While both types release medication slowly to reduce how often you take your pills, they work slightly differently. Sustained-release (SR) is designed to maintain a constant, steady level of the medicine in your bloodstream over a set period. Prolonged-release (PR) simply slows down the release and absorption process, extending the medicine's activity over a longer duration than standard tablets. Both versions, like generic metformin or diltiazem, provide smoother symptom control with fewer side effects. Just remember to always swallow these tablets whole, as crushing or chewing them can release all the medication at once.