Influence of dosing regimen on alprazolam and metabolite serum concentrations and tolerance to sedative and psychomotor effects

Pharmacokinetics of Staccato® alprazolam in healthy adult participants in two phase 1 studies: An open-label smoker study and a randomized, placebo-controlled ethnobridging study

OBJECTIVE

Staccato® alprazolam is a single-use, drug-device combination delivering alprazolam to the deep lung that is being evaluated as treatment for rapid and early seizure termination. This article reports pharmacokinetic (PK) data from two phase 1 studies of Staccato alprazolam in healthy adult participants.

METHODS

The smoker study (EPK-002/NCT03516305) was an open-label, nonrandomized, single-dose, PK study in smokers and nonsmokers aged 21-50 years, administered a single inhaled dose of 1 mg Staccato alprazolam. The ethnobridging study (UP0101/NCT04782388) was a double-blind, placebo-controlled study in Japanese, Chinese, and Caucasian participants aged 18-55 years randomized 4:1 to a single inhaled dose of Staccato alprazolam 2 mg or Staccato placebo.

RESULTS

In the smoker study, 36 participants (18 smokers, 18 nonsmokers) were enrolled and received Staccato alprazolam. Following Staccato administration, alprazolam was rapidly absorbed, with a median time to peak drug plasma concentration (Tmax) of 2 min in both smokers (range = 2-30 min) and nonsmokers (range = 2-60 min). Staccato alprazolam was rapidly absorbed to a similar extent in both smokers and nonsmokers. The most commonly reported treatment-emergent adverse events (TEAEs) were somnolence and dizziness. In the ethnobridging study, 10 participants each of Japanese, Chinese, and Caucasian ethnicities were randomized 4:1 to Staccato alprazolam or Staccato placebo. Following Staccato administration, alprazolam was rapidly absorbed and distributed, with a median Tmax of 1.5-2 min in Japanese (range = 1-2 min), Chinese (range = 1-34 min), and Caucasian (range = 1-120 min) participants. Somnolence and sedation were the most commonly reported TEAEs. In both studies, there were no deaths, and no participants reported serious or severe TEAEs, or discontinued due to TEAEs.

SIGNIFICANCE

Alprazolam was rapidly absorbed, and therapeutic drug levels were achieved within 2 min postdose when administered to the lung with the Staccato device. Staccato alprazolam was generally well tolerated and displayed a safety profile consistent with that known from other alprazolam applications. No new safety signals were identified.

The Effect of Chronic Alprazolam Intake on Memory, Attention, and Psychomotor Performance in Healthy Human Male Volunteers

Alprazolam is used as an anxiolytic drug for generalized anxiety disorder and it has been reported to produce sedation and anterograde amnesia. In the current study, we randomly divided 26 healthy male volunteers into two groups: one group taking alprazolam 0.5 mg and the other taking placebo daily for two weeks. We utilized the Cambridge Neuropsychological Test Automated Battery (CANTAB) software to assess the chronic effect of alprazolam. We selected Paired Associates Learning (PAL) and Delayed Matching to Sample (DMS) tests for memory, Rapid Visual Information Processing (RVP) for attention, and Choice Reaction Time (CRT) for psychomotor performance twice: before starting the treatment and after the completion of the treatment. We found statistically significant impairment of visual memory in one parameter of PAL and three parameters of DMS in alprazolam group. The PAL mean trial to success and total correct matching in 0-second delay, 4-second delay, and all delay situation of DMS were impaired in alprazolam group. RVP total hits after two weeks of alprazolam treatment were improved in alprazolam group. But such differences were not observed in placebo group. In our study, we found that chronic administration of alprazolam affects memory but attentive and psychomotor performance remained unaffected.

Separate and combined impact of acute naltrexone and alprazolam on subjective and physiological effects of oral d-amphetamine in stimulant users

RATIONALE

Opioid antagonists (e.g., naltrexone) and positive modulators of γ-aminobutyric-acidA (GABAA) receptors (e.g., alprazolam) modestly attenuate the abuse-related effects of stimulants like amphetamine. The use of higher doses to achieve greater efficacy is precluded by side effects. Combining naltrexone and alprazolam might safely maximize efficacy while avoiding the untoward effects of the constituent compounds.

OBJECTIVES

The present pilot study tested the hypothesis that acute pretreatment with the combination of naltrexone and alprazolam would not produce clinically problematic physiological effects or negative subjective effects and would reduce the positive subjective effects of d-amphetamine to a greater extent than the constituent drugs alone.

METHODS

Eight nontreatment-seeking, stimulant-using individuals completed an outpatient experiment in which oral d-amphetamine (0, 15, and 30 mg) was administered following acute pretreatment with naltrexone (0 and 50 mg) and alprazolam (0 and 0.5 mg). Subjective effects, psychomotor task performance, and physiological measures were collected.

RESULTS

Oral d-amphetamine produced prototypical physiological and stimulant-like positive subjective effects (e.g., VAS ratings of Active/Alert/Energetic, Good Effect, and High). Pretreatment with naltrexone, alprazolam, and their combination did not produce clinically problematic acute physiological effects or negative subjective effects. Naltrexone and alprazolam each significantly attenuated some of the subjective effects of d-amphetamine. The combination attenuated a greater number of subjective effects than the constituent drugs alone.

CONCLUSIONS

The present results support the continued evaluation of an opioid receptor antagonist combined with a GABAA-positive modulator using more clinically relevant experimental conditions like examining the effect of chronic dosing with these drugs on methamphetamine self-administration.

Alprazolam: just another benzodiazepine?

The literature on alprazolam is reviewed. It is concluded that it is an effective anxiolytic but that it is not an antidepressant. When used in sufficiently high dosage it can block panic attacks, but it is not the only antipanic agent available. It may be used as an alternative to other benzodiazepines in the acute detoxification of alcoholics. It should be avoided where there is strong individual likelihood of abuse. Chronic usage (more than a few weeks) demands a very slow tapering of dosage. Carbamazepine may ameliorate withdrawal symptoms. The use of alprazolam in other conditions remains unproven.

Pharmacologically active drug metabolites: impact on drug discovery and pharmacotherapy

Metabolism represents the most prevalent mechanism for drug clearance. Many drugs are converted to metabolites that can retain the intrinsic affinity of the parent drug for the pharmacological target. Drug metabolism redox reactions such as heteroatom dealkylations, hydroxylations, heteroatom oxygenations, reductions, and dehydrogenations can yield active metabolites, and in rare cases even conjugation reactions can yield an active metabolite. To understand the contribution of an active metabolite to efficacy relative to the contribution of the parent drug, the target affinity, functional activity, plasma protein binding, membrane permeability, and pharmacokinetics of the active metabolite and parent drug must be known. Underlying pharmacokinetic principles and clearance concepts are used to describe the dispositional behavior of metabolites in vivo. A method to rapidly identify active metabolites in drug research is described. Finally, over 100 examples of drugs with active metabolites are discussed with regard to the importance of the metabolite(s) in efficacy and safety.

Microsomal prediction ofin vivoclearance and associated interindividual variability of six benzodiazepines in humans

The intrinsic clearances (CLint) of midazolam, triazolam, diazepam, nordiazepam, flunitrazepam and alprazolam were determined from two liver banks (n=21) by formation kinetics of ten metabolites. A literature-collated database of in vivo CLint values (811 subjects) was used to assess predictions and variability. The in vivo clearance of six benzodiazepines was generally underpredicted by in vitro data and the degree of bias was in agreement with a database of structurally diverse compounds (n=37). The variability observed for in vitro clearances (11--19--fold for midazolam, diazepam and nordiazepam in liver bank 1; 101--269--fold for triazolam, flunitrazepam and alprazolam in liver bank 2) exceeded the in vivo variability for the same compounds (4--59 and 10--29, respectively). This mismatch may contribute to the bias in microsomal predictions and it highlights the need for careful selection of representative livers for human liver banks.

