Venlafaxine

Brand names

• Effexor
• Effexor XR

Usage

To treat symptoms of major depression and generalized anxiety disorder (GAD).

How it works

Venlafaxine helps to balance levels of serotonin and norepinephrine, chemicals that are profoundly linked to mood, emotions, and mental state.

Side effects

Serious

Headache, changes in or blurred vision, decreased sexual ability or desire, difficulty urinating, itching, skin rash, chest pain, heartbeat irregularities, changes in moods or mental state, extreme drowsiness or fatigue.

Common

Fatigue, dizziness or drowsiness, anxiety, dry mouth, changed sense of taste, loss of appetite, nausea, vomiting, chills, diarrhea, constipation, prickly sensation of skin, heartburn, increased sweating, runny nose, stomach gas or pain, insomnia, unusual dreams.

Less common

Frequent yawning, twitching.

Possible interactions

Other medicaments:

Venlafaxine taken concurrently with:

• beta blockers may result in larger than expected pharmacological effects from the beta blockers; because these agents are metabolized in the liver and venlafaxine may block this metabolism.
• calcium channel blockers may result in toxicity; because these agents are metabolized in the liver and venlafaxine may block this metabolism.
• cimetidine (Tagamet) may lead to venlafaxine toxicity.
• dextromethorphan (the DM in many cough and cold preparations) may result in dextromethorphan or venlafaxine toxicity.
• MAO inhibitors may lead to undesirable side effects.
• quinidine (Quinaglute, others) may result in venlafaxine toxicity.
• ritonavir (Norvir) may lead to venlafaxine toxicity.
• medicaments with sedative properties will increase those effects.
• paroxetine (Paxil-a SSRI) or SNRIs can lead to a serotonin syndrome if a sufficient time does not pass between stopping a first medicine and starting an alternative therapy. The time required (washout) may vary patient to patient, but the generally accepted time is two weeks.
• sibutramine (Meridia) increases toxicity risk (serotonin syndrome).
• sumatriptan (Imitrex), naratriptan (Amerge) or rizatriptan (Maxalt) may lead to incoordination and weakness.
• tramadol (Ultram) may increase the risk of seizures.
• tricyclic antidepressants may result in toxicity; because these agents are metabolized in the liver and venlafaxine may block this metabolism.
• warfarin (Coumadin) may result in bleeding; more frequent INR (prothrombin time or protime) testing is needed. Ongoing warfarin doses should be adjusted to laboratory results.
• zolmitriptan (Zomig) may lead to incoordination and weakness.
• zolpidem (Ambien) may increase risk of hallucinations.

Herbal medicines or minerals:

Since venlafaxine and St. John's wort may act to increase serotonin, the combination is not advised. Since part of the way ginseng works may be as an MAO inhibitor, do not combine ginseng with venlafaxine. Ma huang, yohimbe, Indian snakeroot and kava kava are also best avoided while taking this medicine.

Beverages:

Do not take this medicine with grapefruit juice. Water is the best liquid to take this medicine with.

Alcohol:

May increase somnolence if combined.

Marijuana smoking:

Additive effect on somnolence.

Discontinuation:

If this medicine is to be stopped, the dose should be slowly lowered over 2-3 weeks on your doctor's advice. Tapering over this time helps your body best adjust to not having this medicine, minimizing risk of undesirable discontinuation symptoms.

Comments