Rx Update: May 2004
Joan Murhammer, R.Ph., Mary Ross, R.Ph., M.B.A., Kevin Bebout,
R.Ph.
Peer Review Status: Internally Reviewed
Carbapenem - Cross Sensitivity with other Beta - Lactams
Meropenem and imipenem-cilastatin (along with the non-formulary agent ertapenem) are carbapenem antibiotics, which belong to the beta-lactam class of antibiotics. They work by inhibiting cell wall synthesis of gram positive and negative organisms through binding to penicillin-binding proteins. All of the carbapenems are contraindicated in patients with known hypersensitivity or anaphylactic reactions to other beta-lactams, such as penicillins and cephalosporins. Also, patients with a known carbapenem hypersensitivity are not candidates for other beta-lactam therapy. While the incidence of cross sensitivity between meropenem or ertapenem and beta-lactam antibiotics is unknown, the cross sensitivity that occurs with imipenem-cilastatin and beta-lactam drugs approaches 50% in patients who have had a hypersensitivity reaction to penicillin and positive penicillin skin testing. Alternative agents should be considered if a patient has had a true hypersensitivity reaction.
If clinically indicated, the carbapenems should be used with extreme caution and carefully monitored in patients with a previously known hypersensitivity to penicillins and / or cephalosporins.
Sorbitol - Induced Diarrhea
Diarrhea is a common problem in hospitalized patients, especially in those that receive tube feedings or liquid medications. The tube feeding can cause diarrhea because of hypertonic formulations, enteral stimulation after prolonged gut stasis, microbial contamination of the formula, cold temperature of the formula, and rarely, lactose content. Another possible cause of diarrhea in these patients is sorbitol. Sorbitol is a poorly absorbed polyalcohol sugar used therapeutically as a laxative. It is also commonly used as a sweetening agent in many liquid medications.
The cathartic dose of sorbitol is 20 to 50 grams. As little as 10 grams of sorbitol has been shown to cause cramps and diarrhea in patients. Because sorbitol is classified as an inert ingredient, manufacturers do not routinely list the amount of sorbitol contained in their formulations. While many preparations contain only a small amount of sorbitol, its effects are cumulative based on the total daily dose. Patients receiving multiple drugs containing sorbitol are more likely to experience adverse reactions. Sudden-onset diarrhea due to sorbitol or hyperosmolar medications is not a reason to discontinue tube feedings, but may suggest the need for changes in medications or administration routes.
Some formulations of liquid medications contain over 10 grams of sorbitol in a daily dose. Examples of commonly used medications that may contain large amounts of sorbitol include acetaminophen, amantadine, cimetidine, dexamethasone, furosemide, lithium, metoclopramide, propranolol, and theophylline.
If you suspect that a patient may be experiencing diarrhea due to excessive sorbitol intake, contact the Drug Information Center for further information regarding the formulations of the medications he/she is receiving.
Adapted from: Hosp Pharm. 1993; 28:741-4, 755.