Frangula, also called Buckthorn, comes from the dried bark of the Frangula alnus shrub. The bark delivers anthraquinones, compounds that stimulate the bowel. People use it as a short-term aid for occasional constipation, taking a liquid extract or dried herb at bedtime. A bowel movement typically arrives 6 to 12 hours later.
Do not take Frangula for more than a week or two. Extended use can cause laxative dependence and throw off your electrolyte balance. Steer clear if you are pregnant, nursing, or dealing with an intestinal blockage, Crohn's disease, or ulcerative colitis. Frangula may also amplify potassium loss when you take diuretics, corticosteroids, or certain heart drugs.