Updates to the Database of ARV Drug Interactions

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HIV Meds Quarterly Reference Table

Summer 2011

Susa Coffey, MD, HIV InSite Medical Editor

Ian R. McNicholl, HIV InSite Pharmacy Editor

The following table summarizes recent additions to the HIV InSite Database of Antiretroviral Drug Interactions. For a full description of the updates, including references to the studies from which the data were derived, go to the database, click on a specific drug name, and search for the interacting agent.

New ARV Interactions (April 2011-August 2011)
Drug One	Drug Two	Clinical Effects	Mechanisms	Management
Source: McNicholl I. HIV InSite Database of Antiretroviral Drug Interactions. University of California San Francisco: Center for HIV Information; 2011
Atazanavir	Colchicine	Increased colchicine effects	Inhibition of CYP450 3A4 by atazanavir/ritonavir	For treatment of gout, reduce colchicine dosage to 0.6 mg x 1 then 0.3 mg 1 hour later; do not repeat dosing earlier than 3 days thereafter For prophylaxis of gout, reduce colchicine dosage to 0.3 mg QD if on 0.6 mg BID prior to PI therapy, or reduce colchicine dosage to 0.3 mg QOD if on 0.6 mg QD prior to PI therapy
Atazanavir	Telaprevir			No dosage adjustment necessary
Darunavir	Colchicine	Increased colchicine effects	Inhibition of CYP450 3A4 by darunavir/ritonavir	For treatment of gout, reduce colchicine dosage to 0.6 mg x 1 then 0.3 mg 1 hour later; do not repeat dosing earlier than 3 days thereafter For prophylaxis of gout, reduce colchicine dosage to 0.3 mg QD if on 0.6 mg BID prior to PI therapy, or reduce colchicine dosage to 0.3 mg QOD if on 0.6 mg QD prior to PI therapy
Darunavir	Maraviroc		Inhibition of CYP450 3A4 by darunavir/ritonavir	No dosage adjustment necessary
Darunavir	Rilpivirine	Increased rilpivirine effects		No dosage adjustment necessary
Darunavir 600 mg BID with ritonavir 100 mg BID x 20 days	Telaprevir 750 mg Q8H x 10 days	Decreased telaprevir effects; decreased darunavir effects		Do not coadminister *Alternative agents:* Atazanavir/ritonavir
Darunavir 600 mg BID with ritonavir 100 mg BID x 24 days	Telaprevir 1,125 mg Q12H x 4 days	Possible telaprevir effects; decreased darunavir effects		Do not coadminister *Alternative agents:* Atazanavir/ritonavir
Didanosine	Rilpivirine			No dosage adjustment necessary; administer didanosine on an empty stomach and at least 2 hours before or at least 4 hours after rilpivirine (which must be administered with a meal)
Efavirenz 600 mg QD x 16 days	Boceprevir 800 mg TID x 6 days	Possible decreased boceprevir effects		Do not coadminister *Alternative agents:* Telaprevir
Efavirenz	Cisapride	Increased cisapride effects (eg, cardiac arrhythmias)		Do not coadminister *Alternative agents:* Metoclopramide
Efavirenz	Clarithromycin		Induction of CYP450 3A4 by efavirenz	Dosage adjustment not established
Efavirenz 600 mg QD x 7 days, administered with tenofovir 300 mg QD x 7 days	Telaprevir 1,125 mg Q8H x 7 days			No dosage adjustment necessary
Efavirenz 600 mg QD x 20 days	Telaprevir 750 mg Q8H x 10 days	Decreased telaprevir effects	Induction of CYP450 3A4 by efavirenz	Increase telaprevir dosage to 1,125 mg Q8H
Fosamprenavir	Colchicine	Increased colchicine effects	Inhibition of CYP450 3A4 by fosamprenavir/ritonavir	For treatment of gout, reduce colchicine dosage to 0.6 mg x 1 then 0.3 mg 1 hour later; do not repeat dosing earlier than 3 days thereafter For prophylaxis of gout, reduce colchicine dosage to 0.3 mg QD if on 0.6 mg BID prior to PI therapy, or reduce colchicine dosage to 0.3 mg QOD if on 0.6 mg QD prior to PI therapy
Fosamprenavir 700 mg with ritonavir 100 mg BID x 20 days	Telaprevir 750 mg Q8H x 10 days	Decreased telaprevir effects; decreased amprenavir effects		Do not coadminister *Alternative agents:* Atazanavir/ritonavir
Fosamprenavir 700 mg with ritonavir 100 mg BID x 24 days	Telaprevir 1,125 mg Q12H x 4 days			Do not coadminister *Alternative agents:* Atazanavir/ritonavir
Indinavir	Colchicine	Increased colchicine effects	Inhibition of CYP450 3A4 by indinavir	For treatment of gout, reduce colchicine dosage to 0.6 mg x 1 then 0.3 mg 1 hour later; do not repeat dosing earlier than 3 days thereafter For prophylaxis of gout, reduce colchicine dosage to 0.3 mg QD if on 0.6 mg BID prior to PI therapy, or reduce colchicine dosage to 0.3 mg QOD if on 0.6 mg QD prior to PI therapy
Lopinavir/ritonavir	Colchicine	Increased colchicine effects	Inhibition of CYP450 3A4 by lopinavir/ritonavir	For treatment of gout, reduce colchicine dosage to 0.6 mg x 1 then 0.3 mg 1 hour later; do not repeat dosing earlier than 3 days thereafter For prophylaxis of gout, reduce colchicine dosage to 0.3 mg QD if on 0.6 mg BID prior to PI therapy, or reduce colchicine dosage to 0.3 mg QOD if on 0.6 mg QD prior to PI therapy
