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AQOAT - excipient for solid dispersion


Polymer for solid dispersions and gastro-resistant coating

AQOAT® was first approved as gastro-resistant coating in Japan in 1987. Since then, AQOAT® has also been approved in Europe and the United States for a variety of applications such as film-coating in aqueous mediums, film-coating in organic medium, dry coating or solid dispersions.

The AQOAT® range from SHIN ETSU is compliant with JP and USP.

Solid dispersion and enteric film-coating

Solid dispersion

Solid dispersion is a technology that aims to improve the bioavailability of poorly-soluble active ingredients by increasing their solubility. Generally, the active ingredient and the polymer (which acts as support) are solubilized together in a common solvent and the solution is then sprayed so that it can be dried. This results in a solid matrix of the polymer combined with the active ingredient which has become amorphous and which has an improved solubility.

AQOAT® is used as a support for solid dispersions, both in “spray-drying” and also in Hot Melt Extrusion (HME). Due to its relatively low glass transition temperature (Tg), AQOAT® is a leading excipient for pharmaceutical formulations.

Gastro-resistant coating

The principle of a gastro-resistant polymer is its capacity to be insoluble at acid pH (<5) and to become soluble as the pH increases.

It can therefore be used to maintain the integrity of the active ingredient in the stomach and then release it in the intestine. It can also protect gastric mucosa from irritating active ingredients.

Using film-coating, the bioavailability of some drugs can be increased by controlling the release of the active ingredient in the intestine. The bioavailability of some active ingredients is better in the intestine than in the stomach.

Due to its chemical structure, AQOAT® has acetyl and succinyl groups making it gastro-resistant. The solubility of the HPMC-AS can be adjusted depending on the content and ratio of these 2 groups.

SEPPIC markets the AQOAT® product range with dissolution pHs ranging from pH 5.5 to 6.5. These characteristics allow AQOAT® to be used in controlled release forms in order to target the drug at a specific site.

AQOAT® is primarily used in aqueous mediums but can also be used in organic solvents.

Product range

The AQOAT® range has six grades with differing particle sizes and substitutions.

Grade   Acetyl % Succinoyl % Mean Particle Size
  AS-LF 8 15  
Micronized AS-MF 9 11 5 µm
  AS-HF 12 7  
  AS-LG 8 15  
Granular AS-MG 9 11 1 mm
  AS-HG 12 7  


The solubility according to the pH depends on the substitution. The “L” grades with the highest succinyl group content are soluble at pH 5, the “H” grades with the lowest succinyl group content are soluble at pH 6.8.

The “F” grades are recommended particularly in aqueous mediums. The “G” grades are recommended for use in organic mediums.

The products in the AQOAT® range are manufactured in accordance with the Good Manufacturing Practices applicable to excipients.

All the regulatory and quality documents required for registration are available on request.


The Japanese company SHIN ETSU is a leader in cellulose chemistry.

SHIN ETSU develops pharmaceutical excipients and particularly cellulosic polymers for a range of applications such as film-coating, compression and matrices.

SEPPIC™ distributes SHIN ETSU products in Western and Southern Europe and several other countries.



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