D1.247 - Tolerance to intravenous sodium heparin despite a positive subcutaneous challenge test: A case report

Background. Heparins are antithrombotic and anticoagulant drugs used for prophylaxis and in emergency situations. Delayed cutaneous lesions are the most frequent adverse reaction to subcutaneous heparin treatment, with low-molecular-weight heparins (LMWHs) being the most common cause. There are few reports of tolerance to intravenous sodium heparin in patients with delayed skin reactions following subcutaneous administration of this drug.

Case report. A 61-year-old woman was referred to our centre for allergy study. 4 years before she developed erythematous plaques associated with severe pruritus at the sites of administration of bemiparin used as prophylaxis after knee prosthesis surgery with a latency of 2-3 days, with symptoms appearing after the 6th or 8th dose. Prick tests with bemiparin, sodium heparin, enoxaparin, dalteparin and fondaparinux were negative. Intradermal tests were negative with these drugs in both immediate and delayed readings. Subcutaneous challenge tests were performed with enoxaparin, sodium heparin and fondaparinux. 2 days after administration of enoxaparin, she presented with erythematous plaques at the site of administration.  The same clinical picture and latency were observed after subcutaneous administration of sodium heparin. She developed no symptoms after subcutaneous fondaparinux administration and intravenous sodium heparin challenge test.

Conclusion.  The route of administration may determine the tolerability of a drug. As intravenous unfractionated heparin may be required in urgent situations a scheduled allergy work-up should be performed if possible in cases of heparin suspected allergy in order to confirm tolerance.