20.6: Drugs

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Testing New Drugs

Thousands of chemicals, both synthetic and extracted from "natural" sources, are being examined in the hope of finding new drugs with which to combat human and veterinary diseases. The first step is to use laboratory tests to find if these substances have a significant effect on, for example:

cells growing in tissue culture
laboratory animals such as rats and mice.

If the drug achieves the desired effect in laboratory animals, without killing them in the process, the drug developer applies to the U. S. Food and Drug Administration for an IND, an investigational new drug application. Granting of an IND allows testing in humans to begin. This occurs in three phases.

Phase I

A small group (20–100) of healthy volunteers is given the drug to see

if it is safe
how quickly it is absorbed, metabolized, and excreted from the body

Phase II

A group (up to several hundred) of volunteer patients with the disease are given the drug to see

how effective it is against the signs and symptoms of the disease
what doses are best
what side effects may occur

A control group of similar size is given a dummy drug (placebo). Ideally the trials are "blinded" with neither the subjects (nor the investigator) knowing which pill a subject is receiving.

Phase III

Hundreds to thousands of patients with the disease are given the drug to get more reliable data on its

effectiveness
safety
best dose
rare side effects

all compared with the drug(s) that are currently used for the disease.

If all goes well, the drug manufacturer applies to the Food and Drug Administration for an NDA, a new drug application. If it is granted, the generic name of the drug is replaced by a brand name chosen by the manufacturer. For example, one of the first drugs used against AIDS was azidodideoxythymidine (AZT). When placed on the market, this name was replaced by the brand name Retrovir®.