Drug information of Venlafaxine

Venlafaxine


Venlafaxine is an antidepressant in a group of drugs called selective serotonin andnorepinephrine reuptake inhibitors (SSNRIs). Venlafaxine affects chemicals in the brain that may become unbalanced and cause depression.

Mechanism of effect

The exact mechanism of action of venlafaxine is unknown, but appears to be associated with the its potentiation of neurotrasmitter activity in the CNS. Venlafaxine and its active metabolite, O-desmethylvenlafaxine (ODV), inhibit the reuptake of both serotonin and norepinephrine with a potency greater for the 5-HT than for the NE reuptake process. Both venlafaxine and the ODV metabolite have weak inhibitory effects on the reuptake of dopamine but, unlike the tricyclics and similar to SSRIs, they are not active at histaminergic, muscarinic, or alpha(1)-adrenergic receptors.

Pharmacodynamic

Venlafaxine potentiates the neurotransmitter activity in the central nervous system. Furthermore, venlafaxine and its metabolite, O-desmethylvenlafaxine (ODV) potently inhibit the reuptake of serotonin and norepinephrine and weakly inhibit dopamine reuptake.

Pharmacokinetics

Venlafaxine is well absorbed. Food does not effect the absorption of venlafaxine or its subsequent metabolism into ODV. Bioavailability is 45% following oral administration. Time to steady state = 3 days. The degree of binding of venlafaxine to human plasma is 27% ± 2% at concentrations ranging from 2.5 to 2215 ng/mL. The degree of ODV binding to human plasma is 30% ± 12% at concentrations ranging from 100 to 500 ng/mL. Protein-binding-induced drug interactions with venlafaxine are not expected. Undergoes extensive first pass metabolism in the liver to its major, active metabolite, ODV, and two minor, less active metabolites, ODV possesses antidepressant activity that is comparable to that of venlfaxine. Renal elimination of venlafaxine and its metabolites is the primary route of excretion. Half life: 5 hours.

Dosage

Usual Adult Dose for Depression Immediate release: Initial dose: 37.5 mg orally twice a day or 25 mg orally 3 times a day Maintenance dose: May increase in daily increments of up to 75 mg at intervals of no less than 4 days Maximum dose: (moderately depressed outpatients): 225 mg/day Maximum dose (severely depressed inpatients): 375 mg/day Daily dosage may be divided in 2 or 3 doses/day Extended release: Initial dose: 75 mg orally once daily Maintenance dose: May increase in daily increments of up to 75 mg at intervals of no less than 4 days Maximum dose (moderately depressed outpatients): 225 mg/day Maximum dose (severely depressed inpatients): 375 mg/day Usual Adult Dose for Anxiety For generalized anxiety disorder or social anxiety disorder: Extended release: Initial dose: 75 mg orally once daily Maintenance dose: May increase in daily increments of 75 mg at intervals of no less than 4 days Maximum dose: 225 mg/day Usual Adult Dose for Panic Disorder Extended-release: Initial dose: 37.5 mg once a day Maintenance dose: May increase dose in daily increments of 75 mg at intervals of no less than 7 days Maximum dose: 225 mg/day

Alerts

1-Patients with major depressive disorder (MDD), both adult and pediatric, may experience worsening of their depression and/or the emergence of suicidal ideation and behavior (suicidality) or unusual changes in behavior 2- Venlafaxine hydrochloride is not approved for use in treating bipolar depression. 3-The development of a potentially life-threatening serotonin syndrome has been reported with SNRIs and SSRIs, including Venlafaxine hydrochloride. 4-The pupillary dilation that occurs following use of many antidepressant drugs including Venlafaxine tablets may trigger an angle closure attack in a patient with anatomically narrow angles who does not have a patent iridectomy. 5-Venlafaxine treatment is associated with sustained increases in blood pressure in some patients.

Points of recommendation

1-Patients, their families, and their caregivers should be encouraged to be alert to the emergence of anxiety, agitation, panic attacks, insomnia, irritability, hostility, aggressiveness, impulsivity, akathisia (psychomotor restlessness), hypomania, mania, other unusual changes in behavior, worsening of depression, and suicidal ideation, especially early during antidepressant treatment and when the dose is adjusted up or down. 2- Patients may wish to be examined to determine whether they are susceptible to angle closure, and have a prophylactic procedure (e.g., iridectomy), if they are susceptible.

Pregnancy level

C


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