Analysis of low-dose benzodiazepines by HPLC with automated solid-phase extraction

We describe a simple, specific, and sensitive reversed-phase HPLC method with automated solid-phase extraction (SPE) for analyzing alprazolam, clonazepam, and nitrazepam concentrations in human serum or plasma. We prepare samples and calibrators with an automated sample preparer, using 100-mg Bond-Elut C18 SPE columns. The HPLC method uses isocratic elution with acetonitrile:methanol:dipotassium hydrogen phosphate, 10 nmol/L, pH 3.7 (30:2:100 by vol), at a flow rate of 1.5 mL/min to separate the drugs. We detect the benzodiazepines with diode-array detector at 240 nm; analyses of peak purity are performed at 210-365 nm. The recoveries were between 94% and 100%. The intraassay and interassay CVs were between 1.0% and 4.1%. The detection limit is 5 nmol/L. The antiepileptic and antidepressant drugs tested did not interfere with the assay. We developed the method for use in a clinical laboratory for therapeutic drug monitoring.

Determination of alprazolam and alpha-hydroxyalprazolam in human plasma by gas chromatography/negative-ion chemical ionization mass spectrometry

A sensitive and specific method was developed for the determination of alprazolam and its major metabolite alpha-hydroxyalprazolam in plasma. After the addition of deuterium-labeled internal standards, plasma samples were buffered to pH 9 with 1 ml of saturated sodium borate buffer, extracted with toluene-methylene chloride (7:3) and evaporated to dryness. The residues were treated with N,O-bis(trimethylsilyl)trifluoroacetamide containing 1% of trimethylchlorosilane and analyzed on a Finnigan-MAT mass spectrometer operated in the negative-ion chemical ionization mode with methane as the reagent gas. Chromatographic separation was achieved on a Restek-200 capillary column using hydrogen as the carrier gas. The assay was linear from 0.25 to 50 ng ml-1 for both compounds. The intra-assay precision for alprazolam was 16.1% at 0.5 ng ml-1 and 4.6% at 50 ng ml-1 and that for alpha-hydroxyalprazolam was 15.8% at 0.5 ng ml-1 and 4.2% at 50 ng ml-1. The method was used to determine alprazolam and alpha-hydroxyalprazolam in human plasma samples collected after a single 2 mg oral does of alprazolam. A peak concentration of 32.9 ng ml-1 of alprazolam was detected at 1 h following the dose.

Liability to alprazolam abuse in daughters of alcoholics

OBJECTIVE

The purpose of this study was to determine mood changes in women with a parental history of alcohol dependence (daughters of alcoholics) after challenge does of alprazolam and placebo in comparison with responses in women without a history of parental alcohol dependence.

METHOD

Visual analog scales that assess liability to benzodiazepine abuse were administered to 12 adult daughters of alcoholics and 11 comparison subjects after alprazolam challenge.

RESULTS

The daughters of alcoholics had greater pleasant mood responses after a single dose of alprazolam than did the comparison subjects despite having similar plasma alprazolam levels.

CONCLUSIONS

The findings of this study suggest that the mood-enhancing effects of alprazolam are greater in daughters of alcoholics than in subjects without a history of parental alcohol dependence.

A kinetic and dynamic study of oral alprazolam with and without erythromycin in humans: in vivo evidence for the involvement of CYP3A4 in alprazolam metabolism

OBJECTIVE

To assess the possible involvement of CYP3A4 in the metabolism of alprazolam in vivo.

METHOD

Twelve healthy male volunteers were randomly allocated to one of the two different treatment sequences, placebo-erythromycin or erythromycin-placebo, with an at least 6-week washout period between the two trial phases. Each volunteer received 400 mg erythromycin or matched placebo given orally three times a day for 10 days and an oral dose (0.8 mg) of alprazolam on the posttreatment day 8. Plasma concentration of alprazolam was measured up to 48 hours after the administration, and psychomotor function was assessed at each time of blood samplings with use of the Digit Symbol Substitution Test, visual analog scale, and Udvalg for kliniske undersøgelser side effect rating scale.

RESULTS

Erythromycin significantly (p < 0.001) increased the area under the plasma concentration-time curves (200 +/- 43 versus 322 +/- 49 ng . hr/ml from 0 to 48 hours and 229 +/- 52 versus 566 +/- 161 ng . hr/ml from 0 hour to infinity), decreased the apparent oral clearance (1.02 +/- 0.31 versus 0.41 +/- 0.12 ml/min/kg), and prolonged the elimination half-life (16.0 +/- 4.5 versus 40.3 +/- 14.4 hours) of alprazolam. However, any psychomotor function variables did not differ significantly between the erythromycin and placebo trial phases.

