COMPARISON OF HYPERBARIC-OXYGEN AND DAPSONE THERAPY FOR LOXOSCELES ENVENOMATION

Objective: To determine whether hyperbaric O-2 (HBO), dapsone, or HBO plus dapsone affects lesion size in a swine model of Loxosceles enveno mation. Methods: In a randomized controlled animal laboratory experime nt, 32 piglets were assigned to 1 of 4 equal groups. Each piglet recei ved 15 mu L of purified venom intradermally on day zero, Group 1 recei ved no treatment; group 2 received HBO at 2 atm for 2 hours on days 1- 3; group 3 received 50 mg of dapsone orally on days 1-3; and group 4 r eceived dapsone 50 mg orally and HBO at 2 atm for 2 hours on days 1-3. On days 1-7, 14, and 21, an investigator blinded to the treatment gro ups measured necrosis and induration. Mean necrosis and induration rat es were compared using analysis of variance for repeated measures. Res ults: Comparing groups on any day, no significant difference was noted in necrosis, induration, reduction in necrosis from day 1, or rate of change in lesion size from days 1-7. A difference was seen in the red uction of induration between all 3 treatment groups and the control gr oup on days 7 and 14 only. The sample size permitted a power of 0.8 to detect a 12-mm mean change in lesion size. Conclusion: Compared with the control, neither dapsone, HBO, nor the combination of dapsone and HBO reduced necrosis from Loxosceles envenomation on days 3-21. An inc rease was seen in the rate of reduction in induration between all 3 tr eatment groups and the control group on days 7-21. However, the magnit ude of this effect was clinically insignificant. In this animal model, treatment with either dapsone or HBO or a combination offers Little c linical benefit in Loxosceles envenomation.