[Investigations of poisonings with benzodiazepine derivatives mixtures by thin-layer chromatography]

The thin-layer chromatography method was proposed for separation and identification of drugs in mixture alprazolam : brotizolam : clorazepate dipotassium. The mixture of these drugs excreted from body fluid (blood) was investigated by the thin-layer chromatography. Most acceptable is this mobile phase : benzene : dioxane : conc. ammonia : methanol : ethanol (60:25:5:10:10). Rf values for drugs: alprazolam 0.81-0.83, brotizolam 0.59-0.62, clorazepate dipotassium 0.67-0.69.

A comparative evaluation of the effects of oral lorazepam, alprazolam and diazepam on venous admixture

OBJECTIVE

To compare the effects of oral diazepam, lorazepam and alprazolam premedication on venous admixture.

MATERIAL AND METHODS

One hundred fifty patients divided in three groups were included in the study. The venous admixture was determined using the ISO-shunt nomogram. The values obtained 90 minutes after administration of the drugs were compared with the values before the drug administration. The Student's t-test was applied to find out the significance.

RESULTS

These were highly significant change in increase in venous admixture (Qs/Qt) in group I patients 90 minutes after premedication as compared to premedication values. There was statistically insignificant difference in venous admixture (Qs/Qt) in group II and group III patients 90 minutes after premedication as compared to premedication values.

CONCLUSION

From the present study it can be concluded that 2 mg of oral lorozepam given 90 minutes before surgery to healthy patients have significant effects on venous admixture. However, the effects of alprazolam and diazepam had no significant effect on venous admixture.

Differential effects of alprazolam on the baseline and fear-potentiated startle reflex in humans: a dose-response study

RATIONALE

The "fear-potentiated startle" paradigm has been extensively used in animal studies, and more recently in human experimental psychopharmacology to evaluate the effects of anxiogenic and anxiety-relieving drugs. Previous human studies have shown that both the baseline and the fear-potentiated responses can be inhibited by anxiety-relieving drugs, suggesting drug activity on two different emotional states, the former reflecting a resting condition and the latter more akin to pathological anxiety.

OBJECTIVES

To examine to which extent the reductions induced by a benzodiazepine on the basic and the fear-potentiated startle responses are of equal intensity, and whether or not the drug shows a predominant, i.e., selective, effect on either.

METHODS

The effects of three increasing doses of the benzodiazepine alprazolam (0.25, 0.5, and 1.0 mg) were assessed on the human baseline and fear-potentiated startle responses. Twelve healthy volunteers attended the laboratory on four experimental days and received either alprazolam or placebo according to a double-blind crossover balanced design. Startle recordings were undertaken 2 h after drug intake. Fear potentiation was implemented by means of an electric-shock-anticipation experimental procedure. Additionally, subjective self-reports of sedation and anxiety and psychomotor performance were obtained at 2 and 3 h, respectively, after drug administration.

RESULTS

Alprazolam dose-dependently impaired psychomotor performance and produced increases in subjective anxiolytic activity and sedation, although the latter did not reach statistical significance. Additionally, the drug reduced the magnitude of the startle response both in the absence and in the presence of a threat-related cue, although a differentially greater inhibitory effect was seen on the fear-potentiated response as the dose increased.

CONCLUSIONS

Alprazolam showed a greater inhibitory effect on the fear-potentiated startle than on the baseline reflex, suggesting a more selective action of the drug on those structures mediating potentiation of the behavioral response by anxiety.

No correlations between the urinary ratio of 6beta-hydroxycortisol to free cortisol and pharmacokinetics of alprazolam

OBJECTIVE

The urinary ratio of 6beta-hydroxycortisol to cortisol is known as a possible marker of CYP3A4 activity. We investigated the correlation between this ratio and the disposition of alprazolam, which is a substrate of CYP3A4.

METHODS

Twelve healthy volunteers took a single dose (0.8 mg) of alprazolam at 0800 hours. Blood samplings were conducted up to 48 h after the dosing. Urine was collected during the 24 h prior to dosing. Quantification of alprazolam in plasma and that of cortisol and 6beta-hydroxycortisol in urine was performed using high-performance liquid chromatography.