Benzodiazepines in epilepsy: pharmacology and pharmacokinetics

Benzodiazepines (BZDs) remain important agents in the management of epilepsy. They are drugs of first choice for status epilepticus and seizures associated with post-anoxic insult and are also frequently used in the treatment of febrile, acute repetitive and alcohol withdrawal seizures. Clinical advantages of these drugs include rapid onset of action, high efficacy rates and minimal toxicity. Benzodiazepines are used in a variety of clinical situations because they have a broad spectrum of clinical activity and can be administered via several routes. Potential shortcomings of BZDs include tolerance, withdrawal symptoms, adverse events, such as cognitive impairment and sedation, and drug interactions. Benzodiazepines differ in their pharmacologic effects and pharmacokinetic profiles, which dictate how the drugs are used. Among the approximately 35 BZDs available, a select few are used for the management of seizures and epilepsy: clobazam, clonazepam, clorazepate, diazepam, lorazepam and midazolam. Among these BZDs, clorazepate has a unique profile that includes a long half-life of its active metabolite and slow onset of tolerance. Additionally, the pharmacokinetic characteristics of clorazepate (particularly the sustained-release formulation) could theoretically help minimize adverse events. However, larger, controlled studies of clorazepate are needed to further examine its role in the treatment of patients with epilepsy.

Pharmacodynamics in older adults: a review

BACKGROUND

Older individuals experience physiologic changes in organ function related to aging or to specific disease processes. These changes can affect drug pharmacodynamics in older adults.

OBJECTIVE

The goal of this article was to review age-related changes in pharmacodynamics and their clinical relevance.

METHODS

PubMed and International Pharmaceutical Abstracts were searched (January 1980-June 2006) for the following combination of terms: pharmacodynamic and elderly, geriatric or aged. References cited in other reviews were also evaluated. The current review focused on age-related pharmacodynamic changes in agents affecting the central nervous system (CNS), cardiovascular, and endocrine functions.

RESULTS

Older adults frequently demonstrate an exaggerated response to CNS-active drugs. This is in part due to an underlying age-related decline in CNS function and in part due to increased pharmacodynamic sensitivity for some benzodiazepines, anesthetics, and opioids. The most important pharmacodynamic differences with age for cardiovascular agents are the decrease in effect for beta-adrenergic agents. This decline in response in vascular, cardiac, and pulmonary tissue may be due to a decrease in Gs protein interactions. Most studies indicate there is no decrease in cx-receptor sensitivity with age. Angiotensin-converting enzyme inhibitors do not show age-related differences in elderly patients. With the dihydropyridine calcium channel blockers, there was a slight increase in effect for older adults, but this was only for treatment-naive patients and was transient. Nondihydropyridines did not show an age- associated change in pharmacodynamic effect; however, in the elderly, there appeared to be a decrease in the PR interval prolongation normally seen with these agents. Studies of diuretics indicated that the changes in diuretic and natriuretic effects seen in the elderly were associated with pharmacokinetic changes and were not pharmacodynamic in nature. There was a lack of consistent evidence regarding whether sulfonylureas show age-related changes in pharmacodynamic effect.

CONCLUSIONS

There is a general trend of greater pharmacodynamic sensitivity in the elderly; however, this is not universal, and these age-related changes must be investigated agent-by-agent until further research yields greater understanding of the molecular mechanisms underlying the aging process.

Metabolic interaction between ethanol, high-dose alprazolam and its two main metabolites using human liver microsomes in vitro

Alprazolam is widely used as a short-acting antidepressant and anxiolytic agent and its effect appears at very low doses while ethanol is used as a social drug worldwide. Sometimes, toxic interactions occur following combined administration of these two drugs. In this study we have investigated the interaction between ethanol and high-dose alprazolam using human liver microsomes in vitro. The interaction effects between ethanol and alprazolam were examined by a mixed-function oxidation reaction using a human liver microsomal preparation. Alprazolam and its two main metabolites (alpha-hydroxyalprazolam: alpha-OH alprazolam, 4-hydroxyalprazolam: 4-OH alprazolam) were measured by HPLC/UV. The production of 4-OH alprazolam, one main metabolite of alprazolam, was weakly inhibited by higher dose of ethanol, but not alpha-OH alprazolam. These results using a human liver microsomal preparation show that the production of 4-OH alprazolam is weakly inhibited by ethanol but not alpha-OH alprazolam. Toxic levels may be reached by simultaneous administration of ethanol and high-dose alprazolam.

Cognitive, psychomotor and actual driving performance in healthy volunteers after immediate and extended release formulations of alprazolam 1 mg

RATIONALE

Alprazolam extended-release (XR) is approved for the treatment of panic disorder. This sustained formulation is absorbed in a delayed manner and is therefore expected to produce fewer and less severe side effects than its immediate release equivalent (alprazolam IR). The effect of alprazolam XR on potentially dangerous daily activities, such as driving a car, is expected to be less as compared to alprazolam IR.

OBJECTIVES

The present study was designed to compare the effects of alprazolam XR (1 mg) and alprazolam IR (1 mg) on actual driving ability and cognitive function.

METHOD

Eighteen healthy volunteers (aged 20-45 years) participated in a double-blind, placebo-controlled, three-way crossover study. At 4 h post-dose, subjects performed a standardized driving test on a primary highway in normal traffic. Cognitive and psychomotor tests were assessed 1, 2.5, and 5.5 h post-dose. Memory functioning was measured only 1 h after administration.

RESULTS

Both formulations severely impaired driving performance between 4 and 5 h after administration. The magnitude of impairment in the driving test observed with alprazolam XR was about half that observed with alprazolam IR. Laboratory test results were in line with the driving data.

CONCLUSIONS

The acute impairing effects of alprazolam XR 1 mg on driving and psychomotor functions were generally less, as compared to its immediate-release equivalent, but still of sufficient magnitude to increase the risk of becoming involved in traffic accidents.

Simultaneous quantification of alprazolam, 4- and α-hydroxyalprazolam in plasma samples using liquid chromatography mass spectrometry

A sensitive and specific method was developed for quantification of alprazolam and its two metabolites 4-hydroxyalprazolam and alpha-hydroxyalprazolam in plasma. The work up procedure was solid phase extraction. Liquid chromatography-mass spectrometry (LC-MS) was used for separation, detection and quantification of the analytes. The limit of quantitation (LOQ) was 0.05 ng/mL for alprazolam and the two metabolites. The extraction recovery was more than 82% for alprazolam and its metabolites. The within- and between-assay coefficients of variation were in the range of 1.9-17.9%. The method was used for determination of the pharmacokinetics parameters of alprazolam and its two metabolites in healthy Caucasian subjects who ingested 1mg of alprazolam.

Clinical pharmacology, clinical efficacy, and behavioral toxicity of alprazolam: a review of the literature

Alprazolam is a benzodiazepine derivative that is currently used in the treatment of generalized anxiety, panic attacks with or without agoraphobia, and depression. Alprazolam has a fast onset of symptom relief (within the first week); it is unlikely to produce dependency or abuse. No tolerance to its therapeutic effect has been reported. At discontinuation of alprazolam treatment, withdrawal and rebound symptoms are common. Hence, alprazolam discontinuation must be tapered. An exhaustive review of the literature showed that alprazolam is significantly superior to placebo, and is at least equally effective in the relief of symptoms as tricyclic antidepressants (TCAs), such as imipramine. However, although alprazolam and imipramine are significantly more effective than placebo in the treatment of panic attacks, Selective Serotonin Reuptake Inhibitors (SSRIs) appear to be superior to either of the two drugs. Therefore, alprazolam is recommended as a second line treatment option, when SSRIs are not effective or well tolerated. In addition to its therapeutic effects, alprazolam produces adverse effects, such as drowsiness and sedation. Since alprazolam is widely used, many clinical studies investigated its cognitive and psychomotor effects. It is evident from these studies that alprazolam may impair performance in a variety of skills in healthy volunteers as well as in patients. Since the majority of alprazolam users are outpatients, this behavioral impairment limits the safe use of alprazolam in patients routinely engaged in potentially dangerous daily activities, such as driving a car.

