Clinical Q & A: Can lactose-intolerant patients use lactose-containing medications?

Submitted on Nov. 19, 2007

Q. Over the past several months, the International Drug Information Center of the Arnold & Marie Schwartz College of Pharmacy and Health Sciences, Long Island University, Brooklyn, N.Y., has received a number of inquiries concerning intolerabilities to certain medications in patients who are known to be lactose intolerant. Although gastrointestinal complaints are reported with many, if not all, oral medications, we reviewed the literature to determine whether the intolerability experienced by some patients may be due to the lactose content of drug products.

Lactose, also known as milk sugar, is a disaccharide found in many food products, particularly in dairy foods. Lactose intolerance affects between 30 million and 50 million Americans and is more common in certain ethnic groups, such as American Indians, Asians, and African Americans. The elderly and patients with HIV are two subgroups that have been shown to be especially sensitive to lactose. Gender does not seem to play a role in this condition.

Lactose is commonly used as an inactive ingredient, primarily as a filler in the manufacture of tablets and capsules. Case reports describing lactose-intolerant patients experiencing adverse reactions to the lactose content of medications have been published over the past 30 years. The symptoms experienced were ameliorated to some degree with supplemental lactase enzymes and resolved when the patients discontinued the offending medications. Notably, the majority of patients in these cases were extremely sensitive to lactose-containing products.

While it has been reported that the amount of ingested lactose necessary to produce adverse effects varies, it generally ranges between 12 and 18 gm of lactose (approximately 8 to 12 oz of milk). Considering the fact that most oral medications contain quantities of lactose that are far less than 12 to 18 gm, one would theoretically not expect such small quantities to result in gastrointestinal symptoms. Nonetheless, the cases reported in the literature suggest that certain individuals may react to very small quantities of lactose.

In summary, it appears that most patients who are lactose intolerant can probably tolerate the quantities of lactose that are incorporated into oral drug products. However, one must keep in mind that certain highly sensitive patients may present with gastrointestinal complaints even after ingesting the small quantities of lactose found in oral medications. Furthermore, patients ingesting multiple lactose-containing medications may experience symptoms of lactose intolerance due to the cumulative lactose intake from these medications. Patients who experience adverse gastrointestinal effects after ingesting lactose-containing drug products may opt to use lactase enzyme supplementation.

If symptoms persist despite the use of lactase supplements, patients may need to seek an alternative formulation of the same drug or an alternative drug that does not contain lactose. While published lists of lactose-free products exist, one must always refer to the official product labeling to establish lactose content, since these lists may not be comprehensive and/or may not be up to date.
References available upon request

THE AUTHORS of this article are Joseph P. Nathan, M.S., Pharm.D., Assistant Professor of Pharmacy Practice; Sara Schilit, Pharm.D., Drug Information Specialist and Adjunct Assistant Professor of Pharmacy Practice; and Jack M. Rosenberg, Pharm.D., Ph.D., Professor of Pharmacology and Pharmacy Practice, Director, International Drug Information Center, Arnold & Marie Schwartz College of Pharmacy & Health Sciences, Long Island University.