Desvenlafaxine

Is desvenlafaxine safe?

For most monitored adults, yes, with two clear trade-offs. Desvenlafaxine, sold as Pristiq and as generics, is the main active metabolite of venlafaxine, turned into its own extended-release tablet. It is a serotonin and noradrenaline reuptake inhibitor (SNRI), licensed in the US for major depression in adults since 2008. It is not sold in the UK: the UK medicines compendium lists no desvenlafaxine product, and in 2008 Wyeth withdrew an EU application for menopausal hot flushes.

At the standard 50 mg dose it is one of the better tolerated antidepressants in trials: 4.1% stopped for side effects, close to the 3.8% on placebo. It also has few drug-level interactions. The trade-offs are the ones it shares with venlafaxine: it can raise blood pressure, and stopping it is hard for many people. We score it 63, above venlafaxine (59) and below duloxetine (66) and escitalopram (71).

Stopping desvenlafaxine: the biggest drawback

A 2024 meta-analysis in the Lancet Psychiatry pooled 79 studies of people stopping antidepressants. About 31% had at least one symptom after stopping a drug, against 17% after placebo. Desvenlafaxine was among the four drugs linked to more frequent symptoms, and desvenlafaxine or venlafaxine among those linked to more severe ones.

The US label is blunt. It lists nausea, sweating, irritability, dizziness, electric-shock sensations, anxiety, confusion, headache, insomnia and seizures, and reports post-marketing cases that were "protracted and severe". Completed suicide, suicidal thoughts and severe aggression have been reported during dose reductions. Blurred vision and raised blood pressure have also followed stopping.

Desvenlafaxine wears off in about half a day (the venlafaxine label gives its half-life as about 11 hours), so a missed dose can bring symptoms within a day. The label says to taper, to go back to the previous dose if symptoms are intolerable and then reduce more slowly, and that some people need several months. Switching from venlafaxine to desvenlafaxine can also cause withdrawal symptoms. Never stop on your own; plan a reduction with your prescriber.

Blood pressure and the heart

Like venlafaxine and unlike SSRIs, desvenlafaxine raises blood pressure in some people. In the pre-approval trials:

Cases needing immediate treatment have been reported. The label also records uncommon heart events, including heart attacks, in patients with several risk factors, and more falls in blood pressure on standing in people over 65 (8% against 2.5% on placebo). Cholesterol and triglycerides rose at higher doses. Have your blood pressure checked before starting and regularly afterwards.

Side effects at the usual dose

The 50 mg dose is both the starting and the treatment dose; trials of up to 400 mg found no extra benefit, only more side effects. At 50 mg, nausea affected 22% against 10% on placebo, dizziness 13% against 5%, sweating 10% against 4%, and insomnia 9% against 6%. Sexual side effects were dose-related: erectile dysfunction affected 3% of men at 50 mg and 11% at 400 mg.

Other label risks are shared with the class: serotonin syndromeSerotonin syndromeA reaction caused by too much serotonin in the body, usually from combining medicines that raise it. Symptoms range from shivering to high fever.More in the glossary, bleeding (especially with NSAIDs, aspirin or warfarin), low sodium in older people, angle-closure glaucoma, mania in bipolar disorder and seizures. It carries the US boxed warningBoxed warningThe strongest safety warning the US FDA puts on a medicine's label, printed inside a black border at the top.More in the glossary on suicidal thoughts in people under 25, so watch closely in the first months and after dose changes.

Overdose and interactions

The label relies mostly on venlafaxine's overdose record, which includes deaths, seizures and heart rhythm problems. Direct evidence on desvenlafaxine is more reassuring. A 2017 Australian study of 75 overdoses of desvenlafaxine alone (median 800 mg, up to 3,500 mg) found mild high blood pressure in 32% and a fast heart rate in 39%, but no seizures, no abnormal QT or QRS on the ECG, no intensive care admissions and no deaths. Mixed overdoses with other drugs were more serious. Any overdose needs hospital assessment: in the US call Poison Help on 1-800-222-1222, in the UK call 111 or 999.

Its interaction profile is cleaner than venlafaxine's. It is cleared mainly by conjugation and the kidneys, does not depend on CYP2D6CYP450 enzymesA family of liver enzymes that break down many medicines. When another drug or supplement speeds them up or slows them down, drug levels change.More in the glossary and is only 30% bound to blood proteins. At 400 mg it raises levels of CYP2D6 drugs such as metoprolol, but at 50 to 100 mg no dose change is needed. The interactions that matter are pharmacological: MAOIs are contraindicatedContraindicationA situation in which a medicine should not be used, because the risk clearly outweighs any benefit, such as a known allergy to it.More in the glossary, other serotonin drugs such as tramadol, triptans, lithium and St John's wort add serotonin syndromeSerotonin syndromeA reaction caused by too much serotonin in the body, usually from combining medicines that raise it. Symptoms range from shivering to high fever.More in the glossary risk, and blood thinners add bleeding risk.

Who should be careful

Talk to your doctor or pharmacist before starting desvenlafaxine if you have high blood pressure, heart disease or a past stroke, kidney disease (doses are lower), epilepsy, bipolar disorder, glaucoma or a bleeding problem, or if you take blood thinners or another serotonin drug. The label notes a small extra risk of heavy bleeding after birth with SNRI use in the month before delivery. A lower score is not a reason to stop a medicine that works.

How we scored it

Track record (80) and interactions (64) are its stronger factors. Dependence (57) is the weakest, reflecting frequent and sometimes severe withdrawal. Serious side effects (64) balance good tolerability at 50 mg against blood pressure effects, and regulatory warnings (45) reflect the class boxed warningBoxed warningThe strongest safety warning the US FDA puts on a medicine's label, printed inside a black border at the top.More in the glossary and the label's warnings on blood pressure and discontinuation.