Human variability in CYP3A4 metabolism and CYP3A4-related uncertainty factors for risk assessment

CYP3A4 constitutes the major liver cytochrome P450 isoenzyme and is responsible for the oxidation of more than 50% of all known drugs. Human variability in kinetics for this pathway has been quantified using a database of 15 compounds metabolised extensively (>60%) by this CYP isoform in order to develop CYP3A4-related uncertainty factors for the risk assessment of environmental contaminants handled via this route. Data were analysed from published pharmacokinetic studies (after oral and intravenous dosing) in healthy adults and other subgroups using parameters relating primarily to chronic exposure [metabolic and total clearances, area under the plasma concentration-time curve (AUC)] and acute exposure (Cmax). Interindividual variability in kinetics was greater for the oral route (46%, 12 compounds) than for the intravenous route (32%, 14 compounds). The physiological and molecular basis for the difference between these two routes of exposure is discussed. In relation to the uncertainty factors used for risk assessment, the default kinetic factor of 3.16 would be adequate for adults, whereas a CYP3A4-related factor of 12 would be required to cover up to 99% of neonates, which have lower CYP3A4 activity.

Absence of neuropsychologic deficits in patients receiving long-term treatment with alprazolam-XR for panic disorder

Studies to date on the effects of benzodiazepines on neuropsychologic function have yielded conflicting data with respect to the type, severity, and duration of deficits that may be induced by these agents. As part of a placebo-controlled trial of alprazolam-XR (extended release) administered in combination with cognitive-behavioral therapy in patients with panic disorder, a battery of tests was used to measure neuropsychologic function. Thirty-eight outpatients were randomly assigned to receive either alprazolam-XR or placebo. Dosages were titrated up so that the alprazolam group (N = 18) received a mean dose of 4 mg/day (reduced in two patients because of sedative side effects). Neuropsychologic function after 6 weeks of therapy at the target dosage was compared with baseline assessments in each group. Both groups showed a statistically significant improvement from baseline to repeated assessments on measures of attention, executive functioning, psychomotor speed, and visual memory (p < 0.001); these gains were attributed to a practice effect. No significant changes were noted in measures of learning, verbal memory, or reaction time, and neither group showed any deterioration from baseline to retesting in any aspect of neuropsychologic function. These findings call into question the assumption that long-term benzodiazepine therapy produces significant neuropsychologic deficit in patients with diagnosed anxiety disorders.

Clonazepam and sertraline: absence of drug interaction in a multiple-dose study

Thirteen subjects (seven men, six women) completed a placebo-controlled, randomized, double-blind, crossover study to determine whether an interaction occurs between clonazepam and sertraline. Ten days of once-daily doses of either clonazepam 1 mg and placebo (CZ + PL) or clonazepam 1 mg and sertraline 100 mg (CZ + SR) were administered; there was an 11-day washout period. Sertraline did not significantly affect the pharmacokinetics of clonazepam (p > 0.13). Clonazepam apparent oral clearance, volume of distribution, and half-life were 3.9 +/- 0.2 L/hr, 233 +/-11 L, and 40.5 +/- 0.3 hours, respectively. The kinetics of the inactive metabolite 7-aminoclonazepam were marginally affected by sertraline, with a 21% decrease in the elimination half-life (p = 0.03) relative to CZ + PL and no significant difference between treatments in area under the curve or metabolite ratio. Card sorting (CS), digit-symbol substitution test (DSST), nurse-rated sedation scale (NRSS), and self-rated sedation scores were assessed four times daily on days -1 (PL + PL), 1, 4, 7, and 10. There were no differences between treatments in area under the effect curve or maximum observed effect for CS, DSST, or NRSS. Maximum impairment on all assessment days was low, with a less than 10% change from the drug-free values for CS and DSST. Despite higher clonazepam concentrations, predose (time 0) psychomotor and sedation scores did not differ among days -1, 1, 4, 7, and 10 or between treatments. These results in healthy volunteers indicate that sertraline does not affect the pharmacokinetics or pharmacodynamics of clonazepam.

Influence of endogenous progesterone on alprazolam pharmacodynamics

The results of a recently completed study demonstrated that postmenopausal women were more sensitive to triazolam-induced psychomotor performance impairment when progesterone was administered concomitantly. That clinical evidence agrees with the emerging in vitro information regarding the rapid membrane effects of a progesterone metabolite that positively modulates the gamma-aminobutyric acid-A-benzodiazepine receptor complex. The objective of this study in premenopausal women was to determine whether the response to a benzodiazepine is altered when endogenous progesterone concentrations are high (luteal phases of a menstrual cycle) compared with when progesterone concentrations are low (follicular phases of a menstrual cycle). The pharmacokinetics and pharmacodynamics of oral alprazolam were evaluated in twelve healthy, normally menstruating women who were not receiving oral contraceptive agents. On two separate occasions, once during each phase of the menstrual cycle, the women randomly received an oral alprazolam 2-mg dose. Blood samples were collected, and psychomotor performance tests were conducted at selected times before and after dosing. These data show that fluctuations of endogenous progesterone across the menstrual cycle do not influence alprazolam pharmacodynamics. Despite endogenous progesterone concentrations being significantly higher during the midluteal than during the midfollicular drug administrations, no differences were observed in either the digit-symbol substitution test, card sorting by suit, or sedation scores on these two occasions. No pharmacokinetic differences were observed between the two menstrual cycle-phase drug administrations. In conclusion, the lack of changes during the menstrual cycle in demonstrable cognitive impairment and pharmacokinetics after alprazolam administration is reassuring. This implies that a dose adjustment made on the basis of menstrual timing is not required.

Rate of change of blood concentrations is a major determinant of the pharmacodynamics of midazolam in rats

The objective of this investigation was to characterize quantitatively the influence of the rate of increase in blood concentrations on the pharmacodynamics of midazolam in rats. The pharmacodynamics of midazolam were quantified by an integrated pharmacokinetic-pharmacodynamic modelling approach. Using a computer controlled infusion technique, a linear increase in blood concentrations up to 80 ng ml(-1) was obtained over different time intervals of 16 h, resulting in rates of rise of the blood concentrations of respectively, 1.25, 1.00, 0.87, 0.46, 0.34 and 0.20 ng ml(-1) min(-1). In one group of rats the midazolam concentration was immediately brought to 80 ng ml(-1) and maintained at that level for 4 h. Immediately after the pretreatment an intravenous bolus dose was given to determine the time course of the EEG effect in conjunction with the decline of midazolam concentrations. The increase in beta activity (11.5-30 Hz) of the EEG was used as pharmacodynamic endpoint. For each individual animal the relationship between blood concentration and the EEG effect could be described by the sigmoidal Emax model. After placebo, the values of the pharmacodynamic parameter estimates were Emax = 82+/-5 microV, EC50,u = 6.4+/-0.8 ng ml(-1) and Hill factor = 1.4+/-0.1. A bell-shaped relationship between the rate of change of midazolam concentration and the value of EC50,u was observed with a maximum of 21+/-5.0 ng ml(-1) at a rate of change of 0.46 ng ml(-1) min(-1); lower values of EC50,u were observed at both higher and lower rates. The findings of this study show that the rate of change in plasma concentrations is an important determinant of the pharmacodynamics of midazolam in rats.

