Details may vary a bit from country to country. The following is based on the process of clinical trials in the United States, but will be very similar to clinical trials around the world.Phases of Clinical Trials
There are traditionally 4 stages of clinical trials, called ‘phases’. Recently a ‘Phase 0′ clinical trial has been used, though it is not universal.
Phase I – this is the earliest trial of a new treatment in humans. Prior to phase I clinical trials, the treatment is tested in the laboratory and in animal tissue. If a treatment works in the lab, and has no clear and obvious dangers, it goes to Phase I testing. In Phase I testing the new treatment is given to a small group of people, usually between a few dozen and a hundred.
The goal of phase I testing is pretty broad. Scientists want to make sure it is still effective outside of a test tube, too identify potential side effects and to determine safe dosages.
‘Phase 0′ trials are similar to a very small Phase I trial, and use tiny doses of the treatment, well below any expected treatment level, to ensure that the are no highly dangerous side effects.
Phase II – Once it’s established that the new treatment works in some people, is reasonably safe, and the doctors are sure of proper dosages, it moves on to Phase II trials. Phase II trials are the proof that a new treatment works. And especially that it works for nearly everyone who takes it the same way. Phase II trials involve a few hundred people.
Phase III – these are the largest pre-approval trials, usually including several thousand people. Here, the new treatment is evaluated for how effective it is, examined closely for side effects, and compared to existing treatments.
After Phase III trials, the new treatment is submitted – with the results of all trials – to the regulating body for approval. Sometimes the regulating body will request further tests regarding some aspect of the treatment. Sometimes they will approve it. Sometimes they will deny it.
If it is approved, it then moves into Phase IV trials. Phase IV trials include determining what other medications the new treatment may interact with, and refining treatment and dosage guidelines.
Each phase of clinical trials will take at least a year, and sometimes long. So from the announcement of a new possible treatment going into Phase I testing to the approval and spread of a new treatment can easily take 5 years or more.
Placebo and Double Blind Trials
A placebo is a fake medicine, often a sugar pill. Often, a person’s health will improve just from taking a placebo. Sometimes they will even get side effects taking a placebo that don’t exist with the real medicine. By comparing a new treatment with a placebo, doctors can be sure the treatment is helping, and people aren’t just feeling better because they think they should.
Participants in a trial with a placebo are told that they may receive a placebo, and may receive the new treatment, but they won’t know which until after the trial is complete. In many trials, the doctors don’t know who is receiving a placebo either. This is called a double blind. Participants are randomly assigned to get either the treatment or the placebo. They are given all given an identical looking treatment – a pill, and injection, or whatever form the treatment takes. But half of the treatments are placebos. Only after the trial is over will the doctors know who received the real treatment, and who received the placebo.
In double blind trials, there is always someone who is overseeing the trial who does not interact with the patients, but maintains the records and makes sure each patient will receive the correct treatments.