Omidon (Domperidone): A Motility Stimulant and Dopamine Antagonist

Omidon contains Domperidone, a dopamine antagonist that primarily blocks dopamine receptors in the Chemoreceptor Trigger Zone (CTZ) and the stomach. It is classified as a motility stimulant, motility stimulant/dopamine antagonist, and prokinetic drug, used to manage various gastrointestinal symptoms and certain drug-induced side effects.

How Omidon Works (Pharmacology)

Domperidone's actions are based on its dopamine receptor blocking effects:

• Gastroprokinetic Action: It primarily blocks dopamine receptors in the gastrointestinal tract, which influence motility. This restores normal motility and tone of the upper GI tract, facilitates gastric emptying, enhances antral and duodenal peristalsis, and regulates pyloric contraction.
• Anti-emetic Action: By blocking dopamine receptors in the CTZ (located outside the blood-brain barrier), it effectively suppresses nausea and vomiting.
• Limited CNS Effects: Due to its weak penetration across the blood-brain barrier, Domperidone has almost no effect on dopaminergic receptors in the brain, thus minimizing psychotropic and neurological side effects.
• Esophageal Effects: It increases esophageal peristalsis and lower esophageal sphincter pressure, helping to prevent regurgitation of gastric content.

Key Indications & Benefits

Omidon is indicated for:

• Dyspeptic symptom complex, often associated with delayed gastric emptying, gastroesophageal reflux, and esophagitis. Symptoms include:
  • Epigastric sense of fullness, abdominal distension, upper abdominal pain
  • Eructation (belching), flatulence, early satiety (feeling full quickly)
  • Nausea and vomiting
  • Heartburn with or without regurgitation of gastric contents
  • Non-ulcer dyspepsia
• Acute nausea and vomiting of functional, organic, infectious, dietetic origin, or induced by radiotherapy, drug therapy, or migraine.
• Parkinson's disease: For dopamine-agonist induced nausea and vomiting.
• Radiological studies: Speeding barium transit in follow-through radiological studies.

Dosage & Administration

Domperidone should be taken 15-30 minutes before meals and, if necessary, before retiring. Always consult a registered physician for medication use.

Oral Dose (Tablets/Suspension/Paediatric Drops):

• Adults: 10-20 mg (1-2 tablet or 10-20 ml suspension) every 6-8 hours daily. Maximum dose: 80 mg daily.
• Children: 2-4 ml suspension/10 kg body weight or 0.4-0.8 ml paediatric drops/10 kg body weight, every 6-8 hours daily.

Specific conditions:

• In dyspeptic symptom:
  • Adults: 10-20 mg (1-2 tablet or 10-20 ml suspension), every 6-8 hours daily.
  • Children: 0.2-0.4 mg/kg (2-4 ml suspension/10 kg or 0.4-0.8 ml paediatric drops/10 kg) body weight, every 6-8 hours daily.
• In acute and sub-acute conditions (mainly acute nausea and vomiting):
  • Adults: 20 mg (2 tablets or 20 ml suspension), every 6-8 hours daily.
  • Children: 0.2-0.4 mg/kg (2-4 ml suspension/10 kg or 0.4-0.8 ml paediatric drops/10 kg) body weight, every 6-8 hours daily. (Maximum treatment period for acute nausea and vomiting is 12 weeks).

By rectum in suppositories:

• Adults (including elderly): 30-60 mg every 4-8 hours.
• Children: Maximum daily dose rectally is 30 mg for those weighing 10 to 25 kg. The dose may be divided throughout the day if necessary.

Maximum treatment period (for most indications): 12 weeks.

Important Considerations & Warnings

It is crucial to discuss your full medical history with your doctor before taking Omidon.

Contraindications:

• Known hypersensitivity to Domperidone.
• Neonates.
• Whenever gastrointestinal stimulation might be dangerous (e.g., gastrointestinal hemorrhage, mechanical obstruction, or perforation).
• Patients with prolactin-releasing pituitary tumor (prolactinoma).

Side Effects:

• Rare: Transient intestinal cramps.
• Extrapyramidal phenomena: Rare in young children, exceptional in adults; reverse spontaneously upon stopping treatment.
• Hyperprolactinemia: May induce an increase in plasma prolactin levels, which in rare cases can lead to neuroendocrinological phenomena such as galactorrhea (milk discharge) and gynecomastia (breast enlargement in males).
• Neurological side-effects: Possible in infants (under 1 year) or in cases of impaired blood-brain barrier.
• Rare allergic reactions: Rash and urticaria.

Pregnancy & Lactation:

• Pregnancy: Animal studies did not show teratogenic effects. However, Domperidone should only be used during the first trimester of pregnancy if clearly justified by anticipated therapeutic benefit. No evidence of increased risk of malformations in humans so far.
• Lactation: The drug is excreted in breast milk. Domperidone concentrations in breast milk are 4 times lower than plasma concentrations. It is not known whether this is harmful to the newborn. Therefore, nursing is not recommended for mothers taking domperidone, unless the expected benefits outweigh any potential risk.
• Effects on ability to drive and use machines: Domperidone does not affect mental alertness.

Precautions & Warnings:

• Children: Use with absolute caution in children due to increased risk of extrapyramidal reactions in young children because of an incompletely developed blood-brain barrier.
• Hepatic Impairment: Use with caution in patients with hepatic impairment, as domperidone is highly metabolized in the liver.
• Renal Impairment: In severe renal insufficiency (serum creatinine >6 mg/100ml), the elimination half-life is prolonged. While a single acute dose may not need adjustment, for repeated administration, dosing frequency should be reduced (once or twice daily, depending on severity) and the dose may need to be reduced. Patients on prolonged therapy should be reviewed regularly.

Drug Interactions:

• Anticholinergic drugs: May antagonize the antidyspeptic effect of domperidone.
• Antacids and antisecretory drugs: Should not be given simultaneously with domperidone as they lower its oral bioavailability.
• CYP3A4 inhibitors (e.g., azole antifungals, macrolide antibiotics, HIV protease inhibitors, nefazodone): Concomitant use may result in increased plasma levels of domperidone.
• Orally administered drugs (especially sustained release or enteric coated formulations): Theoretically, domperidone's gastro-kinetic effects could influence their absorption, but it did not influence blood levels of digoxin or paracetamol in stabilized patients.
• Neuroleptics: Domperidone does not potentiate their action.
• Dopaminergic agonists (bromocriptine, L-dopa): Domperidone suppresses their unwanted peripheral effects (digestive disorders, nausea, vomiting) without counteracting their central properties.

Overdose Effects

• Symptoms of overdosage: Drowsiness, disorientation, and extrapyramidal reactions (especially in children).
• Management:
  • Administration of activated charcoal and close observation.
  • Anticholinergic, antiparkinson drugs or antihistamines with anticholinergic properties may be helpful in controlling extrapyramidal reactions.

Storage Conditions

Store below 30°C, protected from light & moisture. Keep out of children's reach.