Acute diarrhoea management in pharmacy: rehydration & loperamide

Acute diarrhoea in the community pharmacy is one of the most frequent consultation reasons, where pharmaceutical advice is key to preventing severe complications such as dehydration. Knowing the evidence-based action algorithm allows us to distinguish between a self-limiting condition and a pathology that requires urgent referral to the prescriber.

Pathophysiology and treatment objectives at the counter

Acute diarrhoea is defined as a decrease in stool consistency (liquid or soft) and/or an increase in bowel movement frequency (>3 per day) of less than 14 days' evolution, according to clinical guidelines. In most cases of infectious etiology (viral or mild bacterial), the main goal is not to stop the diarrhoea immediately, but to prevent haemodynamic collapse through adequate hydroelectrolytic replacement.

From comprehensive pharmacy care, the pharmacist must evaluate the patient's general state, ruling out signs of systemic compromise. Early intervention drastically reduces unnecessary emergency visits and optimises health resource utilisation.

Oral rehydration: the cornerstone of treatment

Oral rehydration salts (ORS) recommended by the World Health Organization (WHO) and endorsed by the Spanish agency AEMPS (check your own national regulator for regulatory details) are the first-line treatment. Unlike sports isotonic drinks or commercial juices, ORS possess a specific osmolarity that optimises sodium-glucose cotransport at the intestinal level, ensuring water absorption.

The patient should be advised to start drinking in small sips after each diarrhoeal stool. To delve deeper into interactions or supplement associations during the process, you can consult the supplement and medication guide, useful to avoid interferences with the dietary regimen.

The role of loperamide and antisecretory agents

Loperamide is an opioid agonist that decreases intestinal motility and acts as an antisecretory agent. It is indicated as symptomatic treatment in adults with uncomplicated acute diarrhoea, but it should never be used empirically if there is high fever (>38.5 ºC) or suspected dysenteric diarrhoea (stools with blood or mucus), as it may delay pathogen elimination and worsen the clinical picture (risk of toxic megacolon).

If the patient has doubts about their usual medication or drug interactions derived from diarrhoea, it is recommended to use the drug interaction checker to ensure the safety of the current treatment.

Medical referral criteria and red flags

The pharmacist must remember that the final diagnostic decision and the prescription of empirical antibiotic therapy — in confirmed bacterial cases — rest exclusively with the physician. Patients presenting red flags such as severe dehydration, persistent fever superior to 48 hours, intense non-colicky abdominal pain, stools with blood or mucus, or polymedicated patients at risk of acute renal failure must be referred immediately.

To complement pharmaceutical advice in special populations or in case of doubts about the safety of concomitant drugs, you can review the official vademecum and technical datasheets.