Phases of drug trials: from animals to Phase IV
Walks through the sequence a new drug follows: preclinical animal testing, Phase I (safety), Phase II (does it work, what dose), Phase III (large RCTs), FDA approval, and Phase IV (open-label post-marketing surveillance).
Where this fitsConnects to 2 · Unlocks 1
- Connects to
- Safety: therapeutic index, dosing across species, allergy and polypharmacy — Animal LD50 and human-equivalent dosing happen in the preclinical stage.
- Randomized controlled trials: randomize, control, blind — Phase III is where large RCTs happen.
- Unlocks
- The Controlled Substances Act: schedules I–V and the Analogue Act — Once a drug has an accepted medical use, it can't be Schedule I.
Orient
FDA approval runs from pre-clinical – lab animals – to clinical human trials. Phase I: small numbers (<100) of healthy volunteers, not placebo controlled. Phase II: larger numbers (~200) of volunteers with the to-be-treated disorder, placebo controlled. Phase III: much larger numbers (>1000), placebo controlled. Phase IV occurs after approval and is open-label.
Course terms
Your professor's wording, word for word from the slides. Learn the term and this definition — the explanation underneath is only there to help it make sense.
- Pre-clinical
“Pre-clinical – lab animals”Slides 07, p. 23
Developing the drug, determining therapeutic index, safety, toxicity, primary effects and side effects.
- Phase I
“Small numbers (<100) of healthy volunteers to examine effects in humans. Not placebo controlled”Slides 07, p. 23
Is it safe in people?
- Phase II
“Larger numbers (~200) of volunteers with to-be-treated disorder to determine efficacy. Placebo controlled”Slides 07, p. 23
Does it work in people who have the disorder?
- Phase III
“Much larger numbers (>1000) with broadened sample characteristics, different doses, etc. Placebo controlled”Slides 07, p. 23
Confirms efficacy across a wider range of people and doses.
- Phase IV
“Occurs after approval – continued monitoring for safety and efficacy in real world setting. Open-label”Slides 07, p. 23
Where rare and long-term effects show up.
From your course: Course slides 07, p. 23 · Midterm study guide: Clinical Trials and Policy · Course slides 05, p. 45 (animal testing)
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