A pharmaceutical formulation for prolonged release of the active ingredient 3-(3-dimethylamino-1-ethyl-2-methylpropyl)phenol or a pharmaceutically acceptable salt thereof in a matrix containing between 1 and 80 wt % of at least one pharmaceutically acceptable hydrophilic or hydrophobic polymer as a matrix forming agent and exhibiting in vivo the following release rate: 3 to 35% by weight (based on 100% by weight active ingredient) 3-(3-dimethylamino-1-ethyl-2-methyl-propyl)phenol released after 0.5 hours； 5 to 50% by weight 3-(3-dimethylamino-1-ethyl-2-methyl-propyl)phenol released after 1 hour； 10 to 75% by weight 3-(3-dimethylamino-1-ethyl-2-methyl-propyl)phenol released after 2 hours； 15 to 82% by weight 3-(3-dimethylamino-1-ethyl-2-methyl-propyl)phenol released after 3 hours； 30 to 97% by weight 3-(3-dimethylamino-1-ethyl-2-methyl-propyl)phenol released after 6 hours； more than 50% by weight 3-(3-dimethylamino-1-ethyl-2-methyl-propyl)phenol released after 12 hours； more than 70% by weight 3-(3-dimethylamino-1-ethyl-2-methyl-propyl)phenol released after 18 hours, and more than 80% by weight 3-(3-dimethylamino-1-ethyl-2-methyl-propyl)phenol released after 24 hours.
