Protocol Amendment
A formal, approved modification to a clinical trial protocol made after the study has begun. Amendments may change eligibility criteria, endpoints, sample size, or procedures based on emerging data or practical considerations. All amendments require ethics committee and regulatory approval.
Technical Context
Common reasons for amendments: updated safety information (requiring new exclusion criteria or monitoring), emerging data suggesting dose modification, slower-than-expected recruitment (broadening eligibility criteria), regulatory agency request (modified endpoint or control group), and practical operational issues. Substantial amendments (affecting safety, design, or scientific quality) require IRB/REC and regulatory approval before implementation — this process can take 4-12 weeks. Non-substantial amendments (administrative changes) may require only notification. Amendments affect all subsequently enrolled participants; already-enrolled participants may need re-consent if the changes materially affect their risk-benefit assessment. Frequent amendments can indicate poor initial protocol design.