Is hypromellose acid resistant?

Hypromellose, also known as hydroxypropyl methylcellulose (HPMC), is not inherently acid-resistant. However, the acid resistance of hypromellose can be enhanced through various formulation techniques.

Hypromellose is soluble in water but is relatively insoluble in organic solvents and non-polar liquids. Therefore, in acidic environments, such as the stomach, hypromellose may dissolve or swell to some extent, depending on factors such as the concentration of acid, pH, and duration of exposure.

To improve the acid resistance of hypromellose in pharmaceutical formulations, enteric coating techniques are often employed. Enteric coatings are applied to tablets or capsules to protect them from the acidic environment of the stomach and allow them to pass into the more neutral environment of the small intestine before releasing the active ingredients.

Enteric coatings are typically made from polymers that are resistant to gastric acid, such as cellulose acetate phthalate (CAP), hydroxypropyl methylcellulose phthalate (HPMCP), or polyvinyl acetate phthalate (PVAP). These polymers form a protective barrier around the tablet or capsule, preventing premature dissolution or degradation in the stomach.

In summary, while hypromellose itself is not acid-resistant, its acid resistance can be enhanced through formulation techniques such as enteric coating. These techniques are commonly used in pharmaceutical formulations to ensure the effective delivery of active ingredients to the intended site of action in the body.