RESULTS

Mean (+/-SD) values of peak plasma concentration (Cmax), time to Cmax (tmax), area under the plasma concentration-time curve [AUC(0-48)] and elimination half-life (tl/2) of alprazolam were 12.0+/-3.0 ng/ml, 1.5+/-0.9 h, 200+/-41 ng/ml h and 16.0+/-4.3 h, respectively. Mean (+/-SD) urinary ratio of 6beta-hydroxycortisol to cortisol was 3.28+/-0.67. No significant correlations were found between urinary ratio of 6beta-hydroxycortisol to cortisol and any pharmacokinetic parameters of alprazolam (Cmax: rs= -0.06; tmax: r(s)= 0.34; AUC(0-48): rs=0.08; t1/2: r(s)= -0.36).

CONCLUSION

This study suggests that the urinary ratio of 6beta-hydroxycortisol to cortisol is unlikely to predict pharmacokinetics of alprazolam.

Benzodiazepine pharmacodynamics: evidence for biophase rate limiting mechanisms

Pharmacokinetics do not adequately reflect recovery from cognitive neuromotor impairment induced by most benzodiazepines. This paper examines across time the nature of the relationship of effect to serum concentration of three benzodiazepines. Using the same protocol lorazepam, alprazolam, diazepam and placebo were administered to eight healthy males at doses of 0.057, 0.029, 0.286 and 0.000 mg/kg, body weight, respectively for the first study and at 0.028, 0.014, 0.143 and 0.000 mg/kg, respectively, for the second study. After each dose administration multiple measurements were made over a period of 5.5-11.5 h using two different psychomotor performance tests. Serum drug concentrations were also measured. The profiles for diazepam and alprazolam effects demonstrate a stepwise decrement in the slopes of the concentration versus response curves across time, illustrating the rapid development of acute tolerance. In contrast, lorazepam induced a remarkably constant relationship between concentration and effect across testing intervals.

Negligible tolerance produced by chronic intravenous alprazolam administration: a low serum drug concentration effect

In 3-hr sessions, the authors investigated the onset, peak, and disappearance of the effects of alprazolam on performance under a differential reinforcement of low rate 45-s schedule in rats. Alprazolam was administered chronically as a daily bolus dose (2 mg/kg) via the intravenous route. Alprazolam decreased the reinforcement rate and increased the shorter response (nonreinforced) rate in a dose- and time-related fashion. Tolerance did not develop to the decreases in reinforcement rate; tolerance to increases in shorter response rate was negligible, occurring only at the low-concentration range. Clinically, an optimal dose regimen should be designed to avoid the tolerance development that occurs in the low serum benzodiazepine concentration range.

Opipramol for the treatment of generalized anxiety disorder: a placebo-controlled trial including an alprazolam-treated group

Opipramol, a drug widely prescribed in Germany, is a tricyclic compound with no reuptake-inhibiting properties. However, it has pronounced D2-, 5-HT2-, and H1-blocking potential and high affinity to sigma receptors (sigma-1 and sigma-2). In early controlled trials, anxiolytic effects were revealed. However, those studies were performed before the concept of generalized anxiety disorder (GAD) was established. Because of the interesting receptor-binding profile and promising results of the early clinical trials, the authors performed a state-of-the-art placebo-controlled trial using alprazolam as an active control. Three hundred seven outpatients with GAD were included. After a 7-day single-blind placebo washout, patients were randomly assigned to receive either opipramol (final dose, 200 mg/day), alprazolam (2 mg/day), or placebo and were treated for 28 days. The efficacy of both active compounds was higher than the effects with placebo treatment. There were statistically significant differences (p < 0.05, according to the analysis of covariance) in the main outcome criterion (baseline-adjusted final means of an intent-to-treat analysis of the total scores on the Hamilton Rating Scale for Anxiety) and in secondary efficacy parameters, with global improvement of 47% for placebo and significantly more for opipramol (63%) and alprazolam (64%). Regarding safety and tolerability, no substantial differences in the number of adverse events observed between treatment groups were obvious. Sedation seemed more pronounced with alprazolam treatment than with opipramol or placebo. In this trial, it was demonstrated for the first time that opipramol, a strong but nonselective sigma site ligand, possesses anxiolytic efficacy superior to placebo in the treatment of GAD.

