1. Clinical Overview
Metoclopramide is a potent antiemetic and prokinetic agent. It is a dopamine D2 receptor antagonist and a mixed 5-HT3 receptor antagonist/5-HT4 receptor agonist. It is widely used in the Indian clinical setting for the management of nausea, vomiting, and gastroparesis. Its prokinetic action accelerates gastric emptying and intestinal transit, making it valuable in diabetic gastroparesis and post-operative ileus.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: 30-60 minutes; Intravenous: 1-3 minutes; Intramuscular: 10-15 minutes. | Oral/IV/IM: 1-2 hours. | Oral: 80% (due to significant first-pass metabolism). |
2. Mechanism of Action
Metoclopramide exerts its antiemetic and prokinetic effects through dual mechanisms. It competitively blocks dopamine D2 receptors in the chemoreceptor trigger zone (CTZ) of the area postrema in the brain, preventing nausea and vomiting. Simultaneously, it acts as an agonist at 5-HT4 receptors in the gastrointestinal tract, enhancing acetylcholine release from myenteric motor neurons, which increases lower esophageal sphincter tone, gastric fundus tone, and antral contractions while relaxing the pylorus and duodenal bulb. It also possesses weak 5-HT3 receptor antagonistic activity.
3. Indications & Uses
- Symptomatic relief of acute and recurrent diabetic gastroparesis
- Prevention of chemotherapy-induced nausea and vomiting (CINV) - delayed phase
- Prevention of post-operative nausea and vomiting (PONV)
- Management of nausea and vomiting associated with migraine (adjunct)
4. Dosage & Administration
Adult Dosage: For gastroparesis: 10 mg orally, 30 minutes before each meal and at bedtime. Max: 40 mg/day. For PONV/CINV: 10-20 mg IM/IV, may repeat every 4-6 hours as needed.
Administration: Oral: Take 30 min before meals and at bedtime. Do not crush or chew sustained-release tablets. IV: Administer as a slow bolus over 1-2 minutes to minimize risk of akathisia. Can be diluted in 50 mL of NS or D5W for infusion over 15-30 minutes. IM: Deep intramuscular injection.
5. Side Effects
Common side effects may include:
- Drowsiness/sedation
- Restlessness (akathisia)
- Diarrhea
- Fatigue
- Headache
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Levodopa, Dopamine Agonists (e.g., Bromocriptine) | Antagonizes therapeutic effect of these drugs in Parkinson's disease. | Major |
| Antipsychotics (e.g., Haloperidol, Risperidone) | Additive risk of extrapyramidal symptoms and neuroleptic malignant syndrome. | Major |
| Alcohol, CNS Depressants (e.g., Benzodiazepines, Opioids) | Additive sedative effects, impaired alertness. | Moderate |
| Serotonergic Drugs (e.g., SSRIs, SNRIs, Tramadol) | Increased risk of serotonin syndrome. | Moderate |
| Digoxin | Metoclopramide may decrease absorption of digoxin by accelerating gastric emptying. | Moderate |
| Cyclosporine | Increased absorption of cyclosporine, risk of toxicity. | Moderate |
| Succinylcholine | Prolonged neuromuscular blockade. | Moderate |
| CYP2D6 Inhibitors (e.g., Fluoxetine, Paroxetine) | May increase metoclopramide levels and toxicity risk. | Moderate |
7. Patient Counselling
- DO take the medicine 30 minutes before meals as directed.
- DO report any involuntary movements of face, tongue, or limbs immediately.
- DO inform your doctor if you are pregnant, planning pregnancy, or breastfeeding.
- DO NOT consume alcohol while on this medication.
- DO NOT drive or operate heavy machinery if you feel drowsy.
- DO NOT take it for longer than prescribed duration, especially not beyond 12 weeks.
- DO NOT stop taking suddenly if used for a long time; consult doctor.
8. Toxicology & Storage
Overdose: CNS effects: Drowsiness, confusion, extrapyramidal reactions (severe dystonia, akathisia), seizures, hallucinations. Cardiovascular: Bradycardia, hypotension, cardiac arrest. In children: Methemoglobinemia (cyanosis).
Storage: Store below 30°C, protected from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack. For injections, use immediately after opening the ampoule/vial.