Most of these belong to the aromatic group of bodies, although one of them, antipyrin, belongs rather to the furfurol group. Carbolic acid has an antipyretic action, but on account of its poisonous properties it cannot be employed as an antipyretic. Salicylic acid has a strong antipyretic action, and is most commonly used in the form of its sodium salt, which is much more soluble than the acid itself.
Pain may be stopped by removing the cause of irritation, as, for example, by the extraction of a carious tooth or by rendering the nerveendings insensitive to irritation, as by the application of cocaine; by preventing its transmission along the spinal cord by antipyrin, phenacetin, acetanilide, cocaine, &c.; or by dulling the perceptive centre in the brain by means of opium or its alkaloids, by anaesthetics, and probably also, to a certain extent, by antipyrin and its congeners.
And antipyrin, phenacetin, aspirin and similar analgetics are commonly taken.
Quinine was the first antipyretic used, and after the introduction of such preparations as antipyrin and acetanilide it may still be said to be the safest, though it is much less powerful.