Polymeric orthoesters housing beneficial drug for controlled release therefrom

A composition of matter comprising an orthoester polymer of the formula:

• ##STR40## wherein R.sub.1 is a member selected from the group consisting of hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl of 2 to 20 atoms, cycloalkyl of 3 to 8 carbon atoms, cycloalkyl of 3 to 8 carbons substituted with a member selected from the group consisting of alkyl of 1 to 20 carbon atoms, alkenyl of 2 to 20 carbon atoms and alkoxy of 1 to 20 carbon atoms, cycloalkenyl of 4 to 8 carbon atoms, and cycloalkenyl of 4 to 8 carbon atoms substituted with a member selected from the group consisting of alkyl of 1 to 20 carbon atoms, alkenyl of 2 to 20 carbon atoms and alkoxy of 1 to 20 carbon atoms;
• and R.sub.2 is a member selected from the group consisting of alkylene of 1 to 20 carbon atoms, alkenylene of 2 to 20 carbon atoms, cycloalkylene of 3 to 8 carbon atoms, cycloalkylene of 3 to 8 carbon atoms substituted with a member selected from the group consisting of alkyl of 1 to 20 carbon atoms, alkenyl of 2 to 20 carbon atoms and alkoxy of 1 to 20 carbon atoms;
• cycloalkylene of 4 to 8 carbon atoms, and cycloalkenylene of 4 to 8 carbon atoms substituted with a member selected from the group consisting of alkyl of 1 to 20 carbon atoms, alkenyl of 2 to 20 carbon atoms and alkoxy of 1 to 20 carbon atoms;
• a is 2 to 3, n is greater than 10, and about 0.01% to about 40% by weight of a beneficial drug dispersed in said polymer, and wherein said drug is released at a controlled and continuous rate to the environment of use as said polymer erodes over a prolonged period of time.