A new drug is to be evaluated for its therapeutic effect. The best study design will be -

RCT has questioned the validity of such widely used treatment as oral hypoglycemic agents, varicose vein stripping, tonsillectomy, hospitalization of all patients with myocardial infarction, multiphasic screening and toxicity and applicability of many preventive and therapeutic procedures. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 89