Process for the manufacture of bioerodible poly (orthoester)s and polyacetals

A process for the manufacture of a bioerodible poly(ortho ester) or polyacetal polymer, which contains from 1% to 100% of a biologically active beneficial agent, which comprises:

• (a) mixing, in a dry environment, a diol and a polyol having three or more hydroxyl groups until the mixture is solubilized and a uniform viscosity of solution is achieved;
• (b) adding a biologically active beneficial agent having a hydroxyl functionality of two or more and a poly(ortho ester) bond stabilizer to the mixture of (a) and stirring until a uniform viscosity of solution is achieved;
• and
• (c) adding a diketene acetal or a divinyl ether to the mixture of (b) with stirring and monitoring the rate of polymerization by monitoring the change in viscosity, until the viscosity of the resulting poly(orth ester) or polyacetal is between 2,000 cp and 20,000 cp at 20.degree. C. and 10 sec.sup.-1 ;
• wherein the biologically active beneficial agent is present in the poly(ortho ester) or polyacetal in a stoichiometric ratio of 0.1 to 1.5 equivalents of hydroxyl to 1 equivalent of ketene acetal of vinyl ether.