Liquid-Filled, Hard-Gelatin Capsules Re-Enter the Marketplace

One usually does not think of “hot” trends when thinking of the nutritional delivery systems market, but one that is gaining momentum is the practice of filling two-piece capsules with liquids.

This trend isn’t new, as the ability to fill a two-piece hard shell capsule with a liquid substance has been around for more than 150 years. Its advantages have only recently been rediscovered, making it a popular alternative for the nutritional market.

The ability to fill two-piece capsules with liquid or semi-solid ingredients opens up a whole new range of possibilities for supplement manufacturers and has spawned a viable alternative to soft-gelatin capsule technology. By using a two-piece capsule shell, ingredients that:

Liquid-filled formulations in hard capsules are not merely replicates of those filled into soft capsules because a much wider range of excipients can be used. The sealing temperature in the rotary die process for soft capsules is 37°C and thus, formulations must be in liquid-state below 35°C for this to work. On the contrary, hard capsules can be filled with hot liquids enabling excipients with higher melting points to be used. This benefit can help the formulator overcome the challenges presented by poorly soluble actives. Recent research indicates liquid-filled capsules can also provide improved bioavailability over tablets and a simple way to produce sustained release formulations.

Vitamins, in particular, have benefited from the reemergence of the liquid-filled capsules. Oily products, such as vitamins E and A, can be filled and sealed in this manner without adding thickening agents. This allows the maximum concentration of the substance in the minimum capsule size, while also reducing the risk of product instability.

Several manufacturing issues can be addressed through the use of liquid-filled twopiece capsules versus soft-gelatins, such as:

Although the technology for filling twopiece capsules with liquids on automatic machines has been around since the mid 1980s, more and more capsule manufacturers are now appreciating the benefits that liquid filled two-piece capsules bring to their operations. This simple formulation technique based on readily available excipients solves most formulation challenges. Automatic filling machines are available for all major manufacturers, enabling in-house production that can be easily geared to demand, thus offering a cost effective alternative for liquid-filled products.

Tamara Smith is the department head of marketing at Qualicaps, a manufacturer of empty two-piece capsules and related filling and sealing equipment. She may be reached at [email protected].

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