A hugely popular antidepressant whose measured benefit looks surprisingly small
Duloxetine, sold as Cymbalta, was the 31st most prescribed medicine in the United States in 2023, with more than 18 million prescriptions. Yet a 2025 systematic review found its average effect on depression scores, 1.81 points on a 53-point scale, fell short of the threshold the reviewers had set for a clinically important change.
Duloxetine is a serotonin–norepinephrine reuptake inhibitor, or SNRI, taken by mouth, though exactly how it eases depression and anxiety is not known. Cleared by American and European regulators in 2004 and now sold as a generic, it is used for major depression, generalised anxiety disorder, fibromyalgia, nerve pain and other long-lasting pain. For anxiety it outperforms placebo, and a review in the Annals of Internal Medicine ranks it among first-line drugs alongside sertraline and escitalopram.
Its pain approvals arrived in stages. The FDA cleared it for pain from diabetic peripheral neuropathy, where responses tend to appear within the first two weeks, then for fibromyalgia in June 2008 and for chronic musculoskeletal pain, including osteoarthritis and lower back pain, in November 2010. The American Society of Clinical Oncology names it a first-line option for nerve damage caused by chemotherapy.
The evidence is not uniformly flattering. A 2014 Cochrane review found benefit in diabetic neuropathy and fibromyalgia but called for more head-to-head trials, and the French journal Prescrire judged it no better than alternatives, with more side effects. One systematic review ranked tricyclic antidepressants, older anticonvulsants and opioids ahead of it for diabetic nerve pain. The drug also nudges fasting blood sugar slightly upward.
Common side effects include dry mouth, nausea, constipation, drowsiness, sweating and sexual problems, which in some people persist after stopping. Rarer serious risks include serotonin syndrome, mania and liver problems. Worries about liver toxicity and suicidal events helped block US approval for stress urinary incontinence, although the United Kingdom allows it as an add-on there. A 2013 meta-analysis found 83 per cent of treated participants had adverse effects, against 45 per cent on placebo.
Source: Duloxetine
