Pharmacology of some metabolites of triazolam, alprazolam, and diazepam prepared by a simple, one-step oxidation of benzodiazepines

A Literature Review Focusing on the Antiviral Activity of [1,2,4] and [1,2,3]-triazoles

Out of a variety of heterocycles, triazole scaffolds have been shown to play a significant part in a wide array of biological functions. Many drug compounds containing a triazole moiety with important antimicrobial, anticancer and antidepressant properties have been commercialized. In addition, the triazole scaffold exhibits remarkable antiviral activity either incorporated into nucleoside analogs or non-nucleosides. Many synthetic techniques have been produced by scientists around the world as a result of their wide-ranging biological function. In this review, we have tried to summarize new synthetic methods produced by diverse research groups as well as provide a comprehensive description of the function of [1,2,4] and [1,2,3]-triazole derivatives as antiviral agents. Antiviral triazole compounds have been shown to target a wide variety of molecular proteins. In addition, several strains of viruses, including the human immunodeficiency virus, SARS virus, hepatitis B and C viruses, influenza virus, Hantavirus, and herpes virus, were discovered to be susceptible to triazole derivatives. This review article covered the reports for antiviral activity of both 1,2,3- and 1,2,4-triazole moieties up to 2022.

Pharmacologically active metabolites of currently marketed drugs: potential resources for new drug discovery and development

Biotransformation is the major clearance mechanism of therapeutic agents from the body. Biotransformation is known not only to facilitate the elimination of drugs by changing the molecular structure to more hydrophilic, but also lead to pharmacological inactivation of therapeutic compounds. However, in some cases, the biotransformation of drugs can lead to the generation of pharmacologically active metabolites, responsible for the pharmacological actions. This review provides an update of the kinds of pharmacologically active metabolites and some of their individual pharmacological and pharmacokinetic aspects, and describes their importance as resources for drug discovery and development.

Role of pharmacologically active metabolites in drug discovery and development

Pharmacologically active metabolites can contribute significantly to the overall therapeutic and adverse effects of drugs. Therefore, to fully understand the mechanism of action of drugs, it is important to recognize the role of active metabolites. Active metabolites can also be developed as drugs in their own right. Using illustrative examples, this paper discusses a variety of biotransformation reactions that produce active metabolites and their structure-activity relationships. The paper also describes the role and significance of active metabolites in drug discovery and development, various experimental observations that can be used as indicators of their presence, and methods that can be used to assess their biological activities and contribution to the overall therapeutic and adverse effects of drugs.

Mechanism of triazolo-benzodiazepine and benzodiazepine action in anxiety and depression: behavioral studies with concomitant in vivo CA1 hippocampal norepinephrine and serotonin release detection in the behaving animal

1. Real time, in vivo microvoltammetric studies were performed, using miniature carbon-based sensors, to concurrently detect norepinephrine (NE) release and serotonin (5-HT) release, in 2 separate electrochemical signals, within CA1 region of hippocampus in the freely moving and behaving, male, Sprague Dawley laboratory rat. 2. Concurrently, four parameters of open-field behavior, i.e. Ambulations, Rearing, Fine Movements and Central Ambulatory behavior (a measure of anxiety reduction behavior), were assayed by infrared photobeam detection. 3. Time course studies showed that the mechanism of action of the triazolobenzodiazepine (TBZD), adinazolam, (Deracyn) is dramatically different from that of the classical benzodiazepine (BZD), diazepam (Valium, i.e., adinazolam increased, whereas diazepam decreased, 5-HT release within CA1 region of hippocampus in the freely moving and behaving rat. 4. Adinazolam initially increased NE release and then decreased NE release in CA1 region of hippocampus in the freely moving and behaving rat whereas diazepam only decreased the electrochemical signal for NE; the decrease in NE produced by adinazolam was greater than the decrease in NE release produced by diazepam. 5. The Behavioral Activity Patterns, derived from same animal controls, simultaneously with detection of in vivo microvoltammetric signals for NE release and 5-HT release, showed that the BZD, diazepam, exhibited more potent sedative properties than did the TBZD adinazolam. 6. Hippocampal 5-HT and NE release effects of the TBZD, adinazolam, concomitant with behavioral effects lends explanation to the dual anxiolytic/antidepressant properties of the TBZDs.

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.

