Study phases

Question 1

Phase I Clinical Trial

Answer 1

These are “first in human” studies usually conducted on a small number of healthy volunteers to determine the tolerability and safety of a new drug, as well as its pharmacokinetics and pharmacodynamics

Question 2

Phase II Clinical Trial

Answer 2

These are “dose-finding” trials usually on patients - a lower number than Phase III but larger than Phase I - assessing optimal dosing (giving different doses and following up to determine the efficacy and tolerability/toxicity) and efficacy (biological effect of the drug)

Question 3

Phase III Clinical Trial

Answer 3

These trials assess the effectiveness of a new drug/ intervention, as compared to the gold standard therapy (whilst always ensuring its safety), to inform the value of the new intervention in clinical practice. They are usually multi-centre randomised control trials on large numbers of patients.

Question 4

Post-marketing surveillance (Phase IV)

Answer 4

Monitors safety of the drug after it is being marketed (pharmacovigilance), to detect any rare or long-term adverse events or side effects that were not detected during previous trials