Pharmacokinetics of alprazolam in elderly patients with multiple diseases

The pharmacokinetics of alprazolam (1 mg p.o.) were investigated (using a new developed HPLC-assay) in 10 multimorbid elderly patients (five female, five male; mean age 72.8 +/- 8.2 years, creatinine clearance 63.6 +/- 25.9 ml/min, weight 68.9 +/- 13.9 kg). Compared with young and elderly volunteers from other studies peak plasma concentrations of alprazolam were decreased while peak time and elimination half-life were increased. 'Second peak' plasma levels (correlated with age and creatinine clearance) occurred in eight of 10 elderly patients. The variability associated with the pharmacokinetic parameters in the multimorbid elderly patients was far greater than that observed in young and old healthy volunteers. Mean alprazolam concentrations in multimorbid patients aged 72 years or more were elevated as compared to 'younger' patients (age range: 63-71 years). Dose reduction should be considered in the older multimorbid patients.

Pharmacokinetics and psychomotor performance of alprazolam: concentration-effect relationship

The relationship between the pharmacokinetics of alprazolam and dose and the relationship between the concentration of alprazolam and psychomotor performance in healthy male volunteers were investigated in this double-blind, placebo-controlled, modified crossover study. Twenty-four volunteers received placebo in Phase I and then received single 2-mg, 4-mg, 8-mg, and 10-mg doses of a sustained-release formulation in Phases II through V, according to, a crossover design. Blood samples were collected at several times throughout each phase to 48 hours after the dose; the harvested plasma was assayed for concentrations of alprazolam, 4-hydroxyalprazolam, and alpha-hydroxyalprazolam by high-performance liquid chromatography. Sedation was rated at each blood-sampling time and psychomotor performance tests, consisting of digit-symbol substitution and card-sorting tasks, were conducted at several times after each dose. Area under the concentration-time curve and peak concentration for alprazolam increased proportionally with each higher dose; clearance did not differ significantly between treatments. The concentrations of 4-hydroxyalprazolam and alpha-hydroxyalprazolam increased proportionally with dose and the combined plasma concentration of the metabolites were less than 15% of unchanged concentrations of alprazolam for all doses. Maximum sedation increased with each increase in dose up to 8 mg, and psychomotor performance decreased with each increase in dose. Performance versus concentration curves for alprazolam exhibited a clockwise hysteresis loop in contrast to the counterclockwise hystereses previously reported for both intravenous and oral doses of immediate-release tablets. Data through 6 hours after dose were well described by a sigmoid Emax model. Alprazolam exhibits linear pharmacokinetics after single oral doses of sustained-release tablets between 2 mg and 10 mg. Reversal of the concentration-effect curve to a clockwise loop suggests the counterclockwise hystereses of rapidly absorbed doses was caused by the differing distribution rates into the systemic circulation and effect site and not by metabolite activity.

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.

The pharmacokinetics and pharmacodynamics of adinazolam: multi-ethnic comparisons

The pharmacokinetics and pharmacodynamics of adinazolam and N-demethyladinazolam (NDMAD), its major active metabolite, were compared in 39 healthy male volunteers (13 Asian, 12 Caucasian and 14 African-American). In a four-way, double-blind crossover design, subjects were administered (1) 30 mg oral adinazolam mesylate SR tablets, (2) 10 mg parenteral (i.v.) adinazolam mesylate, (3) 30 mg i.v. NDMAD and (4) placebo. Venous blood samples were collected at specific time intervals after drug administration and assayed for adinazolam and NDMAD concentrations. Sedation was rated at the time of each blood draw according to the Nurse-Rated Sedation Scale, and the digit-symbol substitution test was administered to evaluate psychomotor performance. After i.v. administration of adinazolam, Asians manifested significantly higher Cmax, larger AUC and lower CL of both adinazolam and NDMAD than their Caucasian and African-American counterparts. Likewise, after i.v. NDMAD Asians had significantly higher NDMAD Cmax and AUC than Caucasians and African-Americans. Most of these differences remained statistically significant after controlling for body surface area. With PO adinazolam, Asians also manifested substantially higher Cmax, larger AUC and lower CL for both adinazolam and NDMAD; however, with the exception of Cmax, these differences did not reach statistical significance. These results are in accordance with previous observations for ethnic-related differences in drug pharmacokinetics. In contrast, pharmacodynamic differences were not noted among the three study groups.

Further evidence that the mouse defense test battery is useful for screening anxiolytic and panicolytic drugs: effects of acute and chronic treatment with alprazolam

The Mouse Defense Test Battery (MDTB) has been designed to investigate defensive responses of Swiss-Webster mice confronted with a natural predator, a rat. These behaviors include flight, avoidance, defensive threat/attack responses, and risk assessment activities. Previous studies with the MDTB have suggested that this model may have some utility for the investigation of panicogenic and antipanic compounds. In the present study the MDTB was used to investigate the effects of acute (0.05-1 mg/kg, i.p., 30 min) or chronic (0.5-2 mg/kg, one daily i.p. injection during 10 days) treatment with the benzodiazepine receptor (BZPR) full agonist and panicolytic agent alprazolam. At non motor-impairing doses (0.05-0.5 mg/kg), acute alprazolam failed to alter the avoidance distance between the subject and the predator, the number of avoidances when the rat is approaching, predator assessment activities, defensive threat/attack responses when contact is forced between the subject and the predator or contextual escape attempts after the predator was removed. This was in contrast to chronic treatment which decreased both avoidance variables at 0.5 and 1 mg/kg, defensive threat/attack responses at all doses, and predator assessment responses at 0.5 mg/kg. In addition, the latter treatment reduced post-predator potentiation of escape attempts at 2 mg/kg. These results (1) confirm previous findings with the BZPR full agonist chlordiazepoxide, indicating that these compounds generally attenuate antipredator defensive responses in Swiss-Webster mice; (2) support recent data indicating that panic-altering drugs modulate flight/escape reactions, and suggest that the primary mechanism of action of drugs with efficacy against panic disorder may involve neural systems controlling flight; (3) confirm that the MDTB may be useful for the investigation of panicolytic as well as anxiolytic agents.

Coadministration of nefazodone and benzodiazepines: IV. A pharmacokinetic interaction study with lorazepam

This study was conducted to determine the potential for an interaction between nefazodone (NEF), a new antidepressant, and lorazepam (LOR) after single- and multiple-dose administration in a randomized, double-blind, parallel-group, placebo-controlled study in healthy male volunteers. A total of 12 subjects per group received either placebo (PLA) twice daily, 2 mg of LOR twice daily, 200 mg of NEF twice daily, or the combination of 2 mg of LOR and 200 mg of NEF (LOR+NEF) twice daily for 7 days. Plasma samples were collected after dosing on day 1 and day 7 and before the morning dose on days 4, 5, and 6 for the determination of LOR, NEF, and NEF metabolites hydroxy (HO)-NEF, m-chlorophenylpiperazine (mCPP), and dione by validated high-performance liquid chromatography methods. Steady-state levels in plasma were reached by day 4 for LOR, NEF, HO-NEF, mCPP, and dione. Noncompartmental pharmacokinetic analysis showed that there was no effect of LOR on the single dose or steady-state pharmacokinetics of NEF, HO-NEF, or dione after coadministration. The steady-state mCPP Cmax values decreased 36% for the LOR+NEF group in comparison to that when NEF was given alone. There was no effect of NEF on the pharmacokinetics of LOR after coadministration. The absence of an interaction appears to be attributable to LOR's metabolic clearance being dependant on conjugation rather than hydroxylation. Overall, no change in LOR or NEF dosage is necessary when the two drugs are coadministered.

