<prompt> Randomized controlled multicenter trials of drug:Phase IPhase 2Phase 3Phase 4  <response>: Ans- C Phase 3 - randomized controlled multicenter trials REF: Goodman and Gillmans 11th edition page 82, sctphases.html CLINICAL TRIAL: Designation Study Population Sample size Phase 0 human microdosing studies pharmacodynamics and pharmacokinetics no data on safety or efficacy, being by definition a subtherapeutic dose Healthy volunteers 10 to 15 Phase 1 first stage of testing in human subjects safety pharmacovigilance, dose-ranging tolerability, pharmacokinetics, and pharmacodynamics Healthy volunteers or individuals with target disease 20-100 Phase 2 efficacy how well the drug works, dosing requirements how much drug should be given, toxicity and continue Phase I safety assessments individuals with target disease 100-300 Phase 3 randomized controlled multicenter trials, pre-marketing phase how effective the drug is, in comparison ivith current gold standard treatment most expensive, time-consuming and difficult trials individuals with target disease 300-3,000 or more Phase 4 Postmarketing surveillance Trial safety surveillance pharmacovigilance, designed to detect any rare or long-term adverse effects individuals with target disease as well as new age groups, genders, etc. Thousands 