Aluminum Hydroxide: Structure, Properties, Production, Uses and Adverse Effects

This medication is used to treat symptoms of excess stomach acid, such as upset stomach, heartburn, and acid indigestion.

Aluminum hydroxide is an antacid that works quickly to reduce acid in the stomach. Liquid antacids generally work faster / better than tablets or capsules.

This medicine works only with acid in the stomach.

Aluminum hydroxide

Aluminum hydroxide, Al (OH) 3, occurs in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer polymorphs: bayerite, doyleite, and nordstrandite.

Aluminum hydroxide is amphoteric in nature, that is, it has both basic and acidic properties.

Structure and properties

The aluminum hydroxide builder is not Al (OH) 3, but rather crystalline aluminum oxyhydroxide (AlOOH).

This difference is important because crystalline aluminum hydroxide has a low surface area (about 20-50 m2 / g) and as such is a poor adsorbent.

Crystalline aluminum oxyhydroxide has a surface area of ​​about 500 m2 / g, which makes it an excellent adsorbent.

This large surface area is due to its morphology. Primary particles are fibers that have dimensions of approximately 5 × 2 × 200 nm.

Aluminum oxyhydroxide is a stoichiometric compound. The surface is composed of Al-OH and Al-O-Al groups. Al-OH surface groups can accept a proton, resulting in a positive surface charge, or donate a proton, resulting in a negative surface charge.

The isoelectric point (IEP) of Al-OH is 11.4. Therefore, aluminum oxyhydroxide has a positive surface charge at pH 7.4, the pH of interstitial fluid.

The aluminum phosphate builder is chemically amorphous aluminum hydroxyphosphate in which some of the hydroxyl groups of the aluminum hydroxide are replaced by phosphate groups.

The disordered and amorphous state is responsible for the large surface area and high adsorption capacity.

The surface of the aluminum phosphate builder is composed of Al-OH and Al-OPO3 groups. The isoelectric point ranges from 9.4 to 4.5 depending on the degree of phosphate substitution.

Commercial aluminum phosphate adjuvants have isoelectric point values ​​in the range of 4.5 to 5.5. Unlike aluminum oxyhydroxide, commercial aluminum phosphate builders are negatively charged at pH 7.4.

Alum, which is soluble in water, is chemically aluminum potassium sulfate, AlK (SO4) 2. The first vaccines containing aluminum adjuvants were prepared by precipitation in situ.

A solution of alum was mixed with a solution of the antigen dissolved in a phosphate buffer. It is common practice to refer to the adjuvant produced by in situ precipitation as alum.

The precipitate is amorphous aluminum hydroxyphosphate and has similar composition and properties to aluminum phosphate builder.

Techniques that can be used to characterize aluminum-containing adjuvants have been reviewed by White and Hem.


The naming of the different forms of aluminum hydroxide is ambiguous and there is no universal standard. All four polymorphs have a chemical composition of aluminum trihydroxide (an aluminum atom attached to three hydroxide groups).

Gibbsite is also known as hydrargillite, named for the Greek words for water (hydra) and clay (argylles).

The first compound called hydrargillite was thought to be aluminum hydroxide, but it was later discovered to be aluminum phosphate.

Despite this, both gibbsite and hydrargillite are used to refer to the same polymorphism of aluminum hydroxide, with gibbsite used most frequently in the United States and hydrargillite used most frequently in Europe.

In 1930, it was named α-alumina trihydrate to contrast it with bayerite, which was named β-alumina trihydrate (the alpha and beta designations were used to differentiate the more and less common forms, respectively).

In 1957, a symposium on the nomenclature of alumina attempted to develop a universal standard, resulting in gibbsite being named γ-Al (OH) 3, bayerite becoming α-Al (OH) 3, and nordstrandite becoming named Al (OH) 3.

Based on its crystallographic properties, a suggested nomenclature and designation is for gibbsite to be α-Al (OH) 3, bayerite to be called β-Al (OH) 3, and both nordstrandite and doyleite are called Al (OH) 3.

Under this designation, the prefixes α and β refer to hexagonal, compact structures and altered or dehydrated polymorphisms, respectively, without differentiation between nordstrandite and doyleite.