CONCLUSION

This study suggests that erythromycin, an inhibitor of CYP3A4, inhibits the metabolism of alprazolam, providing an in vivo evidence for the involvement of CYP3A4 in its metabolism. However, the kinetic change of alprazolam by erythromycin does not result in the pharmacodynamic change of this triazolobenzodiazepine, at least after single dosing.

High-performance liquid chromatography of alprazolam in postmortem blood using solid-phase extraction

Screening and analysis of the numerous benzodiazepines presents a challenge for the forensic toxicologist. The newer benzodiazepines, which are prescribed in daily dose regimens of 0.5-3 mg, are particularly difficult to screen and analyze. Frequently, history or careful investigation by the medical examiner is the only clue that the laboratory has to follow. We describe four cases involving alprazolam and the modification of an existing serum high-performance liquid chromatographic (HPLC) procedure, which allowed us to analyze whole blood. This HPLC procedure for alprazolam uses a protein precipitation step followed by solid-phase extraction. The method is sensitive to 18 ng/mL and linear from 18 to 200 ng/mL. Reproducibility was determined by extracting and analyzing duplicate samples on five separate occasions. The recovery averaged 84% using postmortem blood spiked with 18 and 150 ng/mL alprazolam.

The effects of theophylline on serum alprazolam levels

Theophylline and benzodiazepines are frequently combined in clinical practice. Because of a number of case reports about antagonism of benzodiazepine-induced sedation by theophylline, we investigated serum alprazolam levels in a convenient sample of pulmonary medicine inpatients receiving theophylline and no theophylline. One mg of alprazolam was given daily for seven days to 6 patients receiving theophylline and 7 patients not receiving theophylline treatment. On days 2 through 7, trough serum alprazolam levels were measured. On day 7, blood samples were collected before (0 hour), and at 3, 6, 9 and 12 hours after alprazolam administration. In patients receiving theophylline, serum trough alprazolam levels were significantly lower during each day of the study. In patients receiving no theophylline, serum alprazolam levels were in the therapeutic range, except for two patients who had high alprazolam levels. In this small study, serum alprazolam levels were found to be consistently below the therapeutic range in patients receiving chronic theophylline treatment. Previously reported antagonism of anxiolytic effects of benzodiazepines by theophylline is probably due to the lower serum benzodiazepine levels in these patients.

Determination of alprazolam and its major metabolites in serum microsamples by high-performance liquid chromatography and its application to pharmacokinetics in rats

A high-performance liquid chromatographic method using a single-solvent extraction step is described for quantitating alprazolam and its metabolites in rat serum microsamples (50 microliters). The separation used a 2-mm I.D. reversed-phase Ultrasphere C18 column with a mobile phase of methanol-acetonitrile-sodium acetate buffer. By decreasing the methanol content in the mobile phase, triazolam and its metabolites can be extracted and separated using the same method. The detection limit was 5 ng/ml for all the compounds using an ultraviolet detector at 230 nm. The method showed the effect of aging on alprazolam pharmacokinetics following 0.8 mg/kg intravenous bolus alprazolam administration.

A pharmacokinetic and pharmacodynamic evaluation of the combined administration of alprazolam and fluvoxamine

We have assessed the pharmacokinetic and pharmacodynamic interaction between fluvoxamine, a serotonin reuptake inhibitor, and alprazolam, a triazolobenzo-diazepine. Healthy men took fluvoxamine maleate daily for 10 days (50 mg on days 1-3, 100 mg on days 4-10) (n = 20), 1 mg of alprazolam four times daily for four days (days 7-10 of the study period) (n = 20), or a combination of the two (n = 20), according to a parallel study design. Alprazolam and fluvoxamine concentrations were measured in serial plasma samples by HPLC and gas chromatography respectively, and psychomotor performance and memory were assessed on days 1, 7, and 10. Fluvoxamine increased plasma alprazolam concentrations by 100%. The mean apparent half-life of alprazolam was increased from 20 h to 34 h after fluvoxamine co-administration. The increased plasma concentrations of alprazolam resulted in significantly greater reductions in psychomotor performance evident on day 10. Mean fluvoxamine plasma concentrations were about 25% lower in those who took the combination than in those who took only fluvoxamine; this was more likely due to heterogeneity between the treatment groups than to an effect of alprazolam. The dosage of alprazolam should be reduced during co-administration with fluvoxamine.

