Chemistry Reference
In-Depth Information
Fig. 9.3
Drug level in body
tissue (e.g., blood) in case of
(
a
) traditional drug delivery
system (TDS) and (
b
)
controlled drug delivery
system (CDS)
threshold and, after sometime, falls down below the effective therapeutic level [
85
,
86
]. On the contrary, the purpose of controlled release systems (CRS) is to maintain
drug concentration in the target tissues at the therapeutic level as long as possible
(Fig.
9.3b
). Thus, both the high concentrations (peaks) and the subsequent subther-
apeutic levels (troughs) of the drug, associated with TDS, get avoided. As a result,
this minimizes the side effects and also reduces the chances of drug resistance [
85
,
86
]. Further, the low frequency of dosage leads to patient convenience.
The most convenient controlled release system (CRS) consists of the drug
enclosed in a customized matrix, which releases the drug at a predetermined rate.
This maintained the therapeutic level of the drug in blood plasma or in the area of
the intended tissue.
9.3.1 The Concept of Drug Delivery Matrix
Because of low cost and ease of fabrication, one common way of obtaining
controlled release of a drug is by enclosing it in a hydrophobic matrix (such as
wax, polyethylene, polypropylene, ethyl cellulose, etc.) or in a hydrophilic matrix
