Gen Lax Side Effects
Generic Name: bisacodyl
Note: This page contains information about the side effects of bisacodyl. Some of the dosage forms included on this document may not apply to the brand name Gen Lax.
Not all side effects for Gen Lax may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.
For the Consumer
Applies to bisacodyl: oral tablets delayed-release, rectal suppositories, rectal suspension
Side effects include:
Some degree of abdominal discomfort, nausea, cramps, griping, and/or faintness with therapeutic doses.
Diarrhea, GI irritation, and fluid and electrolyte depletion.
Gastric irritation and the possibility of vomiting if enteric coating of tablets is disrupted. (See Advice to Patients.)
Rectal administration of bisacodyl (the active ingredient contained in Gen Lax) suspensions or suppositories may cause irritation and a sensation of burning of the rectal mucosa and mild proctitis.
Hepatotoxicity if sufficient tannic acid is absorbed from bisacodyl tannex.
Risk of electrolyte disturbances with sodium phosphates in kits containing bisacodyl tablets, sodium phosphates oral solution, and bisacodyl suppositories or enemas (Fleet® Prep Kits). (See Fleet® Prep Kits under Cautions.)
For Healthcare Professionals
Applies to bisacodyl: compounding powder, oral delayed release tablet, rectal enema, rectal suppository
Bisacodyl causes acute nonspecific inflammatory injury to the rectal mucosa, which can confound the assessment of patients with suspected inflammatory bowel disease.
The surreptitious abuse of laxatives is a common cause of severe chronic diarrhea. In some cases, the stool contains fecal leukocytes, which, in this case, is indicative of the irritant effect of bisacodyl (the active ingredient contained in Gen Lax) (nonspecific colonic mucosal inflammation), and not necessarily of infection. Surreptitious abuse of laxatives due to bisacodyl can be determined by urinalysis for a metabolite, bisacodyl diphenol. In some cases, stool analysis for bisacodyl could be considered in the diagnostic assessment.
Abdominal cramping has been described as a mild, colicky discomfort. This can be a problem since cramping my indicate not only a side effect of bisacodyl, but underlying gastrointestinal pathology.
Abdominal distension and vomiting are less common gastrointestinal side effects.[Ref]
Gastrointestinal side effects have been reported the most frequently. These have included abdominal cramping, diarrhea, abdominal distention, and vomiting. Severe diarrhea has been reported as a possible result of surreptitious laxative abuse. The sensation of rectal "burning" with administration of bisacodyl enema has been reported.[Ref]
The metabolic consequences of some Fleet bisacodyl (the active ingredient contained in Gen Lax) enema preparation kits that contain monobasic or dibasic sodium phosphate in patients with renal insufficiency can be profound. Due to the sodium and phosphate absorption, severe hypernatremia, hypophosphatemia, and hypocalcemia may occur.[Ref]
Metabolic side effects have included severe hypernatremia, hypophosphatemia, and hypocalcemia. These effects have been reported primarily with Fleet bisacodyl enema preparation kits that contain monobasic or dibasic sodium phosphate and administered to patients with renal insufficiency. Fleet bisacodyl enemas without these ingredients may be used safely in such patients.[Ref]
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2. "Product Information. Dulcolax (bisacodyl)." Ciba Self-Medication Inc, Woodbridge, NJ.
3. Meisel JL, Bergman D, Graney D, Saunders DR, Rubin CE "Human rectal mucosa: proctoscopic and morphological changes caused by laxatives." Gastroenterology 72 (1977): 1274-9
4. Christie D "Drug-associated colitis (reply)." J Pediatr 88 (1976): 705
5. Fonkalsrud EW, Keen J "Hypernatremic dehydration from hypertonic enemas in congenital megacolon." JAMA 199 (1967): 584-6
6. Kacere RD, Srivatsa SS, Tremaine WJ, Ebnet LE, Batts KP "Chronic diarrhea due to surreptitious use of bisacodyl: case reports and methods for detection." Mayo Clin Proc 68 (1993): 355-7
7. Saunders DR, Haggitt RC, Kimmey MB, Silverstein FE "Morphological consequences of bisacodyl on normal human rectal mucosa: effect of a prostaglandin E1 analog on mucosal injury." Gastrointest Endosc 36 (1990): 101-4
8. McConnell TH "Fatal hypocalcemia from phosphate absorption from laxative preparation." JAMA 216 (1971): 147-8
9. Clarkston WK, Smith OJ "The use of GoLYTELY and Dulcolax in combination in outpatient colonoscopy." J Clin Gastroenterol 17 (1993): 146-8
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