Coadministration of nefazodone and benzodiazepines: III. A pharmacokinetic interaction study with alprazolam

This study was conducted to determine the potential for an interaction between nefazodone, a new antidepressant, and alprazolam after single- and multiple-dose administration in a randomized, double-blind, parallel-group, placebo-controlled study in 48 healthy male volunteers. A group of 12 subjects received either placebo twice daily, 1 mg of alprazolam twice daily, 200 mg of nefazodone twice daily, or the combination of 1 mg of alprazolam and 200 mg of nefazodone twice daily for 7 days. Serial blood samples were collected after dosing on day 1 and day 7 and before the morning dose on days 4, 5, and 6 for the determination of alprazolam and its metabolites alpha-hydroxyalprazolam (AOH) and 4-hydroxyalprazolam (4OH) and nefazodone and its metabolites hydroxynefazodone (HO-nefazodone), m-chlorophenylpiperazine (mCPP), and a triazole dione metabolite (dione) by validated high-performance liquid chromatography methods. Steady-state levels in plasma were reached by day 4 for alprazolam, 4OH, nefazodone, HO-nefazodone, mCPP, and dione. Noncompartmental pharmacokinetic analysis showed that at steady state, alprazolam Cmax and AUCtau values significantly increased approximately twofold and 4OH Cmax and AUCtau values significantly decreased by 40 and 26%, respectively, when nefazodone was coadministered with alprazolam. There was no effect of alprazolam on the single-dose or steady-state pharmacokinetics of nefazodone, HO-nefazodone, or dione after the coadministration of alprazolam and nefazodone. However, the mean steady-state mCPP Cmax and AUCtau significantly increased by approximately threefold and t1/2 values significantly increased by approximately twofold after the coadministration of alprazolam and nefazodone in comparison to those when nefazodone was given alone. Competitive inhibition between alprazolam and nefazodone metabolism at cytochrome P450 3A4 may be responsible for the pharmacokinetic interaction when alprazolam and nefazodone were coadministered. No adjustment of nefazodone dosage is required when nefazodone and alprazolam are coadministered. Because alprazolam concentrations in plasma are increased in the presence of nefazodone, a reduction in alprazolam dosage is recommended when the two agents are coadministered.

Coadministration of nefazodone and benzodiazepines: I. Pharmacodynamic assessment

One hundred two healthy men were evaluated in one of three studies conducted to evaluate the coadministration of nefazodone, 200 mg twice daily, and three benzodiazepines: triazolam, 0.25 mg; alprazolam, 1 mg twice daily; or lorazepam, 2 mg twice daily. In the first study, psychomotor performance, memory, and sedation were assessed at 0, 0.5, 1.5, 2.5, and 9 hours after single doses of triazolam alone and again after 7 days of nefazodone. Data from 6 of 12 subjects in this study were evaluable because of a dosing error in the other 6 subjects. In the subsequent two parallel design studies, groups of 12 volunteers received 7 days of either placebo; nefazodone, 200 mg; alprazolam, 1 mg twice daily; or alprazolam plus nefazodone or, in the second study, either placebo; nefazodone; lorazepam, 2 mg twice daily; or lorazepam plus nefazodone; the studies were identical, double-dummy, double-blind designs. Psychomotor performance, memory, and sedation were assessed at 0, 1, 3, and 8 hours after the 8 a.m. dose on days 1, 3, 5, and 7 of the studies. In all studies, blood samples were also obtained at testing times so that effect/concentration comparisons could be made and so full pharmacokinetic analyses could be done for separate studies. Nefazodone had no effect on psychomotor performance, memory, or sedation relative to placebo in any study. The mean maximum observed effect (MaxOE) on psychomotor performance and sedation were increased when triazolam was given after 7 days of nefazodone (p < 0.05); also, triazolam concentration was 60% higher at this time. Alprazolam and lorazepam impaired performance on day 1 (mean MaxOE, 34 and 30%, respectively) relative to placebo and nefazodone. By day 7 of alprazolam or lorazepam, psychomotor impairment decreased, indicating the development of tolerance. Alprazolam plus nefazodone increased psychomotor impairment (MaxOE, approximately 50%) and sedation relative to alprazolam alone on days 3, 5, and 7 (p < 0.05). Higher alprazolam concentrations explained the increased impairment in the alprazolam plus nefazodone treatment group; however, it is also possible that there was a delay in the development of tolerance. There were no differences in psychomotor impairment, memory, sedation, or lorazepam concentration detected between the lorazepam alone and lorazepam plus nefazodone treatments. This is consistent with the absence of a pharmacokinetic interaction between nefazodone and lorazepam. These results indicate that if the coadministration of a benzodiazepine is required in patients receiving nefazodone therapy, clinically significant interactions would be less likely with those eliminated by conjugative metabolism such as lorazepam. In cases where a benzodiazepine eliminated by oxidative metabolism is required, a reduction in initial dosage and careful clinical evaluation for signs of psychomotor impairment may be appropriate.

Pharmacokinetics in lactating women: prediction of alprazolam transfer into milk

1. Alprazolam, a triazolobenzodiazepine, is extensively prescribed for the treatment of anxiety disorders, which predominantly affect women of child-bearing age. The purpose of the present study was to assess the pharmacokinetics of alprazolam and its two hydroxylated metabolites: 4-hydroxy-alprazolam and alpha-hydroxy-alprazolam in lactating human volunteers and to test the predictability of four recently reported models for drug transfer into milk based on physicochemical properties. 2. Multiple milk and serum samples in eight lactating subjects were collected up to 36 h following single oral doses of 0.5 mg alprazolam; suckling of the infant was discontinued after drug administration. 4-Hydroxy-alprazolam was the predominant metabolite in serum samples while alpha-hydroxy-alprazolam was not detected. 3. The mean oral clearance of alprazolam was 1.15 +/- 0.32 ml min-1 kg-1. The time course of alprazolam in milk roughly paralleled the perspective plasma time profile (mean serum residence time = 16.42 +/- 4.69 h; mean milk residence time = 18.93 +/- 7.03 h). The mean terminal half-life in serum was 12.52 +/- 3.53 h. 4. Observed milk/serum concentration ratios were determined in vivo as AUCmilk/AUCserum (mean M/S(obs) = 0.36 +/- 0.11).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the spectrum of cognitive effects of alprazolam and adinazolam after single doses in healthy subjects

Single doses of alprazolam (0, 0.5, 1.5 mg) or adinazolam mesylate sustained release tablets (SR) (0, 15, 45 mg) were administered to separate groups of 12 healthy men in a crossover design. Psychomotor performance was assessed by digit symbol substitution (DSST), and memory was assessed using a test battery which reflects various aspects of memory, including attention/working memory, explicit memory (recall of categorically related words), semantic memory (fragmented picture recognition, generation of category exemplars), and implicit memory (time saved in resolving fragmented pictures on the second exposure). Maximal psychomotor performance and memory decrements for the highest active doses were significantly different from placebo for all tasks at some time after dosing. The maximum decrement in DSST was not significantly different between drugs at the high dose (P = 0.288). Maximum attention/working memory decrements were significantly different between the high doses of the active compounds (P = 0.031), and the difference in maximum category recall decrement was marginally significant (P = 0.067). Access to knowledge memory was not significantly altered by these drugs; these results are similar to those obtained for other benzodiazepines. Both drugs exhibited slight effects on implicit memory. The results suggest that the sedative and memory effects of these triazolobenzodiazepines may not be closely related and suggest that adinazolam has a somewhat different spectrum of cognitive effects relative to alprazolam.