Lopinavir/ritonavir	Rilpivirine	Increased rilpivirine effects		No dosage adjustment necessary
Lopinavir/ritonavir	Telaprevir	Decreased telaprevir effects		Do not coadminister *Alternative agents:* Atazanavir/ritonavir
Nelfinavir	Colchicine	Increased colchicine effects	Inhibition of CYP450 3A4 by nelfinavir	For treatment of gout, reduce colchicine dosage to 0.6 mg x 1 then 0.3 mg 1 hour later; do not repeat dosing earlier than 3 days thereafter For prophylaxis of gout, reduce colchicine dosage to 0.3 mg QD if on 0.6 mg BID prior to PI therapy, or reduce colchicine dosage to 0.3 mg QOD if on 0.6 mg QD prior to PI therapy
Rilpivirine	Acetaminophen			No dosage adjustment necessary
Rilpivirine	Antacids	Possible decreased rilpivirine effects	Decreased gastric acidity, leading to impaired drug solubility and absorption	Administer antacids at least 2 hours before or at least 4 hours after rilpivirine
Rilpivirine	Atorvastatin			No dosage adjustment necessary
Rilpivirine	Chlorzoxazone			No dosage adjustment necessary
Rilpivirine	Ethinyl estradiol/norethindrone acetate			No dosage adjustment necessary
Rilpivirine 150 mg x 1	Famotidine 40 mg x 1 taken 2 hours before rilpivirine	Decreased rilpivirine effects	Decreased gastric acidity, leading to impaired drug solubility and absorption	Administer H2 antagonist at least 12 hours before or at least 4 hours after rilpivirine
Rilpivirine 150 mg x 1	Famotidine 40 mg x 1 taken 4 hours after rilpivirine			No dosage adjustment necessary
Rilpivirine 150 mg x 1	Famotidine 40 mg x 1 taken 12 hours before rilpivirine			No dosage adjustment necessary
Rilpivirine	Ketoconazole	Decreased ketoconazole effects		No dosage adjustment necessary, but monitor for failure of antifungal therapy
Rilpivirine	Methadone	Possible decreased methadone effects (eg, withdrawal)		Monitor for signs and symptoms of methadone withdrawal; some patients may need an increase in the methadone dosage
Rilpivirine	Omeprazole	Decreased rilpivirine effects	Decreased gastric acidity, leading to impaired drug solubility and absorption	Do not coadminister *Alternative agents:* H2 antagonists, if administered at least 12 hours before or at least 4 hours after rilpivirine
Rilpivirine	Rifabutin	Decreased rilpivirine effects		Do not coadminister
Rilpivirine	Rifampin	Decreased rilpivirine effects	Induction of CYP450 3A4 by rifampin	Do not coadminister
Rilpivirine	Sildenafil			No dosage adjustment necessary
Rilpivirine	Tenofovir	Possible increased tenofovir effects		No dosage adjustment necessary
Ritonavir	Boceprevir	Possible decreased boceprevir effects; effect on ritonavir concentrations unknown		Clinical significance unknown, especially when combined with other PIs
Ritonavir	Quinine	Increased quinine effects	Possible competitive displacement from CYP450 3A4 and inhibition of 2D6	Avoid combination if possible; if combination must be used a potential 4-fold reduction in quinine dosage may be needed
Ritonavir 100 mg x 1	Telaprevir 750 mg x 1			Dosage adjustment not established
Ritonavir 100 mg Q12H x 14 days	Telaprevir 750 mg Q12H x 14 days			Dosage adjustment not established
Saquinavir	Colchicine	Increased colchicine effects	Inhibition of CYP450 3A4 by saquinavir	For treatment of gout, reduce colchicine dosage to 0.6 mg x 1 then 0.3 mg 1 hour later; do not repeat dosing earlier than 3 days thereafter For prophylaxis of gout, reduce colchicine dosage to 0.3 mg QD if on 0.6 mg BID prior to PI therapy, or reduce colchicine dosage to 0.3 mg QOD if on 0.6 mg QD prior to PI therapy
Telaprevir 750 mg Q8H x 7 days	Tenofovir 300 mg QD x 7 days	Possible increased tenofovir effects		Dosage adjustment not established
Telaprevir 1,125 mg Q8H x 7 days	Tenofovir 300 mg QD administered with efavirenz 600 mg QD x 7 days	Possible increased tenofovir effects		No dosage adjustment necessary
Telaprevir 1,500 mg Q12H x 7 days	Tenofovir 300 mg QD administered with efavirenz 600 mg QD x 7 days	Possible decreased telaprevir effects		Adjust telaprevir dosage to 1,125 mg Q8H when used with efavirenz
Tenofovir	Boceprevir			No dosage adjustment necessary
Tipranavir	Colchicine	Increased colchicine effects	Inhibition of CYP450 3A4 by tipranavir/ritonavir	For treatment of gout, reduce colchicine dosage to 0.6 mg x 1 then 0.3 mg 1 hour later; do not repeat dosing earlier than 3 days thereafter For prophylaxis of gout, reduce colchicine dosage to 0.3 mg QD if on 0.6 mg BID prior to PI therapy, or reduce colchicine dosage to 0.3 mg QOD if on 0.6 mg QD prior to PI therapy

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