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 astemizole or terfenadine properly.
What might happen:
Your blood level of astemizole or terfenadine 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 you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Rescriptor (delavirdine mesylate) US prescribing information. Pharmacia & Upjohn Company August, 2012.
2.Sustiva (efavirenz) US prescribing information. Bristol-Myers Squibb Company January, 2007.
3.Hismanal (astemizole) US prescribing information. Janssen Pharmaceutica Products, L.P. February, 1998.
4.Seldane (terfenadine) US prescribing information. Hoechst-Marion Roussel September, 1997.
5.Allegra (fexofenadine hydrochloride) US prescribing information. Sanofi-Aventis U.S. LLC October, 2006.
6.Claritin (loratidine) US prescribing information. Schering-Plough Corporation January, 1997.
7.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.