Controlled Release (CR) products are designed to maintain constant therapeutic plasma concentration of the drug within the therapeutic range of the drug over prolonged periods and offer minimum side effects. This can be achieved using a variety of delivery systems and also includes liposomes and drug-polymer conjugates. These products are designed to reduce the frequency of dosing by modifying the rate of drug absorption. Generally CR products administered by any route are designed such that rate of drug absorption should be equal to rate of drug elimination. Literally, the amount that is eliminated should be input into the compartment of interest at the same amount at any given time. These products can be administered by various routes including oral (peroral, buccal, sublingual), parenteral (IM, IV, SC, IP, IT, etc.), transdermal, respiratory, nasal, etc. Other miscellaneous routes such as intravaginal, rectal, etc. can also be used for CR products. Drug eluting stents is a novel concept in CR products. Examples of controlled release drug eluting stents include Cypher® (reservoir) and TAXUS Express® (monolithic). The concept behind CR products was proposed long time ago. Early modified release products were often intramuscular/subcutaneous injection of suspensions of insoluble drug complexes, eg. Procaine penicillin, protamine zinc insulin, insulin zinc suspension or injections of the drug in oil, eg. Fluphenazine decanoate. Advance in technology have resulted in novel modified release dosage forms.