Introduction to Dissolution Testing

One of the main problems facing the pharmaceutical industry is to optimise the amount of drug available to the body i.e. its “bioavailability”. Inadequacies in bioavailability can mean at best that the treatment is ineffective and at worst potentially dangerous (toxic overdose).

Drug release in the human body can be measured in vivo by measuring the plasma or urine concentrations in the subject concerned. However, there are certain obvious impracticalities involved in employing such techniques on a routine basis.

These difficulties have led to the introduction of officialin vitro tests which are now rigorously defined in the respective Pharmacopoeias. Whether or not its numbers have been correlated in vivo, the standard dissolution test is a simple and inexpensive indicator of a products physical consistency.

Initially developed for immediate release (IR) and then later to extended/delayed or modified release (MR) oral dosage forms, the role of the “dissolution test” has now been extended to the “drug release” of various other forms such as semisolids, suppositories, topical and transdermal systems.

The term “dissolution test” is normally used to describe the testing of those forms such as immediate release oral tablets or capsules intended to dissolve rapidly in the test medium.

For non-oral dosage forms such as semisolids, suppositories, topical and transdermal systems, the term “drug release” is normally employed.

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