Dried Aluminium Hydroxide BP
Also known as: Dried Aluminium Hydroxide BP, Aluminum hydroxide gel, Al(OH)₃, Aluminum hydroxide
Overview
Aluminum hydroxide is an inorganic compound primarily utilized for its antacid properties to neutralize stomach acid and alleviate symptoms of heartburn, acid indigestion, and upset stomach. It also serves as a phosphate binder, particularly in individuals with chronic kidney disease, by reducing serum phosphate levels. This compound is available as a white, powdery substance, either naturally derived or synthetically produced. The 'dried' form adheres to British Pharmacopoeia (BP) standards, ensuring a pharmaceutical-grade preparation. Widely incorporated into over-the-counter (OTC) antacid formulations and certain prescription medications, aluminum hydroxide has a well-established research history with extensive toxicological and pharmacological data. While its efficacy as an antacid is well-supported by high-quality evidence, concerns regarding long-term safety, especially in patients with impaired renal function, necessitate careful consideration.
Benefits
Aluminum hydroxide offers significant benefits primarily through its ability to neutralize gastric acid. It achieves this by binding free protons in the stomach, thereby increasing stomach pH and providing rapid relief from symptoms associated with heartburn, acid indigestion, and upset stomach. This antacid effect typically manifests within minutes of ingestion. Beyond its role as an antacid, aluminum hydroxide is also effectively used to reduce elevated serum phosphate levels in patients with chronic kidney disease. It accomplishes this by binding dietary phosphate in the gastrointestinal tract, preventing its absorption. This secondary effect is particularly beneficial for individuals suffering from hyperphosphatemia due to renal failure. For antacid use, FDA-approved oral doses up to 8 grams per day have demonstrated effective symptom relief, indicating a robust effect size for its primary indication.
How it works
Aluminum hydroxide functions by dissociating in the acidic environment of the stomach, releasing aluminum ions (Al³⁺) and hydroxide ions (OH⁻). The hydroxide ions then react with and neutralize gastric hydrogen ions (H⁺), forming water and insoluble aluminum salts. This reaction effectively reduces stomach acidity. Systemic absorption of aluminum is minimal, typically less than 1%, with the majority of the compound being excreted in the feces. In individuals with healthy renal function, any absorbed aluminum is efficiently eliminated via urine, maintaining steady-state levels. In vaccine formulations, aluminum hydroxide acts as an adjuvant, enhancing the immune response by promoting antigen uptake and activating immune cells like macrophages and inflammasome pathways.
Side effects
While generally safe for short-term use in healthy individuals, aluminum hydroxide can cause several side effects. The most common adverse effects, occurring in over 5% of users, include constipation and mild gastrointestinal discomfort. Less common side effects (1-5%) involve hypophosphatemia, which can lead to osteomalacia (softening of bones) with prolonged use, due to its phosphate-binding properties. Rare but serious side effects (less than 1%) include aluminum toxicity, which can manifest as encephalopathy (brain dysfunction) and seizures, particularly in patients with impaired renal function where aluminum accumulation is more likely. Aluminum hydroxide can also interact with other medications, potentially interfering with the absorption of certain drugs such as tetracyclines and fluoroquinolones. It is contraindicated in patients with chronic kidney disease or impaired renal function due to the significant risk of aluminum accumulation and subsequent toxicity. Caution is also advised for elderly individuals and those with any compromised renal clearance.
Dosage
The recommended dosage of aluminum hydroxide varies depending on the intended use. For its antacid effect, doses as low as 320 mg per administration can be effective for symptom relief. The optimal dosage range for antacid use, as per FDA guidelines, is up to 8 grams per day. This daily maximum of 8 grams should not be exceeded to minimize the risk of toxicity. For acid neutralization, it is typically administered as needed for symptom relief. When used as a phosphate binder, dosing must be coordinated with meals to effectively bind dietary phosphate. Aluminum hydroxide is available in various oral forms, including suspensions, chewable tablets, and gels. Systemic absorption is minimal, but co-administration with substances like citrate or other acids may slightly increase absorption. While no specific cofactors are required for its action, monitoring of phosphate and aluminum levels is recommended during long-term therapy, especially in patients with compromised renal function.
FAQs
Is aluminum hydroxide safe long-term?
Long-term use of aluminum hydroxide is generally not recommended without medical supervision due to the risk of aluminum accumulation and potential bone toxicity (osteomalacia) and neurological issues.
Can it cause neurological problems?
Yes, in rare cases, particularly in individuals with kidney failure, aluminum can accumulate in the body and lead to serious neurological problems such as encephalopathy and seizures.
How quickly does it work?
Relief from acid indigestion and heartburn symptoms typically occurs rapidly, often within minutes after ingesting aluminum hydroxide.
Does it interact with other medications?
Yes, aluminum hydroxide can reduce the absorption of certain medications, including some antibiotics. It is advisable to space out the administration times of aluminum hydroxide and other drugs.
Research Sources
- https://www.cir-safety.org/sites/default/files/Alumin_122013_Final.pdf – This safety assessment by the CIR Panel reviewed FDA data and animal studies on aluminum hydroxide. It concluded that oral aluminum hydroxide is safe at approved doses (up to 8 g/day) for healthy subjects, showing no significant clinical toxicity. While animal studies indicated altered calcium metabolism, severe systemic toxicity was not observed at therapeutic doses, though extrapolation to humans has limitations.
- https://www.rivm.nl/bibliotheek/rapporten/2020-0001.pdf – This systematic review focused on aluminum exposure and neurotoxicity, particularly in animal models mimicking vaccine doses. It identified neurobehavioral changes at low doses correlated with increased brain aluminum and microglial activation. The review noted that the human relevance of these findings is uncertain, and no consistent dose-response relationship was observed, highlighting the need for caution in vulnerable populations.
- https://www.ncbi.nlm.nih.gov/books/NBK546669/ – The StatPearls review summarizes clinical toxicities associated with aluminum hydroxide, including seizures, osteomalacia, and encephalopathy, emphasizing their link to impaired phosphate absorption and aluminum accumulation, especially in patients with kidney disease. It strongly advises against its use in individuals with renal impairment and stresses the importance of monitoring during long-term therapy.
