The most important warning: cardiac (QT-interval) risk

Domperidone's defining safety issue is a dose-related risk of prolonging the QT interval, a measurement of the heart's electrical cycle. In rare cases, significant QT prolongation can lead to a dangerous heart rhythm called torsades de pointes. This risk first became clearly apparent with an intravenous (IV) formulation given at high doses, which was withdrawn from clinical use decades ago. Subsequent reviews by regulators including the European Medicines Agency and the UK's MHRA found that the oral formulation carries a smaller, but still real, version of this same risk, particularly at higher doses, in older patients, and in people with existing heart conditions or certain electrolyte imbalances.

In response, regulators in countries where domperidone is approved introduced lower maximum recommended doses, shorter recommended courses, and clearer contraindications. This is also the central reason the FDA has been unwilling to approve oral domperidone for general use in the United States, and specifically why the agency has warned against unsupervised use for increasing milk supply, which we cover on our Breastfeeding & Milk Supply page.

Common side effects

At approved doses, the side effects most frequently reported in clinical literature include:

Dry mouth
Headache
Mild gastrointestinal discomfort, such as stomach cramps
Skin reactions in a small proportion of users

Because domperidone is a dopamine antagonist, there is also a small associated risk of movement-related side effects, though this is far less prominent than with related drugs that cross the blood-brain barrier more readily.

Who should avoid domperidone

In countries where it is approved, product labeling generally lists the following as contraindications or reasons for extra caution, always to be confirmed with a prescriber:

Known heart rhythm abnormalities, including congenital long QT syndrome
Significant electrolyte imbalances (such as low potassium or magnesium)
Moderate to severe liver impairment
Conditions where increased gut motility could be harmful, such as certain bowel obstructions or active gastrointestinal bleeding
Known hypersensitivity to domperidone or its excipients

Drug interactions to flag with a pharmacist

Domperidone levels in the blood can rise when taken together with medicines that strongly inhibit the liver enzyme CYP3A4, increasing cardiac risk. Categories commonly flagged include certain oral antifungal medications, some antibiotics (notably certain macrolides), and some antiviral medications, along with other drugs independently known to affect the QT interval. A full, current medication and supplement list should always be reviewed by a pharmacist before considering domperidone in any form, and this review should be repeated whenever a new medication is added.

What to do if a serious reaction is suspected

Symptoms such as fainting, a racing or irregular heartbeat, or severe dizziness after taking domperidone warrant prompt medical attention rather than a wait-and-see approach, given the specific cardiac risk described above. Anyone prescribed domperidone should be told by their physician what warning signs to watch for and when to seek care.

Safety note: this page summarizes publicly documented warnings; it is not a complete prescribing reference. Always review the full label and discuss personal risk factors with a licensed physician or pharmacist before taking domperidone in any form.

Domperidone Side Effects & Safety Warnings