Time-dependent sensitization to triazolam? An observation in three studies

Evidence of time-dependent sensitization (TDS) to triazolam was observed in three separate clinical studies. Study 1 was conducted in 12 normal-weight and 12 obese men; an intravenous bolus dose of triazolam, 0.5 mg, was administered on two occasions. Study 2 was a balanced crossover of three 0.25-mg oral doses and one 0.20-mg oral dose of triazolam in 11 men. Study 3 was a balanced crossover of one placebo, one 0.5-mg, and two 0.4-mg oral doses of triazolam. In all three studies, treatments were separated by 6 days and included serial blood sampling for characterization of pharmacokinetics. Psychomotor response was assessed with the Digit Symbol Substitution Test and the Continuous Performance Test (CPT). Sedation was rated by an observer. For each measure, an effect ratio was calculated as the area under the effect curve divided by the area under the triazolam concentration curve; this parameter relates the extent of response relative to drug concentration in plasma. Effect ratios increased progressively by week for CPT; the percentage increase ranged from 31.9% in the study 1 normal subjects (week 1 to week 2; p = 0.08) to 631% in study 2 (week 1 to week 4; p = 0.0013). Similar increases were observed for other responses. Overall, the effect ratio data demonstrate increasing responsiveness per unit of triazolam concentration when triazolam was administered as a single dose at 1-week intervals. This observation was incidental to the original objectives of the studies. However, the data suggest that definitive studies to verify the occurrence of this phenomenon need to be conducted.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and pharmacodynamics of triazolam after two intermittent doses in obese and normal-weight men

This study was designed to determine whether differences in alpha-1 acid glycoprotein and free drug concentrations result in an altered response to triazolam. Twelve normal-weight and 12 obese adult male subjects received intravenous doses of triazolam, 0.5 mg, on two occasions separated by 1 week. There was a small difference in the alpha-1 acid glycoprotein concentrations between groups but no difference in free fraction of triazolam. There was a longer terminal half-life (t1/2 beta) in the obese subjects (3.16 +/- 0.87 vs. 3.83 +/- 1.24, p = 0.0098). Overall, week 1 data revealed no difference in effect between normal and obese subjects. However, response data reveal a pattern of increased sensitivity with the second exposure to triazolam. For example, area under the effect curve (AUEC) on all tests was significantly greater in week 2 for both groups of subjects. For a memory test and sedation from 0 to 12 hours, AUEC/free AUC ratios were significantly greater in week 2 for all subjects. The obese had a higher ratio on week 2 than on week 1 for all psychomotor tests and sedation (0 to 4.5 hours; p < 0.05). The results of modeling psychomotor impairment-concentration data pooled by group for each week continue the pattern: week 1 data are similar between the obese and normal-weight subjects. Although EC50 values are up to 15% lower in week 2 for the normal-weight subjects, EC50 values are as much as 66% lower in week 2 for the obese, where a lower EC50 indicates greater sensitivity. Logistic regression of the recognition data is consistent with these results.(ABSTRACT TRUNCATED AT 250 WORDS)

Alprazolam absorption kinetics affects abuse liability

OBJECTIVE

To evaluate the behavioral, subjective, and reinforcing effects of immediate-release (IR) alprazolam and extended-release (XR) alprazolam to assess the effect of release rate on laboratory measures of abuse liability.

METHODS

Fourteen healthy men with histories of sedative abuse participated as subjects in a double-blind crossover study. All subjects received placebo, 1 and 2 mg immediate-release alprazolam, and 2 and 3 mg extended-release alprazolam in random order. Behavioral performance, subjective effects, and alprazolam plasma concentrations were assessed repeatedly 1/2 hour before and 1/2, 1, 3, 5, 7, 9, 12, and 24 hours after drug administration.

RESULTS

Mean peak alprazolam plasma concentrations occurred 1.7 and 9.2 hours after immediate-release alprazolam and extended-release alprazolam, respectively. Compared to placebo, 2 mg immediate-release alprazolam impaired all measures of psychomotor and cognitive performance (Digit Symbol Substitution Test), motor coordination (circular lights and balance), and memory (digit entry and recall); 2 mg extended-release alprazolam did not affect any of these measures and 3 mg extended-release alprazolam impaired circular lights only. Immediate-release alprazolam, 2 mg, increased all six measures of positive drug effects (e.g., ratings of liking or good effects); none of these measures were increased by 2 mg extended-release alprazolam and only three of the six measures were increased by 3 mg extended-release alprazolam. A drug versus money multiple-choice procedure designed to assess the relative reinforcing effects of each condition was administered 24 hour after the drug. The amount of money subjects were willing to "pay" to take the drug was significantly greater than placebo for both doses of immediate-release alprazolam but for neither dose of extended-release alprazolam.

CONCLUSIONS

These data indicate that extended-release alprazolam has less potential for abuse than immediate-release alprazolam.

Orally administered progesterone enhances sensitivity to triazolam in postmenopausal women

An endogenously formed metabolite of progesterone, 3 alpha-hydroxy-5 alpha-dihydroprogesterone (3 alpha-OH-5 alpha-DHP) modulates the gamma-aminobutyric acid receptor complex and plays a physiologic role in brain excitability regulation. On the basis of in vitro observations of 3 alpha-OH-5 alpha-DHP-enhanced [3H]flunitrazepam binding, we investigated the potential clinical effect of coadministering oral progesterone and triazolam. Sixteen postmenopausal women were randomly assigned to receive either intravenous triazolam plus oral progesterone 300 mg (TRZPROG) or intravenous triazolam plus oral placebo (TRZ). Triazolam was infused until 0.5 mg was given or until a predetermined maximal response was attained. Pharmacodynamic evaluation included DSST, continuous performance test, hand-eye coordination, short-term memory, and sedation. Effect ratios were calculated as the ratio of area under the effect-time curve to area under the curve (AUC). Variants of the sigmoid Emax model were fit to the data from the three psychomotor performance tests. A triazolam dose of less than 0.5 mg was administered to seven of eight subjects in the TRZPROG and five of eight subjects in the TRZ group, resulting in lower triazolam AUC values for the TRZPROG than for the TRZ group (p = 0.0275). There was clear evidence for a pharmacodynamic interaction. Mean effect ratios for all tests were greater in the TRZPROG group than in the TRZ group (DSST, p = 0.0097; continuous performance test, p = 0.0338; hand-eye coordination, p = 0.0041). The TRZPROG group had lower EC50 values than the TRZ group (DSST, p = 0.0435; continuous performance test, p = 0.0381; hand-eye coordination, p = 0.0154).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitors of alprazolam metabolism in vitro: effect of serotonin-reuptake-inhibitor antidepressants, ketoconazole and quinidine

1. The biotransformation of the triazolobenzodiazepine alprazolam (ALP) to its hydroxylated metabolites (4-OH-ALP and alpha-OH-ALP) was evaluated in human, monkey, rat, and mouse liver microsomes. 2. In all species 4-OH-ALP was the principal metabolite, accounting for 84% of clearance in human microsomes compared with 16% for alpha-OH-ALP. 3. Among the serotonin-specific reuptake inhibitors fluoxetine (FLU) and sertraline (SERT), and their respective demethylated metabolites norfluoxetine (NOR) and desmethylsertraline (DES), NOR was the most potent inhibitor (mean Ki for 4-OH-ALP formation in humans: 11 microM), FLU the weakest (Ki = 83 microM), with SERT and DES falling in between (Ki = 24 and 20 microM). 4. The in vitro data predict 29% inhibition of ALP clearance at mean FLU and NOR plasma concentrations of 77 ng ml-1 and 72 ng ml-1, respectively, after correction for liver:water partition ratios in the range of 12-14. The observed mean degree of inhibition in a previous in vivo study was 21%. 5. Ketoconazole was a potent inhibitor of ALP metabolism in vitro (Ki = 0.046 microM), suggesting that ALP hydroxylation is mediated by the cytochrome P450-3A sub-family. Quinidine was a weak inhibitor (Ki = 626 microM).