Quantitative analysis of alprazolam and triazolam in hemolysed whole blood and liver digest by GC/MS/NICI with deuterated internal standards

This report describes sensitive and specific methods for the quantitation of alprazolam and triazolam in hemolysed whole blood and liver tissue. Samples of blood and enzyme-digested liver are extracted without pH adjustment with n-butyl chloride, after addition of deuterated internal standards and urea. The evaporated extracts are reconstituted in acetonitrile for analysis by gas chromatography/mass spectrometry/negative ion chemical ionization (GC/MS/NICI). Fatty extracts may be cleaned up by partitioning between pentane and acetonitrile. Two ion pairs are monitored for each drug. Within-day coefficients of variation in the range 10-50 micrograms/L for blood are approximately 5%. Between-day coefficients of variation are less than 10%. The limit of quantitation (based on analysis of 0.2-mL blood samples) is 0.5 microgram/L for triazolam and 4 micrograms/L for alprazolam.

A study of pharmacokinetic interaction between buspirone and alprazolam at steady state

The steady-state pharmacokinetic interaction between buspirone and alprazolam was evaluated in a parallel study with two groups of 12 male volunteers each. On days 1 to 7, group I subjects received a 1-mg alprazolam tablet every 8 hours (q8h) (TRT 1) and group II subjects received 2 x 5-mg buspirone tablets q8h (TRT 2). On days 8 through 14, all subjects received a combination of 1-mg alprazolam and 2 x 5-mg buspirone tablets q8h (TRT 3). Plasma samples, collected 0 to 8 hours after the morning dose on days 7 and 14, were analyzed for buspirone, alprazolam and their metabolites, 1-PP, and alpha-HO-alprazolam, respectively. Additional samples were collected before the morning dose on days 5 and 6 of each session to monitor the attainment of steady state. Steady-state pharmacokinetic parameters Cmax, Tmax, AUC0-8, and Cmin were calculated. The results indicated that for alprazolam, there was a small (< 10%) increase in Cmax and AUC when coadministered with buspirone. For buspirone, there was a 10% and 29% increase in Cmax and AUC, when coadministered with alprazolam. These values were within the normal variability observed with this class of drugs. Except for a 14% decrease in Cmin for alpha-HO-alprazolam, coadministration of buspirone and alprazolam did not affect the parameters for the metabolites. The results of this study suggest that coadministration of buspirone and alprazolam did not markedly affect the steady-state pharmacokinetics of either drug.

Alprazolam pharmacokinetics, metabolism, and plasma levels: clinical implications

The triazolobenzodiazepine alprazolam is biotransformed by hepatic microsomal oxidation, yielding two hydroxylated metabolites (4-hydroxy- and a-hydroxy-alprazolam) as the principal metabolic products. Both metabolites have lower benzodiazepine receptor affinity than the parent compound and at steady state appear in plasma at concentrations considerably lower than intact alprazolam. Thus, clinical activity during treatment with alprazolam is essentially entirely attributable to intact alprazolam. The cytochrome P450 IIIA subfamily appears to mediate alprazolam metabolism in humans. This cytochrome subfamily is not subject to variation due to genetic polymorphism. Ketoconazole, cimetidine, macrolide antibiotics, and serotonin-reuptake-inhibitor antidepressants impair alprazolam biotransformation in vitro. Reduced clearance of alprazolam in vivo has been demonstrated for drugs in this group that have been studied in humans; for those not yet studied, impaired alprazolam clearance should be anticipated during coadministration. Studies of plasma alprazolam concentration versus clinical response during short-term treatment of panic disorder indicate that therapeutic response at steady-state plasma levels of 20 to 40 ng/mL is significantly greater than at levels less than 20 ng/mL. Substantial additional benefit from plasma levels greater than 40 ng/mL is not consistently demonstrated. However, side effects attributable to benzodiazepine agonist activity (e.g., drowsiness, sedation) increase in frequency with increasing steady-state plasma levels. Concentration-response data indicate that monitoring of alprazolam plasma levels can be of considerable clinical value during treatment of panic disorder.

