Significant stimulant laxatives Cascara sagrada

Significant stimulant laxatives Cascara sagrada

Of all the herbs that function as stimulants, the best is certainly cas- cara sagrada. This herb enjoys official status in the USP XXII, where it is described as the dried bark of Rhamnus purshianus DC. (family Rhamnaceae). Obtained from a small tree native to the Pacific Northwest, the bark should be collected at least one year prior to use in order to allow some of the harsh laxative, reduced emodin glycosides (anthrones) origi- nally present in the bark to be oxidized naturally to less active mono- meric anthraquinone glycosides. Cascara owes its action to a mixture of principles consisting largely of cascarosides A, B, C, and D, with other anthraquinone glycosides in minor amounts. Bark of USP quality contains not less than 7 percent total hydroxyanthracene derivatives calculated as cascaroside A on a dried basis. The cascarosides should make up at least

60 percent of this total. Cascara is probably the mildest of the anthraquinone stimulant laxa- tives, producing only minor effects on the small intestine. Because of its relatively mild action, the herb is the least likely of the stimulant laxa- tives to produce undesirable side effects such as griping or dependence. Nevertheless, the active principles are excreted in mother’s milk, so nurs- ing mothers and, for that matter, pregnant women should avoid taking it or other anthraquinone-containing herbs.

34 Tyler's herbs of choice: The therapeutic use of phytomedicinals Although cascara is normally taken in the form of prepared phar-

maceutical dosage forms such as an extract, fluidextract, or aromatic fluidextract, it is also possible to consume the powdered bark in capsule form. Average dose is 1 g (about ½ teaspoonful). Cascara tea is not popular because of its extremely bitter taste. The herb is an ingredient in several popular OTC laxatives. 44

Buckthorn (frangula) bark This product is very similar to cascara because it is obtained from its near-relative Rhamnus frangula L. (family Rhamnaceae), a shrub or small tree that grows in Europe and western Asia. Its laxative effect is due to the presence of anthraquinone derivatives, particularly glucofrangulin

A and B and frangulin A and B. Like cascara, buckthorn bark should

be aged one year prior to use in order to allow the reduced glycosides (anthrones) with their harsh laxative action to be converted to milder oxidized forms. 45

Properly aged buckthorn bark is also comparable to cascara in its rela- tively gentle laxative action. In spite of this, it is not commonly used in the United States, where it is overshadowed by the more popular native species Rhamnus purshianus. It is a very popular drug in its native Europe. Cascara is somewhat less expensive than buckthorn bark in the United States, so there appears to be no particular advantage in using the latter.

The German Commission E has found buckthorn bark to be an effec- tive stimulating laxative. 46 Average dose is 1 g. A fluidextract of the botan- ical, once official in the NF, remains a useful dosage form.

Senna Probably the most widely used of the anthraquinone-containing stimu- lant laxatives is senna. Official in the USP XXII, senna is described there as consisting of the dried leaflet of Cassia acutifolia Delile, known in commerce

as Alexandria senna, or of Cassia angustifolia Vahl, known in commerce as Tinnevelly senna. These low-growing shrubs of the family Fabaceae are native to Egypt or to the Middle East and India, respectively. Dianthrone

glycosides, particularly sennosides A, A 1 , B, C, D, and G, together with various other anthraquinone derivates, account for the laxative action of senna. 47 The total complex of senna glycosides is also official in the USP under the title “sennosides.” Although senna is not as mild in its action as cascara, producing more smooth muscle contractions with attendant cramping, it is never- theless more widely used because it is considerably cheaper. Bulk lots of the herb are only about one-half the price of cascara. A fluidextract and a syrup made from the leaflets are available, as are tablets prepared from a mixture of the purified active ingredients—so-called sennosides.

A bitter-tasting tea can be prepared from 0.5–2 g (0.5–1 teaspoonful) of

Chapter three: Digestive system problems

35 the herb. Some prefer a beverage prepared by soaking the leaflets in

cold water for ten to twelve hours and then straining. Such a prepara- tion will be more active than the customary hot tea and will contain less resinous material. 48