitatively and quantitatively the polymorphic behaviour of PEG6000, has been reported. Unraveling the relationship between the polymorphic behavior of PEG6000 in a solid dispersion and the dissolution characteristics of that dispersion, is a real gain to our knowledge of solid dispersions, since this has never been thoroughly investigated. The aim of the present study was to fill up the three above mentioned gaps in solid dispersion literature. Therefore, physical mixtures and solid dispersions were prepared and in order to unravel the relationship between their physico-chemical properties and dissolution characteristics, pure drugs (diazepam, temazepam), polymer (PEG6000), solid dispersions and physical mixtures were characterised by DSC, X-ray powder diffraction (Guinier and Bragg-Brentano method), FT-IR spectroscopy, dissolution and solubility experiments and the particle size of the drug in the dispersion particles was estimated using a newly developed method. Addition of PEG6000 improves the dissolution rate of both drugs. Mechanisms involved are solubilisation and improved wetting of the drug in the polyethylene glycol rich micro-environment formed at the surface of drug crystals after dissolution of the polymer. Formulation of solid dispersions did not further improve the dissolution rate compared with physical mixtures. X-ray spectra show that both drugs are in a highly crystalline state in the solid dispersions, while no significant changes in the lattice spacings of PEG6000 indicate the absence of solid solution formation. IR spectra show the absence of a hydrogen bonding interaction between the benzodiazepines and PEG6000. Furthermore, it was concluded that the reduction of the mean drug particle size by preparing solid dispersions with PEG6000 is limited and that the influence of the polymorphic behavior of PEG6000 (as observed by DSC) on the dissolution was negligible.

CNS effects of sumatriptan and rizatriptan in healthy female volunteers

This study investigates the CNS effects of sumatriptan and rizatriptan, with temazepam as an active comparator, in healthy female volunteers. Sixteen volunteers completed a randomized, double-blind, crossover study and on four separate occasions received either 100 mg sumatriptan, 20 mg rizatriptan or 20 mg temazepam. The main parameters were eye movements, EEG, body sway, visual analogue scales and a cognitive test battery. Rizatriptan and sumatriptan decreased saccadic peak velocity by 18.3 (95% CI: 5.7, 30.8) and 15.0 (2.2, 27.9) degrees/sec, respectively, about half the decrease induced by temazepam (35.0 (22.1, 47.8) degrees/sec). Body sway increased (30% for rizatriptan (16%, 45%) and 14% for sumatriptan (1%, 27%), respectively). Temazepam caused larger, similar effects. In contrast to temazepam, sumatriptan and rizatriptan decreased reaction times of recognition tasks and increased EEG alpha power (significant for sumatriptan, 0.477 (0.02, 0.935). Therapeutic doses of sumatriptan and rizatriptan caused CNS effects indicative of mild sedation. For EEG and recognition reaction times the effects were opposite to temazepam, indicating central stimulation.

Comparison of the rates of hydrolysis of lorazepam-glucuronide, oxazepam-glucuronide and tamazepam-glucuronide catalyzed by E. coli beta-D-glucuronidase using the on-line benzodiazepine screening immunoassay on the Roche/Hitachi 917 analyzer

The catalytic rates of hydrolysis of lorazepam-glucuronide, oxazepam-glucuronide, and temazepam-glucuronide when catalyzed by E. Coli. beta-glucuronidase both in phosphate buffer and buffered drug-free urine were compared as well as the pH dependence of enzyme activity. In 50 mM phosphate buffer pH 6.4, lorazepam-glucuronide has the highest turnover rate of 3.7 s(-1) with an associated Km of about 100 microM, followed by oxazepam-glucuronide, which has a turnover rate of 2.4 s(-1) with an associated Km of 60 microM. Temazepam-glucuronide has the lowest rate of 0.94 s(-1) with an associated Km of 34 microM. In buffered drug-free urine, a similar trend was observed. In addition, an optimal pH for beta-glucuronidase was determined to be between 6 and 7 when the enzyme hydrolyzes the benzodiazepine conjugates in buffered drug-free urine. Effects of temperature and incubation time were also examined. It can be concluded that the electron donating or withdrawing of the individual benzodiazepine structure may play an important role in the reactivity of the lorazepam-glucuronide, oxazepam-glucuronide and temazepam-glucuronide catalyzed by beta-glucuronidase. This is consistent with other observations made for monosubstituted phenyl-beta-glucuronides by Wang et al. (1).

Drug release from an ensemble of swellable crosslinked polymer particles

This paper presents a new model suitable to describe the drug release from drug delivery systems constituted by an ensemble of drug loaded crosslinked polymer particles. The model accounts for the main factors affecting the drug release such as the particle size distribution, the physical state and the concentration profile of the drug inside the polymeric particles, the viscoelastic properties of the polymer-penetrant system and the dissolution-diffusion properties of the loaded drug. In order to check the validity of the model, release experiments were performed by using crosslinked polyvinyl-pyrrolidone (PVP) particles and two different model drugs, MAP (medroxyprogesterone acetate) and TEM (Temazepam). MAP and TEM were chosen because of their completely different dissolution behaviours in water. In particular, TEM undergoes a phase transition to the crystalline state upon dissolution when it is loaded in the polymeric network in the amorphous state. The comparison with the experimental results confirms that the most important factors determining the drug release kinetics can be properly accounted for.

