Usage
Aluminum phosphate is primarily used as an antacid to relieve symptoms of heartburn, acid indigestion, and upset stomach. It is also used as an adjuvant in some vaccines to enhance the body’s immune response. Its pharmacological classifications include antacid, and adjuvant.
As an antacid, aluminum phosphate works by neutralizing excess stomach acid. As an adjuvant, it is thought to create a depot effect, releasing the antigen slowly over time and enhancing antigen presentation to immune cells.
Alternate Names
- Aluminum phosphate
- Aluminium orthophosphate
Brand names vary depending on the formulation and country. Some examples include Phosphaljel and Alu-Cap.
How It Works
Pharmacodynamics: Aluminum phosphate neutralizes gastric acid by reacting with hydrochloric acid (HCl) in the stomach to form aluminum chloride and phosphoric acid, raising the pH of the gastric contents. This reduces the irritating effects of stomach acid on the esophageal and gastric mucosa. As an adjuvant, it enhances the immune response to vaccines by promoting antigen uptake and presentation by antigen-presenting cells (APCs) and stimulating cytokine production.
Pharmacokinetics: Aluminum phosphate has low systemic absorption following oral administration. The small amount of aluminum absorbed is primarily excreted by the kidneys. The majority of the ingested aluminum phosphate passes through the gastrointestinal tract unabsorbed and is eliminated in the feces.
Mode of Action: Neutralization of gastric acid. As an adjuvant: depot effect, enhanced antigen presentation, cytokine stimulation.
Receptor Binding, Enzyme Inhibition, or Neurotransmitter Modulation: Not applicable for its antacid action. As an adjuvant, it interacts with components of the immune system, but the precise mechanisms are still being investigated.
Elimination Pathways: Primarily fecal excretion; renal excretion of a small absorbed fraction.
Dosage
Standard Dosage
Adults:
- Antacid: 400 to 800 mg (as aluminum phosphate) orally every 4 to 6 hours as needed, taken 1 hour after meals and at bedtime, if needed.
- Adjuvant: Dose varies depending on the specific vaccine formulation.
Children:
- Antacid: Consult a healthcare professional for appropriate pediatric dosing based on weight or age.
- Adjuvant: Dose varies depending on the specific vaccine formulation.
Special Cases:
- Elderly Patients: Use with caution due to potential for decreased renal function and aluminum accumulation.
- Patients with Renal Impairment: Avoid or use with extreme caution due to risk of aluminum toxicity.
- Patients with Hepatic Dysfunction: No specific dose adjustments are typically required.
- Patients with Comorbid Conditions: Consult a healthcare professional for guidance based on the specific comorbid condition.
Clinical Use Cases
The provided sources primarily focus on the use of aluminum phosphate as an antacid and adjuvant. Therefore, dosage recommendations for clinical use cases such as intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations are not readily available from the current sources.
Dosage Adjustments
Dose adjustments based on renal function are critical. Avoid or use with extreme caution in patients with renal impairment. Consult a healthcare professional for individualized recommendations.
Side Effects
Common Side Effects
Constipation is the most common side effect.
Rare but Serious Side Effects
- Aluminum toxicity (in patients with renal impairment)
- Osteomalacia (long-term use)
- Encephalopathy (long-term use)
- Hypophosphatemia (long-term use)
Long-Term Effects
- Osteomalacia
- Encephalopathy
Adverse Drug Reactions (ADR)
Aluminum toxicity, osteomalacia, encephalopathy, and hypophosphatemia are potential ADRs.
Contraindications
- Hypersensitivity to aluminum phosphate
- Severe renal impairment
- Hypophosphatemia
Drug Interactions
Aluminum phosphate can decrease the absorption of several medications, including tetracycline antibiotics, quinolone antibiotics (e.g., ciprofloxacin), iron supplements, digoxin, and bisphosphonates. It is important to separate the administration of aluminum phosphate from these medications by at least 2 hours.
Pregnancy and Breastfeeding
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Pregnancy Safety Category: Not formally assigned. Consult a healthcare professional before use during pregnancy.
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Breastfeeding: Small amounts of aluminum are present in breast milk. Consult a healthcare professional before use during breastfeeding.
Drug Profile Summary
- Mechanism of Action: Antacid: Neutralizes gastric acid. Adjuvant: Enhances immune response to vaccines.
- Side Effects: Constipation, aluminum toxicity (rare), osteomalacia (rare), encephalopathy (rare), hypophosphatemia (rare).
- Contraindications: Hypersensitivity, severe renal impairment, hypophosphatemia.
- Drug Interactions: Tetracyclines, quinolones, iron, digoxin, bisphosphonates.
- Pregnancy & Breastfeeding: Consult a healthcare professional.
- Dosage: Antacid: 400 to 800 mg every 4 to 6 hours. Adjuvant: Varies depending on the vaccine.
- Monitoring Parameters: Serum phosphate levels (in long-term use or renal impairment).
Popular Combinations
Aluminum phosphate is often combined with magnesium hydroxide in antacid formulations to minimize the risk of constipation.
Precautions
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Aluminium Phosphate as an antacid?
A: The recommended dosage for adults is 400 to 800 mg orally every 4 to 6 hours as needed, taken 1 hour after meals and at bedtime, if needed. Pediatric dosages should be determined by a healthcare professional.
Q2: How does Aluminium Phosphate work as an antacid?
A: It neutralizes stomach acid by reacting with hydrochloric acid to form aluminum chloride and phosphoric acid, raising the gastric pH.
Q3: What are the common side effects of Aluminium Phosphate?
A: Constipation is the most common side effect.
Q4: What are the serious side effects of aluminum phosphate?
A: Aluminum toxicity, osteomalacia, encephalopathy, and hypophosphatemia are potential serious side effects, particularly with long-term use or in patients with renal impairment.
Q5: Who should not take aluminum phosphate?
A: Individuals with hypersensitivity to aluminum phosphate, severe renal impairment, or hypophosphatemia should not take it.
Q6: Does aluminum phosphate interact with other medications?
A: Yes, it can decrease the absorption of various medications, including tetracyclines, quinolones, iron supplements, digoxin, and bisphosphonates. Separate administration by at least 2 hours.
Q7: Can aluminum phosphate be used during pregnancy or breastfeeding?
A: Consult a healthcare professional before using aluminum phosphate during pregnancy or breastfeeding.
Q8: What precautions should be taken when prescribing aluminum phosphate?
A: Evaluate renal function, especially in elderly patients. Monitor for constipation and signs of aluminum toxicity, osteomalacia, encephalopathy, or hypophosphatemia.
Q9: What is the role of aluminum phosphate in vaccines?
A: It acts as an adjuvant, enhancing the immune response to the vaccine.
Q10: How should aluminum phosphate be stored?
A: Store at room temperature away from moisture and heat. Liquid formulations should be protected from freezing.