Psychomotor and memory effects of two adinazolam formulations assessed by a computerized neuropsychological test battery

The memory effects of adinazolam were assessed using the computerized neuropsychological test battery (CNTB). In a single-blind crossover study, 12 volunteers received 2 x 20 mg adinazolam mesylate immediate-release (CT) tablets, 2 x 30 mg sustained-release (SR) tablets, and placebo. Plasma adinazolam and N-desmethyladinozolam (NDMAD) were determined by high-pressure liquid chromatography. Choice reaction time and word-list-learning/delayed-recall CNTB modules were administered at 0, 1, 3 and 6 hours after dosing. Adinazolam and NDMAD maximum peak plasma concentration were lower after SR tablets. Immediate-release tablets significantly prolonged reaction time compared with placebo and SR tablets; reaction time after SR tablets did not differ from placebo. Differences between SR and CT tablets in memory were significant only at 1 hour, but memory scores tended to be higher after SR tablet administration than after the CT tablet. At all times, memory scores were significantly lower than placebo for active treatments. Results suggest that memory is more impaired at lower NDMAD concentrations than is psychomotor function.

The use of microcomputer-based psychomotor tests for the evaluation of benzodiazepine effects on human performance: a review with emphasis on temazepam

1. The literature relating to the effects of benzodiazepines in general, and temazepam in particular, on human psychomotor performance as assessed using microcomputer-based testing batteries is surveyed. 2. The adverse effects of central nervous system depressants on performance is an important mediocolegal issue and frequently comes into question in on-the-road and on-the-job accidents. The use of microcomputer-based testing batteries allows for performance evaluation both in the laboratory and at-the-scene, as well as providing the opportunity to model a large number of different behaviours required in routine yet complex psychomotor tasks. 3. The conclusions in general are: (1) The benzodiazepines as a class of drugs impair both cognitive and motor performance. These effects are often subtle when low doses are involved or when testing occurs the morning following evening administration of the medication. (2) No single psychomotor task adequately simulates complex daily tasks such as automobile driving. A battery of tests that evaluates a number of the components of such tasks is necessary to determine adequately the full range of effects of these medications.

Clinical pharmacokinetics of anxiolytics and hypnotics in the elderly. Therapeutic considerations (Part II)

Part I of this article, which appeared in the previous issue of the Journal, discussed the scope of and scientific basis for special pharmacokinetic studies of anxiolytic and hypnotic drugs in the elderly, and examined the methodology and results of such studies and the prediction of pharmacokinetic changes. In Part II the authors continue their review, focusing on age-related pharmacodynamic changes in the effects of these drugs, the attempts to correlate pharmacokinetic with pharmacodynamic findings, and the clinical applications of these data.

Alprazolam in end-stage renal disease: I. Pharmacokinetics

In a double-blind, randomized, placebo-controlled study, the pharmacokinetics of alprazolam and its active metabolite, alpha-hydroxyalprazolam, were determined in 12 normal subjects and 12 dialysis patients [7 hemodialysis (HD) patients and 5 continuous ambulatory peritoneal dialysis (CAPD) patients]. Blood samples were collected over 48 hours after alprazolam 0.5 mg and alprazolam 2 mg administration. Alprazolam and alpha-hydroxyalprazolam concentrations and alprazolam free fraction were determined. The pharmacokinetics of alprazolam were similar in normal subjects and HD patients with the exception of higher free fraction in HD patients. Differences were detected, however, in the pharmacokinetics of alprazolam in CAPD patients when compared with normal subjects and HD patients. These differences included a higher free fraction and a lower apparent oral clearance and free clearance in CAPD patients than in normal subjects or in HD patients. There was also a tendency for a later Tmax and a longer elimination half-life in CAPD patients than in normal subjects or HD patients. Alpha-hydroxyalprazolam concentrations were less than 15% of corresponding alprazolam concentrations in normal subjects and dialysis patients. Thus, end-stage renal disease is associated with changes in absorption, distribution, and/or elimination of alprazolam.

The effects of repeated doses of clomipramine and alprazolam on physiological, psychomotor and cognitive functions in normal subjects

The effects of a 10 day administration of clomipramine (25-50 mg t.i.d.), alprazolam (0.25-0.75 mg t.i.d.) and placebo were assessed in normal volunteers in a double-blind cross-over study. A battery of physiological, psychomotor and cognitive tests was administered both before and 3 h after drug on days 1, 5 and 10. The effects of alprazolam on EEG and evoked potentials were characteristic of benzodiazepines; clomipramine had little effect. In contrast, reaction speed was markedly slowed by clomipramine but little affected by alprazolam. Neither drug produced any accumulation of effect on a verbal recall task but neither did tolerance develop to the acute impairments produced by active treatments. Alprazolam produced an increase in levels of forgetting, especially on day 5. Subjective ratings for mood and bodily symptoms were adversely affected by clomipramine but little altered by alprazolam. It is suggested that some of the differences between drug treatments may be due to differences in the speed of onset of tolerance.

Pharmacokinetic pharmacodynamic evaluation of the combined administration of alprazolam and fluoxetine

The pharmacokinetic and pharmacodynamic effects of concomitant administration of alprazolam and fluoxetine were studied in this double-blind parallel study in 80 healthy, male volunteers. Subjects were randomly assigned to one of four treatment groups. Drug treatments consisted of 4-day regimens of 1 mg alprazolam four times daily, 60 mg fluoxetine every morning, 1 mg alprazolam four times daily and 60 mg fluoxetine every morning, and placebo four times daily. Psychomotor performance, mood status, and degree of sedation were evaluated at designated times. Combined administration of alprazolam and fluoxetine resulted in an approximate 30% increase in plasma alprazolam concentrations relative to plasma concentrations following the administration of alprazolam alone. There were no significant differences in fluoxetine or norfluoxetine plasma concentrations between the alprazolam/fluoxetine and fluoxetine treatments. Psychomotor decrements increased when fluoxetine was administered with alprazolam relative to alprazolam administration alone. Psychomotor performance of the fluoxetine treatment group was not significantly different from that of the placebo group. No significant changes were observed in mood status, and sedation was minimal in all treatment groups. As when any two psychoactive drugs are administered together, increased patient monitoring and patient education is recommended when alprazolam and fluoxetine are prescribed concurrently.

N-desmethyladinazolam pharmacokinetics and behavioral effects following administration of 10-50 mg oral doses in healthy volunteers

Results of previous studies suggest that N-desmethyladinazolam, the major metabolite of adinazolam in man, contributes substantially to psychomotor effects and sedation observed following adinazolam administration. Therefore, the pharmacokinetics and pharmacodynamics of N-desmethyladinazolam were explored following administration of single oral doses of placebo and solutions containing 10, 30, and 50 mg N-desmethyladinazolam mesylate in a double-blind, randomized, four-way crossover design to 15 healthy male volunteers. Plasma concentrations of N-desmethyladinazolam were determined by HPLC. Psychomotor performance tests (digit symbol substitution and card sorting by fours and suits), memory tests and sedation scoring were also performed following drug administration. N-Desmethyladinazolam pharmacokinetics were dose independent over this range. Dose-related performance effects were observed at 1, 2, and 6 h after dosing. Memory was likewise affected at 2 h. Psychomotor performance decrements correlated with log N-desmethyladinazolam plasma concentrations. Analysis of the relationship between percentage decrements in digit-symbol substitution and plasma N-desmethyladinazolam using the Hill equation revealed a EC50 of 325 ng/ml. These results establish the relationship between N-desmethyladinazolam plasma concentrations and performance effects; these data will be helpful in assessing the contribution of N-desmethyladinazolam to clinical effects observed after adinazolam administration.

