Clinical Trial Phases
The sequential stages of clinical drug development: Phase 1 (safety/dosing), Phase 2 (efficacy/safety), Phase 3 (confirmatory efficacy), Phase 4 (post-marketing surveillance).
In Depth
Phase 1 trials (20–80 participants) assess safety, tolerability, pharmacokinetics, and dosing. Phase 2 trials (100–300 participants) provide preliminary efficacy data and further safety information. Phase 3 trials (300–3,000+ participants) are pivotal confirmatory trials required for FDA approval — the Epidiolex approval was based on Phase 3 RCTs. Phase 4 post-marketing studies monitor long-term safety and effectiveness in real-world populations. Most cannabinoid research is at Phase 1–2; few compounds have reached Phase 3.
Further Reading
More in Research Methods
Randomized Controlled Trial (RCT)
The gold standard study design in clinical research. Participants are randomly assigned to treatment or control groups to minimize bias and establish causation.
Systematic Review
A structured synthesis of all available evidence on a specific research question, using predefined criteria to identify, evaluate, and summarize studies.
Meta-Analysis
A statistical technique that combines quantitative data from multiple studies to produce a pooled estimate of effect size with greater statistical power than any individual study.
Placebo-Controlled
A study design in which the control group receives an inert substance (placebo) identical in appearance to the active treatment, to account for the placebo effect.
Observational Study
A study in which researchers observe participants without intervening. Includes cohort studies, case-control studies, and cross-sectional surveys.