Cutaneous reactions to anticoagulants. Recognition and management.

Anticoagulant-induced skin reactions appear as allergic or necrotic responses to vitamin K antagonists or heparins. Cutaneous allergy has been reported with danaparoid sodium and flush reactions have been seen with hirudins. The pathogenesis of the reactions differs between drugs. Generally, they occur between days 3 to 10 after the start of treatment, but may also occur later. In patients experiencing necrosis with a vitamin K antagonist, concomitant protein C deficiency, protein S deficiency or lupus anticoagulant has been described, whereas the precise mechanism of the other reactions is unknown. In patients with allergic reactions to heparins, cutaneous tests may help to identify alternative anticoagulants. Such a test cannot be performed in patients with skin necrosis. In patients with heparin-induced skin reactions danaparoid sodium may be used after negative intracutaneous testing in some patients and a hirudin may be used without testing in all patients. Heparin-induced skin necrosis has been reported to be mediated by immunologic mechanisms and to be associated with a high frequency of heparin-induced thrombocytopenia type II. Surgical excision of the necrosis may be required. If further anticoagulation is indicated in any patient, extreme caution has to be taken when restarting oral anticoagulants. Because a large number of anticoagulants available today, safe treatment of all patients experiencing anticoagulant-induced skin reactions is feasible.