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Common Medications: ARV Interactions

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Common Medications: ARV Interactions

Primary Care of Veterans with HIV

Drug Tables

April 2009; Last reviewed/updated: October 28, 2011

Contents

Common Medications: ARV Interactions
References

Note: Some medications mentioned in this chapter may not be available on the VHA National Formulary. Consult VA pharmacists for alternatives.

For information on potential ARV interactions with the following medications, see the specified chapters:

Acid-lowering medications (see GERD)

Fluticasone (see Asthma; COPD)

Hormonal contraceptives (see Women's Health)

Lipid-lowering medications (see Lipid-Lowering Medications)

PDE5 (see Urology)

Psychoactive medications: antidepressants, sedatives, antipsychotics (see Psychoactive Medications)

St. John's wort (see Food and Supplements)

Common Medications: ARV Interactions

Medication	ARV Interactions	Comments
Antiepileptic Medications: Carbamazepine, phenytoin, and phenobarbital may ↓ PI and NNRTI levels substantially.
Carbamazepine CYP450 inducer	PIs: may ↓ PI levels ATV: ↑ carbamazepine levels DRV: ↑ carbamazepine levels; ↓ DRV levels RTV: ↑ carbamazepine levels TPV: ↑ carbamazepine levels; ↓ TPV levels Other PIs: may also ↑ carbamazepine levels	Avoid concomitant use if possible; use alternative antiepileptics. Two-way interactions also affect PI and NNRTI levels.
	NNRTIs: may ↓ levels of all NNRTIs EFV: ↓ carbamazepine AUC 27%; ↓ EFV levels ETR, RPV: expect ↓ NNRTIs levels	Avoid use with EFV, if possible; use alternative antiepileptics. ETR and RPV should not be coadministered.
	MVC:↓ MVC levels	If used concurrently, give MVC 600 mg BID.
Phenobarbital CYP450 inducer	PIs: may ↓ PI levels DRV: ↓ phenobarbital levels RTV: ↓ phenobarbital levels TPV: ↓ phenobarbital levels and ↓ TPV levels	Avoid concomitant use if possible; use alternative antiepileptics. Two-way interactions also affect PI and NNRTI levels.
	NNRTIs: may ↓ NNRTI levels EFV and NVP: ↓ phenobarbital levels ETR: ↓ ETR levels RPV: expect ↓ RPV levels	Avoid with EFV and NVP, if possible; use alternative antiepileptics. ETR and RPV should not be coadministered.
	MVC:↓ MVC levels	If used concurrently, give MVC 600 mg BID.
Phenytoin CYP450 inducer	PIs: may ↓ PI levels DRV: ↓ phenytoin levels FPV: ↓ phenytoin levels LPV/r: ↓ LPV C_min 46%, ↓ RTV C_min 47%; ↓ phenytoin C_min 34% NFV: ↓ M8 levels 20-30%, ↓ phenytoin C_min 39% RTV: anticipate ↓ phenytoin levels TPV: ↓ TPV levels	Avoid if possible; use alternative antiepileptics. Two-way interactions also affect PI and NNRTI levels.
	NNRTIs: may ↓ NNRTI levels EFV: ↓ phenytoin levels, ↓ EFV levels ETR: ↓ ETR levels	Avoid use with EFV if possible. ETR and RPV should not be coadministered.
	MVC:↓ MVC levels	If used concurrently, give MVC 600 mg BID.
Valproate	PIs LPV/r: ↑ LPV C_max 33%, ↑ AUC 75%, may ↓ valproate levels RTV and TPV: ↓ valproate levels	Titrate to effect.
Valproate	NNRTIs: no significant changes in NNRTI or valproate levels	Titrate to effect.
Lamotrigine	LPV/r: ↓ lamotrigine levels 50% RTV: ↓ lamotrigine levels	Titrate to effect.
Antifungal Medications
Fluconazole Inhibitor of CYP 2C9	PIs ATV/r: no significant change TPV: ↑ TPV levels	TPV: Avoid fluconazole >200 mg daily.
	NNRTIs NVP: 100% ↑ in NVP levels EFV: no significant change ETR, RPV: potential ↑ in NNRTI levels	Avoid use with NVP. EFV, ETR: dosage adjustment not required. RPV: no data
Itraconazole Inhibitor and substrate of CYP 3A4	PIs:↑ PI levels and ↑ itraconazole levels LPV/r: ↑ itraconazole levels	Avoid itraconazole dosages >200 mg daily with patients who take PIs.
	NNRTIs EFV: ↓ itraconazole levels ETR: ↓ itraconazole levels and ↑ ETR NVP: ↓ itraconazole levels and ↑ NVP RPV: not studied	If used concomitantly, consider monitoring itraconazole levels and adjust itraconazole dosage as necessary. Avoid with ETR.
	MVC:↑ MVC levels	MVC 150 mg BID