Efficacy of activated charcoal versus gastric lavage half an hour after ingestion of moclobemide, temazepam, and verapamil

OBJECTIVE

To compare the efficacy of activated charcoal and gastric lavage in preventing the absorption of moclobemide, temazepam, and verapamil 30 min after drug ingestion.

METHODS

In this randomized cross-over study with three phases, nine healthy volunteers received a single oral dose of 150 mg moclobemide, 10 mg temazepam, and 80 mg verapamil after an overnight fast. Thirty minutes later, they were assigned to one of the following treatments: 25 g activated charcoal as a suspension in 200 ml water, gastric lavage (10x200 ml), or 200 ml water (control). Plasma concentrations of moclobemide, temazepam, and verapamil were determined up to 24 h.

RESULTS

Activated charcoal reduced the area under the plasma concentration time curve from 0 h to 24 h (AUC0-24 h) of moclobemide and temazepam by 55% (P<0.05) and by 45% (P<0.05), respectively. The AUC0-24 h of verapamil was not significantly reduced by charcoal. Gastric lavage decreased the AUC0-24 h of moclobemide by 44% (P<0.05), but had no significant effect on that of temazepam or verapamil. The peak plasma concentration (Cmax) of moclobemide, temazepam, and verapamil was reduced by 40%, 29% (P<0.05), and 16%, respectively, by activated charcoal. Gastric lavage did not significantly decrease the Cmax of any of these drugs.

CONCLUSION

The absorption of moclobemide, temazepam, and verapamil can be moderately reduced by activated charcoal given 30 min after drug ingestion, while gastric lavage seems to be less effective.

Site-to-site variability of drug concentrations in skeletal muscle

The homogeneity of drug concentrations in skeletal muscle was assessed in eight fatal overdoses. Ten to 30 random samples were taken from leg muscle weighing 1,650 to 7,985 g. For cases involving paracetamol the mean muscle-to-blood ratio ranged from 0.1 to 1.1 (n = 4) for amitriptyline 1.1 to 3.6 (n = 3), and for dothiepin 0.8 to 2.1 (n = 2). The coefficient of variance was large for all drugs, ranging from 10.5 (carbamazepine) to 50 (thioridazine). Skeletal muscle is not homogeneous with respect to drug concentrations in fatal overdose cases. Of 16 instances of drug detection in blood 2 (nortriptyline and promethazine) were not detected in muscle. Muscle-to-blood drug ratios varied significantly among cases, possibly influenced by survival time after drug ingestion. Quantitative interpretations of muscle drug levels present significant difficulties. However, skeletal muscle can be used for qualitative corroboration of blood analyses and is a suitable specimen for drug detection where none other is available.

A study of the effects of long-term use on individual sensitivity to temazepam and lorazepam in a clinical population

AIMS

The central effects of benzodiazepines may be attenuated after chronic use by changes in pharmacokinetics, pharmacodynamics or both. This attenuation may be influenced by the dosing pattern and the characteristics of the user population. The objectives of this study were to evaluate drug sensitivity in long-term users of temazepam and lorazepam in a clinical population.

METHODS

The sensitivity to benzodiazepine effects in chronic users (1-20 years) of lorazepam (n = 14) or temazepam (n = 13) was evaluated in comparison with age and sex matched controls. Drug sensitivity was evaluated by plasma concentration in relation to saccadic eye movement parameters, postural stability and visual analogue scales.

RESULTS

Pharmacokinetics of lorazepam and temazepam did not differ between patients and control subjects. Chronic users of lorazepam showed clear evidence of reduced sensitivity, indicated by lack of any pharmacodynamic difference between patients and controls at baseline, when drug concentrations were similar to the peak values attained in the control subjects after administration of 1-2.5 mg of lorazepam. In addition, there was a two- to four fold reduction in the slopes of concentration-effect plots for measures of saccadic eye movements and body sway (all; P < or = 0.01). By contrast, sensitivity in chronic users of temazepam was not different from controls. The difference between the temazepam and the lorazepam group appears to be associated with a more continuous drug exposure in the latter, due to the longer half-life and a more frequent intake of lorazepam. This pattern of use may be partly related to the more anxious personality traits that were observed in the chronic users of lorazepam.

CONCLUSIONS

Chronic users of lorazepam show evidence of tolerance to sedative effects in comparison with healthy controls. Tolerance does not occur in chronic users of temazepam. The difference may be related to pharmacological properties, in addition to different patterns of use, associated with psychological factors.

