Antispasmodics are those medicines, which are calculated to relieve persons afflicted with cramps, spasms, or convulsions : such are opium, Peruvian balsam, and the essential oils of different vegetables. The most speedy antispasmodic, with respect to its immediate effects, is doubtless the juice of the poppy ; but the Peruvian balsam produces more permanent benefit, and has frequently been of eminent service, after opium had failed to afford any relief.
Essential oils act principally on some particular part, rather than on the system in general; and are seldom attended with any soporific effects. But, beside these internal medicines, there are some which instantly remove spasmodic contractions by contact ; for instance, cream, oil of almonds, and asses'-milk ; while sulphur, sal ammoniac, nitre, etc. mitigate these painful complaints, by diminishing heat. Where, however, spasms originate from inanition, and a defect of vital heat, the best antispasmodics are, valerian, musk, and castor ; because these medicines tend to restore the animal spirits, and at the same time operate as corroborants.