Aluminum Hydroxide Adjuvant

Aluminum hydroxide adjuvant is a white hydrogel that sediments slowly and forms a clear supernatant.

Nonproprietary Names
  • PhEur: Aluminium Hydroxide, Hydrated, for Adsorption
Adsorbent; vaccine adjuvant.


Alhydrogel; aluminii hydroxidum hydricum ad adsorptionem; aluminium hydroxide adjuvant; aluminium oxyhydroxide; poorly crystalline boehmite; pseudoboehmite; Rehydragel.

Chemical Name and CAS Registry Number
  • Aluminum oxyhydroxide [21645-51-2]

Empirical Formula and Molecular Weight
  • AlO(OH) 59.99

Structural Formula

Structural hydroxyl groups form hydrogen bonds between AlO(OH) octahedral sheets, where hydroxyl groups are exposed at the surface. The surface hydroxyl groups produce a pHdependent surface charge by accepting a proton to produce a positive site, or donating a proton to produce a negative site. 

The pH-dependent surface charge is characterized by the point of zero charge, which is equivalent to the isoelectric point in protein chemistry. The surface hydroxyl groups may also undergo ligand exchange with fluoride, phosphate, carbonate, sulfate, or borate anions.

Functional Category

  • Adsorbent; vaccine adjuvant.

Applications in Pharmaceutical Formulation or Technology

Aluminum hydroxide adjuvant is used in parenteral human and veterinary vaccines. It activates Th2 immune responses, including IgG and IgE antibody responses. It is also used for the isolation of certain serum components such as blood clotting factors.

Method of Manufacture

Aluminum hydroxide adjuvant is prepared by the precipitation of a soluble aluminum salt by an alkali hydroxide, or the precipitation of an alkali aluminate by acid.


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