Site to site variability of postmortem drug concentrations in liver and lung

We evaluated postmortem diffusion of gastric drug residue into tissues and blood in eight suicidal overdoses. Analyses were performed on liver (five sites), lung (four sites), spleen, psoas muscle and kidney (left and right), blood (peripheral and torso), vitreous, pericardial fluid, bile and, urine as well as residual gastric contents. Standard analytical techniques and instrumentation gas chromatograph/mass spectrometer and high performance liquid chromatography (GC-MS and HPLC) were used throughout. These case studies confirm previous studies of an animal and human cadaver model of gastric diffusion, in that in several instances there was drug accumulation in the left posterior margin of the liver and, to a lesser extent, the left basal lobe of the lung. Uncontrollable variables, such as postmortem interval, refrigeration before autopsy, and position of the body appear to influence significantly drug accumulation in a specific site. We suggest that autopsy sampling techniques should be standardized on blood taken from a ligated peripheral (preferably femoral or external iliac) vein, and liver from deep within the right lobe.

Pharmacokinetic aspects of rectal formulations of temazepam

An in vitro/in vivo study was carried out with different rectal formulations of temazepam. Pharmacokinetic data were determined in a cross-over study in 10 volunteers after rectal administration of 10 mg temazepam as a polyethylene glycol based suppository (selected from in vitro data), a liquid-filled capsule and a micro-enema respectively, using oral administration of a liquid-filled capsule as a reference. Serum levels of temazepam indicate an instantaneous and complete release from the micro-enema (Frel = 0.94 +/- 0.21, Cmax 205 +/- 36.9 micrograms/l, tmax 0.49 +/- 0.31 hour) and a slower but complete release of temazepam from the suppository (Frel = 1.10 +/- 0.25, Cmax 202 +/- 41.3 micrograms/l, tmax 1.48 +/- 0.41 hour). A high interindividual variation in absorption profiles was observed after rectal administration of the liquid-filled capsule (Frel 0.72 +/- 0.36, Cmax 182 +/- 122 micrograms/l, tmax 4.08 +/- 4.28 hour), which makes it less suitable for rectal use. The micro-enema and suppository appear to be useful as rectal formulations for temazepam.

Lack of effect of antimycotic itraconazole on the pharmacokinetics or pharmacodynamics of temazepam

The azole antimycotics itraconazole and ketoconazole are potent and relatively nonspecific inhibitors of cytochrome P450 enzymes and have a potentially dangerous interaction with midazolam and triazolam. The possible interaction between itraconazole and a short-acting benzodiazepine, temazepam, was investigated in a double-blind, randomized crossover study. Ten healthy volunteers were given placebo or 200 mg itraconazole a day orally for 4 days. The challenge dose of 20 mg of temazepam was ingested on the fourth day, after which plasma samples were collected, and psychomotor performance tests were carried out for 24 h. Despite a statistically significant small increase of the area under the temazepam concentration-time curve, there was no clinically significant interaction, as determined by the psychomotor performance tests. The different metabolic pathways and the lack of significant firstpass metabolism of temazepam explain the great difference in the interaction potential of temazepam compared with midazolam and triazolam. Temazepam, unlike midazolam and triazolam, can be prescribed in usual doses for patients receiving itraconazole and other inhibitors of P450 3A4.

Pharmacokinetics of temazepam in male surgical patients

The pharmacokinetics of temazepam, the 3-hydroxy1 derivative of diazepam, were studied in nine male surgical patients (age: 28-57 years; weight: 55-87 kg) who had ingested single 40 mg doses, 4 hours prior to minor surgical procedures. Peak plasma temazepam concentrations were achieved rapidly (within 1 h post drug administration) and the estimated volume of distribution (mean: 1.13 1/kg), total clearance (mean: 1.6 ml/min/kg) and terminal elimination half-life (mean: 8 hours) were comparable to previously reported values in healthy subjects. There was no correlation between volume of distribution and either weight or age, and between clearance and age. These findings are broadly consistent with previous reports from studies in healthy subjects. Temazepam can therefore be used as a premedicant in patients requiring minor surgery; the concomitant anaesthetic agents administered and the surgical procedures have no effects on temazepam pharmacokinetics.