Immunoassay detection of nordiazepam, triazolam, lorazepam, and alprazolam in blood

The ability of commercial benzodiazepine immunoassays to detect nordiazepam, lorazepam, alprazolam, and triazolam in blood samples was investigated. Two radioimmunoassays (RIA) (Abuscreen [RIA-a] and the Diagnostic Products Corporation serum kit [RIA-d]), two enzyme immunoassays (EIA) (Emit d.a.u. [EIA-u] and Emit TOX serum assay [EIA-s]), and two fluorescence polarization immunoassays (FPIA) (X-systems urine [FPIA-u] and X-systems serum assay [FPIA-s]) were evaluated for their ability to detect benzodiazepines in fortified drug-free human or bovine blood. Prior extraction of the blood was necessary for analysis on the equipment used for EIA and FPIA. Extraction with an organic solvent, such as butyl chloride used in this study, was preferable to precipitation with methanol or zinc sulfate. For all these assays, extraction eliminated matrix effects and offered the possibility of increased sensitivity by reconstitution of the extract in a smaller volume. Extraction was necessary in bovine blood, as there is some nonextractable substance(s) in this matrix that increases non-specific binding. Using extraction with reconstitution in one-half the original volume, the apparent limit of detection for nordiazepam in blood ranged from 3 ng/mL, with RIA-d, to 30 ng/mL, with EIA-s and FPIA-s. These limits of detection were improved by further reduction of the reconstitution volume. RIA-a, EIA-s, and FPIA-s had cross-reactivity for alprazolam that was equivalent to or slightly better than nordiazepam. RIA-d had enhanced cross-reactivity for alprazolam at 30-300 ng/mL.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma alprazolam concentrations. Relation to efficacy and side effects in the treatment of panic disorder

A series of 237 patients with DSM-III-diagnosed panic disorder, or agoraphobia with panic attacks, received alprazolam as part of the placebo-controlled Cross-National Collaborative Panic Study. After a 1-week drug-free period, alprazolam dosage was titrated upward with the objective of reaching 6.0 mg/d in all patients. At week 3 of treatment, alprazolam plasma levels were significantly correlated with daily dosage (regression slope: 11.7 ng/mL per milligram per day) but with considerable individual variation. Among patients with spontaneous panic attacks, 70% of those with plasma alprazolam levels greater than 20 ng/mL achieved complete remission vs 31% of those with levels less than 20 ng/mL. Situational panic attack remission increased in frequency with increasing plasma levels, but the relationship was not significant. Patient- and physician-rated global improvement and Hamilton Anxiety and Depression Scale score reductions were maximal at 20 to 39 ng/mL, with no further benefit at higher levels. Central nervous system-depressant side effects increased in frequency with higher plasma levels. Between weeks 3 and 8 of treatment, physicians were permitted to adjust dosage (maximum: 10 mg/d) to optimize response. At week 8, the dose-concentration relationship was essentially identical (regression slope: 10.8 ng/mL per milligram per day), but plasma levels were no longer related to efficacy or side effects. Thus, monitoring of plasma alprazolam concentrations may have a clinically useful role during short-term treatment of panic disorder.

Effects of acute and chronic alprazolam treatment on cerebral blood flow, memory, sedation, and plasma catecholamines

The effects of 0.014 mg/kg intravenous alprazolam administration on cerebral blood flow (CBF), memory, sedation, and plasma norepinephrine and epinephrine were determined in eight healthy males at baseline levels and following 1 week of daily oral alprazolam treatment. At baseline, intravenous alprazolam administration caused acute reductions in whole-brain CBF (25% to 30% decrease), memory, plasma epinephrine, and self-rated alertness. Following 1 week of alprazolam treatment, tolerance developed to the acute effects of intravenous alprazolam on CBF, memory, and plasma epinephrine. There were no consistent regional neuroanatomic differences in the CBF effects of acute alprazolam, or in the development of tolerance to these effects, and no correlations between the various measures of acute alprazolam effects on either test day.

Alprazolam plasma concentrations and treatment response in panic disorder and agoraphobia

OBJECTIVE

The authors' goal was to evaluate the relationship between plasma concentrations of alprazolam and both treatment response and side effects in patients with panic disorder and agoraphobia.

METHOD

Ninety-six patients with panic disorder and agoraphobia were treated at three sites in a 6-week, fixed-dose, double-blind, placebo-controlled, dose-response study of 2 mg/day or 6 mg/day of alprazolam. Assessments were made of panic attacks, avoidance behavior, generalized anxiety, and global response. Blood samples were collected throughout the study and analyzed for alprazolam and other benzodiazepines.

