University of California, San Francisco Logo

University of California, San Francisco | About UCSF | Search UCSF | UCSF Medical Center

Home > Treatment > Interactions
Database of Antiretroviral Drug Interactions

Interactions between Antihistamines and Antiretrovirals

Interactions with Astemizole
Antiretroviral (ARV)Dose of ARVDose of AstemizoleEffect on ARV LevelsEffect on Astemizole LevelsPotential Clinical EffectsMechanism of InteractionManagement
Amprenavir63, 60
(APV)(Agenerase)
- - - Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by amprenavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Darunavir161
(DRV)(Prezista)
---Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by darunavir/ritonavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Delavirdine88
(DLV)(Rescriptor)
- - - Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 and 2C9 by delavirdine

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Efavirenz90
(EFV)(Sustiva)
- - - Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by efavirenz

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Indinavir253
(IDV)(Crixivan)
---Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by indinavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Antiretroviral (ARV)Dose of ARVDose of AstemizoleEffect on ARV LevelsEffect on Astemizole LevelsPotential Clinical EffectsMechanism of InteractionManagement
Lopinavir/ritonavir78
(LPV/r)(Kaletra)
- - - Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by lopinavir/ritonavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Nelfinavir254
(NFV)(Viracept)
---Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by nelfinavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Ritonavir178, 55
(RTV)(Norvir)
---Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by ritonavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Saquinavir44
(SQV)(Fortovase, Invirase)
---Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by saquinavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Tipranavir154
(TPV)(Aptivus)
---Not studied; may increase astemizole levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by tipranavir/ritonavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

"-" indicates that there are no data available
Interactions with Cetirizine
Antiretroviral (ARV)Dose of ARVDose of CetirizineEffect on ARV LevelsEffect on Cetirizine LevelsPotential Clinical EffectsMechanism of InteractionManagement
Efavirenz90
(EFV)(Sustiva)
600 mg x 10 days10 mg x 1 doseNo significant changeCetirizine Cmax: decreased 24%- -

No dose adjustment necessary

Ritonavir252
(RTV)(Norvir)
600 mg BID10 mg QDNot studiedCetirizine AUC: increased 42%; half-life: increased 52%; clearance: decreased 29%; Cmax: no significant change--

No dose adjustment necessary

"-" indicates that there are no data available
Interactions with Terfenadine
Antiretroviral (ARV)Dose of ARVDose of TerfenadineEffect on ARV LevelsEffect on Terfenadine LevelsPotential Clinical EffectsMechanism of InteractionManagement
Amprenavir63, 60
(APV)(Agenerase)
- - - Not studied; may increase terfenadine levelsIncreased terfenadine effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by amprenavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Darunavir161
(DRV)(Prezista)
---Not studied; may increase terfenadine levelsIncreased astemizole effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by darunavir/ritonavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Delavirdine88
(DLV)(Rescriptor)
- - - Not studied; may increase terfenadine levelsIncreased terfenadine effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 and 2C9 by delavirdine

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Indinavir16
(IDV)(Crixivan)
- - - - Increased terfenadine effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by indinavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Lopinavir/ritonavir78
(LPV/r)(Kaletra)
- - - Not studied; may increase terfenadine levelsIncreased terfenadine effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by lopinavir/ritonavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Antiretroviral (ARV)Dose of ARVDose of TerfenadineEffect on ARV LevelsEffect on Terfenadine LevelsPotential Clinical EffectsMechanism of InteractionManagement
Nelfinavir24
(NFV)(Viracept)
---Not studied; may increase terfenadine levelsIncreased terfenadine effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by nelfinavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Ritonavir178, 55
(RTV)(Norvir)
---Increased terfenadine levelsIncreased terfenadine effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by ritonavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Saquinavir44
(SQV)(Fortovase, Invirase)
1200 mg TID x 4 days60 mg BID x 11 days-Terfenadine AUC: increased 368%; Cmax: increased 253%Increased terfenadine effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by saquinavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

Tipranavir154
(TPV)(Aptivus)
---Not studied; may increase terfenadine levelsIncreased terfenadine effects (eg, cardiac arrhythmias)Inhibition of CYP450 3A4 by tipranavir/ritonavir

Do not coadminister

Alternative Agents:
Cetirizine Fexofenadine Loratadine

"-" indicates that there are no data available
 16:Crixivan [package insert]. Whitehouse Station, NJ: Merck & Co., Inc.; Oct 2005.
 24:Viracept [package insert]. La Jolla, CA: Agouron Pharmaceuticals, Inc.; Sept 2004.
 44:Fortovase [package insert]. Basel, Switzerland: F. Hoffman-La Roche Ltd.;2003.
 55:Norvir [package insert]. North Chicago, IL: Abbott Laboratories, 2008.
 60:Agenerase [package insert]. Research Triangle Park, NC: Glaxo Wellcome Inc; 2004.
 63:Decker CJ, Laitinen LM, Bridson GW, et al. Metabolism of amprenavir in liver microsomes: Role of CYP3A4 inhibition for drug interactions. J Pharm Sci 1998;87:803-7.
 78:Kaletra [package insert]. North Chicago, IL: Abbott Laboratories; Oct 2005.
 88:Rescriptor [package insert]. La Jolla, California: Agouron Pharmaceuticals, Inc; June 2001.
 90:Sustiva [package insert]. Princeton, NJ: Bristol-Myers Squibb Company; Dec 2011.
 154:Aptivus [package insert]. Ridgefield, CT: Boehringer Ingelheim Pharmaceuticals, Inc.; Nov 2005.
 161:Prezista [package insert]. Raritan, NJ: Tibotec Therapeutics Inc.; April 2010.
 178:Dresser GK, Spence JD, Bailey DG. Pharmacokinetic-pharmacodynamic consequences and clinical relevance of cytochrome P450 3A4 inhibition. Clin Pharmacokinet 2000;38:41-57.
 252:Peytavin G, Gautran C, Otoul C, et al. Lack of clinically relevant pharmacokinetic (PK) interaction between cetirazine (CTZ) and ritonavir in male healthy subjects. [abstract #H-1718]. 42nd Interscience Conference on Antimicrobial Agents and Chemotherapy; 2002 September 27-30; Chicago, Illinois.
 253:Hismanal [package insert]. Titusville, NJ: Janssen Pharmaceutica; 1998.
 254:CDC. Guidelines for the use of antiretroviral agents in HIV-infected adults and adolescents. Jan 28, 2000. [AIDS Treatment Information Service: Current Treatment] Available at: http://www.hivatis.org/trtgdlns.html.