Comparative pharmacokinetics of brotizolam and triazolam in healthy subjects

Expanded studies of the pharmacokinetics and clinical effects of multidose sublingual triazolam in healthy volunteers

Previous work described the pharmacokinetics and clinical effects of multidose sublingual triazolam (Halcion; Pharmacia & Upjohn Co, Kalamazoo, Mich). This laboratory study evaluated the hypothesis that incremental dosing of triazolam produces dose-dependent central nervous system depression that is profound and long lasting. Forty-nine healthy adults between the ages of 21 and 39 years, not receiving dental treatment, were randomly assigned to placebo (n = 12) or 1 of 3 triazolam groups (0.25-mg single dose, n = 12; 0.5 mg divided between 2 equal doses for 60 minutes, n = 12; or 0.75 mg divided among 3 doses for 90 minutes, n = 13). Plasma triazolam concentrations were determined. Bispectral index (BIS) and the Observer Assessment of Alertness/Sedation scale were used to assess sedation. Plasma triazolam concentrations increased with time in all subjects, with Tmax and Cmax both increasing dose dependently. Compared with placebo, all dosing paradigms produced dose-dependent BIS suppression and sedation. The single dose of 0.25 mg reached its peak BIS suppression at 90 (81 +/- 7) minutes and sedation at 120 (3.6 +/- 0.5) minutes and returned to baseline before 360 minutes. In contrast, incremental dosing of 0.5 and 0.75 mg produced profound and long-lasting BIS suppression and sedation that did not plateau until either 180 or 210 minutes as measured by the BIS index (67 +/- 14 and 60 +/- 16 at 0.5 and 0.75 mg, respectively) and 150 minutes as measured by the Observer Assessment of Alertness/Sedation scale (3.2 +/- 1.0 and 2.7 +/- 0.4 at 0.5 and 0.75 mg, respectively). These data more fully characterize the effects of incremental dosing with sublingual triazolam and provide additional insight for discharge safety recommendations.

The influence of the menstrual cycle on triazolam and indocyanine green pharmacokinetics

The aim of this study was to investigate the effects of the menstrual cycle phase on the pharmacokinetics of two high-clearance agents, triazolam and indocyanine green (ICG). Eleven nonsmoking, healthy, eumenorrheic women were enrolled in this study. Triazolam (0.25 mg) was administered orally, and indocyanine green was administered as an i.v. bolus (0.5 mg/kg) during the follicular, ovulatory, and luteal phases of a single menstrual cycle. Blood samples were collected over 10 hours for triazolam and over 30 minutes for ICG. Triazolam and indocyanine green concentrations were quantitated by electron capture gas chromatography and spectrophotometry, respectively. Noncompartmental analysis was used to determine relevant pharmacokinetics parameters, which were statistically assessed using two-way ANOVA (p < 0.05). No statistical differences for triazolam were observed. Vd/F was lower in the luteal phase (107 L) as compared to the follicular (138 L) and ovulatory (133 L) phases. Clearance of triazolam was comparable in the follicular (583 ml/min), ovulatory (565 ml/min), and luteal (538 ml/min) phases. ICG also revealed no significant differences across the phases. These results suggest that the phases of the menstrual cycle do not influence triazolam or ICG pharmacokinetics.

Use of high-performance liquid chromatography as an extraction procedure for analysis of triazolam in decomposed human muscle by gas chromatography-mass spectrometry

A reliable and sensitive method for the determination of triazolam in human muscle using gas chromatography-mass spectrometry (GC-MS) is described. The drug was extracted from decomposed human muscle using three-step liquid-liquid extraction and HPLC which was performed isocratically on a conventional ODS column with a mobile phase of 0.01 M phosphate buffer (pH 6.5)-acetonitrile (7:3). Estazolam was used as an internal standard. GC-MS analysis was performed on a DB-5 capillary column. Excellent linearity was obtained over the concentration range 1-200 ng/g. The lower limit of detection was approximately 0.5 ng/g. Forensic application of the present method was also described.

