This section is from the book "Botanic Drugs Their Materia Medica, Pharmacology and Therapeutics", by Thomas S. Blair. Also available from Amazon: Botanic Drugs, Their Materia Medica, Pharmacology and Therapeutics.
Colocynthis, Bitter Apple, Citrullus colo-cynthis. Official in most standards, but the British and United States pharmacopeias (recent) have recognized the pulp instead of the peeled dried fruit. Colocynth contains a small quantity of a-elaterin, water-soluble glucosides and an amorphous alkaloid.
Colocynth belongs to the anhydride group of cathartics, which are drastic and irritant; and it is seldom used except in combination with other agents. Small doses of colocynth stimulate peristalsis and induce increased intestinal secretion. The average dose is one-half to one grain; but the compound extract (colocynth, aloes, cardamon, scam-mony, and soap) is to be preferred in 5-grain doses. Colocynth enters into many pill formulae.
In small doses of the tincture, colocynth obtained a reputation in the treatment of horse colic. Home-opathists tried it in various forms of colic in man, and gastralgia, enteralgia, and tenesmus often are relieved by small, fractional doses (tr. 1 or 2 minings). Smaller doses will often relieve infantile colic. Of course, colocynth merely relieves the symptoms and does not control diarrhea, food fermentation, etc.