Sequential randomised and double blind trial of promethazine prophylaxis against early anaphylactic reactions to antivenom for bothrops snake bites

OBJECTIVE

To investigate the efficacy of the H1 antihistamine promethazine against early anaphylactic reactions to antivenom.

DESIGN

Sequential randomised, double blind, placebo controlled trial.

SETTING

Public hospital in a venom research institute, São Paulo, Brazil.

PARTICIPANTS

101 patients requiring antivenom treatment after being bitten by bothrops snakes.

INTERVENTION

Intramuscular injection of promethazine (25 mg for adults and 0.5/kg for children) or placebo given 15-20 min before starting intravenous infusion of antivenom.

MAIN OUTCOME MEASURES

Incidence and severity of anaphylactic reactions occurring within 24 hours after antivenom.

RESULTS

Reactions occurred in 12 of 49 patients treated with promethazine (24%) and in 13 of 52 given placebo (25%); most were mild or moderate. Continuous sequential analysis indicated that the study could be interrupted at the 22nd untied pair, without preference for promethazine or placebo.

CONCLUSION

Prophylaxis with promethazine does not prevent early reactions. Patients should be observed carefully during antivenom infusion and the subsequent few hours.

Laboratory characterization of human T cell lymphotropic virus types 1 (HTLV-1) and 2 (HTLV-2) infections in blood donors from Sao Paulo, Brazil

Serologic screening for human T cell lymphotropic virus types 1/2 (HTLV-1/2) infection in blood donors has been recently introduced in Brazil. Analysis of 351,639 blood donations in Sao Paulo from January 1992 to October 1993 identified 1,063 positive (0.30%) and 2,238 indeterminate (0.63%) samples based on serologic confirmation using a 21e Western blot. A detailed analysis (serologic, molecular, and virologic), based on a laboratory diagnostic algorithm for characterization of HTLV-1 and HTLV-2 infections was undertaken in 50 seropositive or seroindeterminate blood donors. Modified serologic assays (2.3 Western blot that incorporate type-specific recombinant peptides) performed in 29 HTLV-1/2 positive and 21 HTLV-1/2 indeterminate donors with the 21e Western blot identified 25 as infected with HTLV-1, four with HTLV-2, five with untypable HTLV-1/2, 15 as HTLV-1/2 indeterminate, and one as seronegative. Polymerase chain reaction (PCR) analysis using DNA amplification of proviral pol and tax sequences from peripheral blood mononuclear cells confirmed HTLV-1 and HTLV-2 infections in all 2.3 Western blot seropositive donors; of the five serologically untypable donors, three were confirmed to be HTLV-1 positive, one HTLV-2 positive, and one negative by PCR. All of the seroindeterminate donors were also negative by PCR. Furthermore, HTLV-1 could be isolated in cocultures from 10 of 18 infected donors. Cell lines developed from two HTLV-1-infected donors were of T cell phenotype (CD2+, CD3+), exhibiting surface markers of activated CD4 cells (CD4+ CD25+ HLA-DR+). Thus, we provide evidence for the high seroprevalence of HTLV infection in blood donor population in Sao Paulo, Brazil compared with North American donors and propose a comprehensive serologic and genotypic diagnostic algorithm for HTLV-infected donors that has strong implications for counseling of these individuals.