Clinical trials are carefully controlled studies that test the safety, efficacy, and side effects of new drugs or treatments in humans. They are conducted in several phases, each with a specific purpose:
Phase 0: Microdosing Trials
- Purpose: Early exploratory phase to understand how a drug behaves in the body.
- Participants: Very few (10–15 healthy volunteers).
- Key Goal: Determine pharmacokinetics (absorption, distribution, metabolism, excretion) using extremely low doses.
- Notes: No therapeutic effect expected; mainly a “first look” at the drug in humans.
Phase I: Safety Trials
- Purpose: Assess safety, tolerability, and dosage range.
- Participants: Small group (20–100 healthy volunteers or patients).
- Key Goal: Find the maximum tolerated dose and identify common side effects.
- Notes: Focus is on safety, not effectiveness.
Phase II: Efficacy and Side Effect Trials
- Purpose: Test if the drug works for a specific disease and continue safety assessment.
- Participants: Larger group (100–300 patients with the disease).
- Key Goal: Determine effectiveness, optimal dose, and short-term side effects.
- Notes: Sometimes split into Phase IIa (dose-finding) and Phase IIb (efficacy confirmation).
Phase III: Large-Scale Efficacy Trials
- Purpose: Confirm effectiveness, monitor side effects, and compare with standard treatments.
- Participants: Large group (1,000–3,000 patients).
- Key Goal: Provide strong evidence of safety and efficacy for regulatory approval.
- Notes: These trials are often randomized, double-blind, and controlled.
Phase IV: Post-Marketing Surveillance
- Purpose: Monitor long-term effects after the drug is approved and sold.
- Participants: General population using the drug.
- Key Goal: Detect rare or long-term side effects and assess real-world effectiveness.
- Notes: Can lead to label changes, dosage adjustments, or even withdrawal of the drug.
In short:
- Phase 0: Microdose, first human exposure
- Phase I: Safety and dosage
- Phase II: Effectiveness and side effects
- Phase III: Large-scale confirmation
- Phase IV: Post-marketing safety