Venlafaxine (Effexor)

Venlafaxine

Venlafaxine is a relatively new antidepressant. It is called a dual uptake inhibitor or mixed uptake inhibitor. It leads to increases in two types of chemical messengers (also called neurotransmitters) in the brain-serotonin and norepinephrine-by blocking the pumps that transport them back into the presynaptic nerves after they are released into the synapses.

In one study, venlafaxine was found to be more effective than Prozac in the treatment of inpatients with melancholic depression. Melancholic depression is a severe depression with many organic features, such as waking up too early and a loss of appetite and sexual drive.

Venlafaxine has also been used for a number of other disorders including chronic pain and adult attention deficit disorder (ADD).

Doses of Venlafaxine

Some experts recommend starting venlafaxine at 18.75 mg twice per day to minimize nausea. Increase the daily dose by 37.5 mg every third day until a total dose of 150 mg per day or above is reached.

Most patients respond to a total dose of 75 mg to 225 mg per day. Higher doses tend to be more effective, but they are also associated with more side effects.

Side Effects of Venlafaxine

The side effects of venlafaxine are:

Dizziness
Dry mouth and throat
Upset stomach
Loss of appetite
Constipation
Sweating
Headache
Drowsiness
Insomnia
Anxiety
Weakness
Tremor
Blurred vision
Problems with orgasm
Loss of interest in sex
Abnormal dreams
Increased blood pressure

In spite of the claim that venlafaxine has fewer side effects than the older tricyclic antidepressants, it can nevertheless cause dry mouth and dizziness in some patients. The dizziness is particularly likely if you go off the drug too quickly.

One distinct side effect seen with venlafaxine is an increase in blood pressure. These increases are typically seen only at higher doses (225 mg per day or above). At doses less than 200 mg per day, the likelihood of an increase in blood pressure is only about 5 percent. The probability increases to 10 or 15 percent at doses greater than 300 mg per day. Blood pressure increases of 20-30 mm of mercury have been observed.

Drug Interactions for Venlafaxine

Because ventafaxine is relatively new, information about its interactions with other drugs is relatively limited.

Several drugs may cause blood levels of venlafaxine to increase, and so lower doses of venlafaxine may be needed. These include:

Venlafaxine may cause the blood levels of several of the major tranquilizers to increase. These include:

Lower doses of these drugs may be needed.

Venlafaxine must not be combined with MAOI antidepressants because of the danger of serotonin syndrome (hyperpyrexic crisis).

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