Oral administration of analgesics for pain management is often the most convenient, safe, and effective means of delivery. For example, analgesics with a well established therapeutic effectiveness and safety profile, such as morphine, are widely employed in orally administered modified release forms in the management of chronic pain. Increasingly, chronic pain management is a therapeutic category in which controlled release provides the most desirable dosing regimens with desirable pharmacokinetic profile and pharmacodynamic response. This approach prevents the patient from experiencing pain intermittently through maintenance of a consistent drug input, and may alleviate the variability involved in the administration of multiple doses per day. Thus, it improves patient compliance and prevents the sudden onset of analgesia seen with immediate release dosage forms.
The term modified release defines preparations that have been designed in such a way that the rate or place at which the active ingredients are released has been modified.
This is an all encompassing term that the BNF now uses to cover preparations such as sustained-release, controlled-release and delayed release. The sole use of the term modified-release is helpful to simplify the confusing terminology. However, its use conceals the differences between the drug delivery systems, which may be defined as:
* Sustained-release - the drug is released slowly at a rate governed by the delivery system.
* Controlled-release - the drug is released at a constant rate and plasma concentrations after administration do not vary with time.
* Delayed-release - the drug is released at a time other than immediately after administration, i.e. the site of release is controlled. There are many mechanisms by which drug release from a preparation can be modified.
Overall M/R preparations help to:
* reduce the dosing frequency and improve patient compliance;
* reduce fluctuations (peaks and troughs) in drug plasma concentrations,