Several forms of dosage formulations are available,perhaps the oldest examples are enteric coating of orally ingested drugs and time release often called as sustained release products. Although coating and compounding techniques can prolong the pharmacological and biological action of the drugs., their rates of release is not uniform. In other words, it is not controlled, similarly the absorption of drugs administered by parenteral route may be prolonged by repository preparation providing for therapeutic effectiveness extending from 12 hours to several days.The best example is that of Penicillin-G.