In order for new drugs to be approved there are a number of stages in the clinical trial process, this can take time.

Animal studies

  • Animal models are used to conduct initial studies into the use of a potential treatment before studies are conducted in patient volunteers.

  • Animal studies identify the effectiveness, tolerability and highlight any side effects of potential treatments to determine whether this can be transferred into patient volunteers.    

Phase 1

  • First trials conducted in human volunteers.

  • Small number of volunteers recruited to partake in phase 1 trials.

  • Correct dose of drug determined with tolerance, effectiveness and any potential side effects observed.

  • Dose of drug increased until minor side effects observed, used to determine correct dosage.

Phase 2

  • Increased number of volunteers partake in study with effects of potential drug treatment tested in the short-term.

Phase 3

  • Drug must have passed phases 1 and 2 to progress into phase 3.

  • Drug tested in increased number of volunteers.

  • Drug compared to current treatments or placebo (drug with no effect).

  • Side effects and drug effectiveness continually monitored.  

Phase 4

  • Drug tolerance, safety and side effects studied over a longer period of time in patient volunteers of study, with the risks and benefits of the drug being compared.

Figure 1 - There are various phases to clinical trials to ensure new drug candidates and potential treatments are effective, well tolerated and safe for use in patient populations. If potential treatments are successful and pass through all phases they may reach the regulatory process and eventually be granted regulatory approval.