Ketoconazole: Inhibitor and substrate of CYP 3A4	PIs: may ↑ PI levels and ↑ itraconazole levels ATV/r, FPV/r: ↑ ketoconazole levels DRV/r: ↑ ketoconazole levels, ↑ DRV levels LPV/r: ↑ ketoconazole levels; may ↑ or ↓ LPV/r levels	Avoid ketoconazole dosages >200 mg daily with patients who take RTV-boosted PIs.
	NNRTIs EFV: no data NVP, ETR, RPV: ↓ ketoconazole levels; ↑ NNRTI levels	Not recommended for use with NVP. Dosage adjustment for interactions with ETR and RPV not established.
	MVC:↑ MVC levels	MVC 150 mg BID
Posaconazole Inhibitor of CYP 3A4	PIs RTV: ↑ RTV levels ATV: ↑ ATV levels	Monitor laboratory values frequently for signs of toxicity.
Posaconazole Inhibitor of CYP 3A4	NNRTIs EFV: ↓ posaconazole levels ETR: ↑ ETR levels RPV: not studied	Consider alternative antifungal or monitor posaconazole level. Monitor for ETR-related adverse effects.
Terbinafine: Inhibitor of CYP 2D6	PIs: no significant changes	No dosage adjustments necessary.
Terbinafine: Inhibitor of CYP 2D6	NNRTIs: no significant changes	No dosage adjustments necessary.
Voriconazole CYP 3A4, CYP 2C9, and CYP 2C19 inhibitor; CYP 2C19 substrate	PIs: limited data RTV: voriconazole AUC ↓ 39% with RTV 100 mg BID	Not recommended for use with RTV 100 mg QD or BID unless benefit outweighs risk. If used, consider monitoring voriconazole levels.
	NNRTIs EFV: substantial ↓ voriconazole and ↑ EFV; similar effect expected for NVP ETR: ↑ voriconazole and ↑ ETR RPV: not studied	EFV: contraindicated at standard dosages; use voriconazole 400 mg BID and EFV 300 mg QD. ETR: dosage adjustments for ETR and voriconazole not established; use alternative antifungal or monitor voriconazole level and ETR adverse effects. RPV: not studied
	MVC: anticipated ↑ MVC levels	MVC 150 mg BID
Calcium Channel Blockers (CCBs)
Amlodipine	FPV, RTV, and SQV: ↑ amlodipine levels IDV: ↑ amlodipine C_max and AUC 89%	Incompletely studied. PIs may inhibit metabolism of CCBs, increasing risk of adverse effects including hypotension, conduction block, and bradycardia. NNRTIs may induce metabolism of CCBs, reducing their effect. Avoid use in patients with CHF. Avoid immediate-release forms.
Diltiazem	ATV: ↑ diltiazem C_max 200% IDV: ↑ diltiazem C_max 25% SQV/r: ↑ diltiazem levels EFV: ↓ diltiazem AUC 70% NVP: ↓ diltiazem levels
Methadone
	PIs ATV: ↓ total methadone AUC 6%; ↑ R-methadone AUC 3%, C_min 11% DRV/r: ↓ methadone AUC 16% FPV: ↓ methadone AUC 18% LPV/r: ↓ methadone AUC 53% NFV: ↓ methadone AUC 47% SQV/r: ↓ methadone AUC TPV/r: ↓ methadone AUC 48%	Most PIs ↓ methadone levels, particularly LPV/r, NFV, and TPV. Of NNRTIs, EFV and NVP ↓ methadone, whereas ETR is anticipated to have no effect. DLV ↑ methadone levels. Monitor for methadone efficacy, and signs and symptoms of opiate withdrawal. Titrate dosage cautiously as needed.
	NNRTIs EFV: ↓ methadone AUC 60% ETR: no change in methadone levels anticipated NVP: ↓ methadone AUC 46% RPV: ↓ methadone AUC 16%, ↓ C_min 22%	Monitor for methadone efficacy and signs and symptoms of opiate withdrawal. Titrate methadone dosage cautiously as needed.
Warfarin
	PIs FPV, IDV, SQV, ATV: ↑ warfarin levels LPV/r: may ↑ or ↓ warfarin levels RTV: may ↓ warfarin levels DRV: ↓ warfarin levels TPV: no change in warfarin levels	Start at low dosage; monitor INR closely. Adjust warfarin dosage as indicated. Monitor INR closely, may need increased warfarin dosage.
	NNRTIs EFV: warfarin levels may ↑ or ↓ NVP: ↓ warfarin levels (anticipated) ETR: ↑ warfarin levels (anticipated) RPV: not studied	Monitor INR closely, adjust dosage as indicated.

References

McNicholl I. HIV InSite Database of Antiretroviral Drug Interactions. San Francisco: UCSF Center for HIV Information. Available at http://arv.ucsf.edu Accessed October 28, 2010.
Micromedex® Healthcare Series [Internet database]. Greenwood Village, CO: Thomson Healthcare. Accessed December 10, 2008.
Panel on Antiretroviral Guidelines for Adult and Adolescents. Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. Rockville, MD: Department of Health and Human Services; December 1, 2009. Accessed October 28, 2010.
Also see product labeling for the individual ARVs.