Venlafaxine is an antidepressant. It has actions common to both the cyclic antidepressants such as imipramine(Tofranil) and amitriptyline(Elavil,) and the selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac), sertraline(Zoloft), and paroxetine(Paxil). It is believed to derive its actions by increasing levels of both norepinephrine and serotonin in the brain.
The therapeutic effects of venlafaxine, like other antidepressants, appear slowly. Maximum benefit is often not evident for at least two weeks after starting the drug. People taking venlafaxine should be aware of this and continue taking the drug as directed even if they do not see immediate improvement.
Venlafaxine is broken down by the liver and eliminated from the body by the kidneys. As a result, the dose of venlafaxine must be lowered in people with liver or kidney disease.
Venlafaxine is available in 25-mg, 37.5-mg, 50-mg, 75-mg, and 100-mg rapid-release tablets and 75-mg and 150-mg extended-action capsules.
The recommended initial dose of venlafaxine is 75 mg daily taken as two or three equal doses. The dose may be increased in 75-mg increments every four days as needed until symptoms of depression or anxiety resolve. Most commonly, dosages range between 150 mg to 225 mg daily. although in severe situations, 375 mg per day may be needed. Once patients are stabilized using the rapid-acting tablets, they may be converted over to the appropriate dose of extended-release capsules.
In people with liver disease, the daily dosage of venlafaxine should be cut in half. In patients with kidney disease, the daily dosage of venlafaxine should be reduced 25–50%, depending upon the extent of kidney damage. When stopping venlafaxine, the dosage should be reduced gradually over a period of at least two weeks before the drug is totally stopped.
Kelly Karpa RPh, Ph.D., The Gale Group Inc., Gale, Detroit,