Case 1: Drug Interactions with Antiretroviral Medications

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Case last updated: June 26, 2006

A 45-year-old HIV-infected male presents to the clinic for a routine visit. He has been on HAART for almost two years and despite occasionally missing doses his most recent HIV RNA is less than 50 copies/mL and his CD4 count is 480 cells/mm3. His current medication regimen includes the following:

Indinavir (Crixivan) 800 mg PO BID
Ritonavir (Norvir) 200 mg PO BID
Lamivudine (Epivir) 150 mg tab PO BID
Didanosine (Videx EC) 400 mg enteric-coated capsule PO QD
Sildenafil (Viagra) 50 mg PO PRN for erectile dysfunction

Which of the following is true regarding a potential drug-drug interaction?

	Didanosine enteric-coated capsules (Videx EC) will markedly decrease the absorption of indinavir.
	Ritonavir can significantly increase levels of sildenafil.
	Ritonavir significantly decreases the half-life of indinavir.
	Lamivudine significantly lowers ritonavir levels.