Analgesia

The treatment of severe pain, like pain that accompanies heart attack, kidney stones, gallstones, or terminal cancer, requires the use of prescription medicines that are far more potent than nonprescription drugs. Morphine, a drug derived from opium, has a long history of effective relief of severe pain, but it also is addictive and has dangerous side effects. Morphine and other drugs like it are called opiates.

Unlike nonaddictive drugs, increasing dosages of opiates also increases their analgesic effects. Thus, when they are self-administered, as pain increases, there is a danger of an overdose. Morphine is both a depressant and a stimulant. As a stimulant, it may cause nausea and vomiting, constriction of the pupils of the eye, and stimulation of the vagus nerve, which regulates heartbeat. This stimulation of the vagus nerve interferes with the treatment of pain in coronary thrombosis. Its main side effects—addictive potential, tolerance (dosages must be increased to get the same effect), constipation, and a marked depression of the respiratory system—restrict morphine's use as an analgesic.