Aluminum Hydroxide

Antacid Phosphate Binder

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 30-100 mg/kg/day divided q8-12h (phosphate binder); 10-30 mg/kg q8h (antacid) q8-12h Duration: Long-term as needed
Notes: Titrate dose to maintain serum phosphorus within target range. Administer with meals to maximize phosphate binding.
Cat PO 30-100 mg/kg/day divided q8-12h (phosphate binder); 10-30 mg/kg q8h (antacid) q8-12h Duration: Long-term as needed
Notes: Titrate to effect. Administer with meals. May cause constipation; monitor for fecal impaction.
Horse PO 60-120 g per adult horse q12-24h (antacid) q12-24h Duration: As needed
Notes: Use with caution; may alter gastric pH and affect digestion. Not a primary treatment for gastric ulcers.
Cattle PO 30-60 g per animal q12-24h (antacid) q12-24h Duration: As needed
Notes: Use for rumen acidosis as adjunct; monitor rumen pH.
Small Ruminants PO 10-30 g per animal q12-24h (antacid) q12-24h Duration: As needed
Notes: Limited data; use with caution.
Rabbit PO 30-100 mg/kg/day divided q8-12h (phosphate binder) q8-12h Duration: Long-term as needed
Notes: Monitor for GI stasis; ensure adequate hydration.
Birds PO 10-50 mg/kg q8-12h (antacid) q8-12h Duration: As needed
Notes: Limited data; use with caution.
Reptiles PO 10-50 mg/kg q24h (phosphate binder) q24h Duration: As needed
Notes: Limited data; use with caution.

Clinical Indications & Species Uses

General Indications
  • Hyperphosphatemia in chronic kidney disease
  • Gastric hyperacidity and peptic ulcer disease
  • Esophagitis
Dog (Canine)
  • Adjunct therapy for hyperphosphatemia in chronic kidney disease (CKD)
  • Antacid for gastritis, gastric hyperacidity, and esophagitis
  • Management of uremic gastropathy
Cat (Feline)
  • Adjunct therapy for hyperphosphatemia in chronic kidney disease (CKD)
  • Antacid for gastritis and esophagitis
  • Management of uremic gastropathy
Horse (Equine)
  • Antacid for gastric ulceration (as adjunct therapy)
  • Phosphate binder in renal failure (rarely used)
Cattle (Bovine)
  • Antacid for indigestion and rumen acidosis (as adjunct)
  • Phosphate binder in hypocalcemia? (not standard)
Small Ruminants (Sheep / Goat)
  • Antacid for indigestion (rarely used)
Rabbit & Small Mammals
  • Phosphate binder for hyperphosphatemia in renal disease
  • Antacid for gastric stasis (as adjunct)
Avian & Poultry
  • Phosphate binder in renal disease (rare)
Exotic & Other Species
  • Phosphate binder in reptiles with renal disease (e.g., tortoises)
  • Antacid in small mammals (e.g., ferrets, guinea pigs)

Pharmacology & Mechanism of Action

Drug Class: Antacid | Pharmacological Group: Phosphate Binder

Mechanism of Action: Aluminum hydroxide acts as an antacid by neutralizing gastric acid through a chemical reaction, producing aluminum chloride and water. As a phosphate binder, it binds dietary phosphate in the gastrointestinal tract to form insoluble aluminum phosphate, which is excreted in the feces, thereby reducing intestinal phosphate absorption and lowering serum phosphorus levels. It also inhibits pepsin activity and may have a cytoprotective effect on the gastric mucosa.

Pharmacodynamics: The antacid effect is rapid and short-lived, typically lasting 20-30 minutes when taken on an empty stomach, but can be prolonged to 2-3 hours when taken after meals. The phosphate-binding capacity is dose-dependent and occurs throughout the gastrointestinal tract. By reducing serum phosphorus, it helps mitigate secondary hyperparathyroidism and soft tissue mineralization in chronic kidney disease. It also reduces gastric acidity, which can alleviate signs of gastritis and esophagitis.

⚑ Pharmacokinetics Summary

Absorption: Aluminum hydroxide is minimally absorbed from the gastrointestinal tract. Only trace amounts (less than 1%) are absorbed systemically, primarily when administered with citrate-containing compounds or in patients with renal impairment.
Distribution: Absorbed aluminum distributes widely, with accumulation in bone, liver, and brain. In animals with normal renal function, absorbed aluminum is rapidly excreted by the kidneys.
Metabolism: Aluminum hydroxide is not metabolized; it reacts chemically in the gastrointestinal tract to form aluminum chloride and aluminum phosphate, which are poorly absorbed.
Excretion: The majority of aluminum hydroxide is excreted in the feces as unabsorbed aluminum salts. The small absorbed fraction is excreted in urine via glomerular filtration and tubular secretion.
Half-Life: Not well-defined due to minimal systemic absorption; the half-life of absorbed aluminum is prolonged in renal failure, potentially days to weeks.
Bioavailability: Oral bioavailability is very low (<1%) in healthy animals, but may increase in renal insufficiency or when administered with citrate.
Protein Binding: Aluminum binds to transferrin and albumin in plasma; protein binding is approximately 80-90%.

