A controlled study on the use of parenteral and oral antihistamines in preventing penicillin reactions

Experience in urticaria with patients attending a dermatological clinic in a referral center in the eastern province of Saudi Arabia

Urticaria is a common cutaneous vascular reaction pattern caused by diverse and multiple factors. However, an etiologic factor can be established in less than 20% of chronic cases. In this study, 274 patients with urticaria were evaluated in the dermatology clinic of King Fahd Hospital of the University (KFHU) between 1989 and 1992. Saudi nationals predominated; 188 patients were males (68.6%) and 86 were females (31.4%) and the peak incidence of urticaria was in young adults. The incidence of urticaria was 3.79% of dermatological cases. The success rate for identification of etiological factors was 41% in acute urticaria and 14% in chronic urticaria. The etiological categories discovered included allergies, physical factors, infections and miscellaneous systemic factors. In conclusion, causative factors remained elusive in the majority of cases. The identification and removal of the possible causative factors is the most aspect of management in urticaria. A detailed history and physical examination are in order; however, extensive laboratory investigations are unnecessary.

Drug allergy

Although allergic drug reactions are just one type of adverse reaction to medications, they are clinically very important because of the morbidity and mortality they cause. An ever-expanding pharmacopeia increases the potential for allergic drug reactions. An understanding of the types of allergic drug reactions, their immunopathologic mechanisms, and the most likely medications involved; an approach to determine the drug responsible for the reaction; and ways to prevent future allergic drug reactions are important features in minimizing patient morbidity.

Allergy to protamine

Recent advances in medicine, such as cardiac catheterization, phoresis, dialysis, and cardiopulmonary bypass technology, have increased the need for heparin anticoagulation. To antagonize heparin's effect and prevent hemorrhagic complications after the procedure, protamine has likewise been used more frequently. With its increased use have come increased reports of adverse protamine reactions consisting of rash, urticaria, elevation of pulmonary artery pressure, systemic hypotension, and, at times, death. The elevation of pulmonary artery pressure, which appears to be a rather common occurrence in animals, may be an isolated finding without clinical consequences in humans. However, this pulmonary vasoconstriction may, when severe, lead to acute right-sided heart failure and systemic hypotension. Other protamine reactions involve a decrease in systemic vascular resistance and systemic hypotension without changes in pulmonary artery pressure. Causes of acute protamine reactions may involve the generation of anaphyatoxins and prostanoids either from protamine-heparin complexes or complement-fixing antiprotamine IgG antibodies, from inhibition of plasma Carboxypeptidase N, from crosslinking of cell-surface antiprotamine IgE on mast cells and basophils with subsequent mediator release, or from potentiation of IgE-mediated release of histamine through a polycationin-recognition site. Although we have come a long way in understanding the mechanisms by which protamine can cause its ill effects in humans, more work is clearly needed to define, in prospective studies, the incidence of and risk factors for protamine reactions in various patient groups, and to delineate more clearly which mechanisms are involved in each clinical type of acute protamine reaction. Hopefully, this will lead to strategies and protamine alternatives that will prevent or diminish, in frequency or severity, adverse protamine reactions. Alternatively, a clearer picture of the risk factors important for protamine reactions and the predictive value of diagnostic tests (e.g., protamine IgE antibody) can also minimize the clinical impact of this increasingly common adverse event.