This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
These are substances which slightly increase the action of the bowels chiefly by stimulating their muscular coat.
They are -
(1) Whole meal bread.
(4) Most fruits, especially -
(7) Prune, and
(8) Stewed apples.
(10) Cassia Fistula.
(13) Olive oil.
These are all domestic remedies employed for slight cases of constipation, especially in children; some, as brown bread, fruits, honey, form articles of diet with persons who are liable to constipation. Ergot, physostigma, nux vomica, belladonna, hyoscyamus, and stramonium are also laxatives, but are not used except under medical orders. Nux vomica is most valuable; it is probably a direct stimulant to the muscular coat, hardly influencing secretion. It is largely used in cases of chronic constipation, especially when occurring in anaemic persons, or in those in whom, for any reason, it is likely that the intestinal peristalsis is feeble.
Belladonna in small doses increases peristaltic movements because it paralyzes the inhibitory fibres of the splanchnics, but in moderate doses it completely arrests peristaltic movements. It is chiefly employed for this latter purpose, especially in combination with opium. Hyoscyamus acts on the intestines in the same way, and small doses of it are often given with other purgatives to prevent griping, for it gives an orderly rhythm to the irregular contractions which the stronger purgatives produce.
Ergot and physostigma are hardly ever used for their laxative effect. Ergot, however, so often produces diarrhoea that its purgative action should be kept in mind.
These are rather more powerful in their action than laxatives. They stimulate peristalsis and also increase secretion. Some of the laxatives, as castor oil and magnesia, when given in large doses become simple purgatives.
The simple purgatives are -
(3) Rhamnus Frangula.
(4) Rhamnus Purshiana.
(6) Fel Bovis.
These are all in common use. The indications for each will be given under the individual drug.
These excite greatly increased secretion and peristaltic movements, and if given in large doses cause severe irritation of the intestine, with much secretion of mucus, great vascular dilatation, and even haemorrhage, severe abdominal pain and collapse, with profuse diarrhoea. The peristaltic contractions are often irregular, and hence there may be much griping pain; therefore it is usual to prescribe hyoscyamus with these drugs, which are in order of efficiency -
(8) Oleum Terebinthinae.
(11) Croton oil.
The most powerful are placed last. Some, as jalap, elaterium, scammony, are often called hydragogue, because of the large amount of secretion they excite.
Drastic purgatives are employed in obstinate constipation, and also to produce very watery evacuations with the object of removing as much fluid from the body as possible. Hence the frequent use of jalap in Bright's disease.