Desvenlafaxine

Brands and Forms

• Pristiq
  • extended-release tablet: 50mg, 100mg

Uses of Desvenlafaxine

Desvenlafaxine has been studied mainly for treating Major Depressive Disorder. However, being a metabolite of Venlafaxine, it would be an appropriate choice for any condition that would respond to Venlafaxine treatment. This would include all Depressive Disorders (including Dysthymia, and Premenstrual Dysphoric Disorder) and Anxiety Disorders (including Panic Disorder, Generalized Anxiety Disorder, Social Phobia, PTSD, and Obsessive-Compulsive Disorder).

How Desvenlafaxine Works

Desvenlafaxine is the active metabolite of Venlafaxine, and is a serotonin and noradrenaline reuptake inhibitor (SNRI). It boosts the actions of serotonin and norepinephrine in the central nervous system, and has similar effects on dopamine.

Its only difference from Venlafaxine is that it does not undergo CYP2D6 metabolism in the liver and thus, theoretically, may have fewer interactions with other medications.

Cautions when Using Desvenlafaxine

Desvenlafaxine can induce Manic or Mixed Episodes and Rapid Cycling in people with Bipolar Disorder.

Children and adolescents who use antidepressants like Desvenlafaxine may develop self-injurious or suicidal behaviors (for more information, see here).

Use with caution in people with a known seizure disorder, and in those who are taking anticoagulant (blood thinning) medication.

Long-term use of Desvenlafaxine may lead to an increased risk of osteoporosis and bone fractures in individuals over age 50.

Desvenlafaxine should not be used during or within 14 days following the administration of an MAOI, because a hypertensive crisis may result.

Dosing of Desvenlafaxine

The recommended dose for this medication is 50mg/day, given once daily at any time of the day. It can be started immediately at this dose. If after 4 weeks there is no significant improvement, it can be increased to 100mg/day.

When wanting to stop Desvenlafaxine, the dose should be decreased gradually over a period of 6-8 weeks. A sudden cessation of the medication can result in a discontinuation syndrome.

Onset of action

Therapeutic effects are not expected before 2-4 weeks. If no significant effects are seen after 6-8 weeks of use then the medication may not work at all.

Kidney impairment

For severe kidney impairment, consider given 50mg every second day. Otherwise, no dose adjustment needed.

Liver impairment

No dose adjustment needed.

Side-effects of Desvenlafaxine

Below is a list of most of the reported side-effects of Desvenlafaxine. Most of these side-effects occur in only a minority of individuals, and many also resolve with time while the medication is continued.

Cardiovascular: palpitations; hot flushes; increased blood pressure; tachycardia; orthostatic hypotension; fainting; seizures (rare).

Central Nervous System: headache; dizziness; insomnia; somnolence; fatigue; tremor; decreased libido in men (see below on managing sexual side-effects); abnormal dreams; paresthesia; weakness; disturbance in attention; convulsions; extrapyramidal symptoms (rare) ; serotonin syndrome (rare).

Dermatologic: excessive sweating; rash; hair loss (rare).

Endocrine/Metabolic: decreased appetite; decreased weight; increased total cholesterol; increased fasting triglycerides; increased LDL; SIADH; increased blood prolactin.

Eyes, Ears, Nose and Throat: pupillary dilation; blurred vision; tinnitus.

Gastrointestinal: nausea; dry mouth; constipation; diarrhea; vomiting; abnormal liver function tests.

Genitourinary: erectile dysfunction (see below on managing sexual side-effects); absent or abnormal orgasm; proteinuria; ejaculation disorder; urinary hesitation.

Hematologic: increases bleeding time (thins the blood).

Psychiatric: anxiety; agitation; irritability; apathy; worsening depression; depersonalization; suicidal thoughts (overall, Desvenlafaxine use helps to lower risk of suicide); self-injurious behaviors among children and adolescents; can induce Manic or Mixed Episodes and Rapid Cycling in people with Bipolar Disorder.

Common side-effects of Desvenlafaxine

Headache, dizziness, insomnia, somnolence, fatigue, tremor, excessive sweating, nausea, dry mouth, constipation, diarrhea, sexual dysfunction (see below on managing sexual side-effects).

Rare but serious side-effects of note of Desvenlafaxine

Children and adolescents who use antidepressants like Desvenlafaxine may develop self-injurious or suicidal behaviors (for more information, see here).

Desvenlafaxine discontinuation syndrome

Individuals who suddenly stop using Desvenlafaxine after taking the medication over a significant period of time are at risk of developing a discontinuation syndrome, which can include the following symptoms: dizziness, electric shock-like sensations, sweating, nausea, insomnia, tremor, anxiety, restlessness, agitation, depressed mood, irritability, confusion, lethargy, and vertigo. These symptoms usually start anywhere from one day to one week after the medication was stopped, and can persists for days or even weeks.

This syndrome can be treated by restarting the medication at its prior dose. It can be prevented by decreasing the dose gradually over a period of a few weeks, which could include as a last step giving the 50mg tablet every second day.

Managing sexual side-effects of Desvenlafaxine

In a minority of individuals, Desvenlafaxine can cause sexual side-effects including erectile dysfunction, absent or abnormal orgasm, and ejaculation disorder. To manage this, either Bupropion, or Sildenafil (Viagra) or Vardenafil (Levitra), can be added [ref]. (Sildenafil and Vardenafil can be effective for female sexual side-effects as well, including difficulty achieving orgasm [ref, ref]). Use caution when combining Bupropion with Desvenlafaxine given the risk of increased blood pressure.

Bupropion and Mirtazepine are two antidepressants that tend to have very low rates of sexual side-effects.

Desvenlafaxine overdose

Agitation, constipation, diarrhea, dizziness, dry mouth, headache, nausea, paresthesia, tachycardia, vomiting, seizures. Fatalities have been reported following overdoses with Venlafaxine.

Desvenlafaxine and pregnancy

Category C: some animal studies show adverse effects at very high doses, but no controlled human studies have been done; should only be used in pregnancy if clearly needed and if benefits outweigh potential risks. For further information, see the section on treating Depression in pregnancy.

Drug Interactions with Desvenlafaxine

• Caution should be used when combining Desvenlafaxine with other medications that can increase bleeding time and reduce blood clotting, including Aspirin, NSAIDs, anti-platelet agents, Heparin and Coumadin.
• Combination with other serotonergic medications, including SSRI medications, can precipitate a serotonin syndrome.
• Desvenlafaxine should not be used during or within 14 days following the administration of an MAOI, because a hypertensive crisis may result.

Consumer information on Desvenlafaxine from the manufacturer