What we learned about excipients in animal medicines
Excipients are the ingredients in a medicine formulation other than the therapeutic substance(s). Practically all medicines contain at least one excipient. They are incorporated in medicines for various reasons, including to help in the manufacturing process, to optimise absorption of the therapeutic ingredient, to maintain stability (and therefore extend shelf life) of the product, and to enhance palatability. They used to be called inactive ingredients but that is not an accurate description, not least because they can sometimes caused unwanted effects in the treated animal and in humans who handle medicines. Here’s what we learned about excipients when putting together Veterinary Prescriber’s learning module, Understanding excipients:
Excipients in licensed veterinary and human medicines are highly regulated. Excipient content in a licensed medicine cannot be changed without the permission of the regulator.
A list of 18 substances used as excipients has been identified by researchers as “excipients of concern” because they have been reported in the published literature to have caused adverse effects in animals.
However, inclusion in the list does not mean an excipient should never be in an animal medicine. Indeed many of the 18 are included in licensed veterinary medicines.
There are occasions when it is necessary to find out what excipients are in a product:
when the animal being treated has a known allergy or intolerance
when a human who may handle the product has a known allergy
when doing an exclusion trial in an animal with allergy or intolerance
when prescribing a human medicine or unfamiliar or unlicensed product
when investigating a suspected adverse reaction.
In human medicines, certain excipients that are known allergens (e.g nut oils, sesame oil) must be declared in the package information. This requirement appears not to extend to veterinary medicines. We found that sesame oil is an ingredient in some veterinary products and while its presence was declared in the products’ summaries of product characteristics (the official regulatory data sheet), it was not always declared in the package leaflet, which should be available with the product at the time of use. We think known human allergens should be declared in the packaging information of veterinary medicines. This is important for the safety of veterinary practice employees and clients who administer medicines.
There is no requirement for the manufacturers of unlicensed compounded medicines (also known as ‘specials’) to declare excipient content. We think these companies should routinely declare the excipients in their products.
Having a good understanding of the potential adverse effects of excipients and circumstances in which they might occur enables confident prescribing decisions. Veterinary Prescriber’s learning module “Understanding excipients” discusses each of the 18 substances explaining when and how they might be problematic and describes how to be sure of finding out what excipients are in licensed veterinary and human medicines. Log in or subscribe now to see the full CPD module (read and/or listen), together with reflective exercises, MCQs and certificate.