Metoclopramide can cause dystonia, a movement disorder characterized by involuntary muscle contractions, through its effects on dopamine receptors in the brain.

Mechanism:

1. Dopamine Receptor Blockade: Metoclopramide is a dopamine D2 receptor antagonist. It blocks dopamine receptors in the basal ganglia, particularly in the nigrostriatal pathway, which regulates motor control.
2. Disruption of Dopamine-Acetylcholine Balance: Dopamine normally inhibits acetylcholine release in the basal ganglia. By blocking dopamine receptors, metoclopramide increases acetylcholine activity, leading to an imbalance that can trigger abnormal muscle contractions.
3. Extrapyramidal Symptoms (EPS): This dopamine-acetylcholine imbalance in the basal ganglia results in extrapyramidal symptoms, including acute dystonia (sustained muscle spasms, often in the neck, face, or limbs).

Risk Factors:

• Higher doses or prolonged use.
• Younger patients (especially children and adolescents).
• Rapid dose escalation or intravenous administration.
• Individual susceptibility (e.g., genetic predisposition or underlying neurological conditions).

Clinical Features:

• Acute dystonic reactions typically occur within hours to days of starting metoclopramide.
• Symptoms include oculogyric crisis (eyes rolling upward), torticollis (neck twisting), or limb dystonia.

Management:

• Discontinue metoclopramide.
• Administer anticholinergics (e.g., benztropine, diphenhydramine) or benzodiazepines to relieve symptoms.
• Monitor for recurrence and avoid re-administration.

This side effect is more common with metoclopramide than with other prokinetic drugs due to its strong central dopamine antagonism.

Disclaimer: owerl is not a doctor; please consult one. Don’t share information that can identify you.