Drug release vaccine systems

Intramuscular. The large quantity of skeletal muscle in the body allows this route to be an easily accessible site for parenteral administration. Intramuscular injections can be used to treat a problem located directly in the injected muscle. For example, botu-linum toxin and other substances can be injected directly into hyperexcitable muscles to control certain types of muscle spasms or spasticity (see Chapter 13).7,78 Alternatively, intramuscular injection can be used as a method for a relatively steady, prolonged release of the drug into the systemic circulation to control conditions such as psychosis,2 or to administer certain vaccines. 

The development of peptides and proteins as commercially viable therapeutic agents has presented some unique challenges to the drug delivery scientist. Areas where expanded research efforts are important include development of delivery systems with precisely controlled release kinetics—with a particular emphasis on a fundamental understanding of the mechanism of drug release (Shah et ah, 1992) —and further development of pulsatile (e.g., for vaccine delivery), and temporal release systems where the release of drug is consistent with the biochemistry of the disease state. 

Microcapsules can be used for mammalian cell culture and the controlled release of drugs, vaccines, antibiotics and hormones. To prevent the loss of encapsulated materials, the microcapsules should be coated with another polymer that forms a membrane at the bead surface. The most well-known system is the encapsulation of the alginate beads with poly-L-lysine. 

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