Concentration-dependent metabolism of diazepam in mouse liver

Previous mouse liver studies with diazepam (DZ), N-desmethyldiazepam (NZ), and temazepam (TZ) confirmed that under first-order conditions, DZ formed NZ and TZ in parallel. Oxazepam (OZ) was generated via NZ and not TZ despite that preformed NZ and TZ were both capable of forming OZ. In the present studies, the concentration-dependent sequential metabolism of DZ was studied in perfused mouse livers and microsomes, with the aim of distinguishing the relative importance of NZ and TZ as precursors of OZ. In microsomal studies, the Kms and Vmaxs, corrected for binding to microsomal proteins, were 34 microM and 3.6 nmole/min per mg and 239 microM and 18 nmole/min per mg, respectively, for N-demethylation and C3-hydroxylation of DZ. The Kms and Vmaxs for N-demethylation and C3-hydroxylation of TZ and NZ, respectively, to form OZ, were 58 microM and 2.5 nmole/min per mg and 311 microM and 2 nmole/min per mg, respectively. The constants suggest that at low DZ concentrations, NZ formation predominates and is a major source of OZ, whereas at higher DZ concentrations, TZ is the important source of OZ. In livers perfused with DZ at input concentrations of 13 to 35 microM, the extraction ratio of DZ (E[DZ]) decreased from 0.83 to 0.60. NZ was the major metabolite formed although its appearance was less than proportionate with increasing DZ input concentration. By contrast, the formation of TZ increased disproportionately with increasing DZ concentration, whereas that for OZ decreased and paralleled the behavior of NZ. Computer simulations based on a tubular flow model and the in vitro enzymatic parameters provided a poor in vitro-organ correlation. The E[DZ], appearance rates of the metabolites, and the extraction ratio of formed NZ (E[NZ, DZ]) were poorly predicted; TZ was incorrectly identified as the major precursor of OZ. Simulations with optimized parameters improved the correlations and identified NZ as the major contributor of OZ. Saturation of DZ N-demethylation at higher DZ concentrations increased the role of TZ in the formation of OZ. The poor aqueous solubility (limiting the concentration range of substrates used in vitro), avid tissue binding and the coupling of enzymatic reactions in liver, favoring sequential metabolism, are possible explanations for the poor in vitro-organ correlation. This work emphasizes the complexity of the hepatic intracellular milieu for drug metabolism and the need for additional modeling efforts to adequately describe metabolite kinetics.

Drug accumulation and elimination in Calliphora vicina larvae

Calliphora vicina larvae were fed on drug-laden muscle from three suicides involving amitriptyline, temazepam and a combination of trazodone and trimipramine; triplicate daily harvestings were analysed. The limit of detection for all four drugs was 0.01 micrograms drug/g larvae. Mean drug concentrations (microgram/g) in the initial muscle were:amitriptyline, 2.68; temazepam, 4.04; trazodone, 21.56; and trimipramine, 19.58. Larval rearings for days 4-8 (15 larval samples per drug) had mean and ranges of drug concentrations (microgram/g) of 0.10 (r, 0.02-0.24) for amitriptyline; 0.52 (r, 0.26-0.78) for temazepam; 0.13 (r, 0.05-0.32) for trazodone; and 0.28 (r, 0.10-0.59) for trimipramine. After day 8 there was a precipitous fall in larval drug concentrations associated with pupariation. At day 11 ranges of drug concentrations (microgram/g) were: amitriptyline, < 0.01-0.01; temazepam, 0.01-0.08; trazodone, < 0.01-0.01; and trimipramine, 0.04-0.04. Day 16 pupae had corresponding ranges (microgram/g) of < 0.01, 0.01-0.01, < 0.01 and < 0.01-0.02. Transfer to drug-free food at day 5 led to similar falls in drug concentrations (microgram/g) from day 5 to day 6: 0.08-0.03 for amitriptyline, 0.61-0.09 for temazepam, 0.13-0.01 for trazodone, and 0.30-0.02 for trimipramine. The results show considerable variation in larval drug concentrations, both at the same developmental stage and at different stages of the life cycle, under conditions which closely reflect case situations. In practice, the precipitous decrease in drug concentrations in non-feeding larvae and at pupariation make it desirable to sample only larvae actively feeding on a corpse.

Lack of interaction of erythromycin with temazepam

Erythromycin is a strong inhibitor of cytochrome P450 [CYP3A4] and has a potentially dangerous interaction with midazolam and triazolam. The possible interaction between erythromycin and a short-acting benzodiazepine, temazepam, was investigated in a double-blind, randomized crossover study. Ten healthy volunteers received 500 mg erythromycin or placebo orally three times a day for 6 days followed by a challenge dose of 20 mg temazepam. Plasma samples were collected for the determination of temazepam, oxazepam, and erythromycin, and psychomotor effects were measured during the 24 h after intake of temazepam. Erythromycin did not change the pharmacokinetics or pharmacodynamics of temazepam to a statistically significant degree. The metabolic fate of temazepam and its almost complete bioavailability explain the lack of interaction. Temazepam, unlike midazolam or triazolam, can thus be prescribed in the usual doses for patients receiving erythromycin.

Diazepam metabolism by human liver microsomes is mediated by both S-mephenytoin hydroxylase and CYP3A isoforms

1. The primary metabolism of diazepam was studied in human liver microsomes in order to investigate the kinetics and to identify the cytochrome P450 (CYP) isoforms responsible for the formation of the main diazepam metabolites, temazepam and N-desmethyldiazepam. 2. The formation kinetics of both metabolites were atypical and consistent with the occurrence of substrate activation. A sigmoid Vmax model equivalent to the Hill equation was used to fit the data. The degree of sigmoidicity was greater for temazepam formation than for N-desmethyldiazepam formation, so that the ratio of desmethyldiazepam:temazepam formation increased as the substrate (diazepam) concentration decreased. 3. alpha-Naphthoflavone activated both reactions but with a greater effect on temazepam formation than on N-desmethyldiazepam formation. In the presence of 25 microM alpha-naphthoflavone the kinetics for both pathways were approximated by Michaelis-Menten kinetics. 4. Studies with a series of CYP isoform selective inhibitors and with an inhibitory anti-CYP2C antibody indicated that temazepam formation was carried out mainly by CYP3A isoforms, whereas the formation of N-desmethyldiazepam was mediated by both CYP3A isoforms and S-mephenytoin hydroxylase.

