A range of materials have been employed to control the release of drugs and other active agents. The earliest of these polymers were originally intended for other, nonbiological uses, and were selected because of their desirable physical properties, for example:
- Poly(urethanes) for elasticity.
- Poly(siloxanes) or silicones for insulating ability.
- Poly(methyl methacrylate) for physical strength and transparency.
- Poly(vinyl alcohol) for hydrophilicity and strength.
- Poly(ethylene) for toughness and lack of swelling.
- Poly(vinyl pyrrolidone) for suspension capabilities.