Changes of cyclic alternating pattern (CAP) parameters in situational insomnia under brotizolam and triazolam

The standardized scoring criteria of sleep can serve as a rough tool for monitoring the effects of psychoactive compounds, both in normal sleepers and in insomniac patients. More sensitive information on the impact of perturbing factors and drugs during sleep is supplied by the cyclic alternating pattern (CAP) parameters. In particular, CAP rate, which measures the amount of arousal instability during NREM sleep, has been proved of high reliability in a variety of clinical and pharmacological settings. The present study aimed at evaluating the activity of brotizolam (Br) 0.25 mg and triazolam (Tr) 0.25 mg on both conventional and CAP parameters in a model of situational insomnia of intermediate severity. Six middle-aged healthy subjects (three males and three females, aged 40-55 years) with no complaints about sleep, underwent a polysomnographic investigation according to a double-blind crossover design: placebo without noise (night 1), placebo with noise (night 2), brotizolam or triazolam without noise (nights 3 and 5), brotizolam or triazolam with noise (nights 4 and 6). The unperturbed nights consisted of standard recording conditions in a sound-protected sleep laboratory, whereas situational insomnia was accomplished by means of continuous white noise at 55 dBA delivered throughout the night. Subjects received medication orally at bedtime. An interval of at least 48 h was secured between consecutive recordings in the same individual. Compared to baseline conditions, situational insomnia was characterized by a shorter amount of total sleep (-40 min) and by an extension of intrasleep awakenings (+62 min).(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo high intrinsic efficacy of triazolam: a positron emission tomography study in nonhuman primates

The triazolobenzodiazepine triazolam is a central-type benzodiazepine receptor (BZR) ligand that is widely prescribed as a hypnotic agent. Triazolam produces its effects through potentiation of gamma-aminobutyric acid-mediated neurotransmission. Findings reported from in vitro binding studies showed some discrepancies concerning the pharmacological characteristics of triazolam. The present study aims to characterize in vivo the biochemical properties of triazolam, i.e., cerebral pharmacokinetics, interaction with BZR, potency, and intrinsic efficacy. Triazolam was studied in living nonhuman primates using positron emission tomography. Two different studies were carried out: (a) a direct study using [11C]triazolam and (b) an indirect competition study using the radiolabeled BZR antagonist 1C]flumazenil. Results showed that, in the brain in vivo, triazolam binds specifically and competitively to the BZR. Its rapid cerebral kinetics is consistent with a hypnotic profile (maximal binding after 23 min, elimination half-life of 202 min). Triazolam is very potent in displacing [11C]flumazenil (ID50 = 28 +/- 6 micrograms/kg). Hill analysis of the displacement curve does not show obvious binding-site heterogeneity. Triazolam is 20 times more potent in displacing [11C]flumazenil and 50 times more potent in inhibiting pentylenetetrazol-induced paroxysmal activity than the full benzodiazepine agonist diazepam. Interestingly, the simultaneous use of positron emission tomography and EEG recording allowed us to show that triazolam-positive intrinsic efficacy is slightly higher (20%) than that of diazepam. An attractive hypothesis proposes that the severity of side effects of BZR ligands is proportional to their intrinsic efficacy. Therefore, our study shows that triazolam side effects, as for other benzodiazepines, may be related to its high intrinsic efficacy in vivo.

Classification of benzodiazepine hypnotics in humans based on receptor occupancy theory

Benzodiazepine (BZP) hypnotics are now classified into four groups according to their plasma elimination rates: ultrashort-, short-, intermediate-, and long-acting drugs. Since the specific binding affinities for the BZP receptor vary widely among the BZPs and their active metabolites, it may be more reasonable to correlate their pharmacological activities with the BZP receptor occupancy rather than with their plasma concentrations. The time courses of total plasma concentrations of BZPs and their active metabolites after a single oral administration were obtained from the literature, and their unbound concentrations (Cu) were calculated from the reported values of their plasma unbound fractions. The data of the receptor binding affinities of the BZPs, reported as dissociation constants (Kd) determined by in vitro binding experiments, were also obtained from the literature. Using these values, the time courses of receptor occupancies [Cu/(Kd + Cu) x 100%] were calculated for the various BZPs. A mutual competitive inhibition was considered in the case of the drugs that had active metabolites. Although plasma total and unbound concentration time profiles of the BZPs showed a wide variation, similar patterns were obtained for the time courses of the receptor occupancy among the BZPs in each group, indicating that the BZP hypnotics can be classified more conveniently based on receptor occupancy theory.

