22 May 2019

Does it matter that pills contain allergens?

Allergies Clinical

Almost all pills contain at least one inactive ingredient that some people are intolerant or allergic to, a US analysis reveals.

The study, published in Science Translational Medicine, examined the inactive ingredients of around 42,000 oral solid dose medications using The Pillbox database from the National Institutes of Health in the US. It found that the vast majority of pills (92.8%) contained at least one of 38 potential allergens.

The most common allergens were lactose, corn starch, polyethylene glycol, povidone, carboxymethylcellulose, gelatin and food dyes.

Only 28% of drugs had a formulation available without these potential allergens. Even though around two-thirds of the world’s population is lactose intolerant, lactose was found in around 45% of oral drugs.

The inactive ingredients might be problematic for a minority of patients with severe allergies or intolerances, Associate Professor Richard Loh, an allergist and clinical immunologist at Perth Allergy, said.

“Some patients have what we have congenital lactase deficiency, so they are born without any of the enzymes that break down lactose, so even small amounts of lactose in a medication taken three times a day can cause diarrhoea.”

Professor Loh recalls one patient whose diarrhoea improved after switching to an equivalent medication without lactose.

However, for the majority of patients with allergies or intolerances, medications were unlikely to pose a problem because the doses were so small, he said.

More than half of oral medications (55%) contained at least one FODMAP sugar, which are known to cause IBS symptoms in some patients. The main FODMAPs in pills were lactose and mannitol.

People could still maintain a low FODMAP diet if they had less than 1g per serve of lactose and less than 2g per serve of mannitol, said Dr Jane Varney (PhD), a research dietitian at Monash University.

Pills don’t usually contain more than about 770mg of inactive ingredients, according to the study, so people with FODMAP intolerances probably don’t need to find alternative medications.

Most people with lactose intolerance could consume up to 250ml of milk a day, or around 10-12g of lactose, without developing symptoms, Dr Varney said. “It is unlikely that the lactose is a problem in medication.,” she said.

“Some syrups with mannitol can be a problem for children and adults with a sensitive tummy and it is easier to get larger doses in,” she said. “There can also be large amounts of sorbitol in some syrup medications.”

Allergens are not always listed on consumer leaflets inside medication packaging in Australia. 

But the TGA asked pharmaceutical manufacturers to start listing more allergens on packaging in 2016 and will insist on this by 2020.