Anticonvulsant pharmacodynamics and disposition of triazolam in rats

Triazolam (TZ) is a triazolobenzodiazepine used in the treatment of insomnia that possesses significant anticonvulsant properties. Despite the widespread use of this drug, detailed pharmacokinetic-pharmacodynamic information is lacking, especially with respect to inhibition of seizure activity. TZ disposition has been described previously by methods with limited specificity, and the concentration-anticonvulsant effect relationship has not been characterized. The current studies were undertaken to examine TZ disposition with a specific HPLC method, and to evaluate the relationship between anticonvulsant effect and concentration in Sprague-Dawley rats. TZ pharmacokinetics were characterized after bolus or infusion administration; in a separate experiment, TZ pharmacodynamics were assessed with pentylenetetrazol-induced seizures. The systemic disposition of TZ could be described with a two-compartment model; systemic clearance ranged from 2.45 to 5.30 L/h/ kg, steady-state volume of distribution ranged from 2.10 to 4.02 L/kg, and mean residence time ranged from 47 to 65 min. The concentration-effect relationship was well described by a simple Emax model: Emax, expressed as the ratio of post-TZ to pre-TZ threshold convulsant doses of pentylenetetrazol, was 9.9 +/- 0.7, and the EC50 values were 10.0 +/- 4.6 ng/mL and 34.8 +/- 9.0 ng/g in serum and whole brain tissue, respectively. Under single-dose conditions, TZ is a very potent anticonvulsant in the rat pentylenetetrazol seizure model.

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

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

The effects of alprazolam on corticotropin-releasing factor neurons in the rat brain: implications for a role for CRF in the pathogenesis of anxiety disorders

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 effects of the anxiolytic triazolobenzodiazepine, alprazolam, on the activity of the hypothalamic-pituitary-adrenal (HPA) axis and of CRF neurons following acute and chronic administration. In addition, because many of the signs and symptoms observed in animals and humans following abrupt discontinuation of benzodiazepines resemble those of 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 0.5-3.0 hours following acute injection. Similarly, chronic (14 days) alprazolam administration also results in decreased CRF concentrations in the locus coeruleus. CRF concentrations return to control values 24 hours following abrupt alprazolam withdrawal. Moreover, abrupt alprazolam withdrawal results in increased plasma ACTH and corticosterone concentrations and decreased anterior pituitary CRF receptor concentrations 24 hours following drug discontinuation. Thus, abrupt alprazolam withdrawal profoundly activates the HPA axis. These indices of HPA axis activity return to control values by 48 hours post-withdrawal. These actions of alprazolam on CRF neurons are opposite to those observed following acute or chronic stress. These results support the hypothesis that CRF-containing neurons innervating the locus coeruleus may be involved in the pathogenesis of anxiety, and in the actions of clinically efficacious anxiolytics.

Suppressive effects of alprazolam on the immune response of mice

The purpose of this study was to examine the effects of alprazolam on the response of murine immune cells. Splenic cells of young BALB/c mice were first cultured with an optimum dose of various mitogens in the presence or absence of varying doses of alprazolam to assess effects of alprazolam on concanavalin A (Con A)-induced T-cell proliferation, bacterial lipopolysaccharide (LPS)-induced B-cell proliferation, and production of interleukin 2 (IL2). Then, peritoneal adherent cells (macrophages) from young BALB/c mice were cultured with an optimum dose of LPS in the presence or absence of alprazolam to assess the effects of alprazolam on the ability of peritoneal adherent cells to produce interleukin 1 (IL1) and tumor necrosis factor (TNF). The results of this study clearly demonstrated that alprazolam is a potent immunosuppressive agent that can inhibit the proliferative responses of both B- and T-cells to LPS and Con A, respectively. It also can reduce production of IL2 by splenic T-cells and production of both IL1 and TNF by peritoneal macrophages. Furthermore, it was also shown that (a) the magnitude of suppression of T-cell proliferation and of IL2 production occurs in a dose-dependent manner and (b) B-cells are more vulnerable than T-cells to the effect of alprazolam.

