Introduction
Capsules are solid preparations made with a hard or soft gelatin shell and intended for oral administration. One or more medicament is enclosed within the gelatin container. Most capsules are swallowed whole, but some contain granules which provide a useful premeasured dose for administering in a similar way to a powder, e.g. formulations of pancreatin.
Some capsules enclose enteric-coated pellets.
Advantage of Capsules Dosage Form
- Capsules are elegant
- They are easy to swallow
- They are useful in masking unpleasant tastes and odour of some drugs
- Capsules may also be used to hold powder or oils for inhalation, e.g. IntalR capsules (sodium cromoglycate) or KarvolR, or for rectal and vaginal administration, e.g. Gyno-DaktarinR (miconazole nitrate).
- Fewer excipients are required than tablets for their formulation
- Easily and rapidly digested.
- It’s easy to handle and take.
- Capsules dosage form is economical
- Capsules can be used to protect light sensitive drugs
- The shells of capsules are physiologically inert.
Disadvantages of Capsules
- Hygroscopic, efflorescent and deliquescent drugs cannot be formulated into capsules
- Concentrated preparations which require previous dilution before use are unsuitable for formulation as capsules
- Capsules are unsuitable for children and the unconscious patients
- Manufacturing of Softgel capsules are relatively expensive
- Special conditions are required for their storage
Types of Capsules Dosage Form
1. Soft shell capsules
Soft gelatin capsules consist of a flexible solid shell containing powders, non-aqueous liquids, solutions, emulsions, suspensions or pastes. Such capsules allow liquids to be given as solid dosage forms, e.g. cod liver oil. They also offer accurate dosage, improved stability and overcome some of the problems of dealing with powders. They are formed, filled and sealed in one manufacturing process.
2. Hard shell capsules
Empty capsule shells are made from gelatin and are clear, colourless and essentially tasteless. Colourings and markings can be easily added for light protection and to ease identification. The shells are used in the preparation of most manufactured capsules and for the extemporaneous compounding of capsules. The shell comprises two sections, the body and the cap, both being cylindrical and sealed at one end. Powder or particulate solid, such as granules and pellets, can be placed in the body and the capsule closed by bringing the body and cap together. Some capsules have small indentations on the body and cap which ‘lock’ together. If not, they must be sealed by moistening the outside top of the body before putting the top in place.
Other types of Capsules Include:
- Modified Release Capsules: Modified-release capsules are hard or soft gelatin capsules in which the contents or the shell, or both are prepared by a special process to modify the rate of releasing the active ingredients of the capsule.
- Enteric Capsules: Enteric Capsules are hard or soft gelatin capsules that are resisted against the gastric fluid but dissolves in the intestinal fluid to release its contents.
Shelf life and storage of capsules
If stability data are not available for extemporaneously filled capsules, then a short expiry date (up to 4 weeks) should be given. Manufactured capsules will generally be very stable and will be assigned expiry dates on the container or on the packed strips or blister packs. Most capsules need to be stored in a cool, dry place. Some capsules need to be stored in a cool place, e.g. Restandol (testosterone), which needs to be stored in the refrigerator at 2-8oC until it is dispensed to the patient, when it can be stored at room temperature for 3 months.
Containers for Capsules
Containers used are similar to those for tablets. Some capsules are susceptible to moisture absorption, and desiccants may be included in the packaging, either integrally (e.g. in the cap of the container for Losec capsules) or as separate sachets. These capsules have a limited shelf life once dispensed to a patient. Desiccant sachets should not be dispensed to patients, in case they are mistaken for a capsule and ingested.
Special Labels and Advice on Capsules
Capsules should be swallowed whole with a glass of water or other liquid. Advice may be sought from the pharmacist about whether it is acceptable to empty the contents of a capsule onto food or into water for ease of swallowing. In giving this advice, the release characteristics of the dosage form should be considered; for instance, whether it is an enteric-coated or prolonged-release formulation. Additional labels and advice may be required for capsules, depending on the drug contained.
References
- Somtoo H. Ibegbunam. Pharmaceutical Dosage Forms. Pharmabiro
- Hoag, S. (2017). Capsules Dosage Form: Formulation and Manufacturing Considerations. In Y. Qui, Y. Chen, G. Zhang, L. Yu, and R. Mantri (Eds.), Developing Solid Oral Dosage Forms – Pharmaceutical Theory and Practice, (2nd ed.) (pp. 723-747). UK: Elsevier Inc
- S.W.Hoag. Capsules Dosage Form: Formulation and Manufacturing Considerations. Science Direct. Accessed August 25, 2021