Q. I rarely take pharmaceutical medicines but when I must, I always seem to have side effects. Are some people just more sensitive to medicines in general?

A. Yes. Some people are more sensitive to medications.

In 1978, a pharmacologist who was part of a research team in London took a test dose of the blood pressure drug debrisoquine and promptly collapsed to the floor. He was subsequently found to be a poor metabolizer of the drug, which caused him to suffer a precipitous drop in blood pressure.

Some people have allergies to specific medications, and others may experience idiosyncratic reactions to individual drugs. But differences in the way your body metabolizes drugs might render you prone to side effects. Some people metabolize drugs very slowly or very quickly, either of which can cause high levels of drugs or drug metabolites to accumulate in the blood.

Doctors began to recognize individual differences in drug metabolism in the 1950s. By the 1970s, the London researchers found that slow metabolism of drugs can be an inherited genetic trait. In 1980, they showed that approximately 9 percent of the British population were slow metabolizers. Since then, extensive variations in drug metabolism have been documented across many populations and ethnicities.