How long do clinical trials last?
Trial duration varies enormously by phase and disease area. The shortest trials — single-dose pharmacokinetic studies in healthy volunteers — last a single overnight stay. Most Phase 2 outpatient studies in chronic conditions last 12 weeks to 12 months. Phase 3 studies in chronic conditions often last 1-3 years, with monthly or quarterly visits. Phase 4 (post-approval) studies and registries can run 5+ years. Oncology trials are typically open-ended: you stay in the study as long as the drug is helping. Long-term follow-up phases — common after gene therapy and vaccine trials — can run 5-15 years to track long-term safety. The total time commitment for any specific study is spelled out in the informed consent document, including the number of visits, visit length, and total duration. You can withdraw at any time, so the duration in the consent form is a maximum, not a contract.