As an efflux pump, p-glycoprotein decreases the 'absorption' across a membrane. Thus, less drug will enter the site when the efflux pump is active compared to when it is not present or inhibited. In this case, the efflux pump works to decrease the amount of nelfinavir that enters the CNS. Inhibiting this efflux pump will result in more drug entering the CNS and a higher CNS:plasma ratio.

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