Dimemorfan (INN) (or dimemorphan) (brand names Astomin, Dastosirr, Tusben), or dimemorfan phosphate (JAN), also known as 3,17-dimethylmorphinan, is an antitussive (cough suppressant) of the morphinan family that is widely used in Japan and is also marketed in Spain and Italy.

[5] Adverse effects include nausea, somnolence, dry mouth, and decreased appetite.

[5] Dimemorfan is an analogue of dextromethorphan (DXM) and its active metabolite dextrorphan (DXO), and similarly to them, acts as a potent agonist of the σ1 receptor (Ki = 151 nM).

[6][7] However, unlike DXM and DXO, it does not act significantly as an NMDA receptor antagonist (Ki = 16,978 nM), and for this reason, lacks dissociative effects, thereby having reduced side effects and abuse potential in comparison.

[8][9] Similarly to DXM and DXO, dimemorfan has only relatively low affinity for the σ2 receptor (Ki = 4,421 nM).