Methods, compounds, and medicinal formulations utilizing biocompatible polymers for delivery of a drug, particularly for solubilizing, stabilizing and/or providing sustained release of drug from topical, implantable, and inhalation systems. Many of the methods, compounds, and medicinal formulations are particularly suitable for oral and/or nasal inhalation and use polymers of the formula --[X--R.sup.1--C(O)]-- wherein each R.sup.1 is an independently selected organic group that links the --X-- group to the carbonyl group, and each X is independently oxygen, sulfur, or catenary nitrogen.