Aluminum hydroxide is amphoteric. In acid, it acts as a Brønsted-Lowry base by collecting hydrogen ions and neutralizes the acid, producing a salt:

  • 3HCl + Al (OH) 3 → AlCl3 + 3H2O

At bases, it acts like a Lewis acid by taking a pair of electrons from the hydroxide ions:

  • Al (OH) 3 + OH- → Al (OH) 4-


There are four aluminum hydroxide polymorphs, all based on the common combination of an aluminum atom and three hydroxide molecules in different crystalline arrangements that determine the appearance and properties of the compound.

The four combinations are:

  • Gibbsite.
  • Bayerite.
  • Nordstrandite.
  • Doyleita.

All polymorphs are composed of layers of octahedral aluminum hydroxide units with the aluminum atom in the center and the hydroxyl groups on the sides, with hydrogen bonds holding the layers together.

Polymorphisms vary in the way the layers come together, with the arrangements of the molecules and the layers determined by acidity, the presence of ions (including salt), and the surface of the minerals on which the substance is formed.

Under most conditions, gibbsite is the most chemically stable form of aluminum hydroxide. All crystal forms of Al (OH) 3 are hexagonal.


Virtually all commercially used aluminum hydroxide is manufactured by the Bayer process which involves dissolving bauxite in sodium hydroxide at temperatures up to 270 ° C (518 ° F).

The solid residue, bauxite tailings, is removed and the aluminum hydroxide precipitates from the remaining sodium aluminate solution. This aluminum hydroxide can be converted to aluminum oxide or alumina by calcination.

Bauxite waste or tailings, which is primarily iron oxide, is highly caustic due to residual sodium hydroxide.

Historically it was stored in lagoons; This led to the 2010 Ajka alumina plant accident in Hungary, where a dam failure led to the drowning of nine people.

An additional 122 sought treatment for chemical burns. The mud contaminated 40 square kilometers (15 square miles) of land and reached the Danube.

While the mud was considered non-toxic due to low levels of heavy metals, the associated mud had a pH of 13.


One of the main uses of aluminum hydroxide is as a raw material for the manufacture of other aluminum compounds, such as:

Special calcined aluminas, aluminum sulfate, polyaluminum chloride, aluminum chloride, zeolites, sodium aluminate, activated alumina and aluminum nitrate.

Fire retardant

Aluminum hydroxide is also used as a flame retardant material for polymer applications similar to magnesium hydroxide and huntite and hydromagnesite mixtures.

It decomposes at approximately 180 ° C (356 ° F), absorbing a considerable amount of heat in the process and emitting water vapor.

In addition to behaving as a fire retardant, it is very effective as a smoke suppressant in a wide range of polymers, especially in polyesters, acrylics, ethylene vinyl acetate, epoxy resins, PVC and rubber.


Under the generic name “algeldrate”, aluminum hydroxide is used as an antacid in humans and animals (mainly cats and dogs).

Both aluminum hydroxide and magnesium hydroxide are effective treatments for gastroesophageal reflux disease.

However, in infants, aluminum hydroxide formulations can increase plasma levels of aluminum which are reported to cause osteopenia, microcytic anemia, and neurotoxicity.

Aluminum hydroxide is used in the treatment of:

  • Úlcera duodenal.
  • Dyspepsia.
  • Esophagitis, peptic.
  • Gastroesophageal reflux.
  • Acidity.
  • Stomach ulcer.

Aluminum hydroxide is used in the prevention of:

  • Gastrointestinal bleeding.

This medicine may be prescribed for other uses. Consult your doctor or pharmacist for more information.

This compound is also used to control hyperphosphatemia (high levels of phosphate or phosphorus in the blood) in people and animals with kidney failure.

Normally, the kidneys filter excess phosphate from the blood, but kidney failure can cause phosphate buildup.

Aluminum salt, when ingested, binds to phosphate in the intestines and reduces the amount of phosphorus that can be absorbed.

Precipitated aluminum hydroxide is included as an adjuvant in some vaccines (eg, anthrax vaccine).

Aluminum hydroxide, aluminum phosphate, and aluminum potassium sulfate (alum) are used as adjuvants in vaccines designed to stimulate systemic immunity.

Aluminum salts are used in vaccines against diphtheria, tetanus and pertussis, pneumococcal conjugate, hepatitis A, papilloma, anthrax, and rabies.

Like other systemic adjuvants, they form an insoluble deposit and slowly release antigen, which stimulates an antibody response.

Although adjuvants containing aluminum salts are safe, they induce granulomas at the vaccination site. In some individuals, there is an increased risk of immunoglobulin E (IgE) production and neurotoxicity.

