Inactive Medicine Ingredients May Be Actively Harmful, Study Warns

The inactive ingredients found in medication, including things like fillers and dyes, may not be as inactive as they seem, according to a new study. Some of these compounds may have an active effect on the body and, in some cases, may be harmful, the research suggests. Though inactive ingredients are often an important part of various drugs, the study suggests that additional research is necessary to determine their individual effects.

Medication is often composed of two types of ingredients: the active compound and excipients, which are inactive compounds used for things like delivering the active ingredients. In most cases, tablets and certain other types of medication contain more excipients than active ingredients, though that doesn't mean they aren't a necessary part of the overall drug delivery.

The new study out of the American Association for the Advancement of Science warns that while most excipients are indeed inactive, some may have an impact on the parts of the body targeted by active ingredients, including things like receptors and enzymes.

The inactive ingredients are studied on animals for potential toxicity, but the new study warns that there isn't much research on whether these compounds also impact the 'medically relevant molecular targets.' As part of the research, it was found that 38 approved inactive ingredients have 134 effects on molecular targets that were previously unknown.

Of particular relevance is that a minority of excipients may have a harmful effect, with the study noting that:

...several excipients exhibit evidence predictive of tissue-level toxicity in cellular models. While most of these are suspected not to reach dangerous exposure levels, the results suggest that two – thimerosal and cetylpyridinium – are capable of reaching in vivo concentrations, that overlap their in vitro binding activity to the dopamine receptor D3.

Ultimately, the study found that additional research into the potential impact of these active ingredients — toxicity aside — is necessary to determine whether some inactive ingredients may have their own direct effects on the body.