Avoiding the blanket approach to insomnia. Targeted therapy for specific causes

A systematic approach to the common complaint of insomnia usually results in a specific clinical diagnosis with clear therapeutic implications. Use of effective treatment strategies tailored to the situation can make treating insomnia a gratifying experience instead of a frustrating one.

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.

Single and multiple dose pharmacokinetics of etizolam in healthy subjects

The pharmacokinetics of etizolam, a new thienodiazepine derivative, has been examined after single and multiple (0.5 mg tablet) (0.5 mg b.d for 1 week) oral therapeutic doses in healthy volunteers. The single-dose kinetic profile of etizolam suggested that absorption after oral dosage was reasonably rapid, the maximum plasma concentration (Cmax) being attained within 0.5-2 h in all subjects. The mean elimination half-life (t1/2) averaged 3.4 h. Consistent with this, steady-state concentration were rapidly achieved and accumulation was extremely limited. Predicted average plasma concentrations (Cp) did not differ significantly from those actually measured at steady-state, suggesting that the kinetics of etizolam was linear, at least at therapeutic doses. The mean wash-out t1/2 was comparable to the elimination t1/2 of the single dose, which means that the drug probably has no effect on hepatic microsomal enzymes and other kinetic variables after repeated dosing. At steady state plasma concentrations of the main metabolite, alpha-hydroxyetizolam, were higher and disappeared more slowly (mean t1/2 8.2 h) than those of the parent compound. Taken with the fact that in animals the metabolite shows almost the same potency of pharmacological action as etizolam, this suggests that it may contribute significantly to the clinical effects of the parent compound. Based on the kinetic characteristics of the parent drug and its metabolite, etizolam can be regarded as a short-acting benzodiazepine, with elimination kinetics between those of short-intermediate derivatives and ultra-rapidly eliminated benzodiazepines.

Pharmacokinetics of the newer benzodiazepines

The assay methods used to determine the concentrations of the newer benzodiazepines include electron-capture gas-liquid chromatography, high performance liquid chromatography with ultraviolet detection, gas chromatography-mass spectrometry, radioassay and radioreceptor assay. The method used frequently is the highly sensitive and specific electron-capture gas-liquid chromatography. Other methods are associated with limitations. The triazolo- and imidazolebenzodiazepines differ structurally from the 'classical' benzodiazepines such as diazepam, and offer distinct differences in pharmacological activity and in time-course of effect. Alprazolam and triazolam, both 1,4-triazolobenzodiazepines, have high affinities for the benzodiazepine receptor as do midazolam and loprazolam, which are 1,4-imidazolebenzodiazepines. Absorption is characteristically rapid, with peak alprazolam and triazolam concentrations occurring within 1 hour after oral administration. Sublingual administration results in peak alprazolam and triazolam concentrations that are higher and occur earlier than with the oral route. The volume of distribution of alprazolam and triazolam is approximately 1L. Alprazolam is 70% bound to plasma proteins and the extent of binding is independent of concentration. Similarly, triazolam is approximately 85% bound to plasma proteins, variability in binding being explained by variations in alpha 1-acid glycoprotein concentration. The 1,4-triazolo ring prevents the oxidative metabolism of the classical benzodiazepines which results in formation of active metabolites with long elimination half-lives. Alprazolam is extensively metabolised: 29 metabolites have been identified in the urine, and its major metabolite, alpha-hydroxyalprazolam, has pharmacological activity. alpha-Hydroxyalprazolam and 4-hydroxyalprazolam are detectable in plasma in amounts which account for less than 10% of the administered dose. Mean alprazolam elimination half-life in healthy adult subjects ranges from 9.5 to 12 hours; liver disease prolongs alprazolam elimination, but renal insufficiency does not. Triazolam also undergoes oxidation and subsequent glucuronidation. alpha-Hydroxytriazolam is the major metabolite, in addition to which 4-hydroxyalprazolam and alpha-4-hydroxytriazolam have been identified in plasma and urine. The elimination half-life of triazolam ranges between 1.8 and 5.9 hours, while that of the conjugated metabolites is short, approximately 3.8 hours. Accumulation of triazolam or its metabolites after multiple doses does not occur. Liver disease prolongs triazolam elimination from the body, but renal disease does not.(ABSTRACT TRUNCATED AT 400 WORDS)

