Can Metoclopramide Cause Diarrhea?
Yes, metoclopramide can cause diarrhea as a documented adverse effect, though it is not among the most common side effects of this medication. 1
Evidence for Gastrointestinal Side Effects
Metoclopramide is known to cause gastrointestinal upset, which can manifest as diarrhea. 2 The 2023 ACC expert consensus specifically lists "headache, abdominal pain, nausea, and diarrhea" among the observed adverse effects of prucalopride (a related prokinetic agent), and notes similar gastrointestinal disturbances across the prokinetic drug class. 1
Historical pharmacology reviews from the early 1980s documented that metoclopramide causes "GI disturbances" as one of its side effects, typically described as mild, transient, and reversible with discontinuation. 3, 4 These gastrointestinal effects may occur in up to 20% of patients. 4
Mechanism and Clinical Context
The diarrhea associated with metoclopramide likely relates to its prokinetic effects on the gastrointestinal tract:
- Metoclopramide enhances gastric emptying and small intestinal transit time through dopamine antagonism and acetylcholine release augmentation 3, 4
- Accelerated intestinal motility can lead to decreased water absorption and looser stools 5
- In diabetic gastroparesis patients, metoclopramide actually improved constipation (patients had more frequent bowel movements), which in some cases could manifest as diarrhea 5
Important Clinical Considerations
The gastrointestinal side effects of metoclopramide are generally less concerning than its neurological risks. 1, 6 The more serious adverse effects that should prompt immediate discontinuation include:
- Extrapyramidal symptoms (dystonia, akathisia, parkinsonism) 1, 6
- Tardive dyskinesia, particularly with use exceeding 12 weeks 1, 6
- QT prolongation 1
If diarrhea develops on metoclopramide, consider:
- Whether the symptom is mild and tolerable versus requiring intervention 3
- Alternative causes of diarrhea (infection, other medications, dietary factors) 1
- The duration of metoclopramide therapy—FDA warnings recommend against use beyond 12 weeks due to tardive dyskinesia risk 1, 6
Risk Factors for Side Effects
Certain patient populations experience more side effects from metoclopramide:
- Females are more prone to side effects (83% vs 64% in males) 7
- Non-diabetic patients experience more adverse effects than diabetics (77% vs 47%) 7
- Elderly patients have increased risk of irreversible tardive dyskinesia 1, 6
- Genetic polymorphisms in CYP2D6, KCNH2, and HTR4 genes are associated with side effect susceptibility 7