Gelling agents carbomers

Among the gelling agents used are synthetic macromolecules as acrylic acid polymers such as Carbomer 934, cellulose derivatives such as carboxymethyl cellulose or hydroxypropylmethyl cellulose, and natural gums such as xanthan gum. Appendix IV shows the commonly used gelling agents in commercially available pharmaceutical gels. 

Combinations of bases are sometimes used to acquire better stability. Gelling agents such as carbomers and PEG are also included in some ointment and cream preparations. Table 3 shows examples of cream bases used in some commercial cream preparations. 

Semi-solid gel type preparations have also been developed for ophthalmic delivery as an alternative to traditional ointments, based on the effect of increasing the viscosity to prolong the retention of drug in the eye (for example, Pilopine HS gel, Alcon Laboratories, Inc.). Several types of gelling agents have been used, such as polyacrylic acid derivatives, carbomer and hypromellose. 

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