The dogs blog no 8 - When a patient can't or won’t swallow tablets or capsules

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When a patient can’t or won’t swallow tablets or capsules, if there is no suitable alternative (e.g. a flavoured or liquid formulation), a potential solution is to crush the tablets or open the capsules and mix the fragments or powder from tablets or the contents of capsules with food or a liquid. But it’s important to be aware that doing this can lead to problems. What can go wrong?

Crushing a tablet or opening a capsule changes its pharmaceutical form so the rate and extent to which the active ingredient is absorbed by the body may be altered. In some circumstances this can lead to over- or underdosing.

Drugs with a narrow therapeutic index: overdosing is a risk when the drug has a narrow therapeutic index (i.e. when therapeutically effective plasma concentrations are very close to toxic plasma concentrations). Examples are theophylline and phenobarbital. In such cases, a small difference in plasma concentration can provoke sometimes serious adverse effects.

Modified-release forms: when a modified-release dosage form is crushed or opened, the active ingredient is no longer released and absorbed gradually, resulting in overdose.

Tablets with a gastro-resistant coating: gastro-resistant (or enteric-coated) tablets and capsules containing gastro-resistant granules are designed to release the active ingredient beyond the stomach. The purpose is usually to protect the active ingredient from gastric acid. When the gastroresistant layer is destroyed by crushing, underdosing is possible. 

Other problems

Loss of active ingredient: studies have shown that the dose administered after crushing or cutting a tablet is lower than the dose originally present in the tablet. This is because drug particles are adsorbed onto the walls of the container in which the drug was crushed, and the rougher the walls, the more drug is lost. Mixing the powder from a crushed tablet or the contents of a capsule with food can also reduce the amount of drug absorbed. Variation in the doses administered is more likely to have a clinical impact when the drug has a narrow therapeutic index. 

Drug degradation: some active ingredients are sensitive to light or moisture (e.g. furosemide is light sensitive). Crushing a tablet or opening a capsule that contains a light- or moisture-sensitive active ingredient exposes it to degradation. Cutting a tablet several days in advance can have the same effect. Once the tablet has been crushed or a capsule opened and the medication has been mixed with water, another fluid or food, the patient should take it quickly before the active ingredient degrades.

Exposure from handling: people who crush tablets or open capsules are exposed to the active ingredients they contain. This can lead to contact allergies or more serious problems if the drug is cytotoxic or has teratogenic or fetotoxic effects. It’s important that the people involved in drug preparation or administration are aware of the drug’s nature so that they can avoid handling the drug or take steps to prevent skin contact and inhalation by wearing gloves and face mask.

Another potential solution is to find someone to make a special formulation that the patient can and will take. Look out for our module on specials in the next few months.