Controlled delivery of systemic therapy

Viral diseases are a significant cause of disability and death. Many deadly viral diseases—such as smallpox and polio—are now under control, due largely to the development of protective vaccines, but vaccines for certain viral illnesses 

Sections 10.1 and 10.3 were co-authored by Rebecca K. Willits and W. Mark Saltzman. Section 10.2 has appeared elsewhere in a different form [1]. 

The highest dose T-20 regimen (100 mg, twice daily) was effective at reducing viral load in patients. Viral concentration dropped by 99% over the 14-day treatment period this corresponds to a half-life of viral clearance of 2 days. 

Required Rate of Release. Controlled-release delivery systems are an alternative to frequent intravenous administration. Here, we consider the design of an implantable controlled-release matrix for T-20 delivery to human patients. The objective is to provide sustained plasma levels after a single administration. A one-compartment pharmacokinetic model provides a useful means for estimating the required rate of release from the matrix. Equation 7-1 can be modified to account for a continuous release of drug into the central compartment  

Plasma concentration at steady state is obtained from Equation 10-2 in the limit as t —oo  

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