Table 1:

Mechanisms of pharmacokinetic drug interactions between antiretrovirals and medications commonly used in older adults

Mechanism	Relevant antiretrovirals	Coadministered agents	Possible management strategy
Absorption
Gastric acidity	Atazanavir Rilpivirine	Antacids	Separate administration times by at least 2 h26,27
		H2-receptor antagonists	Alter timing of administration and limit dose of H2-receptor antagonist Consider increasing atazanavir dose to 400 mg (along with 100 mg ritonavir)
		Proton pump inhibitors	Avoid concomitant use
Chelation	Dolutegravir Elvitegravir Raltegravir	Antacids	Separate administration times by at least 2 h28–30
Metabolism
CYP450 3A4	Protease inhibitors, cobicistat NNRTIs	Fentanyl, oxycodone Anticonvulsants (e.g., carbamazepine, phenytoin) Antiplatelet agents Anticoagulants Calcium-channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil) Corticosteroids (e.g., inhaled fluticasone–budesonide, triamcinolone by injection) Phosphodiesterase inhibitors Psychotropics (e.g., aripiprazole, quetiapine, ziprasidone) Statins (e.g., lovastatin, simvastatin)	Concentrations of coadministered agents may be increased or decreased Consider agents less likely to interact Monitor patient’s response and adjust dose of coadministered agent accordingly
Other CYP450 isoenzymes (e.g., CYP2D6, CYP2B6, CYP2C9, CYP2C19)	Protease inhibitors, cobicistat NNRTIs	Antidepressants Oral hypoglycemic agents (e.g., repaglinide, nateglinide, rosiglitazone) Warfarin	Concentrations of coadministered agents may be increased or decreased Consider agents less likely to interact Monitor patient’s response and adjust dose of coadministered agent

Note: CYP450 = cytochrome P450, NNRTI = non-nucleoside reverse transcriptase inhibitor.