Dosulepin, also known as dothiepin and sold under the brand name Prothiaden among others, is a tricyclic antidepressant (TCA) which is used in the treatment of depression.

[4][6][7] Dosulepin was once the most frequently prescribed antidepressant in the United Kingdom, but it is no longer widely used due to its relatively high toxicity in overdose without therapeutic advantages over other TCAs.

[6][8][9] It acts as a serotonin–norepinephrine reuptake inhibitor (SNRI) and also has other activities including antihistamine, antiadrenergic, antiserotonergic, anticholinergic, and sodium channel-blocking effects.

[4][5][12][13] There is clear evidence of the efficacy of dosulepin in psychogenic facial pain, though the drug may be needed for up to a year.

[5] It is also advised that patients are not prescribed any medications that are known to increase the risk of toxicity in those receiving dosulepin due to the potential for mixed overdoses.

[5] TCAs potentiate the sedative effects of barbiturates, tranquilizers and CNSTooltip central nervous system depressants.

[21][22] Unlike the sulfoxide metabolites, northiaden is thought to play an important role in the effects of dosulepin.

[18] Dosulepin is readily absorbed from the small intestine and is extensively metabolized on first-pass through the liver into its chief active metabolite, northiaden.

[5] Dosulepin is a tricyclic compound, specifically a dibenzothiepine, and possesses three rings fused together with a side chain attached in its chemical structure.

[1][2][32][3] Its generic name in Spanish and Italian and its DCITTooltip Denominazione Comune Italiana are dosulepina, in French and its DCFTooltip Dénomination Commune Française are dosulépine, and in Latin is dosulepinum.