Don-A (Domperidone): A Motility Stimulant and Dopamine Antagonist

Don-A contains Domperidone, a dopamine antagonist that acts as a motility stimulant and prokinetic drug. It is primarily used to relieve symptoms associated with delayed gastric emptying and to control nausea and vomiting.

How Don-A Works (Pharmacology)

Domperidone primarily works by blocking dopamine receptors located in the Chemoreceptor Trigger Zone (CTZ) and the stomach.

• Gastroprokinetic Action: Its prokinetic effect is due to blocking dopamine receptors in the gastrointestinal tract, which influences motility. This action 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, it 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, minimizing psychotropic and neurological side effects.
• Esophageal Effects: It also increases esophageal peristalsis and lower esophageal sphincter pressure, which helps prevent the regurgitation of stomach contents.

Key Indications & Benefits

Don-A is indicated for:

• Dyspeptic symptom complex often associated with delayed gastric emptying, gastroesophageal reflux, and esophagitis, including:
  • Epigastric fullness, abdominal distension, upper abdominal pain
  • Eructation (belching), flatulence, early satiety
  • Nausea and vomiting
  • Heartburn with or without regurgitation of gastric contents
  • Non-ulcer dyspepsia
• Acute nausea and vomiting of functional, organic, infectious, or 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:

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

Specific Indications:

• In dyspeptic symptoms:
  • 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 pediatric 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 pediatric drops/10 kg) body weight, every 6-8 hours daily.
  • Maximum period of treatment for acute nausea and vomiting is 12 weeks.

Rectal (Suppositories):

• Adults (including elderly): 30-60 mg every 4-8 hours.
• Children: Maximum daily rectal dose is 30 mg for those weighing 10 to 25 kg. The dose may be divided throughout the day if necessary.
• The maximum period of treatment is 12 weeks.

Important Considerations & Warnings

It is crucial to discuss your full medical history with your doctor before taking Don-A.

Contraindications:

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

Side Effects:

• Side effects are rare.
• Occasionally: Transient intestinal cramps.
• Rare: Extrapyramidal phenomena (more common in young children, exceptional in adults; reverse spontaneously upon stopping treatment).
• Hyperprolactinemia: Domperidone may increase plasma prolactin levels, which can rarely lead to neuroendocrinological phenomena such as galactorrhea (milk discharge) and gynecomastia (breast enlargement in males).
• Allergic reactions: Rare reports of rash and urticaria.
• Neurological side effects in infants: Cannot be totally excluded if the blood-brain barrier is immature or impaired.

Pregnancy & Lactation:

• Pregnancy: Animal studies did not show teratogenic effects at high doses. However, Domperidone should only be used during the first trimester of pregnancy if justified by the anticipated therapeutic benefit. There's no evidence of increased risk of malformations in humans.
• Lactation: The drug is excreted in breast milk of lactating rats, and human breast milk concentrations are 4 times lower than plasma. It is not known if this is harmful to the newborn. Therefore, nursing is not recommended for mothers taking domperidone, unless benefits outweigh potential risks.

Precautions & Warnings:

• Children: Use with absolute caution in children due to increased risk of extrapyramidal reactions in young children (due to an incompletely developed blood-brain barrier).
• Hepatic Impairment: Use with caution in patients with hepatic impairment, as Domperidone is highly metabolized in the liver.

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: Concomitant use of drugs that significantly inhibit CYP3A4 (the main metabolic pathway for domperidone) may result in increased plasma levels of domperidone. Examples include azole antifungals, macrolide antibiotics, HIV protease inhibitors, nefazodone.
• Drugs with sustained release or enteric-coated formulations: Theoretically, domperidone's prokinetic effects could influence their absorption. However, no influence on blood levels was observed for digoxin or paracetamol in stabilized patients.
• Neuroleptics: Domperidone does not potentiate their action.
• Dopaminergic agonists (bromocriptine, L-dopa): Domperidone suppresses their unwanted peripheral effects (e.g., digestive disorders, nausea, vomiting) without counteracting their central properties.

Overdose Effects

• Symptoms: Drowsiness, disorientation, and extrapyramidal reactions (especially in children).
• Management:
  • Administration of activated charcoal.
  • Close observation of the patient.
  • 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.