<prompt> Approximate number of patients recruited in phase II clinical trials of a drug are?20-100100-500500-10001000-5000  <response>: Phase Name Conducted on I Human Pharmacology and safety Healthy Volunteers II Therapeutic Exploratory 20-200 patients III Therapeutic Confirmatory Upto 5000 patients from several centres IV Post-Marketing Surveillance Large number of patients 0 ZERO Microdosing studies Healthy volunteers Small numbers 