3-Monoacetylmorphine (3-MAM) or 3-acetylmorphine is a less active metabolite of heroin (diacetylmorphine), the other two being morphine and more active 6-monoacetylmorphine (6-MAM).
Because of the acetyl-group in 3-position, 3-MAM has relatively weak affinity to ü-opioid receptors.
As 3-O-acetylmorphine-6-O-sulfate (C<sub>19</sub>H<sub>23</sub>NO<sub>7</sub>S), where 6-OH is changed to 6-O-SO<sub>3</sub>, it can act as a potent, centrally acting morphine derivative and has important analgesic properties.