Legend: As substrates of metabolizing enzymes, cabotegravir and/or rilpivirine concentrations can be increased or decreased when co-administered with drugs that either inhibit or induce those enzymes. The black line shows a theoretical concentration vs time profile of a drug given in the absence of an enzyme inhibitor or inducer. It would be anticipated that concentrations would be maintained above 4xPAIC₉₀ prior to the next dose being given. However, in the presence of an enzyme inducer (blue line), concentrations would be expected to fall more rapidly and may fall below the 4xPAIC₉₀ prior to the next scheduled dose. The areas highlighted in grey represents the window of concentrations where selection for mutant drug-resistant virus is most at risk as concentrations may be effective against susceptible strains, but not resistant strains. The bottom blue area represents where concentrations are expected to be ineffective, and risk of viral rebound occurs. Conversely, when given with an enzyme inhibitor (top blue line) concentrations are expected to persist or perhaps accumulate to higher concentrations, increasing the risk of toxicities or adverse events, e.g. QTc prolongation with rilpivirine.