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Oral use of injectable drugs: uncertain efficacy and known risks

Healthcare professionals sometimes administer an injectable form of a drug by mouth when no suitable oral liquid form exists. It is a risky and often ineffective practice. There is an old saying in France that if a substance can be injected it can also be swallowed, but despite its appeal, this idea is misleading and dangerous.

It is sometimes impossible or too dangerous to take a dry oral form of a drug in certain situations, for example if the patient is a young child, receiving palliative care or has a swallowing disorder. If the drug is not marketed in an oral liquid form, it is tempting to administer an injectable form orally.

In France, as of 2022, besides the rare substances marketed for both oral and injectable use, such as vitamin K1 and vitamin B12, there are no explicit official warnings about the oral administration of injectable forms.

There are many uncertainties around this practice. The drug is usually less effective due to degradation in the gastrointestinal tract, which may be extensive. Some harmful effects have been established, such as irritation of the gastrointestinal mucosa, gastrointestinal disorders and accidental aspiration.

Errors and serious adverse effects can occur when healthcare professionals are unaccustomed to giving an injectable form orally. It is often preferable to use a different pharmaceutical form or a different drug that is suited to oral use.

When considering administering an injectable drug by mouth, it is prudent to reflect on whether it is the best choice of treatment, to make sure there is no alternative and, if there is not, to search for information about its potential toxicity and how the oral route might reduce its efficacy. When oral administration of an injectable form of a drug is the chosen course of action, it is useful to document the reasons behind this often-difficult decision in the patient’s records, to inform other healthcare professionals.

©Prescrire 1 October 2022

Source: "Oral administration of an injectable form: a little-studied practice with known risks" Prescrire International 2022; 31 (241): 245. Subscribers only.

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