Drug-Induced Diarrhoea: A Far From Rare Adverse Event

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Diagnosis a Process of Elimination

When drug-induced diarrhoea does occur, an impor-tant step towards the diagnosis of the condition involves taking the patient's medical history; in particular, a careful drug history must be taken.[1] In the clinical examination, symptoms such as fever, rectal emission of blood and mucus, dehydration and bodyweight loss indicate a severe condition. Establishing a possible relationship between a drug and a case of diarrhoea or colitis can be difficult when the time elapsed between the start of the drug and the onset of symptoms is long, sometimes up to several months or years, and the diagnosis can be unrecognised.[6]

Acute benign diarrhoea is often self-limited and the diagnosis can usually be made by history and physical examination.[7]

Usually, in chronic diarrhoea, an extensive and long work-up is performed.[1] It is helpful to consider a list of the most likely diagnostic possibilities to avoid multiple tests.[8] However, some tests should be carried out (e.g. blood count, stool culture), unless a diagnosis is apparent. In clinical practice, endoscopy and biopsy are only performed in patients who have chronic and/or severe diarrhoea.

The diagnosis of drug-induced diarrhoea often relies on the absence of other obvious aetiologies established by simple tests, on the rapid disappearance of the diarrhoea after withdrawal of the suspected drug, and sometimes on a positive rechallenge.

Occasionally, the diagnostic procedure requires specialised tests, and a trial therapy such as metronidazole or a lactose-free diet is sometimes proposed.[9] After a complete and negative evaluation, almost half of the cases of chronic diarrhoea are likely to be related to surreptitious laxative abuse.[1]


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