High-speed liquid chromatography/tandem mass spectrometry using a monolithic column for high-throughput bioanalysis

With the ever-increasing workload from a variety of in vitro and in vivo screening procedures, new analytical methodologies to perform bioanalysis in an accurate and high-throughput manner are in great demand. In this work, monolithic columns were used instead of conventional particulate HPLC columns to perform chromatographic separations. Because the pressure drop on a monolithic column was considerably lower than that on a particulate column, a high flow rate (6 mL/min) was used for a 4.6 x 50 mm monolithic column with a total backpressure of about 61 bar measured using acetonitrile/water (50:50). The capability of using a regular column length at high flow rates, combined with the extremely small dependency of separation efficiency on linear flow velocity, allowed for the generation of sufficient chromatographic resolving power in a significantly reduced runtime. As demonstrated in this work, a plasma extract of a mixture of tempazepam, tamoxifen, fenfluramine, and alprozolam were baseline separated within a total analysis time of one minute. An average peak width at half maximum of approximately one second was noted using a generic broad gradient. It was also found that the separation efficiency and signal/noise (S/N) ratios for this separation remained almost constant at flow rates of 1, 3, and 6 mL/min, respectively. The ruggedness of the separation was evaluated by injecting 600 plasma extracts containing the replicates of a standard curve of the above mixture during an overnight run. The chromatographic retention time, separation quality, peak response and sensitivity were highly reproducible throughout the run. This high-speed liquid chromatography/tandem mass spectrometry (LC/MS/MS) system has been used routinely in the authors' laboratory to support drug discovery programs.

A comparative pharmacokinetic and dynamic evaluation of alprazolam sustained-release, bromazepam, and lorazepam

Sustained-release (SR) alprazolam may facilitate compliance with oral benzodiazepine treatment of panic disorders that currently requires doses administered three or four times daily. To compare the pharmacokinetic, psychomotor performance, and subjective effects of alprazolam SR (1.5 mg), bromazepam (3 mg taken three times daily), and lorazepam (1 mg taken three times daily), 13 male volunteers (aged 20-45 years) randomly received on four separate occasions one of these medications or placebo. Once before and 11 times after drug administration, the subjects were tested using psychomotor performance tests (manual tracking and digit-symbol substitution test [DSST]) and computerized questionnaires (such as the Tufts University Benzodiazepine Scale [TUBS], the Addiction Research Center Inventory, and the visual analog scales) to determine the subjective effects of the drugs. Blood samples for the determination of the plasma levels of the drugs were collected before and 17 times after the drug was administered. A peak plateau of plasma alprazolam began approximately 6 hours after the dose, which was later than the initial peaks for lorazepam and bromazepam (1-2 hours after the dose). Once this plateau had begun, alprazolam SR sustained that concentration better than did the other two formulations. Of the 10 measures on which the response averaged for the first 14 hours differed among drugs (p < 0.05), bromazepam differed from placebo on two measures, lorazepam on four (including DSST Performance and TUBS Sedation), and alprazolam SR on nine (including all four affected by lorazepam). Lorazepam and alprazolam, but not bromazepam, produced significantly more sedation than placebo. The doses of the three drugs were not equipotent in sedation and mood effects. None of the drugs tested differed from placebo on measures relevant to abuse liability.

A comparison of plasma alprazolam concentrations following different routes of chronic administration in the Sprague-Dawley rat: implications for psychotropic drug research

RATIONALE

Benzodiazepines are effective in the treatment of anxiety disorders over a prolonged period of time. This results in relatively stable plasma concentrations over the course of a day. However, due to differences in drug clearance in rats, which generally metabolize and clear drugs much more rapidly than humans, it is difficult to model this steady level in rats.

