Clopidogrel Densensitization without Discontinuation

Russell T. Attridge, Pharm.D.
The University of Texas at Austin College of Pharmacy
The University of Texas Health Science Center at San Antonio
ClotCare Editorial Board Review by Henry I. Bussey, Pharm.D.
July, 2009

A report from the American College of Cardiology 2009 Scientific Sessions shows the promise of a 6-day regimen in preventing clopidogrel discontinuation in patients displaying an allergy to the drug.¹ Twenty-one of 24 post-stent (bare-metal or drug-eluting) patients were successfully treated with corticosteroids (19 patients), antihistamines (20 patients) or both (15 patients) and were able to successfully complete the recommended duration of dual antiplatelet therapy.²

In this study, the mean time to hypersensitivity to clopidogrel was 6 days, manifesting as a rash in 83% of patients. The mean duration of steroid therapy was 6 days with no death, MI, CVA, or stent thrombosis reported in follow-up. Based on their findings, the authors propose a 6-day treatment protocol consisting of a methylprednisolone taper (Medrol Dosepak) and two antihistamines (fexofenadine 180mg in the morning and diphenhydramine 25-50mg every night at bedtime).

This follows a 2007 JACC publication detailing the use of a more traditional desensitization strategy involving the continued administration of diluted clopidogrel concluding with the administration of a standard 75mg tablet.³ While this method is effective, it is time-consuming and either clopidogrel discontinuation or a switch to ticlopidine is required for a pre-protocol 5-day washout period.

Clopidogrel allergies are uncommon (4-6% of patients) but may have dire consequences (i.e., stent thrombosis) when resulting in interruption or discontinuation.^{1, 2, 3} Use of the 6-day desensitization protocol is relatively simple and seemingly effective, making it an attractive alternative to traditional densensitization, switching to ticlopidine, or discontinuing clopidogrel all together.

References

1. Short course of steroids, antihistamines, can keep allergic patients from stopping clopidogrel. April 3, 2009. (Accessed May 5, 2009, at theheart.org/article/957393.do.)
   
   
2. Von Tiehl KF, Price MJ, Valencia R, Ludington KJ, Teirstein PS, Simon RA. Clopidogrel desensitization after drug-eluting stent placement. J Am Coll Cardiol 2007;50:2039-43.
   
   
3. Campbell KL, Mallya R, Jaffrani W, et al. Treatment of clopidogrel hypersensitivity without drug interruption: acute and long-term outcomes [abstract]. Presented at the American College of Cardiology 58th Annual Scientific Session, March 29-31, 2009. E-abstract 2515-739.