The influence of ciprofloxacin on the pharmacokinetics and pharmacodynamics of a single dose of temazepam in the young and elderly

The effect of pretreatment with a 4-day course of ciprofloxacin (500 mg twice daily) on the pharmacokinetics and pharmacodynamics of a single oral dose of temazepam (10 mg) was investigated in 12 healthy young and nine elderly patient volunteers in a crossover design study. Temazepam clearance was lower in the elderly than in the young, but this difference was not statistically significant. Ciprofloxacin had no significant effect on temazepam pharmacokinetics or pharmacodynamics in either age group.

Bioavailability of temazepam: comparison of four 7.5-MG capsules with a single 30-MG capsule

OBJECTIVE

To compare the bioavailability of four temazepam 7.5-mg capsules (Restoril, Sandoz Pharmaceuticals) with that of a single temazepam 30-mg capsule.

DESIGN

Single-dose, open-label, two-period, crossover (replicated Latin square).

SETTING

Domiciled environment for clinical testing.

PARTICIPANTS

Twenty-six healthy male volunteers aged 18-40 years; 25 completed the study.

INTERVENTIONS

Subjects randomly received either four temazepam 7.5-mg capsules or one temazepam 30-mg capsule. Blood samples were drawn at various time points after each period (0-48 h), and analyzed for plasma concentration of temazepam. The washout period between doses was five days.

MAIN OUTCOME MEASUREMENTS

Five parameters of both dosage forms were compared: (1) area under curve (AUC), (2) peak concentration (Cmax), (3) time to peak concentration (Tmax), (4) apparent rate constant for absorption, and (5) lag time for appearance of drug in plasma. Statistical procedures included ANOVA, power analysis, and confidence limits.

RESULTS

The mean AUC for the four 7.5-mg capsules and one 30-mg capsule differed by less than 2 percent and the mean Cmax differed by less than 14 percent for the two dosage strengths; neither of these differences reached statistical significance (p > 0.05). The 7.5-mg capsules reached peak plasma concentrations significantly faster than the 30-mg dosage form (mean Tmax 1.18 and 1.73 h, respectively; p = 0.01).

CONCLUSIONS

The two formulations of temazepam were bioequivalent with respect to the extent of bioavailability. Regarding the rate of absorption, however, the 7.5-mg capsules reached peak plasma concentrations significantly faster than the 30-mg dosage form.

Effects of temazepam on saccadic eye movements: concentration-effect relationships in individual volunteers

Saccadic eye movements were analyzed after single oral doses of 20 mg temazepam and placebo in a randomized, double-blind crossover study in eight healthy volunteers. For an optimal evaluation of concentration-effect relationships, 18 blood samples and 43 effect measures were obtained over 33 1/2 hours. After placebo, saccadic peak velocity decreased within the first hour, with average values remaining 6.2% to 12.1% below baseline up to 15 hours after intake. After temazepam, significant changes in peak velocity occurred for 5 hours, with maximum decreases averaging 29.2% (95% confidence interval, 10.0 to 37.2). The apparent duration of effects ranged from 3 to 9 hours in individual subjects. Linear concentration-effect relationships were demonstrated for peak velocity, with individual slopes ranging from -0.11 to -0.46 deg/sec.(ng/ml)-1 (average r = -0.82, all p < 0.01). Differences in protein binding of temazepam did not account for the approximate fourfold variability in individual sensitivities to temazepam. By increasing the frequency of measurements, the accuracy of pharmacodynamic evaluations was clearly enhanced in this study.

The influence of particle size on the bioavailability of inhaled temazepam

1. Temazepam was administered by aerosol using a standard protocol to healthy volunteers. Two studies are reported in which different dosage formulations were used: a) 30 mg of the 5 mu diameter particle (n = 6); b) 10 mg of the 2 mu diameter particle (n = 6). 2. An open crossover design was followed in each study. On one occasion in both studies subjects used a gargling procedure to remove drug which had been deposited in the mouth and oropharynx. 3. Serial venous blood samples were drawn for a period of 24 h. The mean total AUC of the 5 mu preparation was significantly reduced by gargling (3153 ng ml-1 h to 1066 ng ml-1 h) (F = 0.32). Gargling also had a significant effect on the mean AUC(0-1 h). 4. In contrast gargling had no significant effect on the mean AUC associated with the smaller diameter particle preparation (630 ng ml-1 h) vs 397 ng ml-1 h (F = 0.74). 5. These findings also indicate that temazepam deposition in the pulmonary tree is enhanced by the use of a 2 mu rather than a 5 mu diameter particle. However, the plasma drug concentrations achieved are unlikely to produce a sufficiently marked sedative effect for endoscopic investigations such as gastroscopy.

