The challenges inherent in Excipients

The challenges inherent in Excipients

Have you ever wondered how a cough lozenge dissolves just at the right speed or how some medicines smell and taste so good? We have ‘excipients’ to thank for these useful properties in our medicines. So, what exactly are excipients?

In fact, the total excipient content of a medicine is likely to be much higher than the amount of active drug itself. Excipients are ingredients added to the formula to, say, help dissolve the drug, or make the medication taste sweet, smell nice, or keep its goodness. And so, while some excipients are added to secure the quality of the product, others are added to help make the medicine more acceptable to users or to help the medicine get to the right part of the body. But rather than thinking of excipients as harmless components, some excipients come with their own warnings and cautions. For example, excipients can break down within the final drug formulation, losing their potency and use, and some even have their own effects on the body, causing allergies and other unwanted effects. An added issue is when someone’s beliefs prevents them from taking a medicine with a forbidden excipient. What do we know about problematic excipients?

Actually, scientists now know quite a lot about pharmaceutical excipients and their various properties. 2017 saw the publication of the 8th edition of the Handbook of Pharmaceutical Excipients. This 1000+ page publication brings together detailed information about more than 400 excipients, their different chemical features, as well as their stability and safety. In addition to that, in 2017 the European Medicines Agency published updated guidance to drug manufacturers about which excipients to display on the label of medicines and how to draw attention to their adverse effects on the package leaflets. For example, excipients such as glucose, invert sugar, sucrose are harmful to teeth. The same excipients also need to be used with caution in people with diabetes. And some excipients have a laxative effect and can cause diarrhoea, such as glycerol, mannitol, sorbitol, xylitol.

Another potential problem is when people are allergic to an excipient. For example, a range of colouring agents (e.g. tartrazine, amaranth, cochineal red) when swallowed in a medicine could cause an allergic reaction. Ingredients commonly added to creams and ointments too can be problematic (e.g. chlorocresol, fragrances, lanolin) causing skin irritation or allergic reactions. And because some excipients come from foods these could be problematic for those with foods allergies. For example, some medicines contain peanut oil also known as arachis oil. Others could contain extracts of egg, fish, gelatine, milk, sesame or soy. These are all potential triggers for allergy sufferers. Manufacturers are obliged to highlight the presence of these ingredients and their features clearly in writing to users, on the package labelling or in the information leaflet inserted within the medicine pack. In this way, manufacturers warn users about the potential for problems, at least within the written material that accompanies the medicine. As well as that, guidelines are given to health professionals who administer medicines such as vaccines in cases of allergy. For example, the influenza vaccine (which contains an egg component) should only be given to an individual with a history of egg allergy in a specialist hospital setting, unless an egg free vaccine can be sourced.

But despite scientific advances in discovering the harmful effects of excipients and steps taken to highlight these, people using medicines can still experience problems and confusion when it comes to excipients. Why would that be the case? Well, for one, it is widely accepted that not every patient will read the text that accompanies their medication. This is a problem if the main mode of communicating with patients is assumed to be through written material. And even if patients do read the material, there are some who will not fully understand the information and what to do with it. For example, if a cream for eczema warns about skin irritation, then what does this irritation look and feel like, how many patients are actually likely to experience this, and what should someone do if they do experience it or are unsure? Added to this, not everyone will know beforehand if they are, for example, allergic to an excipient in their medicine. These patients could end up experiencing an allergy quite by accident. And when people do experience symptoms, not everyone will automatically recognise this as an allergic reaction. This is easy to understand. Although some allergic reactions are almost immediate and extreme (e.g. anaphylaxis, severe asthma), some skin reactions don’t happen until 3-10 days or even up to 6 weeks after first contact.

Now consider a different problem where some people’s beliefs prevent them from using a medicine with a prohibited excipient. This is the case with gelatine, which poses a problem for vegans/vegetarians, because they do not consume anything derived from meat: gelatine is made from collagen obtained from the connective tissue of animals. Pork gelatine is also problematic for muslins whose religion prohibits the use of products derived from pigs. Pork gelatine is an excipient in a number of vaccines including the nasal influenza vaccine, vaccines against chickenpox and shingles as well as one brand of the measles, mumps, Rubella (MMR) vaccine. In these instances, therefore, patients need reliable information about safe alternatives. This long list of problems at the patient interface is where the pharmacist comes in.

Pharmacists are trained professionals who bridge the information gap between medicines and patients. Pharmacy degrees in the UK typically take 4 years to complete with a further one year of workplace training before a specialised registration exam. Pharmacists therefore learn extensively about how new drugs are discovered, as well as their formulation into medicines such as tablets, creams and injections. They learn how the different medicines affect the body and how ill bodies handle different medicines. As well as that, pharmacists get to understand the patient perspective, and patient worries and concerns. A mainstay of pharmacist training is about communicating with patients and being able to interpret complex scientific information and to break this information down for patients to understand. This makes pharmacists not only experts in medicines but also people who are best placed to advise patients about the potential for an allergic reaction, what signs and symptoms to looks out for, what to do in case of an allergy, as well as the alternatives to potentially problematic medicines.

And the scope of this work does not stop with medicines. Community pharmacists, for example, are often called upon to help consumers make sense of the excipients in products such as make-up, nutritional supplements and even liquids for vaping devices!

The Reading School of Pharmacy runs a fully accredited 4-year pharmacy degree helping fully equip the next generation of scientists on the high street to answer questions about medicines and their excipients.

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