Dependence-producing properties of alprazolam in the dog

Alprazolam (48 mg/kg/day) administered orally to dogs 4 times a day in equally divided doses produced physical dependence. This dependence was revealed by a precipitated abstinence syndrome which occurred after either oral administration of flumazenil (6, 18 and 36 mg/kg) or intravenous administration of a liposomal suspension of flumazenil. Flumazenil alone (18, 36 and 72 mg/kg) produced no significant signs of precipitated abstinence in naive dogs. This precipitated abstinence syndrome in alprazolam-dependent dogs was characterized by both clonic and tonic-clonic seizures. Other signs of precipitated abstinence which comprise the NPAS score were less intense in the alprazolam-dependent than in diazepam-dependent dogs. Alprazolam is extensively metabolized in the dog and does not accumulate whereas its predominant metabolite, alpha hydroxyalprazolam, does accumulate. The data suggest that alpha hydroxyalprazolam plays a role in the dependence-producing properties of alprazolam in the dog as revealed by the precipitated abstinence syndrome.

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

The relationships between alprazolam and metabolite concentrations and CNS effects were determined in a double-blind placebo controlled four-way crossover trial in 16 normal male volunteers. Active drug treatments consisted of 4-day regimens of 4 mg alprazolam PO daily as 2 mg bid., 1 mg qid, and 0.25 mg each hour. On days 1 and 4, the kinetics, sedative and psychomotor effects were evaluated. Plasma concentrations of the 4- and alpha-hydroxy metabolites of alprazolam were less than 10% of unchanged alprazolam levels on both days. Accumulation of these metabolites and alprazolam was dependent on alprazolam half-life (11.6 h). Acute and chronic tolerance to the sedative and psychomotor effects was observed with all active drug treatments. All alprazolam treatments resulted in significantly greater sedation than placebo on days 1 and 4. However, on day 4, sedation was 16-36% less than observed on day 1, despite plasma concentrations 1.4-2.76 times the day 1 concentrations. Sedation from alprazolam was reduced in each successive study phase, suggesting a tolerance which was sustained during the 10-day washout between phases. By day 4, psychomotor performance was not different from placebo, indicating more complete development of tolerance than occurred for the sedative effect. Sedation and psychomotor impairment on day 1 were greatest with 2 mg alprazolam bid. During the initiation of therapy, the patient will likely experience less sedation and psychomotor impairment with smaller, more frequent doses. Since tolerance develops to these effects, the advantage of more frequent dosing regimen dissipates by the 4th day.

Determination of biological activity of adinazolam and its metabolites

Adinazolam and its metabolites inhibit [3H]flunitrazepam binding in-vitro. The binding affinities of these compounds is significantly enhanced in the presence of 10-5 M muscimol, indicating that both adinazolam and its metabolites are benzodiazepine agonists. In-vivo metabolism of adinazolam results in the formation of active metabolites.

A double-blind comparison of alprazolam vs. imipramine and placebo in the treatment of major depressive disorder

In a 6-week double-blind trial 129 outpatients with major depressive disorder received either alprazolam, imipramine or placebo. Dosage was adjustable from 0.5 mg alprazolam, 25 mg imipramine or two capsules placebo b.i.d. to 4.5 mg alprazolam, 225 mg imipramine or three capsules placebo t.i.d. Both active drugs were more effective than placebo according to all the rating scales used. Alprazolam and imipramine did not differ consistently except in the somatic symptom cluster on the Hamilton Anxiety Rating Scale. Mean final daily dosage was 2.7 mg alprazolam, 117.3 mg imipramine and 7.2 capsules placebo. Patients on alprazolam reported fewer side effects than patients on imipramine and approximately the same number as patients on placebo. Anticholinergic side effects were commonly associated with imipramine; drowsiness was the most frequent side effect with alprazolam.

Comparative pharmacokinetics of brotizolam and triazolam in healthy subjects

Pharmacokinetics of oral brotizolam (0.50 mg) and triazolam (0.50 mg) were studied in healthy young volunteers. The plasma concentration profile of brotizolam can be described as a one compartmental open model with first-order absorption. The absorption of triazolam was less regular and in half of the subjects was not consistent with first-order kinetics. Inter-individual variability in absorption rate (peak times) was larger for brotizolam. Mean peak times were 1.1 +/- 1.0 h for brotizolam and 1.2 +/- 0.5 h for triazolam. Mean peak concentrations were 7.3 +/- 3.1 ng/ml and 5.0 +/- 3.9 ng/ml respectively. The elimination half-life of brotizolam was twice that of triazolam with mean values of 5.0 +/- 1.1 h and 2.6 +/- 0.7 h respectively. There was no correlation between the half-lives of the two drugs. Protein unbound fraction was similar for triazolam and brotizolam with mean values of 9.9 +/- 1.5% and 8.4 +/- 0.7% respectively.

