Antipyrine is a coal-tar derivative, being prepared from chinolin. It is an alkaloidal body, combining with acids to form salts. A whitish, crystalline powder of slightly bitter taste, soluble in water in a proportion of ten parts to six parts of water.
When first introduced it was a proprietary medicine and was known principally as an antipyretic. With further use and investigation other therapeutic qualities have been manifested.
It is a general nerve sedative and anodyne, having a considerable degree of power in the relief of pain in various conditions of nervous origin. It is slightly antiseptic and disinfectant, diaphoretic, and has some diuretic action. It is also credited with being to some extent a haemostatic. Antipyrine does not lower the normal temperature, but in fever its action is very marked. There is a short period of stimulation, with flushing of the face, a feeling of heat, and increased action of the heart. In about half an hour or more perspiration breaks out and usually becomes very profuse. The pulse is then slowed, but not always weakened. The skin is cool; there may be chilly feelings, and the temperature falls from one to several degrees, according to the amount taken, and remains down for a length of time also proportioned to the dose - usually two or three hours, and often longer.
There results very often - especially in subjects weakened by a long illness - a decided state of depression, sometimes so marked as to be alarming, and the pulse, though not always weakened, is in some cases seriously so. The use of antipyrine in acute illness often causes nausea and vomiting, though it is not a gastric irritant in any special sense, but in small doses tonic, increasing the appetite. Symptoms which indicate danger in giving antipyrine are cyanosis, muscular weakness, disturbed and rapid respirations, weakened irregular pulse, dyspnoea, and sensations of heat over the body. Collapse may result from its use, and death in one instance followed the administration of fifty-odd grains. An eruption of the skin frequently occurs, with some constitutional disturbance and considerable suffering and annoyance from the itching, which is severe. It lasts for several days, and in the majority of cases resembles the measles rash; but sometimes appears as a general and intense erythema, with swelling of the face, especially about the eyes, burning sensations, and rise of temperature. Antipyrine has been given hypodermi-cally, but is irritant and liable to cause abscesses. If so given it should be injected deeply into the gluteal muscular tissue.