Hydroxypropyl Methyl Cellulose (HPMC) is a semi-synthetic polymer derived from renewable, plant resource, cellulose. It is widely used as a capsule shell material and is considered safe for human consumption. It is also a viscolizing, thickening and coating polymer and bio-adhesive.

HPMC Capsules versus GelatinCapsule Shell: Challenges and Solutions
Although hard gelatin capsules have been a preferred two-piece dosage form in the pharmaceutical industry for over 170 years, it has several shortcomings that have led to the development of alternative shell-forming materials. These include cross-linking, variable mechanical strength under altered conditions of processing or storage temperature and relative humidity, preferential compatibility with only certain types of fill materials and excipients and varying degrees of hygroscopicity.

Puncture Profile: Physiological and Chemical Properties
Compared to gelatin, the puncture force profile of HPMC is typically less affected by the type of fill material or excipient used in its formulation. Hence, it is a more appropriate choice for filling hygroscopic drugs and excipients.
Moisture Uptake Studies: Protection against oxidation of sensitive APIs and excipients is enhanced by HPMC capsules as evidenced from dynamic vapor sorption studies conducted in different relative humidity percentages at 25 degC. These studies have shown that the permeability of HPMC film is considerably lower than that of gelatin films, even at the same relative humidity percentages.
Disintegration Time: Acute Drug Release from HPMC Capsules Without Gelling Agent 30 min Conclusion: The disintegration times of green tea extract loaded HPMC capsules prepared without gelling agent were found to be less than 30 minutes, which is in accordance with USP guidelines for herbal formulations. However, when gelatin capsules were encapsulated with carrageenan, the initial burst of the capsules took more time to disintegrate in acidic medium but after a short delay, the drug release profile was comparable.