Histamine 2 receptor blocker in the treatment of protamine related anaphylactoid reactions: two case reports.

Two case reports are described of acute anaphylactoid reactions following the administration of protamine to reverse the anticoagulation effect of heparin in patients undergoing coronary artery bypass graft surgery. The administration of cimetidine seemed to reverse the anaphylactoid reaction after conventional treatment with epinephrine, H1 receptor blocker, and steroids had failed. We recommend that H2 receptor blockade be included with other drugs in the treatment of anaphylactoid reactions following protamine, and possibly after anaphylactoid reactions associated with other substances.