VA Class:GA209

ATC Class:A06AB02

AHFS Class:

• Cathartics and Laxatives 56:12

Generic Name(s):

• Bisacodyl

Diphenylmethane laxatives (e.g., bisacodyl) are stimulant laxatives.

Administration

Bisacodyl is administered orally. Bisacodyl also is administered rectally as a suppository or enema. Bisacodyl tannex is administered rectally as an enema. For occasional use as an oral laxative, bisacodyl should be administered the evening before a morning bowel movement is desired. Rectal bisacodyl suppositories and enemas may be administered at the time a bowel movement is desired. To avoid gastric irritation and the possibility of vomiting, enteric-coated bisacodyl tablets must be swallowed whole and not crushed, chewed, or taken within 1 hour of antacids or milk.

Dosage

The recommended dosages of the diphenylmethane laxatives should not be exceeded.

Bisacodyl and Bisacodyl Tannex

The usual oral laxative dosage of bisacodyl for adults and children 12 years of age and older is 5-15 mg daily given as a single dose. Children older than 3 years of age may be given bisacodyl in an oral dosage of 5-10 mg or 0.3 mg/kg daily given as a single dose. The usual rectal dosage of bisacodyl for adults and children 12 years of age and older is 10 mg daily given as a single dose, and for children 2-11 years of age the usual rectal dosage is 5-10 mg (one-half to one suppository) daily given as a single dose. For children younger than 2 years of age, the usual rectal dosage is 5 mg (one-half suppository) daily given as a single dose.

For surgical, radiologic, proctoscopic, or sigmoidoscopic preparation, the usual dose of bisacodyl may be given orally on the night preceding and rectally on the morning of surgery or examination. Up to 30 mg of the drug may be given orally to adults when complete evacuation of the colon is required for special procedures. In preparation for barium sulfate enemas, the patient should not eat following administration of the tablets and a bisacodyl suppository should be given 1-2 hours before the procedure. Preparatory regimens using magnesium citrate, which acts mainly on the small intestine, in addition to administration of the usual oral and rectal dose of bisacodyl have also been used. The usual dose of bisacodyl as a rectal suppository may be used to cleanse the colon prior to delivery if administered at least 2 hours before onset of the second stage of labor.

Alternatively, bisacodyl tannex may be used prior to radiologic examinations or sigmoidoscopic or proctoscopic procedures. Patients should receive a residue-free diet one day before, and 30-60 mL of castor oil should be administered 16 hours before the examination or procedure. A cleansing enema is prepared by dissolving bisacodyl tannex equivalent to 1.5 mg of bisacodyl and 2.5 g of tannic acid (one packet of the commercially available bisacodyl tannex product) in 1 liter of lukewarm water. When used as a radiopaque enema adjuvant, bisacodyl tannex equivalent to 1.5-3 mg of bisacodyl (1-2 packets of the commercially available product) is dissolved in 1 liter of barium sulfate suspension. The concentration of bisacodyl tannex should not exceed 0.5% (2 packets of the commercially available product per liter). The cleansing enema containing bisacodyl tannex may be administered on the day of the examination. If necessary, the cleansing enema may be repeated, but the total dosage for one entire colonic examination (including the cleansing enema) should not exceed 4.5 mg of bisacodyl and 7.5 g of tannic acid (3 packets of the commercially available preparation), and no more than 6 mg of bisacodyl and 10 g of tannic acid (4 packets of the commercially available product) should be administered during a 72-hour period.

Diphenylmethane laxatives share the toxic potentials of other stimulant laxatives, and the usual precautions of such laxative therapy should be observed. (See Cautions in the Cathartics and Laxatives General Statement 56:12.)

Since current evidence indicates that phenolphthalein is potentially genotoxic and carcinogenic in humans (see Cautions: Stimulant Laxatives, in the Cathartics and Laxatives General Statement 56:12), all preparations containing phenolphthalein for self-medication (over-the-counter [OTC] use) are no longer generally recognized as safe and effective.100 Therefore, US manufacturers have reformulated phenolphthalein-containing preparations to include other laxatives.100

Pharmacology

Bisacodyl shares the actions of the stimulant laxatives. The tannic acid present in the bisacodyl tannex complex precipitates protein and its astringent effect decreases mucus secretion in the large intestine. Tannic acid also reportedly facilitates adherence of contrast media to mucous membranes, but this is disputed by some clinicians. Although some reports state that tannic acid increases evacuation of the colon, others state that its astringent effect produces constipation.

Pharmacokinetics

Absorption of bisacodyl or bisacodyl tannex is minimal following oral or rectal administration. Any bisacodyl that is absorbed is metabolized in the liver and excreted in the urine and/or distributed into milk. Tannic acid may be absorbed following rectal administration; however, very little is known about the degree of absorption and circumstances under which absorption may occur with bisacodyl tannex.

Following oral administration of therapeutic dosages of diphenylmethane derivatives, evacuation is produced in 6-8 hours. Rectally administered bisacodyl or bisacodyl tannex produces evacuation of the colon within 15 minutes to 1 hour.

Chemistry and Stability

Chemistry

Bisacodyl and Bisacodyl Tannex

Bisacodyl and bisacodyl tannex are diphenylmethane derivative stimulant laxatives.

Bisacodyl occurs as a white to off-white, crystalline powder and is practically insoluble in water and sparingly soluble in alcohol. Bisacodyl tannex is a complex of bisacodyl and tannic acid which occurs as a light tan, microcrystalline powder and is very soluble in water and in alcohol.

Stability

Bisacodyl and Bisacodyl Tannex

Bisacodyl rectal suppositories and enteric-coated tablets should be stored at less than 30°C. Reconstituted solutions of bisacodyl tannex should be used immediately following preparation.

Additional Information

For further information on pharmacology, uses, cautions, drug interactions, laboratory test interferences, and dosage and administration of the diphenylmethane laxatives, see the Cathartics and Laxatives General Statement 56:12.

Only references cited for selected revisions after 1984 are available electronically.

100. Food and Drug Administration. Laxative drug products for over-the-counter human use. 21 CFR Part 310. Final rule. [Docket No. 78N-036L.] Fed Regist . 1999; 64:4535-40.