BMA Concise Guide to Medicine & Drugs

Venlafaxine

Brand names Alventa XL, Bonilux XL, Depefex XL, Efexor XL, Foraven XL, Politid XL, Tifaxin XL, Venaxx XL, Venlalic XL, Winfex XL

Used in the following combined preparations None

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Drug group Antidepressant drug

Overdose danger rating High

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Venlafaxine is an antidepressant with a chemical structure unlike any other available antidepressant. It combines the therapeutic properties of both the tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs), without anticholinergic adverse effects. Venlafaxine is used in the treatment of depression and generalized anxiety disorder. It acts to elevate mood, increase physical activity, and restore interest in everyday activities.

Nausea, dizziness, drowsiness or insomnia, and restlessness are common adverse effects. At high doses, the drug can elevate blood pressure.

INFORMATION FOR USERS

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, XL preparations (MR tablets and capsules).

Frequency and timing of doses Twice daily (tablets); once daily (XL preparations). The drug should be taken with food.

Dosage range 75–150mg daily for outpatients; up to 375mg daily in severely depressed patients.

Onset of effect Can appear within days, although full antidepressant effect may not be felt for 2–6 weeks. Anxiety may take longer to respond.

Duration of action About 8–12 hours (tablets); 24 hours (XL preparations). Antidepressant effects may persist for up to 6 weeks following prolonged treatment.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Do not make up for a missed dose. Just take your next regularly scheduled dose.

Stopping the drug Do not stop the drug without consulting your doctor. Stopping abruptly can cause withdrawal symptoms.

OVERDOSE ACTION

Seek immediate medical advice in all cases. Take emergency action if seizures, slow or irregular pulse, or loss of consciousness occur.

POSSIBLE ADVERSE EFFECTS

The most common adverse effects of venlafaxine are weakness, nausea, constipation, restlessness (which may take the form of anxiety, nervousness, tremor, abnormal dreams, agitation, or confusion), blurred vision, drowsiness, dizziness, and sexual dysfunction. Some of these effects may wear off in 1–2 weeks. Discuss with your doctor if they persist or are severe. Rarely, high blood pressure develops when the high doses are taken; you should have your blood pressure monitored periodically. Palpitations may also rarely occur and should be reported to your doctor promptly. If there are suicidal thoughts or attempts, you should stop taking the drug and seek immediate medical help.

INTERACTIONS

Sedatives All drugs with a sedative effect may increase those of venlafaxine.

Antihypertensive drugs Venlafaxine may reduce the effectiveness of these drugs.

Warfarin Venlafaxine may increase the effect of warfarin; dosage of warfarin may need to be reduced.

Monoamine oxidase inhibitors (MAOIs) Venlafaxine may interact with these drugs to produce a dangerous rise in blood pressure. At least 14 days should elapse between stopping MAOIs and starting venlafaxine.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have had an adverse reaction to any other antidepressants.

· You have long-term liver or kidney problems.

· You have diabetes.

· You have a heart problem, raised blood pressure, or a history of bleeding disorders.

· You have a history of epilepsy or mania.

· You have glaucoma.

· You have had problems with alcohol or drug misuse/abuse.

· You are taking other medicines.

Pregnancy Safety in pregnancy not established. Discuss with your doctor.

Breast-feeding Not recommended. Discuss with your doctor.

Infants and children Not recommended under 18 years.

Over 60 Increased likelihood of adverse effects. Reduced dose may therefore be necessary.

Driving and hazardous work Avoid such activities until you have learned how venlafaxine affects you; it can cause dizziness, drowsiness, and blurred vision.

Alcohol Avoid. Alcohol may increase the sedative effects of this drug.

PROLONGED USE

Withdrawal symptoms (e.g. dizziness, headache, anxiety, nausea, and insomnia) may occur if the drug is not stopped gradually over at least 4 weeks. There is also a small risk of suicidal thoughts and self-harm in children and adolescents, although the drug is rarely used for this age group.

Monitoring Blood pressure should be measured periodically if high doses are prescribed. Anyone experiencing confusion, drowsiness, muscle cramps, or seizures should be monitored for low sodium levels in the blood. Under-18s should be monitored for suicidal thoughts and self-harm.