Your Choice of Capsule Shell – Gelatin or HPMC?

Gelatin, obtained from animal sources has been the traditional material of choice for manufacturing capsules. Gelatin has excellent gelling and robust film-forming properties. Gelatin capsules disintegrate within 5 to 10 minutes in biological media and are non-toxic. They help achieve the desired specification criterion necessary for in vitro dissolution of immediate-release (IR) solid oral dosage forms, an indication of acceptable in vivo performance. They have great mechanical strength and therefore perform very well on high-speed filling machines. It is for these reasons that gelatin capsules have gained considerable popularity among pharmaceutical manufacturers and is preferred for making IR formulations. rnBut Can Gelatin Stand the Test of Time? Despite several advantages of gelatin capsules, their limitations often come in the way of successful product development. Their significantly high inherent moisture content makes them incompatible with moisture-sensitive ingredients. Hygroscopic ingredients when filled in gelatin capsules absorb moisture from the shells and cause them to chip away or become brittle. If stored under high humid conditions, the shells tend to absorb ambient moisture and turn soggy. These capsules are also highly susceptible to react with ingredients containing an aldehydic functional group. Interaction of gelatin capsules with such ingredients or even their storage in hot/humid conditions can cause them to undergo crosslinking reactions which in turn adversely affects their in-vitro dissolution performance. As a result, the active contents are not released from these capsules as intended. Additionally, since derived from animal sources, their risk associated with TSE/BSE contamination cannot be overruled. These major shortcomings of gelatin capsules call for the need to usher in newer polymers or sophisticated materials for producing capsule shells. A Better Alternative to GelatinrnHydroxypropyl methylcellulose (HPMC) or hypromellose is a cellulose-based polymer that is derived from plant sources. It has been in use in the pharmaceutical industry as an excipient and is considered safe for human consumption. HPMC capsules successfully address a lot of limitations posed by its gelatin counterpart.rnWith a low inherent moisture content HPMC capsules are suitable to contain hygroscopic or moisture-sensitive ingredients and unlike gelatin capsules pose no incompatibility issues. They are inert and issues of chemical incompatibility or cross-linking are also not associated with them. This enables a larger variety of active ingredients to be delivered through capsules. Additionally, HPMC capsules also have excellent machinability that allows easy capsule filling on any encapsulation machine.rnThe advantages of HPMC capsules are manifold which allows for greater formulation flexibility. Therefore, the use of HPMC capsules is now gradually increasing among pharmaceutical and nutraceutical manufacturers. So, what would be your choice of capsule shell now – gelatin or HPMC?