Sustained release preparation are used for prolonged duration of action of drug . So, used when drug has sho half life and when we require the action of drug for longer duration. Anti-hypeensive drug are used for lifelong. So, sustained release preparations are required. Anti-arrhythmic drugs used in treatment of PSVT are not to be used as sustained release preparation as we need action for only a sho duration. Anti-inflammatory drug with the half life of 24 hrs is already acting for long duration we don't need sustained release preparation. Hypnotic drug with a half life of 2hrs will work for 5-6 hrs. So, no need of sustained release preparation.