Brotizolam. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy as an hypnotic

Brotizolam is a new thienotriazolodiazepine derivative with a pharmacological profile similar to that of benzodiazepines. It is indicated for use as an hypnotic in the management of insomnia, although it also has anticonvulsant, antianxiety and muscle relaxant properties in animals. In clinical trials brotizolam 0.125 to 0.5mg improved sleep in insomniacs similarly to nitrazepam 2.5 and 5mg, flunitrazepam 2mg and triazolam 0.25mg, whilst brotizolam 0.5mg was shown to be superior to flurazepam 30mg in some studies. Brotizolam is an effective hypnotic for hospital patients awaiting surgery, in whom it also reduces anxiety. Brotizolam has an elimination half-life of about 5 hours, which is 'intermediate' compared with the shorter-acting hypnotic, triazolam, and longer-acting benzodiazepines. Consequently, it is able to induce sleep without producing early morning rebound insomnia, and can also maintain sleep throughout the night. Brotizolam at dosages below 0.5mg at night usually produced minimal morning drowsiness; no residual impairment of psychomotor performance occurs following dosages within the recommended range of 0.125 to 0.25 mg/kg. No serious side effects have been reported to date and the most frequently observed adverse experiences are drowsiness, headache and dizziness. Mild rebound insomnia may occur in some patients when treatment is stopped. Thus, brotizolam is a useful hypnotic which can be used in patients who have difficulty in falling asleep and also in patients who are troubled by night-time awakenings. Used in the recommended dosage it may be particularly useful for patients in whom daytime impairment of performance is unacceptable.

Hypnotics. Their place in therapeutics

Sleep disturbance has become a subject of serious study only over the past few years, but even so there is already an increasing awareness of the nature of insomnia and a greater understanding of the role which hypnotics should play in clinical medicine. An hypnotic may be used to shorten sleep onset when there is difficulty in falling asleep, to reduce nocturnal wakefulness, or to provide an anxiolytic effect during the next day when insomnia is accompanied by a marked element of anxiety. The purpose of an hypnotic is to meet one or more of these clinical problems; to ensure that the patient is given the most useful medication, consideration must be given to duration of activity. This depends on the absorption, distribution and elimination characteristics of the drug. It is now appreciated that the most appropriate use of hypnotics is in the individual with insomnia of recent origin. An hypnotic with the most relevant pharmacokinetic profile should be used for the shortest period of time and then only as required, while low doses will ensure freedom from adverse effects. The place of hypnotics in chronic insomnia remains less certain. Their careful use may well be of benefit, though it must be part of a well defined clinical strategy. Assessment of the patient is essential to identify any specific conditions which would impair sleep.

Brotizolam radioimmunoassay: development, evaluation, and application to human plasma samples

A radioimmunoassay for the determination of the hypnotic agent brotizolam (11) was developed. With this procedure, an antiserum was used which was obtained from rabbits immunized with the hapten 10 (We 934) covalently bound to bovine serum albumin and tritium-labeled brotizolam as the radioligand. Compound 10 represents a structural analogue of brotizolam: the bromine was replaced by a carboxyethyl group. By such manipulation high assay specificity against the primary human metabolites was achieved. The sensitivity limit of the assay was about 100 pg of brotizolam per mL of plasma when 0.1-mL samples were used. The assay showed good accuracy and high precision. Repeated assays after keeping plasma samples frozen for various periods again indicated high precision as well as the stability of the brotizolam molecule under these conditions. Application of the assay to plasma samples of eight subjects who received single oral 0.25-mg doses of brotizolam showed a mean maximum plasma concentration of 4.6 ng of unchanged drug per mL at 0.9 h after administration. The brotizolam plasma concentration declined with a mean elimination half-life of 5.1 h. The pharmacokinetic parameters estimated by RIA agree well with those obtained with other specific brotizolam determination procedures.

