Medications in the lactose intolerant adult: Lactose is the carbohydrate naturally found in all kinds of milk, including human milk. It can also be used as an ingredient in some foods and is commonly used as a filler or excipient in pharmaceutical preparations (both tablets and capsules) including prescription, over the counter and complementary medicines. Lactose can also be used in dry-powder inhalations and rarely in liquid preparations. Approximately one in five prescription products contain lactose.
Lactose intolerance can occur when person has insufficient lactase, resulting in the inability to break down lactose and causing maldigestion that leads to undigested lactose passing through to the colon. In the lower bowel natural bacteria ferment the lactose, producing acid and gas which may cause symptoms of lactose intolerance (including abdominal pain, bloating and diarrhoea). Deficiency of lactase varies with race and increases with age. Nutrition Australia suggest that most people with lactose maldigestion do not need to eliminate lactose from their diet completely and the majority of people with low lactase can consume at least one cup of milk (about 12 grams of lactose) per day.
A randomised double-blind controlled trial comparing the effect of 400 mg of lactose or placebo on patients with proven lactose intolerance showed no difference (in either symptoms or breath H2 excretion test), leading the authors to suggest that lactase deficiency should not be considered a contraindication for most medicines. However there have been isolated reports in the literature of individuals who have developed gastrointestinal symptoms with lactose doses of 100 – 200 mg.
The lactose content of most medications is generally small. One study analysed the lactose content of many commonly used gastrointestinal medications, with most preparations containing less than 100mg of lactose per tablet. Even with preparations containing higher lactose content, the total daily lactose is small: for example, one brand of loperamide contains 125 mg lactose/tablet and allowing for a dose of eight tablets per day to treat diarrhoea, this would result in exposure to 1000 mg of lactose per day.
The presence of lactose (though not the amount of lactose) found in individual medication products is usually indicated in the Product Information, but at times it can be difficult to determine the exact amount of lactose per tablet.
It is common to find lactose maldigesters who believe that the ingestion of a minimal amount of lactose will result in gastrointestinal symptoms, but in the vast majority of cases the patient can be reassured this is not the case.
Consideration may need to be made for patients with severe lactose intolerance or on multiple medications where total lactose content may be higher. In many cases (but not all) there may be an alternative brand that does not contain lactose. Even so, there may be clinical issues that require consideration: for instance there is no lactose-free combined oral contraceptive product currently available in Australia.
RGH Pharmacy E Bulletin Volume 46 (10): June 25, 2012
Your Accredited Pharmacist: Susan Gao
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