This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.
Severe. These medicines may interact and cause very harmful effects and are usually not taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
When these two medicines are taken together, your body may not process the antihistamine properly.
What might happen:
Your blood level of antihistamine may increase and cause life-threatening effects to your heart.
What you should do about this interaction:
Contact your healthcare professionals (e.g. doctor or pharmacist) as soon as possible about taking these two medicines together. They may already be aware of this interaction and may be monitoring for you it. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Mathews DR, McNutt B, Okerholm R, Flicker M, McBride G. Torsades de pointes occurring in association with terfenadine use. JAMA 1991 Nov 6; 266(17):2375-6.
2.Woosley RL, Chen Y, Freiman JP, Gillis RA. Mechanism of the cardiotoxic actions of terfenadine. JAMA 1993 Mar 24-31;269(12):1532-6.
3.Cortese LM, Bjornson DC. Comment: the new macrolide antibiotics and terfenadine. Ann Pharmacother 1992 Jul-Aug;26(7-8):1019.
4.Peck CC, Temple R, Collins JM. Understanding consequences of concurrent therapies. JAMA 1993 Mar 24-31;269(12):1550-2.
5.Peters DH, Friedel HA, McTavish D. Azithromycin. A review of its antimicrobial activity, pharmacokinetic properties and clinical efficacy. Drugs 1992 Nov;44(5):750-99.
6.Honig PK, Woosley RL, Zamani K, Conner DP, Cantilena LR Jr. Changes in the pharmacokinetics and electrocardiographic pharmacodynamics of terfenadine with concomitant administration of erythromycin. Clin Pharmacol Ther 1992 Sep;52(3):231-8.
7.Ballow CH, Amsden GW. Azithromycin: the first azalide antibiotic. Ann Pharmacother 1992 Oct;26(10):1253-61.
8.Snook J, Boothman-Burrell D, Watkins J, Colin-Jones D. Torsade de pointes ventricular tachycardia associated with astemizole overdose. Br J Clin Pract 1988 Jun;42(6):257-9.
9.Sakemi H, VanNatta B. Torsade de pointes induced by astemizole in a patient with prolongation of the QT interval. Am Heart J 1993 May;125(5 Pt 1):1436-8.
10.Eller M, Russell T, Ruberg S, Okerholm R, McNutt B. Effect of erythromycin on terfenadine metabolite pharmacokinetics. Clin Pharmacol Ther 1993;53(2):161.
11.Harris S, Morse I, Hilligoss DM, Colangelo PM, Eller M, Okerholm R. Azithromycin and terfenadine: lack of drug interaction, a double-blind, placebo-controlled study. 33rd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) 1993 Oct 17.
12.Biglin KE, Faraon MS, Constance TD, Lieh-Lai M. Drug-induced torsades de pointes: a possible interaction of terfenadine and erythromycin. Ann Pharmacother 1994 Feb;28(2):282.
13.Garteiz DA, Hook RH, Walker BJ, Okerholm RA. Pharmacokinetics and biotransformation studies of terfenadine in man. Arzneimittelforschung 1982;32(9a):1185-90.
14.Personal communication. Marion Merrell Dow 1991.
15.Seldane (terfenadine) US prescribing information. Hoechst-Marion Roussel September, 1997.
16.Data on file. Marion Merrell Dow 1991.
17.Honig PK, Wortham DC, Zamani K, Cantilena LR. Comparison of the effect of the macrolide antibiotics erythromycin, clarithromycin and azithromycin on terfenadine steady-state pharmacokinetics and electrocardiographi parameters. Drug Invest 1994;7(3):148-56.
18.Goss JE, Ramo BW, Blake K. Torsades de pointes associated with astemizole (Hismanal) therapy. Arch Intern Med 1993 Dec 13;153(23):2705.
19.Brannan MD/Reidenberg P, Radwanski E, Shneyer MA, Lin C, Affrime MB. Evaluation of pharmacokinetic and electrocardiographic parameters following 10 days of concomitant loratadine and erythromycin administration. Presented at the annual meeting of the American College of Clinical Pharmacy 1994 Jun.
20.Affrime MB, Lorber R, Danzig M, Cuss F, Brannan MD. Three month evaluation of electrocardiographic effects of loratatdine in humans. J Allergy Clin Immunol 1993;91(1):259.
21.Data on file. Janssen Pharmaceutica Products, L.P. 1991.
22.Yumibe N, Huie K, Chen KJ, Clement RP, Cayen MN. Identification of human liver cytochrome P450s involved in the microsomal metabolism of the antihistaminic drug loratadine. J Allergy Clin Immunol 1994 Jan;93(Part 2):234.
23.Chen Y, Gillis RA, Woosley RL. Block of delayed rectifier potassium current, IK, by terfenadine in cat ventricular myocytes. J Am Coll Cardiol 1991 Feb;17(2):140A.
24.Biaxin (clarithromycin) US prescribing information. AbbVie, Inc. January, 2015.
25.Hismanal (astemizole) US prescribing information. Janssen Pharmaceutica Products, L.P. February, 1996.
26.Claritin (loratadine) US prescribing information. Schering-Plough Corporation January, 1997.
27.Allegra (fexofenadine hydrochloride) US prescribing information. Sanofi-Aventis U.S. LLC October, 2006.
28.Dear Doctor Letter. Janssen Pharmaceutica Products, L.P. February 1998.
29.Mizollen (mizolastine) US prescribing information. Lorex Synthelab September 29, 1997.
30.Drew BJ, Ackerman MJ, Funk M, Gibler WB, Kligfield P, Menon V, Philippides GJ, Roden DM, Zareba W. Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation. J Am Coll Cardiol 2010 Mar 2;55(9):934-47.
31.Phansalkar S, Desai AA, Bell D, Yoshida E, Doole J, Czochanski M, Middleton B, Bates DW. High-priority drug-drug interactions for use in electronic health records. J Am Med Inform Assoc 2012 Sep-Oct; 19(5):735-43.