One of the best known brands of aluminum hydroxide adjuvant is Alhydrogel, manufactured by Brenntag Biosector.

Since it absorbs proteins well, it also works to stabilize vaccines by preventing vaccine proteins from precipitating or sticking to the container walls during storage.

Aluminum hydroxide is sometimes mistakenly called “alum,” which refers to potassium aluminum sulfate.

Vaccine formulations containing aluminum hydroxide stimulate the immune system by inducing the release of uric acid, an immunological danger signal. This strongly attracts certain types of monocytes that differentiate into dendritic cells.

Dendritic cells pick up the antigen, carry it to the lymph nodes, and stimulate T and B cells. It appears to contribute to the induction of a good Th2 response, making it useful for immunizing against antibody-blocked pathogens.

However, it has little ability to stimulate cellular immune responses (Th1), important for protection against many pathogens, nor is it useful when the antigen is peptide-based.

Aluminum hydroxide, an effective phosphate binder, was the binder of choice for many years, but due to the gradual accumulation of absorbed aluminum tissue, long-term use of this binder was associated with cognitive impairment, osteomalacia, microcytic anemia refractory and myopathy.

There is no evidence to suggest that even low levels of aluminum exposure are safe for chronic use.

How to use aluminum hydroxide suspension

Take this medicine by mouth between meals and at bedtime. Follow all directions on the product package or use as directed by your doctor.

This product contains aluminum, which can react with other medications (including digoxin, iron, tetracycline antibiotics, pazopanib, quinolone antibiotics, such as ciprofloxacin), preventing them from being fully absorbed by the body.

If your heartburn problems persist or worsen after using this product for 1 week, or if you think you have a serious medical problem, seek immediate medical attention. Ask your doctor if this is the right medicine for you.

Using an antacid that contains magnesium along with this product can help prevent constipation. Stool softeners can also be helpful. Ask your doctor or pharmacist about other antacids, stool softeners, and laxatives.

Possible side effects

Antacids, including aluminum hydroxide, magnesium hydroxide, and calcium carbonate, can be quite effective against occasional gastroesophageal reflux disease. Antacids increase gastrointestinal (GI) pH.

However, as with any over-the-counter medicine, adverse effects and drug interactions can occur (for example, aluminum, magnesium, and calcium can form insoluble complexes with tetracyclines or fluoroquinolones, reducing the bioavailability of antibiotics).

Because the gastrointestinal pH is elevated by antacids, the absorption of many other medications can be limited. It is recommended that the administration of antacids be separated from other drugs for at least 2 hours.

In the 1960s and 1970s, it was speculated that aluminum was linked to several neurological disorders, including Alzheimer’s disease.

Since then, multiple epidemiological studies have found no connection between aluminum exposure and neurological disorders.

Depending on the antacid formulation chosen, adverse effects may include electrolyte disturbances, nausea, flatulence, diarrhea, or constipation.

Constipation can occur. This could lead to other problems like hemorrhoids and intestinal obstruction.

Because alternative therapies are available and generally well tolerated, antacids should be reserved for intermittent treatment of symptoms rather than chronic treatment of gastroesophageal reflux disease.

This drug can cause low phosphate levels if your kidneys are normal, especially if you use large doses for a long time.

Aluminum-based antacids should be avoided in patients with kidney failure. The efficacy of calcium carbonate antacids has not been demonstrated in pediatric patients.

An interaction of aluminum hydroxide with clozapine (4A) has been described.

A 26-year-old man with an unspecified psychotic disorder, violence, and alcohol abuse received clozapine 100 mg bd. The serum concentration of clozapine was stable at 382 ng / ml.

A few weeks later he became more sleepy and drool more than before. The clozapine concentration was 739 ng / ml. There were no changes to his other medications, except that he was taking less aluminum hydroxide.

The clozapine dose was adjusted and the signs of clozapine overdose disappeared. Aluminum hydroxide can adsorb clozapine and reduce its gastrointestinal absorption.

Seek immediate medical attention if you develop any of these rare but very serious side effects or symptoms of a serious medical problem: black or tarry stools, mental and / or mood changes.

If you notice other effects not listed above, contact your doctor or pharmacist.

If you have any of the following health problems, consult your doctor or pharmacist before using this product: frequent use of alcohol, severe loss of body water (dehydration / fluid restriction), constipation problems, kidney problems (including kidney stones ).