Editorial: Difficult to Compound, Part III
There have been many technological advances in the last 20 years that provide compounding pharmacy the necessary equipment and supplies to address some of the dosage forms that previously could not be compounded. This includes some metered dose inhalers and modified-release tablets/capsules, as follows:
Metered Dose Inhalers
There are generally two types of metered dose inhalers; the dry powder inhalers and those that contain a solution that is metered with each activation. The dry powder inhalers are not amenable to compounding because of the critical powder particle size distribution required for effective and consistent delivery. The solution inhalers can be compounded today; the equipment for compounding aerosol inhalers on a small scale is available.
Modified-release Tablets/Capsules
Modified-release tablets/capsules are divided into two categories in the USP; delayed release and extended release.
Delayed-release tablets/capsules, or enteric-coated tablets/capsules, have been successfully compounded by pharmacists for decades.
Extended-release tablets/capsules include those designated as "prolonged release," "repeat action," "controlled release," and "sustained release." There are numerous technologies that are used by manufacturers for extended-release products. The question involves the release pattern and the ability to control and make consistent formulations due to the variables involved. In some cases, these can be adequately controlled and compounding is appropriate; but, in many cases, it is not appropriate. Generally, dissolution testing is required for conformance to a pre-determined release rate requirement. Compounding for clinical studies using controlled-release formulations has been successfully used.1 For this category of dosage forms, there must be flexibility to allow patients to be successfully and efficiently treated and for clinical studies to continue, and this may require dissolution testing by a suitable laboratory.
Transdermal Systems (Patches)
Transdermal Systems are designed to deliver the API(s) through the skin into the systemic circulation. Transdermal systems are typically composed of an outer covering (barrier), a drug reservoir (that may incorporate a rate-controlling membrane), a contact adhesive to affix the transdermal system to the administration site, and a protective layer that is removed immediately prior to application of the transdermal system. These very sophisticated dosage systems are beyond the scope of contemporary compounding practice and should not be compounded.
Next week, we will discuss "inordinate amounts."
Loyd V. Allen, Jr., PhD, RPh
Editor-in-Chief
International Journal of Pharmaceutical Compounding
Remington: The Science and Practice of Pharmacy Twenty-second edition
- Thombre AG, Berchielli A, Rogers JF. Extemporaneously prepared controlled release formulations for accelerating the early phase development of drug candidates. Drug Discovery Today February 2014: 1-7.
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