OBJECTIVES

Several methods of chronic alprazolam administration were compared to determine which would best result in reproducible, therapeutically relevant levels of the drug.

METHODS

Male Sprague-Dawley rats were administered alprazolam via two subcutaneous routes, Alzet 2ML2 osmotic minipumps and commercially produced slow-release pellets, for 1 week and 2 weeks, respectively. Additionally, alprazolam was orally administered for 2 weeks by mixing the compound into a commercially available liquid, fat emulsion-based diet. The use of silastic implants to deliver several different benzodiazepines was also evaluated in vitro.

RESULTS

Following 7 days of alprazolam administration at 2 mg/kg per day via osmotic minipump, plasma concentrations in ten identically treated rats ranged from <1 ng/ml to 97 ng/ml. Slow-release pellets produced more consistent plasma concentrations, but were only minimally effective at raising plasma concentrations. In vitro studies utilizing silastic implants containing 90 mg drug in 6 cm of tubing revealed stable release of only 45-55 microg/day alprazolam versus 625-650 microg/day diazepam. In contrast to these methodologies, incorporation of alprazolam into a commercially available liquid diet (approximately 25-150 mg/kg per day) provided consistent, dose-dependent increases in plasma concentrations of alprazolam and its metabolites in a range appropriate for mimicking clinical exposure.

CONCLUSIONS

These findings indicate that the most effective technique to produce plasma concentrations of alprazolam that are reproducible, clinically pertinent, and consistent between rats is to incorporate the drug into a liquid diet. These findings may also be of value in determining dosing routes for other benzodiazepines or psychotropic drugs.

Effects of repeated ingestion of grapefruit juice on the single and multiple oral-dose pharmacokinetics and pharmacodynamics of alprazolam

The effects of repeated ingestion of grapefruit juice, an inhibitor of cytochrome P450 3A4 (CYP3A4), on the pharmacokinetics and pharmacodynamics of both single and multiple oral doses of alprazolam, a substrate of CYP3A4, were examined. In study 1, eight healthy volunteers ingesting 600 ml/day water or grapefruit juice for 10 days took a single oral 0.8-mg dose of alprazolam on the eighth day. Plasma drug concentrations were monitored up to 48 h after alprazolam dosing together with evaluation of psychomotor function. Grapefruit juice altered neither the plasma concentrations of alprazolam at any time points, any pharmacokinetic parameters, nor the majority of psychomotor function parameters in subjects. In study 2, 11 patients with anxiety disorders receiving alprazolam (0.8-2.4 mg/day) ingested grapefruit juice (600 ml/day) for 7 days. Blood samples were collected before and during grapefruit juice ingestion and 1 week after its discontinuation together with an assessment of clinical status. Grapefruit juice altered neither the steady-state plasma concentration of alprazolam nor the clinical status in patients. The present study shows that grapefruit juice is unlikely to affect pharmacokinetics or pharmacodynamics of alprazolam due to its high bioavailability.

Alprazolam-ritonavir interaction: implications for product labeling

BACKGROUND

Pharmacokinetic interactions involving antiretroviral therapies may critically influence the efficacy and toxicity of these drugs, as well as pharmacologic treatments of coincident or complicating diseases. The viral protease inhibitor ritonavir is of particular concern since it both inhibits and induces the activity of cytochrome P450 3A (CYP3A) isoforms.

METHODS

The inhibitory effect of ritonavir on the metabolism of alprazolam, a CYP3A-mediated reaction in humans, was tested in vitro using human liver microsomes. In a double-blind clinical study, volunteer subjects received 1.0 mg of alprazolam concurrent with low-dose ritonavir (four doses of 200 mg) or with placebo.

