A hard gelatin capsule shell consists of two pieces: a cap and a body. The body has slightly lower diameter than the cap and fits inside the cap. They are produced empty and are then filled in a separate operation. During the capsule filling unit operation, the body is filled with the medicament, followed by the insertion of the cap over the body.
Most capsule products manufactured today are of the hard gelatin type. It is estimated that the utilization of hard gelatin capsules to prepare solid dosage forms exceeds that of soft gelatin capsules by about 10-fold.
This article focuses on the advantages and disadvantages of hard gelatin capsules as a dosage form.
Advantages of Hard Gelatin Capsules
Some of the advantages of hard gelatin capsules as a dosage form include:
1. Hard gelatin capsules often have been assumed to have better bioavailability than tablets. Most likely, this assumption is derived from the fact that the gelatin shell rapidly dissolves and ruptures, which affords at least the potential for rapid release of the drug.
2. Hards gelatin capsules allow a degree of flexibility of formulation not obtainable with tablets. Often, they are easier to formulate because there is no requirement that the powders be formed into a coherent compact that will stand up to handling. However, the problems of powder blending and homogeneity, powder fluidity, and lubrication in hard capsule filling are similar to those encountered in tablet manufacture.
3. Modern capsule filling equipment makes possible the multiple filling of diverse systems such as beads, granules, small tablets, powders, and even semisolids.
4. Capsules make possible the filling of bead-type modified-release products since they are filled without a compression process that could rupture the particles.
5. Hard gelatin capsules are ideally suited for clinical trials and are widely used in preliminary drug studies. For comparative bioequivalence studies, tablets can even be hidden in capsules to ensure the test being blinded.
Disadvantages of Hard Gelatin Capsules
1. From a manufacturer’s point of view, there is perhaps some disadvantage in the fact that the number of suppliers of shells is limited.
2. Filling equipment is slower than tableting, although that gap has narrowed in recent years with the advent of high-speed automatic-filling machines.
3. Generally, hard gelatin capsule products tend to be more costly to produce than tablets; however, the relative cost-effectiveness of capsules and tablets must be judged on a case-by-case basis.
4. This cost disadvantage diminishes as the cost of the active ingredient increases or when tablets must be coated. Furthermore, it may be possible to avoid the cost of a granulation step by choosing encapsulation in lieu of tableting.
5. Highly soluble salts (e.g., bromides, chlorides, and iodides) generally should not be dispensed in hard gelatin capsules. Their rapid release may cause gastric irritation owing to the formation of a high drug concentration in localized areas.
6. Both hard gelatin capsules and tablets may become lodged in the esophagus, where the resulting localized high concentration of certain drugs (e.g., doxycycline, potassium chloride, indomethacin) may cause damage.
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Advantages and Disadvantages of Hard Gelatin Capsules