Capsules are solid preparations with hard or soft shells of various shapes and capacities, usually containing a single dose of active substance(s). They are intended for oral administration.

The capsule shells are made of gelatin or other substances, the consistency of which may be adjusted by the addition of substances such as glycerol or sorbitol. Excipients such as surface-active agents, opaque fillers, antimicrobial preservatives, sweeteners, coloring matter authorized by the competent authority and flavouring substances may be added. The capsules may bear surface markings.

The contents of capsules may be solid, liquid or of a more paste-like consistency. They consist of one or more active substances with or without excipients such as solvents, diluents, lubricants and disintegrating agents. The contents do not cause deterioration of the shell. The shell, however, is attacked by the digestive fluids and the contents are released.

Several categories of capsules may be distinguished:

– Hard capsules;

 – Soft capsules;

– Gastro-resistant capsules;

– Modified-release capsules;

– Cachets.

References

Steen Hansen, Stig Pedersen-Bjergaard and Knut Rasmussen, Introduction to Pharmaceutical Chemical Analysis, First Edition, Published 2012 by John Wiley & Sons, Ltd