RESULTS

Ritonavir was a potent in vitro inhibitor of alprazolam hydroxylation. The 50% inhibitory concentration was 0.11 micromol/L (0.08 microg/mL); this is below the usual therapeutic plasma concentration range (generally exceeding 2 microg/mL). In the clinical study, ritonavir reduced alprazolam clearance to 41% of control values (P < .001), prolonged elimination half-life (mean values, 30 versus 13 hours; P < .005), and magnified benzodiazepine agonist effects such as sedation and performance impairment.

CONCLUSION

Consistent with in vitro results, administration of low doses of ritonavir for a short duration of time resulted in large impairment of alprazolam clearance and enhancement of clinical effects. Removal from product labeling of a warning against coadministration of ritonavir and alprazolam was based on a previous study only of extended exposure to ritonavir, in which CYP3A induction offset inhibition. Kinetic interactions involving antiretroviral therapies may be complex and time dependent. Product labeling should reflect this complexity.

Fatal overdose of tramadol and alprazolam

A 30-year-old woman, with history of depression, was found dead after the ingestion of an unknown quantity of Xanax (alprazolam), Tramal (tramadol) and alcohol. At the autopsy only a slight decomposition and a diffuse visceral congestion were noticed. Biological samples obtained at autopsy were analysed to detect the presence of alprazolam, tramadol and alcohol. Blood concentrations of alprazolam, alcohol and tramadol were 0.21 mg/l, 1.29 g/kg and 38.3 mg/l, respectively.

Quantitation of alprazolam and alpha-hydroxyalprazolam in human plasma using liquid chromatography electrospray ionization MS-MS

A sensitive and specific electrospray ionization high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) method has been developed for the quantitative determination of alprazolam (AL) and alpha-hydroxyalprazolam (OH-AL) in plasma. After the addition of deuterium labeled internal standards of AL and OH-AL, plasma samples were buffered to alkaline pH and extracted with toluene/methylene chloride (7:3). Dried extract residues were reconstituted in HPLC mobile phase and injected onto a reversed-phase C18 HPLC column. The analytes were eluted isocratically at a flow rate of 250 microL/min using a solvent composed of methanol and water (60:40) containing 0.1% formic acid. The analyses were performed using selected reaction monitoring. The assay was sensitive to 0.05 ng/mL for both the parent drug and metabolite and linear to 50 ng/mL. The intra-assay percent coefficients of variation (%CV) for AL at 2, 5, and 20 ng/mL were all < or = 5.6. At these concentrations, and all OH-AL intra-assay %CVs were < or = 8.4. The interassay variabilities for AL were 11.8%CV, 8.7%CV, and 8.7%CV at 2.0, 5.0, and 20.0 ng/mL, respectively. The OH-AL interassay variabilities were 9.6%CV, 9.2%CV, and 7.8%CV at the same concentrations, respectively. The assay accuracy was less than or equal to +/- 6.6% for both analytes at the three concentrations. The method was used to quantitate AL and OH-AL in plasma samples collected from 10 subjects who were administered a 1-mg oral dose of AL. The mean AL concentration peaked at 11.5 ng/mL 1 h after the dose and AL was detectable for 48 h. The mean OH-AL concentration peaked at 0.18 ng/mL 4 h after the dose and was undetectable by 36 h. Hydrolysis of the plasma samples had little effect on the detected AL concentrations but increased OH-AL concentrations substantially. Plasma/blood ratios for AL and OH-AL exceeded 1 in the study samples.

Changes of benzodiazepine receptors during chronic benzodiazepine administration in humans

Changes of central type GABA(A)/benzodiazepine receptors during 24-day per-oral administration of alprazolam (2 mg/day) were measured with single photon emission computed tomography (SPECT) in nine healthy human subjects. Receptor densities were measured on days -4 (baseline), 3, 10, 17 and 24. Comparison of baseline and day 3 SPECT images was used to assess receptor occupancy; comparisons of the four scans on medication were used to assess alterations in receptor levels. Clinical effects were evaluated by subjective ratings of mood and the Hopkins verbal learning test. Alprazolam induced sedation associated with a 16% receptor occupancy. Unoccupied receptor levels decreased 10% from day 3 to day 10 but then normalized to baseline values by day 17. Clinical effects showed corresponding changes 1-2 weeks after the changes in the receptor. Thus, the decrease of benzodiazepine receptor densities may be one of the major mechanisms for tolerance development in humans.

