Britannica Concise Encyclopaedia defines a drug as any chemical agent that affects the function of living things. Some, including antibiotics, stimulants, tranquilizers, antidepressants, analgesics, narcotics and hormones, have generalized effects. Others, including laxatives, heart stimulants, anticoagulants, diuretics and antihistamines, act on specific systems. Although a drug can also refer to any type of medicine, in [...]