Diazepam metabolism by rat and human liver in vitro: inhibition by mephenytoin

1. Diazepam metabolism and its association with mephenytoin hydroxylase were studied in vitro using human and rat livers. 2. Enzyme kinetic parameters were obtained for the formation of p-hydroxydiazepam (p-hydroxy-DZP), N-desmethyldiazepam (NDZ), and temazepam (TMZ) from diazepam (DZP) in rat liver fractions. The Km values for formation in rat of p-hydroxy-DZP, NDZ and TMZ were 14 +/- 3 (SEM) microM, 44 +/- 4 and 63 +/- 8, respectively; clearance values calculated from Vmax/Km were 5.7, 3.2 and 4.9 ml/g per min, respectively. 3. Mephenytoin (MP) competitively inhibited, in rat liver, the formation of NDZ, but not the formation of p-hydroxy-DZP or TMZ; in human liver neither NDZ nor TMZ formation was inhibited by MP. 4. In seven different human livers the formation of p-hydroxy-DZP represented a minor pathway compared to the formation of NDZ and TMZ.

The relationship between the concentration of temazepam in cerebrospinal fluid and sedation in man

Twenty-six patients received oral temazepam and subsequently spinal anaesthesia. Blood and lumbar cerebrospinal fluid temazepam levels were measured together with the degree of sedation. The plasma and cerebrospinal fluid concentrations correlated well with the temazepam dose but even better with the weight standardised dose (r = 0.65, p = 0.0003 and r = 0.75, p = 0.00001 respectively). Both the plasma and cerebrospinal fluid concentrations of temazepam were correlated with the patient's sedation (r = 0.42 p = 0.037, and r = 0.46 p = 0.021 respectively), but neither was strong. Thus, although the drug concentration at the receptor may be a major factor in producing sedation, other factors, possibly the receptor population or their responsiveness, are also important contributors.

A single-dose study of the pharmacodynamic effects of chlormethiazole, temazepam and placebo in elderly parkinsonian patients

Nine elderly parkinsonian volunteers took single doses of 384 mg of chlormethiazole, 10 mg of temazepam and placebo capsules in a double-blind three-way cross-over study on separate visits at least one week apart. In the 6 hours following the dose, the level of drowsiness, performance on a series of psychomotor tests, effects on parkinsonian symptoms and signs, and standing and lying blood pressure were recorded. Chlormethiazole produced drowsiness on all tests and impaired psychomotor performance, as compared with placebo, without affecting parkinsonian symptoms and signs, or postural blood pressure. Temazepam was consistently less potent than chlormethiazole on tests of drowsiness and psychomotor performance. Both treatments were well tolerated. It is suggested that chlormethiazole is safe to use as a hypnotic at this dosage in this group of patients with Parkinson's disease, while temazepam did not appear to be effective as a hypnotic at this dosage.

Comparative pharmacokinetics of temazepam Gelthix and liquid-filled soft gelatin capsules

An open, randomized, cross-over study involving 24 healthy volunteers, shows that a novel formulation of temazepam (temazepam Gelthix, TG) in soft gelatin capsules designed to resist i.v. abuse has a similar pharmacokinetic (P-K) profile to that of a liquid-filled, reference formulation (TL) when administered as a single oral dose of 20 mg. The relative bioavailability of the two formulations assessed in terms of the area under the time versus plasma concentration profile (AUC), although statistically different (P less than 0.05), is well within the acceptable 80-120% limits for bioequivalence. Although the mean Cmax for TG (616.6 ng/ml) is lower than for TL (707.9 ng/ml) and the median time to reach Cmax (Tmax) is 40 min (TG) vs. 30 min (TL), there is no significant difference between TG and TL either in their absorption constant (Ka) (0.123 vs. 0.138 min-1 respectively) or their distribution (a) (29.5 vs. 32.4 min) and elimination (beta) (6.3 vs. 6.6 h) half-lives (t1/2). Thus the essential P-K characteristics for the use of temazepam as a hypnotic and premedicant, specifically a rapid rise followed by a prompt fall in blood levels, are conserved by the Gelthix formulation.

A comparison of the sensitivities of adaptive tracking, eye movement analysis and visual analog lines to the effects of incremental doses of temazepam in healthy volunteers

The effects of single oral doses of 5, 10, and 20 mg temazepam were evaluated with the adaptive tracking test, analysis of smooth-pursuit and saccadic eye movements, and visual analog lines in a placebo-controlled, double-blind, crossover experiment with 12 healthy volunteers. Pharmacodynamic testing was performed until 10 hours and pharmacokinetics were evaluated until 24 hours. Temazepam, 20 mg, caused effects in all tests, with peak effects occurring at 30 minutes. The 10 mg dose caused effects on saccadic eye movements and subjective scores of alertness, whereas 5 mg temazepam was detected only by analysis of saccadic eye movements. Linear relationships between plasma concentrations and effects were found in nine subjects for saccadic peak velocity and eight subjects for subjective scores of alertness. The results of this study demonstrate manifest differences in the sensitivities of performance tests and stress the importance of validation of methods when effects of drugs on human performance are studied.

