Controlled release refers to the release of drug into a patient’s body at a predetermined rate, at specific times, or with specific release profiles. Its advantages are reduction of dosing frequency, reduction in the fluctuation in circulating drug levels, increase in patient compliance, uniform effect, and reduction in GI irritation and other dose-related side effects. However, it suffers from the drawbacks of higher cost, unpredictability, and often poor in vitro–in vivo correlations and dose dumping.