venlafaxine hydrochloride

venlafaxine hydrochloride

(vin lah facks' in)

Effexor, Effexor XR

Pregnancy Category C

Drug class

Antidepressant

Anxiolytic

Therapeutic actions

Potentiates the neurotransmitter activity in the CNS; inhibits serontonin, norepinephrine, and dopamine reuptake leading to prolonged stimulation at neuroreceptors.

Indications

·        Treatment of major depressive disorder

·        Treatment of panic disorder, with or without agoraphobia

·        Treatment of generalized anxiety disorder (extended release—ER only)

·        Treatment of social anxiety disorder (ER only)

·        Unlabeled uses: PMDD, hot flushes, PTSD

Contraindications and cautions

·        Contraindicated with allergy to venlafaxine, use of MAOIs within last 14 days.

·        Use cautiously with pregnancy, lactation, patients whose underlying medical condition might be compromised by increased heart rate (hyperthyroidism, CHF, recent MI).

Available forms

Tablets—25, 37.5, 50, 75, 100 mg; ER capsules—37.5, 75, 150 mg

Dosages

ADULTS

·        Depression: Starting dose, 75 mg/day PO in two to three divided doses (or once a day, ER capsule) taken with food. May be increased slowly up to 225 mg/day to achieve desired effect, maximum dose 375 mg/day in three divided doses.

·        Transfer to or from MAOI: At least 14 days should elapse from the discontinuation of the MAOI and the starting of venlafaxine; allow at least 7 days to elapse from the stopping of venlafaxine to the starting of an MAOI.

·        Generalized anxiety disorder/Social anxiety: 75–225 mg/day PO should be taken on a daily basis, not as needed (ER only).

·        Panic disorder: 37.5 mg/day PO for 7 days, then increase based on patient response to 75 mg/day for 7 days, and then 75 mg/day weekly increases to a maximum of 225 mg/day.

PEDIATRIC PATIENTS

Safety and efficacy not established.

PATIENTS WITH RENAL OR HEPATIC IMPAIRMENT

For patients with creatinine clearance of 10–70 mL/min, reduce dosage by 25%–50%. For patients on dialysis, reduce dosage by 50% (give after dialysis completion on dialysis days). For patients with hepatic impairment, reduce total daily dose by 50%, and increase very slowly to achieve desired effect.

Pharmacokinetics

Route	Onset	Duration
Oral	Slow	48 hr

Metabolism: Hepatic; T_1/2: 1.3–2 hr

Distribution: Crosses placenta; may enter breast milk

Excretion: Urine

Adverse effects

·        CNS: Somnolence, dizziness, insomnia, nervousness, anxiety, tremor, dreams

·        CV: Vasodilation, hypertension, tachycardia

·        Dermatologic: Sweating, rash, pruritus

·        GI: Nausea, constipation, anorexia, diarrhea, vomiting, dyspepsia, dry mouth, flatulence

·        GU: Abnormal ejaculation, impotence, urinary frequency

·        Other: Headache, asthenia, infection, chills, chest pain

Interactions

Drug-drug

·        Increased serum levels and risk of toxicity with MAOIs (within last 14 days), cimetidine

·        Serotonin syndrome may occur if combined with trazodone

·        Increased sedation with alcohol

Drug-alternative therapy

·        Increased sedation and hypnotic effects with St. John's wort

Nursing considerations

Assessment

·        History: Allergy to venlafaxine; use of MAOIs within last 14 days; pregnancy, lactation

·        Physical: Skin color, T, lesions; reflexes, gait, sensation, cranial nerve evaluation; mucous membranes, abdominal examination, normal output; P, BP, peripheral perfusion

Interventions

·        Give with food to decrease GI effects.

·        Advise patient to use contraceptives.

·        Monitor patient for suicidal ideation, especially when beginning therapy or changing dosage.

Teaching points

·        Take with food to decrease GI upset.

·        Avoid alcohol while using this drug.

·        This drug cannot be taken during pregnancy; use birth control. If you become pregnant, consult with your health care provider.

·        You may experience these side effects: Loss of appetite, nausea, vomiting, dry mouth (use frequent mouth care, eat frequent small meals, suck sugarless lozenges); constipation (request bowel program); dizziness, drowsiness, tremor (avoid driving or operating dangerous machinery).

·        Report rash, hives, increased depression, pregnancy.

Adverse effects in Italic are most common; those in Bold are life-threatening.