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There are currently 4 entries in this directory beginning with the letter P.
Phases of drug trials
• Phase I: relates to the safety of the drug under investigation in healthy volunteers. The aim is to establish the appropriate doses of a drug to be investigated in later trials and understand how the drug is dealt with in the body.

• Phase IIa: Phase IIa trials are similar to Phase I studies but aim to link to Phase II by capturing data more typically associated with a straight Phase II trial.

• Phase II/IIb: usually involves a small (usually randomised) trial investigating the potential benefits of a drug among patients with a particular disease. These trials are also used to establish which therapies have the potential to be investigated in full-scale, Phase III randomised trials.

• Phase III: these trials are full-scale randomised controlled trials evaluating the benefits of a drug against a placebo or standard therapy in a substantial number of patients. This is the key stage in establishing the impact of a drug.

• Phase IV: relates to the stage after a drug has been approved and involves the long-term monitoring of the safety of the drug. It sometimes refers to the marketing process by which the drug is brought to the attention of a large number of medical practitioners.
A placebo is a dummy treatment that is designed to be harmless and to have no effect. It looks, smells and tastes like the treatment being tested, so that people don’t know if they are taking the dummy treatment or the treatment being tested (see blinding). It allows researchers to test whether a new intervention has any benefit other than a psychological response, where people feel better because they have received a treatment. This response is called the ‘placebo effect’. By comparing people’s responses to the placebo and to the treatment being tested, researchers can tell whether the treatment is having any real benefit.
Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)
Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses. The aim of the PRISMA Statement is to assist authors to improve the reporting of systematic reviews and meta-analyses. The PRISMA Statement is comprised of a checklist and flow diagram.
A protocol is the plan for a piece of research. All protocols for clinical trials need to be approved by an ethics committee. A protocol usually includes information about:

What question the research is asking and its importance/relevance

The background and context of the research, including what other research has been done before

How many people will be involved

Who can take part

The research method

What will happen to the results and how they will be publicised

A protocol describes in great detail what the researchers will do during the research. Usually, it cannot be changed without going back to a research ethics committee for approval.