Prevalence of IgE antibodies to morphine. Relation to the high and low incidences of NMBA anaphylaxis in Norway and Sweden, respectively.

Background: Anaphylactic reactions to a neuromuscular blocking agent (NMBA) is more than six times as common in Norway as in Sweden, probably due to differences in preoperative sensitization. The prevalence of IgE-sensitization to morphine (MOR) and suxamethonium (SUX) in comparable populations in Bergen, Norway, and Stockholm, Sweden, was studied and related to possible sensitizing agents.
Methods: Three hundred sera of 'allergics' and 500 blood donors in Bergen and Stockholm were tested for IgE antibodies to MOR and SUX using Pharmacia Diagnostics ImmunoCAP(Uppsala, Sweden) assay and the results compared to those of 65 patients from Bergen with documented anaphylaxis to NMBA. In addition, 84 different household chemicals were tested, by IgE antibody inhibition, for SUX and MOR.
Results: In Norway 0.4% of blood donors, 3.7% of allergics and 38.5% of anaphylactics were IgE-sensitized to SUX, and 5.0, 10.0 and 66.7%, respectively, to MOR. No serum from Sweden was positive. The majority of those sensitized (69%) were women. Several household chemicals contained SUX and/or MOR activity, but the only difference between Norway and Sweden was cough mixtures containing pholcodine (PHO). IgE antibodies to PHO were present in 6.0% of blood donors from Norway and in no serum from Sweden. Of the anaphylactics, 65-68% were sensitized to MOR or PHO but only 39% to SUX.
Conclusions: IgE-sensitization to SUX, MOR and PHO was detected in Norway but not in Sweden. One possible explanation is the unrestricted use of cough mixtures containing MOR derivatives in Norway.