Alprazolam: pharmacokinetics, clinical efficacy, and mechanism of action

Alprazolam, a triazolobenzodiazepine, is the first of this new class of benzodiazepine drugs to be marketed in the United States and Canada. It achieves peak serum levels in 0.7 to 2.1 hours and has a serum half-life of 12 to 15 hours. When given in the recommended daily dosage of 0.5 to 4.0 mg, it is as effective as diazepam and chlordiazepoxide as an anxiolytic agent. Its currently approved indication is for the treatment of anxiety disorders and symptoms of anxiety, including anxiety associated with depression. Although currently not approved for the treatment of depressive disorders, studies published to date have demonstrated that alprazolam compares favorably with standard tricyclic antidepressants. Also undergoing investigation is the potential role of alprazolam in the treatment of panic disorders. Alprazolam has been used in elderly patients with beneficial results and a low frequency of adverse reactions. Its primary side effect, drowsiness, is less than that produced by diazepam at comparable doses. Data on toxicity, tolerance, and withdrawal profile are limited, but alprazolam seems to be at least comparable to other benzodiazepines. Drug interaction data are also limited, and care should be exercised when prescribing alprazolam for patients taking other psychotropic drugs because of potential additive depressant effects.

Alprazolam (Xanax, the Upjohn Company)

Alprazolam is a triazolobenzodiazepine, a derivative of the benzodiazepines. Comparison studies of alprazolam and diazepam or chlordiazepoxide in patients suffering from clinical anxiety secondary to anxiety neurosis or chronic alcohol withdrawal suggest an equal efficacy of those agents. Studies examining the use of alprazolam for the treatment of "primary depression" suggest that it is as effective as imipramine in the treatment of exogenous (reactive) depression. Although alprazolam may be effective in patients with exogenous depression, no extrapolation can be made to the treatment of endogenous depression. Mechanisms of action have not been fully elucidated, but probably are similar to those of other benzodiazepines. Peak blood levels are reached in 0.7-1.6 hours and the elimination half-life after steady state is approximately 19 hours. Daily dosages established from clinical studies ranged from 1 to 6 mg. Clinically, alprazolam appears to be ten times more potent than diazepam. Drowsiness, headaches, lightheadedness, dry mouth, and depression appear to be the most common side effects of the drug. It is concluded that alprazolam offers no striking therapeutic advantage over currently marketed benzodiazepines.

Metabolism of 8-chloro-6-(o-chlorophenyl)-1-methyl-4H-s-triazolo [4,3-alpha] [1,4]benzodiazepine, triazolam, a new central depressant. II. Identification and determination of metabolites in rats and dogs

1. Eight metabolites of triazolam have been identified, namely, triazolam, dichlorotriazolobenzophenone (DCTB), 1'-hydroxytriazolam, dichloro-alpha-hydroxytriazolobenzophenone (1'-hydroxy-DCTB), Ar-hydroxytriazolam, 4-hydroxytriazolam, Ar-1'-dihydroxytriazolam and 1',4-dihydroxytriazolam. 2. Major metabolites found in the urine were 1',4-dihydroxytriazolam, 1'-hydroxy-DCTB and DCTB in rats; 1'-hydroxytriazolam, 4-hydroxytriazolam and conjugated 1'-hydroxytriazolam in dogs. 3. Major metabolites found in the faeces were 4-hydroxytriazolam in rats; 1'-hydroxytriazolam and 4-hydroxytriazolam in dogs. 4. Conjugated 4-hydroxytriazolam was the major metabolite in both the original and reabsorbed bile of rats. 5. Major metabolites in free form in the plasma were 4-hydroxytriazolam and 1'-hydroxytriazolam in rats; triazolam and 1'-hydroxytriazolam in dogs. 6. The major metabolite in the brain was triazolam, but those in the liver were 4-hydroxytriazolam and triazolam, and in the kidneys were 4-hydroxytriazolam and 1',4-dihydroxytriazolam. 7. Major metabolites in the urine, faeces, plasma and brain after 7-, 14- or 21-day repeated dosing in rats were not much different in type and ratio from those after single dosing. 8. Unchanged triazolam and 1'-hydroxytriazolam were the major metabolites in the plasma, placenta, foetus and amniotic fluid in pregnant rats. 9. There was no change in hepatic aniline hydroxylase and aminopyrine-N-demethylase activity from controls in rats given oral dose of [14C]triazolam for 14 days.