RESULTS

Patient compliance with the protocol was judged to be good on the basis of plasma concentrations. According to logistic regression analysis, the relationships between plasma alprazolam concentration and response, as reflected by number of panic attacks reported, phobia ratings, physicians' and patients' ratings of global improvement, and the emergence of side effects, were significant. However, there was no significant relationship between plasma alprazolam concentration and the degree of generalized anxiety symptoms.

CONCLUSIONS

The authors conclude that plasma concentration of alprazolam is related to treatment response, particularly in panic attacks. The alprazolam concentration associated with treatment response or with emergence of a given side effect varied widely among individuals, highlighting the necessity for individualized dose adjustment to obtain optimal treatment response while minimizing side effects.

Influence of alprazolam on opioid analgesia and side effects during steady-state morphine infusions

The primary purpose of this study was to examine whether alprazolam pretreatment can increase the analgesic potency of morphine without increasing opioid side-effect intensities. We employed computer-controlled, variable-rate morphine infusions based on each subject's pharmacokinetic profile for morphine derived from a tailoring bolus dose of the drug administered 1 or 2 weeks before the infusion test sessions. On each of 2 test days, we used dental electrical stimulation to determine stimulus intensity that produced consistent reports of strong (but tolerable) pain; this intensity was used for the rest of that session. Then, we measured baseline (no drug) pain intensity reports, pain-related evoked potentials recorded from vertex, and other parameters typically affected by opioids (subjective side effects). We administered alprazolam (1 mg) or placebo (lactose) orally to the subject and then repeated the test battery 30 min later. One hour after the alprazolam or placebo dose, we initiated the tailored morphine infusion to reach target plasma morphine concentration plateaus of 16, 32 and 64 ng/ml (45-min duration each) on both test days. The test battery used during baseline was then repeated at each target concentration plateau. The order of alprazolam versus placebo pretreatments was counterbalanced across subjects and known only to the investigator operating the infusion system. Results suggest that alprazolam at the dose studied did not alter analgesic potency of morphine. However, alprazolam did clearly decrease the intensity of nausea reported by subjects during and after termination of the morphine infusions. Of special interest, alprazolam alone (30 min after oral dosing) decreased evoked potential amplitude consistently without affecting pain intensity reports.(ABSTRACT TRUNCATED AT 250 WORDS)

High-performance liquid chromatographic method for the determination of alprazolam in plasma using the column-switching technique

A reversed-phase high-performance liquid chromatographic method is described for the quantitative determination of alprazolam in the plasma of geriatric patients in the presence of 4-hydroxyalprazolam, alpha-hydroxyalprazolam, bromazepam, oxazepam, lorazepam, clobazam, desmethylclobazam, diazepam and desmethyldiazepam. The procedure is based on the enrichment of alprazolam on a PRP-1 pre-column, followed by the transfer of the compound in a forflush mode to the analytical column. Alprazolam can be quantified reliably down to a minimum concentration of 1 ng/ml of plasma.

Alprazolam in end-stage renal disease. II. Pharmacodynamics

The sensitivity to the psychomotor and memory effects of alprazolam was evaluated in 12 normal subjects and 12 dialysis patients (seven patients receiving hemodialysis and five patients receiving continuous ambulatory peritoneal dialysis). Subjects received a single oral dose of 0.5 mg alprazolam, 2 mg alprazolam, and placebo in a double-blind, placebo-controlled, balanced, three-way crossover study with a Latin square design. After administration of the test drug, blood was obtained for alprazolam concentration and protein-binding determinations, and psychomotor performance, memory, and sedation were assessed. The maximum psychomotor impairment corrected for free alprazolam concentration was 5.0%, 8.2%, and 10.1% per nanogram per milliliter in normal subjects, patients receiving hemodialysis, and patients receiving continuous ambulatory peritoneal dialysis, respectively (p less than 0.01), after administration of 2 mg alprazolam. Free alprazolam concentrations at which 50% of maximum effect is elicited for psychomotor impairment were 10, 7.40, and 5.31 ng/ml in normal subjects, patients receiving hemodialysis, and patients receiving continuous ambulatory peritoneal dialysis, respectively. The maximum memory impairment corrected for the maximum free alprazolam concentration was 4.4%, 7.2%, and 8.9% per nanogram per milliliter, respectively (p less than 0.09), after administration of 2 mg alprazolam. Thus our group of patients receiving dialysis showed enhanced sensitivity to some psychomotor and memory effects of alprazolam.