Direct high pressure liquid chromatographic analysis and preliminary pharmacokinetics of enantiomers of oxazepam and temazepam with their corresponding glucuronide conjugates

Three high pressure liquid chromatographic systems for the separation of oxazepam, temazepam and their glucuronides (system A), the separation of their R,S glucuronide diastereomers (system B) and the chiral separation of the parent drugs (system C) are described. Preliminary pharmacokinetics of R,S-oxazepam and R,S-temazepam in a human volunteer reveal that the protein binding of the glucuronides is lower than that of the parent drugs, but that there is no difference in protein binding between the R-oxazepam/temazepam and S-oxazepam/temazepam and their corresponding glucuronides. The S-glucuronide is the main metabolite formed and excreted by man. The plasma ratio R/S-glucuronide is 1:1 for both oxazepam and temazepam. The renal clearance of R-temazepam, and S-temazepam are similar, and those of R-oxazepam and S-oxazepam tend to be different.

Comparative effects of rifampin and/or probenecid on the pharmacokinetics of temazepam and nitrazepam

The pharmacokinetics of nitrazepam and temazepam were investigated in 16 healthy volunteers before and after seven days of the administration of rifampin 600 mg/d and/or probenecid 500 mg/d. In order to determine the endoplasmatic reticulum enzyme function, 6-beta-hydroxycortisol excretion and antipyrine pharmacokinetic parameters were evaluated. After the administration of rifampin, the total body clearance of antipyrine and nitrazepam increased by 87% and 83%, respectively. After the combined treatment with rifampin and probenecid, the elimination of the two drugs was also increased, even though to a lesser extent (33%, 31%). After the administration of probenecid only, the total clearances of antipyrine and nitrazepam were decreased by 22% and 25%, respectively. The urinary clearance of the antipyrine metabolites also decreased. In norantipyrine and 4-OH-antipyrine, this was due to a significant reduction of glucuronide fraction (211 +/- 32 to 159 +/- 26 mg, and 259 +/- 39 to 191 +/- 25 mg). The sulphate fraction of norantipyrine increased by 18% and that of 4-OH-antipyrine by 21%. Apart from a reduced excretion of the glucuronide fraction, the pharmacokinetics of temazepam were neither altered significantly by probenecid nor by rifampin. According to the outcome of this investigation, probenecid seems to bring about not merely an inhibition of phase II but also an inhibition of phase I metabolization.

Oxidative versus conjugative biotransformation of temazepam

Twenty-four healthy volunteers, aged 21-59 years, received single 30 mg oral doses of the benzodiazepine hypnotic temazepam. Levels of intact temazepam were determined in multiple plasma samples drawn during 48 h after dosage. Intact temazepam, its direct glucuronide conjugate, and the conjugate of its demethylated (oxidized) metabolite oxazepam were measured in two consecutive 24-h urine collections. Mean kinetic variables for temazepam in plasma were: peak plasma level (Cmax), 873 ng ml-1; time of peak, 1.36 h after dosage; volume of distribution, 0.961 kg-1; elimination half-life 9.9 h; clearance, 1.16 ml min-1 kg-1. Volume of distribution increased significantly with body weight (r = 0.67, p less than 0.001), and Cmax decreased with weight (r = -0.58, p less than 0.01). Only 0.2 per cent of the dose was excreted as intact temazepam, and negligible amounts as intact oxazepam. However, 39 per cent of the dose was recovered as temazepam glucuronide, and oxazepam glucuronide accounted for another 4.7 per cent of the dose. The remainder was not accounted for. Thus, a significant fraction of temazepam clearance occurs by direct glucuronide conjugation, with the conjugate temazepam glucuronide excreted in urine. A much smaller fraction undergoes parallel oxidation to form oxazepam, which is subsequently conjugated to oxazepam glucuronide and excreted in urine.

Plasma and cerebrospinal fluid concentration of temazepam following oral drug administration

Thirteen male patients were administered 20 mg of temazepam orally 1 to 2 h prior to undergoing spinal anaesthesia for a urological procedure. Samples of blood and CSF were drawn just before insertion of the spinal and the concentration of drug estimated in these two media. The results obtained indicated that a highly significant correlation existed between the unbound concentration of temazepam in plasma and the concentration of drug present in CSF. Temazepam appeared to be an effective light pre-medicant in all of the subjects studied.

Premedication with temazepam in minor surgery. The relationship between plasma concentration and clinical effect after a dose of 40 mg

Fourteen patients received oral premedication of temazepam in soft gelatin capsules before minor surgery. The plasma concentrations of temazepam and its sedative, anxiolytic and amnesic effects were measured for 24 hours. Absorption was rapid and peak concentrations occurred 49 minutes after administration. Clinical effects were evident at 30 minutes and persisted for about 4 hours. The decline in plasma concentration was biexponential with a distribution half-life of 1.24 hours. The end of the distribution phase coincided approximately with the termination of its clinical effects. A relationship between plasma concentration and effect was observed; concentrations above 300 ng/ml produced measurable changes in tests of mental function. Patients had recovered fully from the effects of temazepam after 24 hours. This dose of temazepam is reliable and effective as premedication before surgery.

