n. an opium alkaloid first isolated in the 1840s. It has no psychopharmacological activity but is a potent vasodilator. It is occasionally used to increase blood flow in the cerebral arteries in the treatment of angina pectoris, or—when injected into the corpora cavernosa (see corpus cavernosum) of the penis—to produce erection in the management of impotence. U.S. trade name: Para-Time S.R.