Polycarbophil

• USP–NFPolycarbophil

Noveon AA-1; acrylic acid polymer cross-linked with divinyl glycol; polyacrylic acid cross-linked with divinyl glycol

Poly(acrylic acid) cross-linked with divinyl glycol (3,4-dihydroxy-1,5-hexadiene) · [9003-97-8]

(C3H4O2)n

Gelling agent, viscosity modifier

Typical concentrations: — · Dosage forms: Semi-solid

Used as a bioadhesive (mucoadhesive) polymer to prolong residence time on mucosal surfaces, for example in ophthalmic solutions, vaginal moisturising gels and buccal or nasal formulations, and as a thickening and controlled-release agent. It is normally used at low concentrations, generally a few percent or less, adjusted to the viscosity and adhesion required. Its calcium salt (calcium polycarbophil) is used orally as a bulk-forming laxative and antidiarrhoeal.

A high-molecular-weight polymer of acrylic acid lightly cross-linked with divinyl glycol, supplied as a white to off-white, fluffy powder. In water it does not dissolve but forms a highly swollen, viscous dispersion.

Physical form

white to off-white, fluffy, hygroscopic powder with a slight characteristic odour

Solubility

insoluble in water and organic solvents, but swells strongly in water; swelling increases as the carboxyl groups are neutralised

pH

acidic in unneutralised aqueous dispersion (about pH 3)

Bioadhesion

strongly mucoadhesive through hydrogen bonding of the carboxyl groups with mucin

Stable but hygroscopic. Dispersions are susceptible to microbial growth and normally need a preservative. Store in an airtight container in a cool, dry place.

As a polyacid it is incompatible with strong bases and oxidising agents. Viscosity and swelling are reduced by electrolytes and polyvalent cations, and it may interact with cationic drugs and preservatives such as benzalkonium chloride.

Prepared by polymerising acrylic acid in the presence of a small amount of divinyl glycol as the cross-linking agent, followed by drying of the polymer.

Polycarbophil is not absorbed from the gastrointestinal tract and is regarded as non-toxic; large oral doses of the calcium salt are taken therapeutically as a laxative. It is generally well tolerated on mucous membranes, though mild local irritation can occur.

Observe normal precautions for the quantity handled. The fine powder is easily airborne; avoid inhalation and contact with the eyes, and use eye protection, gloves and a dust mask.

Included in the FDA Inactive Ingredient Database (ophthalmic and other non-parenteral preparations).

Calcium polycarbophil; carbomer.

Polycarbophil is closely related to the carbomers but differs in its cross-linking agent. Its mucoadhesion is greatest when the polymer is only partly ionised (roughly pH 4–6); full neutralisation increases swelling but weakens adhesion. Like carbomer, the powder should be dispersed slowly with good agitation to avoid lumps.