Determination of benzodiazepines in human urine and plasma with solvent modified solid phase micro extraction and gas chromatography; rationalisation of method development using experimental design strategies

Solid phase micro extraction (SPME) and gas chromatographic analysis was used for the analysis of several benzodiazepines (oxazepam, diazepam, nordiazepam, flunitrazepam and alprazolam) in human urine and plasma. Several factors likely to affect the analyte recovery were screened in a fractional factorial design in order to examine their effect on the extraction recovery. Parameters found significant in the screening were further investigated with the use of response surface methodology. The final conditions for extraction of benzodiazepines were as follows: Octanol was immobilised on a polyacrylate fibre for 4 min. The fibre was placed in the sample and extraction took place at pH 6.0 for 15 min. Urine samples were added to 0.3 g ml(-1) sodium chloride. In plasma, the extraction recovery was less than in urine and releasing the benzodiazepines from plasma proteins followed by protein precipitation was found necessary prior to sampling. The method was validated and found linear over the range of samples. The limits of detection in urine were determined to be in the range 0.01-0.45 micromol l(-1). The corresponding limits of detection in plasma were in the range 0.01-0.48 micromol l(-1). Finally, the method developed was applied to determine some benzodiazepines after administration of a single dose. This method offers sufficient enrichment for bioanalysis after a single dose of high dose benzodiazepines as diazepam, but for low dose benzodiazepines as flunitrazepam, further sensitivity is needed.

Benzodiazepines: toxic serum concentrations in positive enzyme immunoassay responses

A total of 588 blood specimens collected in an emergency unit were screened for benzodiazepines (BZDs) using enzyme-multiplied immunoassay and gas chromatography. Two-hundred eighty-five samples were positive for BZDs, and 303 samples that were negative by EMIT included 20 samples with BZDs detectable by gas-liquid chromatography. A total of 15 BZDs were identified, and the most frequently occurring were nordiazepam, bromazepam, diazepam, and alprazolam. Individual BZDs were found in 74% of cases, but some samples contained two, three, or even four BZDs. There is a risk of missing intoxication by BZDs with low therapeutic range and/or low cross-reactivity (alprazolam, bromazepam, flunitrazepam). There is a risk of misinterpreting a positive result for some BZDs with high therapeutic range and/or high cross-reactivity (nordiazepam), which may reflect a pharmacologically ineffective concentration. A semiquantitative analysis is inappropriate even when the identity of BZD is known. Immunoassays are the only methods presently available for use in emergencies, but physicians must be clearly informed of their limitations and interpret results with caution.

Laboratory validation study of drug evaluation and classification program: alprazolam, d-amphetamine, codeine, and marijuana

The Drug Evaluation and Classification (DEC) program is used by police agencies to identify drivers impaired because of drug use and to determine the class(es) of drug causing the impairment. The primary goal of this study was to determine the validity of the DEC evaluation in predicting whether research volunteers were administered alprazolam, d-amphetamine, codeine, or marijuana. A secondary goal was to determine the accuracy of Drug Recognition Examiners (DREs) in detecting if subjects were dosed with these drugs. Community volunteers (n = 48) were administered alprazolam (0, 1, 2 mg), d-amphetamine (0, 12.5, 25 mg), codeine (0, 60, 120 mg), or marijuana (0, 3.58% THC) in a double-blind, randomized, between-subject design. A single drug dose or placebo was administered at each experimental session, and blood samples were obtained before and after dosing. With the exception of marijuana, plasma drug concentration was at or near maximum during the DEC evaluation. The ability of the DEC evaluation to predict the intake of alprazolam, d-amphetamine, codeine, or marijuana was optimal when using 2-7 variables from the evaluation. DREs' decisions of impairment were consistent with the administration of any active drug in 76% of cases, and their drug class decisions were consistent with toxicology in 32% of cases, according to standards of the International Association of Chiefs of Police. These findings suggest that the DEC evaluation can be used to predict accurately acute administration of alprazolam, d-amphetamine, codeine, and marijuana and that predictions of drug use may be improved by focusing on a subset of variables.

