Venlafaxine (Effexor): Uses, Warnings, and Key Facts

What is venlafaxine?

Venlafaxine is an active ingredient used in medicines for the treatment of depression and certain anxiety disorders. In the United States, it is sold under trade names such as Effexor and Effexor XR.

The ingredient is commonly listed as venlafaxine hydrochloride.

How venlafaxine works

Venlafaxine is related to the potentiation of monoaminergic activity in the central nervous system.

Preclinical studies have shown that venlafaxine and its main metabolite, O-desmethylvenlafaxine, inhibit the reuptake of serotonin and noradrenaline. It weakly inhibits dopamine reuptake.

What venlafaxine is used for

• Major depression
• Prevention of recurrences of major depressive episodes
• Generalized anxiety disorder, social anxiety disorder, and panic disorder with or without agoraphobia in prolonged-release forms

Dosage forms and strengths

Venlafaxine is taken by mouth and may be available in strengths such as 25 mg, 37.5 mg, 50 mg, 75 mg, 100 mg, 150 mg, and 225 mg.

The exact dose and schedule depend on the product type, the condition being treated, and the prescribing information.

Important safety information

Venlafaxine should not be used with MAO inhibitors. The original content notes that treatment should not be started until 14 days after an MAOI has been stopped, and an MAOI should not be started until at least 7 days after venlafaxine has been stopped.

Extra caution is noted in people with a recent heart attack, unstable heart disease, a history of seizures, elevated eye pressure, or risk of acute angle-closure glaucoma.

Other situations that require careful review include a family history of bipolar disorder, a history of aggression, bleeding disorders, kidney or liver impairment, older age, diabetes, and use in people under 18 years.

Monitoring and precautions mentioned in the source

• Blood pressure should be checked periodically.
• Watch for possible hyponatremia or inappropriate ADH secretion, especially in dehydrated people or those with low volume.
• Gradual dose reduction over weeks or months may help avoid withdrawal reactions.
• Monitor for akathisia or psychomotor agitation.
• Cholesterol monitoring is recommended in the source content.
• There is a risk of serotonergic syndrome, especially with other serotonergic medicines.
• Use caution with medicines that may prolong the QTc interval.

Kidney and liver impairment

The source content advises caution in both kidney and liver impairment.

• Severe renal failure or hemodialysis: reduce the dose by 50%.
• Mild to moderate liver failure: reduce the dose by 50%.
• Severe liver failure: reductions greater than 50% may be necessary.

If you have kidney or liver disease, the exact dose should be confirmed in the official leaflet or by a clinician.

Interactions to verify

Venlafaxine may interact with several medicines and substances. The list below reflects the original content and should be checked carefully with a pharmacist or prescriber.

• Triptans, SSRIs, SNRIs, lithium, sibutramine, fentanyl and related medicines, dextromethorphan, tapentadol, pethidine, methadone, pentazocine, St. John’s wort, and other serotonergic agents
• Warfarin
• Cimetidine
• Haloperidol
• Imipramine
• Metoprolol
• Medicines that prolong the QTc interval, including some antiarrhythmics, antipsychotics, antihistamines, quinolone antibiotics, and macrolide antibiotics
• Alcohol

The source also notes possible false-positive urine immunoassay results for phencyclidine (PCP) and amphetamines.

Pregnancy and breastfeeding

The source states that effectiveness and safety in pregnancy have not been established, and use should be considered only when the potential benefit outweighs the risk.

Venlafaxine and its active metabolite are excreted in breast milk. A risk to the infant cannot be excluded. The source also reports post-marketing notifications of infants with crying, irritability, and abnormal sleep patterns, and withdrawal-like symptoms after breastfeeding stopped.

These decisions should be reviewed with a healthcare professional.

Effects on driving and daily activities

Venlafaxine can cause sedation or dizziness. If these effects occur, the source advises avoiding tasks such as driving or using machines.

Possible side effects reported in the source

The following adverse reactions are listed in the original content:

• Asthenia, chills, fatigue
• Hypertension, vasodilatation, palpitations
• Decreased appetite, constipation, nausea, vomiting, dry mouth, dyspepsia
• Hypercholesterolemia, weight loss
• Abnormal dreams, decreased libido, dizziness, headache, insomnia, nervousness, paresthesia, sedation, drowsiness, tremor, confusion, depersonalization
• Yawning, sweating, accommodation problems, mydriasis, visual disorders, tinnitus
• Sexual and urinary effects, including abnormal ejaculation/orgasm, anorgasmia, erectile dysfunction, impaired urination, menstrual disorders, dysuria, and urinary frequency
• Persistence of sexual dysfunction

Not everyone experiences these effects, and this list is not complete.

Frequently asked questions

Sources and official references

The original content states that the information was prepared using clinical and molecular data from FDA- and USP-related sources. For product-specific details, consult the FDA medication guide and official drug information.