The present invention relates to a solid oral pharmaceutical composition comprising naloxone, or a pharmaceutically acceptable salt thereof, as an active substance, wherein the composition releases the active substance in a prolonged manner. In order to provide a composition that is suitable for an administration period of at least twelve-hours for the treatment of opioid-induced constipation, it is proposed that the composition should have an in vitro release rate of the active substance measured using the paddle stirrer method according to Ph. Eur. at 75 rpm in 500 ml 0.1 N hydrochloric acid at 37° C., of 0% to 75% in 2 h, of 3% to 95% in 4 h, of 20% to 100% in 10 h, of 30% to 100% in 16 h, of 50% to 100% in 24 h, and of more than 80% in 36 h, wherein the composition has a IC50/Cmax value of at least 40. In an alternative embodiment, the composition can be a multilayer tablet.