Ketoconazole inhibition of triazolam and alprazolam clearance: differential kinetic and dynamic consequences

BACKGROUND

Kinetic and dynamic consequences of metabolic inhibition were evaluated in a study of the interaction of ketoconazole, a P4503A inhibitor, with alprazolam and triazolam, two 3A substrate drugs with different kinetic profiles.

METHODS

In a double-blind, 5-way crossover study, healthy volunteers received (A) ketoconazole placebo plus 1.0 mg alprazolam orally, (B) 200 mg ketoconazole twice a day plus 1.0 mg alprazolam, (C) ketoconazole placebo plus 0.25 mg triazolam orally, (D) 200 mg ketoconazole twice a day plus 0.25 mg triazolam, and (E) 200 mg ketoconazole twice a day plus benzodiazepine placebo. Plasma concentrations and pharmacodynamic parameters were measured after each dose.

RESULTS

For trial B versus trial A, alprazolam clearance was reduced (27 versus 86 mL/min; P < .002) and apparent elimination half-life (t1/2) prolonged (59 versus 15 hours; P < .03), whereas peak plasma concentration (Cmax) was only slightly increased (16.1 versus 14.7 ng/mL). The 8-hour pharmacodynamic effect areas for electroencephalographic (EEG) beta activity were increased by a factor of 1.35, and those for digit-symbol substitution test (DSST) decrement were increased by 2.29 for trial B versus trial A. For trial D versus trial C, triazolam clearance was reduced (40 versus 444 mL/min; P < .002), t1/2 was prolonged (18.3 versus 3.0 hours; P < .01), and Cmax was increased (2.6 versus 5.4 ng/mL; P < .001). The 8-hour effect area for EEG was increased by a factor of 2.51, and that for DSST decrement was increased by 4.33. Observed in vivo clearance decrements due to ketoconazole were consistent with those anticipated on the basis of an in vitro model, together with in vivo plasma concentrations of ketoconazole.

CONCLUSION

For triazolam, an intermediate-extraction compound, impaired clearance by ketoconazole has more profound clinical consequences than those for alprazolam, a low extraction compound.

Do alprazolam-induced changes in saccadic eye movement and psychomotor function follow the same time course?

The purpose of this study was to determine whether short-term tolerance develops to GABA-agonist-induced changes in saccadic eye movements (SEMs), and whether the time course for GABA-agonist induced onset and offset of impairment is similar for SEMs and for psychomotor function. An additional goal was to determine whether there are differences in sensitivity between SEMs and psychomotor function. Six healthy volunteers participated in this balanced double-blind, three-way crossover, single-dose study of placebo and two different dosage forms of the GABA-agonist alprazolam: a rapidly absorbed oral 1.5-mg compressed tablet (CT) and a 3.0-mg sustained release (SR) tablet. Treatments were separated by a 7-day washout period. Peak concentrations did not differ between CT and SR treatments, although area under the concentration-time curve (AUC) of alprazolam was greater after administration of SR than after CT, because plateau concentrations were attained after SR. Both SEM and psychomotor tests showed time-dependent responses consistent with the development of tolerance. SEMs discriminated the differences in rate of drug input of the CT and SR formulations, with impairment evident at low concentrations during absorption. SEM impairment also persisted longer than did psychomotor impairment. Peak saccade velocity is a more sensitive indicator of pharmacologic effects mediated by the GABA-benzodiazepine receptor complex than are psychomotor responses. This is probably the result of the very high GABA dependency of SEMs, along with their limited sensitivity to motivation.

