Gepirone

N - Nervous system

QN - Nervous system

The pharmacological activity of gepirone is attributed to the parent drug and its major metabolites 3’-OH-gepirone and 1- PP. Gepirone and its 3’-OH metabolite bind to 5HT_1A receptors (K_i = 38 nM and 58 nM, respectively), where they act as agonists, while the 1-PP metabolite binds to α₂ receptors (K_i = 42 nM). In a thorough QT study, the largest mean increase in baseline- and placebo-corrected QTc interval with administration of 100 mg per day immediate-release formulation of gepirone was 18.4 msec (upper 90% confidence interval [CI] = 22.7 ms) on Day 1 and 16.1 msec (upper 90% CI = 20.7 ms) on Day 7. The exposure in this study was 2-fold the exposure of the maximum recommended dose.

The mechanism of the antidepressant effect of gepirone is not fully understood but is thought to be related to its modulation of serotonergic activity in the CNS through selective agonist activity at 5HT_1a receptors. Particularly, gepirone

Gepirone is extensively metabolized and both major metabolites 1-PP and 3’-OH-gepirone are present in plasma in higher concentrations than the parent compound. CYP3A4 is the primary enzyme catalyzing the metabolism of EXXUA to its major pharmacologically active metabolites.

Gepirone has known human metabolites that include 3-Hydroxygepirone, 3-Hydroxy-1-[4-[4-(5-hydroxypyrimidin-2-yl)piperazin-1-yl]butyl]-4,4-dimethylpiperidine-2,6-dione, 2-(1-piperazinyl)pyrimidine, and 1-[4-[4-(5-Hydroxypyrimidin-2-yl)piperazin-1-yl]butyl]-4,4-dimethylpiperidine-2,6-dione.

Mood-stimulating drugs used primarily in the treatment of affective disorders and related conditions. Several MONOAMINE OXIDASE INHIBITORS are useful as antidepressants apparently as a long-term consequence of their modulation of catecholamine levels. The tricyclic compounds useful as antidepressive agents (ANTIDEPRESSIVE AGENTS, TRICYCLIC) also appear to act through brain catecholamine systems. A third group (ANTIDEPRESSIVE AGENTS, SECOND-GENERATION) is a diverse group of drugs including some that act specifically on serotonergic systems.

Agents that alleviate ANXIETY, tension, and ANXIETY DISORDERS, promote sedation, and have a calming effect without affecting clarity of consciousness or neurologic conditions. ADRENERGIC BETA-ANTAGONISTS are commonly used in the symptomatic treatment of anxiety but are not included here.

Endogenous compounds and drugs that bind to and activate SEROTONIN RECEPTORS. Many serotonin receptor agonists are used as ANTIDEPRESSANTS; ANXIOLYTICS; and in the treatment of MIGRAINE DISORDERS.

The pharmacokinetics of gepirone are linear and dose-proportional from 18.2 mg to 72.6 mg. Steady-state plasma concentrations are typically achieved within two to four days of daily dosing. The absolute bioavailability is 14% to 17%. The maximal plasma gepirone concentration (Cmax) after dosing is reached within 6 hours post-dose (Tmax). After a high-fat meal, Tmax is reached at 3 hours. A significant effect of food has been observed on the peak plasma concentration (Cmax) of gepirone and, to a lesser extent, on the total exposure (AUC0-tlast, AUC0-∞) to gepirone. The magnitude of the food effect was dependent of the fat content of the meal. The systemic exposure of gepirone and major metabolites was consistently higher under fed conditions as compared to the fasted state. Gepirone Cmax after intake of a low-fat (~ 200 calories) breakfast was 27% higher, after medium-fat (~500 calories) breakfast 55% higher, and after a high-fat (~ 850 calories) breakfast 62% higher as compared to the fasted state. The AUC after intake of a low-fat breakfast was about 14% higher, after a medium-fat breakfast 22% higher, and after a high-fat breakfast 32 to 37% higher as compared to the fasted state. The effect of varying amounts of fat on Cmax and AUC of the major metabolites 3-OH-gepirone and 1PP were similar to that found for gepirone.

Following a single oral dose of [¹⁴C]-labeled gepirone, approximately 81% and 13% of the administered radioactivity was recovered in the urine and feces, respectively as metabolites. 60% of the gepirone was eliminated in the urine within the first 24 hours. The presence of hepatic or renal impairment did affect the apparent clearance of gepirone.

The apparent volume of distribution of gepirone is approximately 94.5L.

After the administration of 80 mg of gepirone, the apparent clearance of gepirone and its 2 metabolites, 1-PP and 3’-OH-gepirone, was calculated to be 692 ± 804 L/h, 417 ± 249 L/h, and 146 ± 61.7 L/h respectively.