Available Formulations & Strengths

Oral Suspension 320 mg/5 mL, 600 mg/5 mL (PO)
Oral Tablet 500 mg, 600 mg (PO)
Oral Capsule 500 mg (PO)
Oral Gel Various concentrations (PO)

Contraindications & Clinical Warnings

Contraindications:
  • Hypophosphatemia
  • Intestinal obstruction
  • Fecal impaction
  • Known hypersensitivity to aluminum hydroxide
  • Concurrent use with citrate-containing products (increases aluminum absorption)
Warnings & Clinical Precautions:
  • Use with caution in patients with renal impairment; monitor serum aluminum levels if long-term use.
  • May cause constipation; use with stool softeners if needed.
  • May interfere with absorption of other drugs; separate administration by at least 2 hours.
  • In cats, may cause metabolic alkalosis if used in high doses.
  • In horses, prolonged use may affect digestion and nutrient absorption.
  • In food animals, observe withdrawal times.
  • Do not use in animals with GI obstruction or severe dehydration.

Adverse Effects & Reactions

Common:

  • Constipation
  • Fecal impaction
  • Anorexia
  • Vomiting (rare)

Serious / Severe:

  • Aluminum toxicity (with prolonged use or renal impairment) - neurological signs, osteomalacia
  • Hypophosphatemia (with excessive dosing)
  • Metabolic alkalosis (with high doses in cats)
  • Intestinal obstruction

Rare:

  • Hyperaluminemia
  • Encephalopathy
  • Osteomalacia
  • Microcytic anemia

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Tetracyclines Aluminum binds to tetracyclines, reducing their absorption and efficacy. High
Fluoroquinolones (e.g., enrofloxacin, ciprofloxacin) Reduced absorption of fluoroquinolones due to chelation. High
Digoxin Reduced absorption of digoxin. Moderate
Iron supplements Reduced absorption of iron. Moderate
Corticosteroids May increase aluminum absorption and risk of toxicity. Moderate
Citrate-containing products (e.g., potassium citrate) Increases aluminum absorption, risk of toxicity. High
H2 antagonists (e.g., cimetidine) May alter gastric pH, affecting aluminum hydroxide's antacid effect. Mild

Overdose & Toxicity Management

Signs of Toxicity:

  • Constipation
  • Fecal impaction
  • Intestinal obstruction
  • Hypophosphatemia
  • Metabolic alkalosis
  • Neurological signs (if aluminum toxicity develops)

Emergency Treatment Protocol: Discontinue drug, provide supportive care. For constipation, administer laxatives or enemas. For aluminum toxicity, chelation therapy with deferoxamine may be considered in severe cases, but is rarely needed. Monitor serum electrolytes and phosphorus levels. Ensure adequate hydration.

Food Animal Withdrawal Times

πŸ₯© Meat: 0 daysπŸ₯› Milk: 0 daysπŸ₯š Eggs: 0 days

No withdrawal periods are required for aluminum hydroxide in food animals as it is minimally absorbed and not a risk to consumers. However, always follow local regulations.

Storage, Handling & Regulatory Information

Storage Temperature: Store at room temperature (15-30Β°C)

Handling & Special Conditions: Keep container tightly closed. Do not freeze. Shake suspension well before use.

Dispensing Status: Over-The-Counter (OTC)

Approval Status: Not FDA-approved for veterinary use; human OTC product used extra-label.

Extra-Label (Off-Label) Use: Aluminum hydroxide is an over-the-counter product in many countries. In the US, it is not FDA-approved for veterinary use, but may be used extra-label under AMDUCA with a valid veterinarian-client-patient relationship. For food animals, extra-label use requires a withdrawal period established by the veterinarian.

Clinical Pearls & Practice Notes

πŸ’‘ Clinical Insights: Aluminum hydroxide is primarily used in veterinary medicine as a phosphate binder in the management of chronic kidney disease (CKD) in dogs and cats. It is also used as an antacid for gastric hyperacidity. Dosing should be individualized based on serum phosphorus levels, with the goal of maintaining phosphorus within the normal range (dogs: 2.5-4.5 mg/dL; cats: 2.5-5.5 mg/dL). Administer with meals to maximize phosphate binding. Monitor for constipation, which is the most common adverse effect; consider concurrent use of stool softeners if needed. Because aluminum hydroxide can interfere with the absorption of many drugs, separate administration by at least 2 hours. In patients with renal impairment, long-term use may lead to aluminum accumulation; consider alternative phosphate binders (e.g., calcium carbonate, sevelamer) if toxicity is a concern. In food animals, no withdrawal times are required, but local regulations should be followed.

References & Literature

  • πŸ“š Plumb's Veterinary Drug Handbook
  • πŸ“š Papich Veterinary Pharmacology and Therapeutics
  • πŸ“š Compendium of Veterinary Products (CVP)