Therapeutic device for osmotically dosing at controlled rate

An osmotic device for dispensing a drug to an animal comprising:

• (a) a shaped wall that is substantially inert and maintains its physical and chemical integrity during the controlled dispensing of the drug, said wall a composition comprising (1) a polymer that is permeable to the passage of an external fluid and substantially impermeable to the passage of drug, said polymer having the following formula:
• ##STR3## wherein R.sub.1, R.sub.2 and R.sub.3 are a member selected from the group consisting of hydrogen;
• alkyl;
• alkenyl;
• amino;
• alkanoyl;
• alkanoyl substituted with a member selected from the group consisting of alkoxy, halogen, hydroxyl, alkanoyl, carboalkyl, carboalkoxy and cyanoalkoxy;
• aroyl;
• aroyl substituted with a member selected from the group consisting of hydroxyl, carboxyl, carboalkyl and cyano;
• benzyl;
• carboalkyl;
• carboxyalkyl;
• dialkoxyalkyl;
• dithiocarbonyl;
• hydroxyalkyl;
• cyanoalkyl;
• nitro;
• phenyl;
• sulfoalkyl;
• the alkali metal salts thereof;
• and wherein said polymer exhibits a degree of substitution at R.sub.1, R.sub.2 and R.sub.3 of greater than 0 up to 3, and n is greater than 5, and (2) a wall forming polymer that is a different polymer than (1) which polymer (2) has the following formula:
• ##STR4## wherein R.sub.5, R.sub.6 and R.sub.7 are a member selected from the group consisting of hydroxyl, nitrate;
• hydroxyalkyl;
• alkoxy;
• aryloxy;
• hydroxyalkoxy;
• hydroxyalkalkoxy;
• trityloxy;
• with at least one of R.sub.5, R.sub.6 and R.sub.7 a member selected from the group consisting of aryloxy;
• alkanoyloxy;
• carboxyalkoxy;
• carbamoyloxyalkoxy;
• carboxyalkoxyacyloxy;
• carboxy;
• carboxybenzoyl;
• carboxybenzoyloxy;
• carboxybenzoyloxyalkoxy;
• and dialkylaminohydroxyalkoxy;
• the alkali metal salts thereof;
• and wherein n is greater than 5 up to 3.times.10.sup.6 and the polymer exhibits a degree of substitution at R.sub.5, R.sub.6 and R.sub.7 of greater than 0 up to 3;
• (b) a compartment formed by the shaped wall, said compartment containing a drug formulation selected from the group consisting of locally and systemically acting physiologically and pharmacologically acceptable drugs;
• (c) a passageway in the wall communicating with the compartment and the exterior of the device for dispensing drug from the device;
• and
• (d) wherein in operation, when the device is dispensing the drug to the animal, fluid from the environment is imbided through the wall into the compartment in a tendency towards osmotic equilibrium at a rate determined by the permeability of the wall and the osmotic pressure gradient across the wall, thereby forming a solution containing drug which is dispensed through the passageway at a controlled rate, with the device substantially maintaining its physical and chemical integrity in the presence of the drug and solution thereof during the dispensing period over a prolonged time.