Clinical trials are classified in four phases, phase I – phase IV.

Phase I clinical trials follow a period of research where the drug to be tested shows promise as an effective new treatment.

The research can be quite extensive, sometimes lasting up to six years. Phase I clinical trials generally involve 20 – 100 participants. The dosage of a drug is slowly increased with the main goal of determining safe doses of the drug.

Phase I trials are often conducted on healthy people who are kept under close observation the entire time they are on the medication. Compensation for participation in phase I clinical trials can vary from a small amount up to several thousand dollars for extended stays in a facility for observation. Occasionally real patients are used when they have no other options.

This phase of clinical trials is often when the pharmacodynamics and pharmacokinetics of the drug are tested. Pharmacodynamics is the study of what the drug does to the body and pharmacokinetics is what the body does to the drug. There are different types of Phase I clinical trials including single ascending dose (SAD), multiple ascending dose (MAD) and food effect. In single ascending dose trials subjects are given a dose of the drug and if there are no side effects a new group is given a larger dose.

In multiple ascending dose trials the same participants are given multiple low doses of the medications. Food effect studies look at the absorption rates of medication when someone has eaten versus when they have an empty stomach.

Approximately 70% of experimental drugs pass phase I testing and move onto phase II testing. At each step the findings of the trial must be submitted to the FDA for their approval before testing can continue onto the next phase.