Overview
DESCRIPTION Venlafaxine hydrochloride is a structurally novel antidepressant for oral administration. It is designated (R/S)-1-[2-(dimethylamino)-1-(4-methoxyphenyl)ethyl] cyclohexanol hydrochloride or (±)-1-[α-[(dimethyl-amino)methyl]-p-methoxybenzyl] cyclohexanol hydrochloride and has the molecular formula of C 17 H 27 NO 2 HCl. Its molecular weight is 313.87.
Mechanism of Action
CLINICAL PHARMACOLOGY Pharmacodynamics The mechanism of the antidepressant action of venlafaxine in humans is believed to be associated with its potentiation of neurotransmitter activity in the CNS. Preclinical studies have shown that venlafaxine and its active metabolite, O-desmethylvenlafaxine (ODV), are potent inhibitors of neuronal serotonin and norepinephrine reuptake and weak inhibitors of dopamine reuptake. Venlafaxine and ODV have no significant affinity for muscarinic, histaminergic, or α-1 adrenergic receptors in vitro . Pharmacologic activity at these receptors is hypothesized to be associated with the various anticholinergic, sedative, and cardiovascular effects seen with other psychotropic drugs. Venlafaxine and ODV do not possess monoamine oxidase (MAO) inhibitory activity.
Indications
- INDICATIONS AND USAGE Venlafaxine tablets, USP are indicated for the treatment of major depressive disorder. The efficacy of venlafaxine tablets, USP in the treatment of major depressive disorder was established in 6 week controlled trials of adult outpatients whose diagnoses corresponded most closely to the DSM-III or DSM-III-R category of major depression and in a 4 week controlled trial of inpatients meeting diagnostic criteria for major depression with melancholia (see CLINICAL TRIALS ).
Common Doses
- 75 mg
- 150 mg
- 225 mg
- 350 mg
Dosage
DOSAGE AND ADMINISTRATION Initial Treatment The recommended starting dose for venlafaxine tablets is 75 mg/day, administered in two or three divided doses, taken with food. Depending on tolerability and the need for further clinical effect, the dose may be increased to 150 mg/day. If needed, the dose should be further increased up to 225 mg/day. When increasing the dose, increments of up to 75 mg/day should be made at intervals of no less than 4 days.
Black Box Warning
Suicidality and Antidepressant Drugs Antidepressants increased the risk compared to placebo of suicidal thinking and behavior (suicidality) in children, adolescents, and young adults in short-term studies of Major Depressive Disorder (MDD) and other psychiatric disorders. Anyone considering the use of venlafaxine tablets or any other antidepressant in a child, adolescent, or young adult must balance this risk with the clinical need.
Contraindications
- CONTRAINDICATIONS Hypersensitivity to venlafaxine hydrochloride or to any excipients in the formulation. The use of MAOIs intended to treat psychiatric disorders with venlafaxine tablets or within 7 days of stopping treatment with venlafaxine tablets is contraindicated because of an increased risk of serotonin syndrome. The use of venlafaxine tablets within 14 days of stopping an MAOI intended to treat psychiatric disorders is also contraindicated (see WARNINGS and DOSAGE AND ADMINISTRATION ).
Side Effects
- ADVERSE REACTIONS Associated with Discontinuation of Treatment Nineteen percent (537/2897) of venlafaxine patients in Phase 2 and Phase 3 depression studies discontinued treatment due to an adverse event. The more common events (≥ 1%) associated with discontinuation and considered to be drug-related (i.e., those events associated with dropout at a rate approximately twice or greater for venlafaxine compared to placebo) included: CNS Venlafaxine Placebo * Percentages based on the number of males.
Interactions
- Drug Interactions As with all drugs, the potential for interaction by a variety of mechanisms is a possibility. Alcohol A single dose of ethanol (0.5 g/kg) had no effect on the pharmacokinetics of venlafaxine or ODV when venlafaxine was administered at 150 mg/day in 15 healthy male subjects. Additionally, administration of venlafaxine in a stable regimen did not exaggerate the psychomotor and psychometric effects induced by ethanol in these same subjects when they were not receiving venlafaxine.