Relationship between single oral dose pharmacokinetics of alprazolam and triazolam

The relationship between the single oral dose pharmacokinetics of alprazolam and triazolam was studied in 10 healthy male volunteers. Each subject took single oral doses of alprazolam 0.8 mg and triazolam 0.5 mg with at least a 2 week interval between each dose. Blood samplings were performed up to 48 h after alprazolam dosing and up to 12 h after triazolam dosing. Plasma concentrations of both drugs were measured by high-performance liquid chromatography. The means +/- standard deviation of the peak plasma concentration, the total area under the plasma concentration-time curve and the elimination half-life of alprazolam were 11.3 +/- 3.1 ng/ml, 232.4 +/- 59.2 ng/h/ml and 16.5 +/- 4.6 h, respectively, and those of triazolam were 3.2 +/- 1.0 ng/ml, 11.8 +/- 5.2 ng/h/ml and 2.5 +/- 1.1 h, respectively. There was no significant correlation between the two drugs in any pharmacokinetic parameters (r = 0.35, 0.25 and 0.50). The present study thus suggests that the single oral dose pharmacokinetics of alprazolam and triazolam do not correlate well in individuals.

A fatality due to alprazolam intoxication

Alprazolam is one of the most widely prescribed benzodiazepines in the United States. It is generally considered a safe and effective drug for the treatment of anxiety disorders and panic attacks. Few overdoses that are due to the sole ingestion of alprazolam have been reported. This paper documents a fatality due to alprazolam intoxication and describes the distribution of alprazolam and an active metabolite, alpha-hydroxyalprazolam, in tissues obtained at autopsy. Qualitative identification of the drugs was achieved by full-scan gas chromatography-mass spectrometry, and quantitative analysis was performed by high-performance liquid chromatography. High concentrations of alprazolam were found in all specimens analyzed, but the metabolite was detected only in subclavian blood, urine, bile, and liver. A postmortem heart blood alprazolam concentration of 2.1 mg/L is the highest reported in the literature to date.

Nonlinear mixed effects modeling of single dose and multiple dose data for an immediate release (IR) and a controlled release (CR) dosage form of alprazolam

PURPOSE

NONMEM was applied to single dose and multiple dose bioavailability data for an immediate release (IR) and a controlled release (CR) dosage form of alprazolam to acquire additional information from the data which are not easily obtainable by traditional means.

METHODS

The objective function value (OBJ) and diagnostic plots were used as measures of goodness of fit of the model to the data. A change in the OBJ value of 7.9 was necessary to show statistical significance (p < 0.005) between two models when the two models differed by 1 parameter.

RESULTS

A two-compartment linear model with first-order absorption and elimination best describes the data. Including a lag time, two different rates of absorption (KAIR and KACR), and bioavailability for the CR relative to the IR dosage form significantly improved the fit of the model to the data. Cigarette smoking was associated with a 100% increase in clearance of alprazolam as compared to non-smokers. The higher residual variability observed in this study, where interoccasion variability (IOV) was not initially modeled, could be explained to a large extent by the presence of significant interoccasion variability (IOV).

CONCLUSIONS

Since alprazolam has been suggested to be mainly metabolized by the CYP3A4 isozyme in humans, it appears that tobacco could be an inducer of CYP3A4 and/or alprazolam may be metabolized by other isozyme(s) (specifically, CYP1A1/1A2) that are induced by cigarette smoke. The population pharmacokinetic model approach combined with exploratory graphical data analysis is capable of identifying important covariates from well-controlled "data rich" Phase I studies early in drug development.

Detection of alprazolam in three cases of methadone/benzodiazepine overdose

Benzodiazepine abuse is common among clients at methadone maintenance clinics. Diazepam and lorazepam are readily detected by immunological screening methods and confirmed by GC/MS. Alprazolam has been relatively difficult to confirm. We recently reported a modification of an existing serum HPLC procedure which allows us to analyze whole blood. We report here three cases of fatal drug overdose caused by co-ingestion of methadone and alprazolam. In all three cases, alprazolam was detected by HPLC and could not be identified by alkaline extraction GC/MS. Postmortem blood concentrations of methadone were at the lower range or below the concentrations previously identified in methadone overdose fatalities, suggesting an increased risk from co-ingestion of methadone and alprazolam.