Anthelmintics are remedial agents used to cause the expulsion of parasites from the intestinal canal. Vermifuges are remedies which expel worms; vermicides are remedies which kill as well as expel worms. Some of these agents act mechanically, as mucuna and powdered tin; others are administered in such quantity as to sicken and disable the worms, when their expulsion is easily effected: for example, pumpkin-seed emulsion. Others again possess narcotic and toxic properties, as turpentine, chenopodium, santonin, etc.

Anthelmintics are conveniently divided into those employed against ascarides vermiculares, those employed against ascarides lumbricoides, and those employed against the different varieties of taenia.

Ascarides vermiculares infest the rectum and large intestine, extending up occasionally as high as the ileo-caecal valve; in females, they may also spread into the vagina. As they deposit their ova in the folds of the anus, and in the vagina, it is obvious that the parasiticide, to be effective, must be applied in these situations.

Infusion of quassia, decoction of aloes, and a weak solution of carbolic acid, are the most frequently-prescribed remedies for the destruction of ascarides. If carbolic acid is used, the strength of the injection for children should not exceed ten grains to the pint, and it should not be retained. Infusion of quassia is at the same time safe and effective; but, when this injection is used, a solution of carbolic acid should be applied also, by means of a sponge, to the folds of the anus, and, in the case of female children, to the external genitals. If the ascarides extend up into the large intestine beyond the sigmoid flexure, a dose of santonin and calomel should precede the use of the rectal parasiticide.