Curariform Agents

substances of the muscle relaxant group that, like curare, block neuromuscular transmission.

The curariform agents include the curarines (curare alkaloids) and other alkaloids and synthetic compounds that exert an analogous effect: relaxing first the mimetic musculature and the muscles of the pharynx, then the muscles of the neck and extremities, and finally paralyzing the respiratory musculature (especially the diaphragm).

Curariform agents are administered mainly parenterally (usually intravenously; more rarely, intramuscularly) in surgical practice and mainly enterally (that is, by mouth) with nervous diseases, in order to counteract elevated tonus of the skeletal muscles. The degree to which motor activity is diminished (from insignificant changes to the complete relaxation of all muscles and the cessation of breathing) depends on the dosage.

Parenterally administered curariform agents of short-term effect (5–15 min), such as Ditilin (suxamethonium iodide), are used in medical practice to perform short-term manipulations (for example, intubations, setting dislocations, and repositioning bone fractures). Longer operations are possible with drip or fractional dosing. Curariform agents with a somewhat longer lasting effect (20–40 min), such as d-tubocurarine chloride and Diplacin, are used for operations on organs of the thoracic and abdominal cavities when rapid and complete exclusion of the respiratory muscles is necessary. Decamethonium and Anatruk-sonii (truxipicurium iodide), which have only a slightly inhibitory effect on respiration, are used for operations on the abdominal cavity and the extremities. Curariform agents with a prolonged effect (60–120 min and more), such as Imbretil and Anatruksonii (in large doses), are used for long operations and in the treatment of tetanus.

The group of preparations that are active when taken internally includes condelphine and methyllycaconitine hydroiodide, which are long lasting and depress respiration minimally. The curariform agents (with the exception of Ditilin) are contrain-dicated with diseases of the kidneys. Increased sensitivity to Ditilin may be observed with liver diseases. All curariform agents are contraindicated with myasthenia.