Pharmacokinetic determinants of dynamic differences among three benzodiazepine hypnotics. Flurazepam, temazepam, and triazolam

Healthy adult volunteers (n = 52) received single oral doses of flurazepam hydrochloride (15 mg), temazepam (15 mg), triazolam (0.25 mg), or placebo in a parallel, double-blind study. Sedative effects were greatest with triazolam, followed next by temazepam; peak effects closely coincided with peak plasma concentrations. Differential recovery from sedation corresponded in part to differences in mean elimination halflife, although sedative effects returned to baseline before plasma drug concentrations became undetectable. Sedation following flurazepam administration was less intense than with triazolam and temazepam. When tested at three hours after dosing, none of the active treatments impaired learning of a 16-item word list. However, at 24 hours, triazolam recipients could not recall a significant fraction of what was learned. Thus, dynamic differences among three benzodiazepine hypnotics may be partly explained by kinetic differences, as well as, we should caution, by possible "clinical inequivalence" in dosage.

A methodological comparison of two formulations of temazepam in pharmacokinetic and pharmacodynamic aspects

In a double-blind and cross-over study 12 healthy subjects took temazepam 20 mg in two different formulations (soft gelatine capsule or uncoated tablet) and matched placebo at one-week intervals. Plasma temazepam concentrations at 0.5, 1, 2, 3, 8, 12 and 24 hours after treatment were analyzed by gas chromatography. Psychomotor performance was measured objectively (digit symbol substitution, letter cancellation, Maddox wing test) and subjectively (visual analogue scales) before the drug intake and 1, 2 and 3 hours later and the plasma benzodiazepine concentrations were analyzed also by radioreceptor bioassay. The two different formulations were compared in pharmacokinetic and pharmacodynamic terms, and the gas chromatographic and radioreceptor assays were compared. The soft gelatine capsule produced higher peak plasma concentrations than the uncoated tablet. The computed AUCs and elimination half-lives proved to be similar after either formulation. A satisfactory correlation between the bioassayed benzodiazepine concentrations and chemically assayed temazepam was shown. In pharmacodynamic terms the results suggest a shorter and somewhat smaller subjective response for the capsule than for the tablet form.

Comparison of sedation with temazepam by mouth and diazemuls i.v. for dental surgery. Variability in absorption may influence clinical effect

Temazepam elixir 30 mg by mouth was compared with i.v. Diazemuls titrated to a maximum dose of 20 mg in a double-blind study of 50 patients undergoing elective minor oral surgery. The treatments produced a similar reduction in anxiety score and similar degrees of patient relaxation and co-operation. The diazepam group had greater amnesia during surgery, but also showed significant slowing of reaction time at the time of discharge. Patients given temazepam elixir showed wide variations in plasma concentrations. Patients with low plasma temazepam concentrations at the time of surgery showed no significant reduction in anxiety scores.

Pharmacokinetics of a new sublingual formulation of temazepam

The pharmacokinetics of a new 10 mg sublingual tablet formulation of temazepam and those of a currently marketed 10 mg oral capsule formulation were evaluated in a group of ten healthy volunteers. No significant differences were observed between the two formulations with respect to any of the pharmacokinetic parameters assessed. Lethargy and somnolence were reported on both capsule and tablet by several subjects at a time which corresponded with the maximum concentration of drug in plasma. The data indicate that the sublingual tablet and orally administered capsule have a similar pharmacokinetic and pharmacodynamic profile.

Pharmacokinetics of temazepam after day-time and night-time oral administration

The pharmacokinetic disposition of temazepam was compared after a day-time and night-time dose in an open randomised crossover study. Twelve healthy male volunteers received a single oral dose of 20 mg temazepam in a soft gelatine capsule at 0900 h or 2200 h. Blood samples were taken immediately before dosing and at selected times over the 36-h period after each dose. The absorption of temazepam was slower after evening administration; the absorption half-life and time to reach maximal plasma concentration being 0.53 h and 1.67 h respectively, compared to 0.38 h and 1.02 h following morning administration. Considering distribution characteristics, evening administration produced a lower peak plasma temazepam concentration (362 ng/ml) compared with a day-time level of 510 ng/ml. Distribution half-life after night-time administration was increased compared with day-time administration (1.76 h vs 1.03 h). A significantly higher percentage of the drug, relative to Cmax, remained in the plasma at 8 and 24 h after evening dosing (39.3 and 15.4% compared to 24.7 and 11.2% following day-time administration). In spite of the half-lives of absorption, distribution and elimination all being longer after the evening dose, the overall bioavailability, as measured by the area under the curve (AUC) was comparable after the two times of administration. Similarly the difference in the mean residence time (MRT) of the two doses was within accepted limits. It is concluded that a chronopharmacokinetic effect was seen for temazepam; however it is unlikely to be of any clinical significance.