Comparative study on the efficacy of and the tolerance to the triazolodiazepines, triazolam and brotizolam

Efficacy of and tolerance to 0.25 mg brotizolam and 0.25 mg triazolam were compared in hospitalised patients (aged 20 to 69 years) with sleep difficulties. Over 6 days there were no differences in efficacy and tolerance. The physicians reported the effectiveness of the drugs as good-to-satisfactory in 88.6% with brotizolam and 92.0% with triazolam. The patients reported with both drugs reduced time to fall asleep, less awakenings, increased duration of sleep and improved condition on awakening.

Pharmacokinetics of oral brotizolam in patients with liver cirrhosis

Disposition of oral brotizolam (0.5 mg) was studied in male patients with liver cirrhosis (patients) and in other patients (control) matched for age, weight, smoking and drinking habits. Absorption of brotizolam was relatively rapid in both groups with a median peak time (range) of 1.0 (0.5-2.0) h. Peak concentrations were also similar with median values of 7.1 (3.2-10.7) ng/ml in patients and 9.4 (2.9-19.0 ng/ml) in controls. Elimination half-life was longer in patients than in controls. The median values were 12.8 (9.4-25) h and 6.9 (4.4-8.4) h respectively (P less than 0.01). In two patients hardly any drug elimination was observed, indicating severe impairment of drug metabolizing activity. The prolongation of the elimination half-life was likely to be due to a decrease in clearance (45 ml/min in patients compared with 64 ml/min in controls), and an increase in volume of distribution (0.62 l/kg and 0.39 l/kg respectively). Median values of protein unbound fraction of brotizolam were 9.2 (7.8-10.4) % in controls and 12.4 (10.4-18.9) % in patients. Clearance of unbound drug was 612 ml/min and 380 ml/min respectively.

Pharmacokinetics of brotizolam in healthy subjects following intravenous and oral administration

Pharmacokinetics and bioavailability of brotizolam after i.v. and oral administration were studied in healthy young volunteers. Kinetic parameters after i.v. administration were: volume of distribution 0.66 +/- 0.19 1/kg, total plasma clearance 113 +/- 28 ml/min, distribution half-life 11 +/- 6 min, and elimination half-life 4.8 +/- 1.4 h (mean values +/- s.d.). Kinetic parameters after oral administration were: absorption lag-time 8 +/- 12 min, absorption half-life 10 +/- 11 min, and elimination half-life 5.1 +/- 1.2 h (mean values +/- s.d.). Bioavailability of brotizolam was 70 +/- 22% when calculated by comparing oral and intravenous area-under-curve values, corrected for intra-individual half-life differences. An alternative calculation method, which is relatively independent of large clearance variations, provided a bioavailability of 70 +/- 24% (range: 47-117%).

Pharmacokinetics of brotizolam in the elderly

Disposition of brotizolam in patients aged 71-93 years was compared with that of healthy young subjects aged 21-26 years. The mean elimination half-life of brotizolam was about twice as long in the elderly as in the young subjects: 9.3 (4.0-19.5) h and 4.8 (3.1-6.3) h respectively. Increase in elimination half-life was attributable to a decrease in hepatic clearance, i.e. 40 (20-58) ml/min in the elderly and 109 (77-156) ml/min in the young. Volume of distribution and protein binding were the same with mean values of 0.56 (0.45-0.72) l/kg and 9.0 (6.8-11.9) % in the elderly and 0.63 (0.40-0.77) l/kg and 8.4 (7.5-9.4) % in the young. Absorption rate of brotizolam was relatively slow in the elderly with a mean peak time of 1.7 h compared with 1.1 h in the young. Mean bioavailability was almost 70% for both groups. Normalized for body weight and dose (0.25 mg) mean peak concentrations were 247 (137-395) ng ml-1 kg in the young and 343 (251-446) ng ml-1 kg in the elderly. It is unlikely that substantial drug accumulation will occur if elderly patients ingest 0.25 mg brotizolam nightly.