Effect of alprazolam (Xanax) on esophageal motility and acid reflux

Recent studies suggest that psychotropic drugs may help the symptoms associated with spastic esophageal motor disorders. However, the physiologic effects of central nervous system depression (a side effect of such therapy) on esophageal function is not known. Therefore, we studied the effect of alprazolam (Xanax), a popular new benzodiazepine anxiolytic, in 10 healthy volunteers, using a randomized, placebo-controlled design. Stationary esophageal motility, 24-h pH monitoring, and 24-h ambulatory motility monitoring was done while on placebo or one tablet (0.25 mg) of alprazolam taken three times a day. Alprazolam had no significant effect on lower esophageal sphincter pressure or motility in the esophagus. Upper esophageal sphincter pressure, however, was significantly decreased. What is more important, one-third of the healthy volunteers had abnormal amounts of nocturnal acid reflux during the alprazolam phase of the study. This effect was probably due to alprazolam-induced central nervous system depression interfering with normal nocturnal acid clearance mechanisms triggered by arousal from sleep.

Influence of menstrual cycle and gender on alprazolam pharmacokinetics

The effects of menstrual cycle phases and gender on alprazolam pharmacokinetics were evaluated in normal volunteers. Alprazolam (1 mg) was administered to seven women during the late follicular and luteal phases of the menstrual cycle and to eight men on one occasion. No difference in alprazolam pharmacokinetic parameters was observed during the menstrual cycle phases. Mean alprazolam clearance (+/- SD) was 0.0037 +/- 0.0009 ml/hr during the follicular phase and 0.0036 +/- 0.001 ml/hr during the luteal phase (p greater than 0.05, difference not significant). With use of weight as a covariant, there was no difference in alprazolam pharmacokinetic parameters between women and men. Mean alprazolam clearance (+/- SD) was 0.0036 +/- 0.0009 ml/hr in women compared with 0.0041 +/- 0.0006 ml/hr in men (p greater than 0.05, difference not significant). Although alprazolam metabolism was similar on the 2 days tested, alterations may occur at other times during the menstrual cycle. Further investigation is needed to understand the effects of menstrual cycle phases and gender on drug metabolism.

New high-performance liquid chromatographic method for the determination of alprazolam and its metabolites in serum: instability of 4-hydroxyalprazolam

A high-performance liquid chromatographic method was developed for the determination of alprazolam (ALP) and its active metabolites, alpha-hydroxyalprazolam (AOH) and 4-hydroxyalprazolam (4OH) in human serum. During assay development, the instability of 4OH was revealed. Factors affecting stability of 4OH were then investigated. In this report, the assay methodology for the determination of ALP and AOH, the instability of 4OH, subsequent interference of 4OH breakdown products with AOH quantification, and factors affecting 4OH stability are described. The clinical significance of our findings are reported.

The effects of alprazolam on corticotropin-releasing factor neurons in the rat brain: acute time course, chronic treatment and abrupt withdrawal

Considerable evidence indicates that corticotropin-releasing factor (CRF) is responsible for integrating not only the endocrine, but the autonomic and behavioral responses of an organism to stress. We have investigated the time course of action of the anxiolytic triazolobenzodiazepine, alprazolam, on the activity of the hypothalamic-pituitary-adrenal (HPA) axis and of CRF neurons after acute and chronic administration. In addition, because many of the signs and symptoms observed in animals and humans after abrupt discontinuation of benzodiazepines resemble the stress response, we examined the effect of alprazolam withdrawal on CRF neurons and HPA axis activity. Alprazolam decreases CRF concentrations in the locus coeruleus between 0.5 and 3.0 h following acute injection. The half-life of alprazolam in rats is less than 1 h in both plasma and brain. Similarly, chronic (14 days) alprazolam administration also results in decreased CRF concentrations in the locus coeruleus. CRF concentrations return to control values 24 h after abrupt withdrawal. Moreover, abrupt alprazolam withdrawal results in increased plasma adrenocorticotrophic hormone and corticosterone concentrations and decreased anterior pituitary CRF receptor concentrations 24 h after drug discontinuation. These indices return to control values by 48 h postwithdrawal. These results support the hypothesis that both acute and chronic alprazolam administration alters CRF-containing neurons innervating the locus coeruleus. Additionally, abrupt alprazolam withdrawal profoundly activates the HPA axis.

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.