Types of Trials

After a drug has been tested in the lab and in animals, it is tested in people. There are three types, or phases, of trials that are done with people.

Phase 1: Is the drug safe?

A Phase 1 trial is usually the first time a new drug is given to people after tests are done in animals. This type of trial is done to find out if the drug is safe for people to take. Everyone in a Phase 1 trial gets the drug being studied, but because most Phase 1 trials also try to find out what the best dose (amount) of the drug is, people are often given different doses. A drug in a Phase 1 trial has not been tested in many people, so very little is known about it. This makes Phase 1 trials riskier than Phase 2 or Phase 3 trials. Phase 1 trials are short, usually less than 2 or 3 months long, and usually involve less than one hundred people. Phase 1 trials usually study how safe a drug is, but they may also look at how the drug affects the body.

Phase 2: Does it work?

If a Phase 1 trial finds that the drug is safe for use in people, a Phase 2 trial will be done. In a Phase 2 trial more people are given the drug to see if it works and to study the side-effects more carefully. In this type of trial, researchers try to find out if the drug has a good effect and continue testing its safety. Phase 2 trials can last from a few months to a few years. There may be hundreds of people in a Phase 2 trial. In Phase 2 trials there are still risks that go along with possible benefits.

Phase 3: What if many people take it?

If the Phase 2 trial shows that the drug seems to work, a Phase 3 trial is started. In this type of trial, many people, sometimes thousands, are given the drug to see how well it works and if it causes problems when people take it for a long period of time. Researchers look for rare side effects, which are only seen in a few people, or only after someone has been taking the drug for many months or years. Most drugs will go through all three phase before they are approved, although drugs for life-threatening illnesses, such as AIDS, may be approved after Phase 2 trials and go through Phase 3 trials after FDA approval.

Sometimes phases are combined and you will see a trial described as Phase 1/2 or Phase 2/3. For some drugs, this speeds up the drug testing process.

An additional type of drug research is called a Phase 4 trial. At the same time that a drug has gone through all three preceding types of trials, and is approved for marketing, the FDA may require the drug manufacturer to obtain further information about the drug’s risks, benefits or better ways of administration.

Such studies could include differing dosages and the best time for taking the drug, studies of the side effects over much longer periods of time, or in a different patient population, or other factors affecting safety and effectiveness such as gender, race or age.

Some trials may be linked to the presence of some abnormality in a gene or genes in a patient’s genetic background and will try to determine whether this plays a role in the action of a drug.

Will I know what drug I’m taking?

Not always. In a Phase 1 trial, you’ll know what drug you’re taking and how much. In a Phase 2 or 3 trial you probably won’t know what drug you’re taking. Phase 2 and 3 trials are usually controlled trials, and people in these trials are divided, by chance, into different groups. Each group takes either the new drug or an approved drug or a placebo.

The group that takes an approved drug or a placebo is called the “control” group. Usually no one, not even the people running the trial, knows who is taking what until the trial is over. This is called a Double-Blind study. If everyone knows who is taking which drug, the trial is called an Open-Label study.

Sometimes the control group takes a placebo. A placebo is a fake pill or shot. Trials use placebos so the researchers can be certain that the benefits or side effects seen are due to the drug and not some other cause. A placebo used in a trial looks exactly like the drug being tested.

If the drug is a pill, the placebo will be a pill. But if the drug is injected into a vein for two hours, the placebo will probably be injected into a vein for two hours.

Controlled trials are done to make sure the drug really works. If everyone in a trial gets the new drug, there’s no way to tell if the drug is making them better or if something else is doing it. They may get better because they’re seeing a doctor for the first time, or because they’re eating better and taking better care of themselves. So, a new drug is compared to something else or nothing, to see which is better.

If the people in the trial believe they’re taking a drug that works, they may feel better even if the drug doesn’t work. For example, in one trial that tested a drug to fight diarrhea, half of the people taking the new drug got better, but almost half of the people taking the placebo got better too. This means the drug didn’t work any better than a sugar pill.