CHAPTER 8Poison, Medicine, and Pharmacology
We can think of a drug as a chemical that in small amounts has a sig-
nificant effect on body function. Medicines used to decrease the like-
lihood of seizures are examples of drugs. Other drugs will, if ingested,
increase the likelihood of having a seizure. Tropicamide, a parasym-
patholytic, and phenylephrine, a sympathomimetic, are drugs used to
dilate the pupil of the eye for eye examinations. However, ingest too
much of either of these drugs and a heart attack may be the result.
Pharmacology is the scientific study of drugs: their origins,
compositions, and effects on the body. The word pharmacology—as
well as related words like pharmacy, pharmacist, and pharmaceuti-
cal—derives from the Greek word pharmakon. This is a remarkable
term, because it means medicine and poison—at the same time. A
medicine is a substance used for promoting health or treating disease.
Medicines are understood to have beneficial effects on one’s state
of health. A poison is a dangerous or deadly substance. The ancient
Greeks, in formulating pharmakon, understood that poisons may be
medicines and that medicines are also poisons.
Centuries later this important notion was articulated by the
sixteenth-century Swiss physician and alchemist Paracelsus (Fig. 8.1).