Interactions between Antihistamines and Antiretrovirals

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Database of Antiretroviral Drug Interactions

Interactions between Antihistamines and Antiretrovirals

Interactions with Astemizole
Antiretroviral (ARV)	Dose of ARV	Dose of Astemizole	Effect on ARV Levels	Effect on Astemizole Levels	Potential Clinical Effects	Mechanism of Interaction	Management
Amprenavir^{63, 60} (APV)(Agenerase)	-	-	-	Not studied; may increase astemizole levels	Increased 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 levels	Increased 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 levels	Increased 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 levels	Increased 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 levels	Increased astemizole effects (eg, cardiac arrhythmias)	Inhibition of CYP450 3A4 by indinavir	Do not coadminister Alternative Agents: Cetirizine Fexofenadine Loratadine
Antiretroviral (ARV)	Dose of ARV	Dose of Astemizole	Effect on ARV Levels	Effect on Astemizole Levels	Potential Clinical Effects	Mechanism of Interaction	Management
Lopinavir/ritonavir⁷⁸ (LPV/r)(Kaletra)	-	-	-	Not studied; may increase astemizole levels	Increased 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 levels	Increased astemizole effects (eg, cardiac arrhythmias)	Inhibition of CYP450 3A4 by nelfinavir	Do not coadminister Alternative Agents: Cetirizine Fexofenadine Loratadine
Ritonavir^{178, 55} (RTV)(Norvir)	-	-	-	Not studied; may increase astemizole levels	Increased 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 levels	Increased 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 levels	Increased 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 ARV	Dose of Cetirizine	Effect on ARV Levels	Effect on Cetirizine Levels	Potential Clinical Effects	Mechanism of Interaction	Management
Efavirenz⁹⁰ (EFV)(Sustiva)	600 mg x 10 days	10 mg x 1 dose	No significant change	Cetirizine Cmax: decreased 24%	-	-	No dose adjustment necessary
Ritonavir²⁵² (RTV)(Norvir)	600 mg BID	10 mg QD	Not studied	Cetirizine 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 ARV	Dose of Terfenadine	Effect on ARV Levels	Effect on Terfenadine Levels	Potential Clinical Effects	Mechanism of Interaction	Management
Amprenavir^{63, 60} (APV)(Agenerase)	-	-	-	Not studied; may increase terfenadine levels	Increased 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 levels	Increased 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 levels	Increased 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 levels	Increased terfenadine effects (eg, cardiac arrhythmias)	Inhibition of CYP450 3A4 by lopinavir/ritonavir	Do not coadminister Alternative Agents: Cetirizine Fexofenadine Loratadine
Antiretroviral (ARV)	Dose of ARV	Dose of Terfenadine	Effect on ARV Levels	Effect on Terfenadine Levels	Potential Clinical Effects	Mechanism of Interaction	Management
Nelfinavir²⁴ (NFV)(Viracept)	-	-	-	Not studied; may increase terfenadine levels	Increased terfenadine effects (eg, cardiac arrhythmias)	Inhibition of CYP450 3A4 by nelfinavir	Do not coadminister Alternative Agents: Cetirizine Fexofenadine Loratadine
Ritonavir^{178, 55} (RTV)(Norvir)	-	-	-	Increased terfenadine levels	Increased 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 days	60 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 levels	Increased 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.