Adult: Available preparations:
Aluminium hydroxide 200 mg and magnesium hydroxide 200 mg per 5 mL susp
Aluminium hydroxide 220 mg and magnesium hydroxide 195 mg per 5 mL susp
Aluminium hydroxide 175 mg and magnesium hydroxide 200 mg per 5 mL susp
10-20 mL 4 times daily, given 20 minutes to 1 hour after meals and at bedtime or as required. Max: 80 mL per 24 hours.
Aluminium hydroxide 160 mg and magnesium hydroxide 105 mg chewable tablet
Chew 2-4 tab 4 times a day or as required. Max: 16 tab per 24 hours. Child: ≥12 years Same as adult dose.
Contraindications
Severe abdominal pain and/or possibility of bowel obstruction. Severely debilitated patients. Renal failure.
Special Precautions
Patient with porphyria (and undergoing haemodialysis), diarrhoea or constipation. Renal impairment. Pregnancy and lactation.
Adverse Reactions
Significant: Hypophosphataemia (prolonged use), diarrhoea or constipation. Gastrointestinal disorders: Abdominal pain. Injury, poisoning and procedural complications: Hyperaluminaemia. Metabolism and nutrition disorders: Hypermagnesaemia (prolonged use).
Overdosage
Symptoms: Abdominal pain, diarrhoea, vomiting. Large doses may aggravate intestinal obstruction and ileus in patients at risk. Management: Correct fluid deficiency if necessary. Acute overdose may be treated by administration of calcium gluconate IV, rehydration, and forced diuresis.
Drug Interactions
Interferes with the absorption of ciprofloxacin, chloroquine, hydroxychloroquine, chlorpromazine, cefdinir, cefpodoxime, ketoconazole, levothyroxine, rifampicin, rosuvastatin, tetracyclines, vitamins. May reduce the effect of polystyrene sulphonate. Decreased serum concentration of velpatasvir. Increased absorption with citrate-containing preparations. May decrease absorption of Fe salts.
Magnesium hydroxide: Increases the excretion of salicylates.
Action
Description: Mechanism of Action: Aluminium hydroxide is a slow-acting antacid that binds phosphate in the gastrointestinal tract to form insoluble complexes and reduces phosphate absorption. It also acts as an astringent and may cause diarrhoea.
Magnesium hydroxide is a fast-acting antacid which counteracts the constipating effect of aluminium hydroxide. Pharmacokinetics: Metabolism: Aluminium hydroxide: Slowly converted to aluminium chloride in the stomach. Excretion: Via urine.
Chemical Structure
Aluminium hydroxide Source: National Center for Biotechnology Information. PubChem Database. Aluminum hydroxide, CID=10176082, https://pubchem.ncbi.nlm.nih.gov/compound/Aluminum-hydroxide (accessed on Jan. 20, 2020)
Magnesium hydroxide Source: National Center for Biotechnology Information. PubChem Database. Milk of magnesia, CID=73981, https://pubchem.ncbi.nlm.nih.gov/compound/Milk-of-magnesia (accessed on Jan. 20, 2020)
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