Effects of single doses of alprazolam and diazepam, alone and in combination with ethanol, on psychomotor and cognitive performance and on autonomic nervous system reactivity in healthy volunteers

Effects of alprazolam, alone and in combination with ethanol, on psychomotor and cognitive performance were studied in healthy male volunteers and compared to effects of diazepam. Alprazolam 2 mg produced relatively long-lasting impairments on tests of tracking, verbal and nonverbal information processing, and memory, and decreased blood pressure without a change in heart rate or plasma norepinephrine levels. Although ethanol consumption was demonstrated to produce additive decrements in performance on certain tasks, there was little evidence to support a synergistic effect. Alprazolam 2 mg was accompanied by increased self-reports of side effects, especially drowsiness. Low dose alprazolam, diazepam, and ethanol produced significantly fewer side effects than 2 mg alprazolam, but significantly more than placebo.

Oral premedication in children: a comparison of chloral hydrate, diazepam, alprazolam, midazolam and placebo for day surgery

A double-blind study consisting of 339 randomly selected children investigated the effects of several premedicants on the preoperative and postoperative behaviour of children who underwent day-stay surgery. Patients were allocated into two groups. Group 1 consisted of 165 children aged between 6 and 47 months. Group 2 consisted of 174 children aged four years and older to a body weight of 50 kg. Each child received one premedicant. Both groups included alprazolam 0.005 mg/kg, midazolam 0.3 mg/kg and placebo. In addition Group 1 included chloral hydrate 40 mg/kg and Group 2 diazepam 0.25 mg/kg. Chloral hydrate produced superior conditions (more patients calm or asleep) at induction of anaesthesia. Postoperative behaviour and incidence of vomiting were similar for all drugs. No premedicant reduced anxiety in the older group. The time to awaken postoperatively with diazepam was longer than with placebo. Alprazolam and midazolam were unpalatable for children over four years and conferred no advantage over placebo.

Alprazolam in the elderly: pharmacokinetics and pharmacodynamics during multiple dosing

Previous studies have suggested that elderly men eliminate alprazolam more slowly than young adults. This study in the elderly was designed to determine whether a change in pharmacokinetics influences the response to alprazolam during multiple dose regimens. In addition, the study was designed to determine alprazolam pharmacokinetics and the degree to which its hydroxymetabolites accumulate, the degree of psychomotor impairment, and whether tolerance to impairment and sedation develops during three different multiple dose regimens. Twenty-six subjects completed this study. The subjects were randomized into one of three treatment groups: 0.25 mg q8h, 0.5 mg q8h, and 2 mg q12h. Subjects remained in the clinic for 8 days (day -2-day 5). Day 0 was used as a drug free testing day to establish baseline scores for sedation, digit symbol substitution (DSS), card sorting (CS) tasks, and two computer tests. Subjects received the drug according to schedule on days 1 through 4, with day 5 as the washout day. Blood samples were assayed for alprazolam, alpha-hydroxyalprazolam and 4-hydroxyalprazolam. Alpha-hydroxyalprazolam concentrations were below assay detection limits in all subjects in the 0.25 and 0.5 mg q8h groups and less than or equal to 2.6 ng/ml in the 2 mg q12h group. When detectable, 4-hydroxyalprazolam concentrations were less than 10% of the corresponding alprazolam concentration. Mean alprazolam oral clearance values in the three treatment groups ranged between 0.54 and 0.62 ml/min/kg and half-lives were in excess of 21 h. Degree of sedation and impairment was dose related. Sedation and impairment was not higher on day 4 despite concentrations 2-3 times as great as on day 1, indicating development of tolerance. Subjects were not, however, back to baseline level of performance on day 4.

Absence of effect of food on alprazolam absorption from sustained release tablets

This study examined the effect of food on alprazolam absorption from a mixed polymeric matrix sustained release (SR) tablet in 21 healthy adults. Each subject received each of three treatments according to a crossover design: 1 mg alprazolam SR tablet while fasting; 1 mg alprazolam SR tablet immediately after a standardized breakfast; 1 mg alprazolam conventional tablet while fasting. The breakfast contained approximately 33 g protein, 55 g fat, and 58 g carbohydrate (850 calories). Serial blood samples were obtained and plasma alprazolam levels determined by HPLC. Results indicate that the SR tablet was minimally affected by food. Relative bioavailabilities of the SR tablet while fasting and with food were 100 per cent and 97 per cent, respectively. Although statistically significant, differences in mean Cmax values between SR tablets administered with and without food were small (12 per cent increase with food). Rates of absorption as measured by mean tmax values were also nearly the same: 7.2 h while fasting and 7.0 h with food. Absorption was relatively uniform with the SR tablets. Coefficients of variation for Cmax, tmax, and AUC were somewhat smaller with the SR tablet than with the conventional tablet.

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)

Pharmacokinetics and pharmacodynamics of alprazolam following single and multiple oral doses of a sustained-release formulation

The pharmacokinetics and pharmacodynamics of alprazolam after IV and oral sustained-release (SR) tablet administration were evaluated in 42 healthy, normal, male volunteers. All 42 subjects received a single 1-mg intravenous (IV) alprazolam dose. After a 1-week washout period, the subjects received one of three SR treatments as a single dose: one 1-mg SR tablet, three 1-mg SR tablets, or six 1-mg SR tablets. Beginning 2 days after single-dose SR treatment, each subject received the above SR doses for 3 days. The daily dose for the multiple-dose study was the same as the subject received in the single-dose study. Serial blood samples were collected after each treatment (single-dose IV, single-dose SR, and after the last SR multiple dose), and plasma samples were analyzed by high performance liquid chromatography. Sedation was assessed by a blinded observer at each blood sampling time. Mean pharmacokinetic parameters for IV administration were consistent with previous results. Pharmacokinetic parameters for the SR doses were consistent with linear kinetics over the dosage range studied. The mean absolute bioavailabilities of the SR tablets were greater than 0.84 after single SR doses. Maximal sedation was related to dose after single-dose SR administration. During multiple dosing, chronic tolerance was observed. Maximal sedation scores after 3 days of alprazolam SR administration were independent of the dose administered and were lower after multiple-dose administration than scores observed after single oral SR doses, although plasma alprazolam concentrations were at least 1.5 times higher with multiple dosing. Sedation data indicate that oral SR doses were well tolerated in multiple dosing.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple-dose pharmacokinetics and pharmacodynamics of adinazolam in elderly subjects

The pharmacokinetics and pharmacodynamics of adinazolam (AD) were evaluated in 21 elderly subjects (mean age, 69 +/- 4 years) at four dose levels during a placebo-controlled, double-blind, dose escalation regimen in which the oral dose was varied from 10 to 60 mg daily, in divided doses. Fifteen subjects received adinazolam mesylate; six received placebo. Plasma samples collected during a single dosing interval in each dosing period (3 days) were assayed for adinazolam and monodesmethyl adinazolam (NDMAD) by high-performance liquid chromatography (HPLC). Urine samples were collected during a single interval during the 20- and 40-mg daily dose periods and assayed for NDMAD by HPLC. Pharmacologic effects of adinazolam were assessed using psychomotor performance tests and sedation ratings. Adinazolam pharmacokinetics were linear over the dosage range studied. Daily dose had no significant effect on dose-normalized AUC and Cmax for AD. Dose-normalized NDMAD AUC values as well as beta values were not significantly affected by the daily dose of adinazolam. The ratio NDMAD/AD was not substantially affected by the dose. Renal clearance of NDMAD for the 20- and 40-mg daily doses were 5.6 +/- 2.1 and 5.5 +/- 2.2 liters/hr, respectively, and did not correlate with creatinine clearance. Adinazolam and NDMAD did not substantially accumulate in elderly subjects, even upon multiple dosing at 8-hr intervals. The dosing regimens in this experiment appeared to be well tolerated in the elderly, as performance tests and sedation scores indicated no substantial dose-related effects of adinazolam on psychomotor performance.