| abstract |
A polymeric wall adapted to release drug at a controlled rate for a prolonged period of time from a reservoir comprising a drug and a carrier which is permeable to the drug and saturated therewith during said prolonged period of time, to a body environment or a drug receptor site, the wall comprising a mixture of a polymer which is biologically compatible with said environment or site and maintains its integrity while in contact therewith, has a glass transition temperature between ambient temperature and 150 DEG C, a crystallinity of 5% to 95%, or is rubbery, and is permeable to the drug but at a rate less than that of the carrier and as a minor constituent a polymeric additive such as a polyester prepared from a glycol and a dibasic acid, polyethylene glycol, chlorinated polyethylene or copolymers of ethylene and vinyl esters or vinyl esters or vinyl halides, the amount of additive being sufficient to make the permeability of the wall to the drug substantially different than the permeability of the polymer to the drug but still less than the permeability of the carrier to the drug. |