Your clever liver uses chemicals called enzymes to process meds and everything else you swallow, smoke or otherwise absorb. Enzymes can chop up only one drug at a time; multiple meds vie for service. The PI Norvir is a fierce competitor, pouncing on the enzyme before any other med can come close. Forced to wait their turn, other PIs loiter in the bloodstream, hanging around longer than they would without Norvir. Their delay is our delight—as the drugs pile up, more of them are available to fight HIV. The perfect booster club.