Duloxetine: new indication. Depression and diabetic neuropathy: too many adverse effects.

Prescrire international 2006 Oct

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1) Several classes of antidepressants are available. The main difference between these classes is in their short-term pharmacological effects, leading to different patterns of adverse effects. Some antidepressants, especially tricyclics, have positive risk-benefit balances in the treatment of diabetic neuropathy. (2) Duloxetine, a compound chemically related to fluoxetine, appears to have a short-term mechanism of action similar to that of venlafaxine. In the European Union, duloxetine was first approved for female urinary stress incontinence. Another brand of duloxetine has since been marketed for depression and neuropathic pain in diabetic patients. (3) Duloxetine at a dose of 60 mg once a day showed moderate efficacy in 2 placebo-controlled trials. At this dose, however, there are no other comparative trials. It is therefore not possible to know whether duloxetine is as effective as other antidepressants. (4) Two placebo-controlled trials involving patients with pain due to diabetic neuropathy concluded that a dose of 60 mg/day had efficacy, although of doubtful clinical relevance. In the absence of comparative trials, however, we do not know if this efficacy is even equivalent to that of a tricyclic antidepressant used as an analgesic. (5) In fibromyalgia, a controversial clinical diagnosis, two double-blind placebo-controlled trials involving 207 and 354 patients failed to prove that duloxetine had tangible analgesic efficacy. It is therefore appropriate that this use is not mentioned in the "Indications" section of the summary of product characteristics (SPC). (6) The assessment of duloxetine in depression and neuropathic pain confirms existing data on its gastrointestinal, neuropsychological and hepatic adverse effects. In these trials, duloxetine increased blood pressure in a dose-dependent manner. (7) Duloxetine is metabolized by cytochrome P450 isoenzymes CYP 1A2 and CYP 2D6, creating an important risk of interactions with other drugs. (8) In practice, duloxetine currently has no place in the treatment of depression or diabetic neuropathy. Its efficacy has not yet been demonstrated to be even equivalent to that of other available drugs, and it has too many adverse effects, given this degree of uncertainty.