Chemistry Reference
In-Depth Information
Figure 10.1:
Siloxane polymer used in tubing and catheters for medical applications. The photograph
was provided by the Dow Corning Corporation of Midland, MI.
within the therapeutic range. It is obviously important to minimize the
amount of time the concentration is in the low, ineffective range, and to elim-
inate completely the time it is in the high, toxic range (figure 10.2).
Figure 10.3 illustrates the use of polysiloxanes in such drug-delivery systems.
The goal mentioned is approached by placing the drug inside a siloxane elas-
tomeric capsule, which is then implanted in an appropriate location in the
body. The drug within the capsule can be in the free state, in a fluid suspen-
sion, or mixed or dissolved into an elastomeric matrix. Release rates for drugs
that are much more hydrophilic than the polysiloxanes (e.g., melatonin and
sulfanilamide) are frequently relatively slow. Rates can be increased by incor-
porating solvents, channeling agents, or fillers in the capsule.
Typical nonmedical applications include high-performance elastomers,
membranes, electrical insulators, water repellents, antifoaming agents,
