While real doctors like Andy can speak (and understand) double blinded, randomized, quasi, intergalactic, multi-species language and turn to the methods to see if they are worth while, I judge a study solely on its name. That’s why I love Geoff Isbister and crew's new paper on the RAVE II study. How can you not like a study titled RAVE. Additionally, it also verifies my practice.
RAVE II (Redback AntiVenom Evaluation) is the largest randomized, placebo-controlled trial yet of antivemon efficacy in widow spider envenomation/latrodectism. Widow spiders (Redback in Australasia, Black Widow in the US) are the most common, severe spider envenomations worldwide. While the bite is not immediately painful, intense local pain soon develops along with sweating (may be regional) and piloerection. Hypertension, tachycardia and severe abdominal pain are also described.
Their two primary endpoints were 1) clinically significant pain reduction from baseline and 2) resolution of systemic features of envenomation, both at 2 hours after study treatment. They enrolled 227 with three exclusions so 224 were randomised and the results showed that antivenom was no better than placebo for either endpoint (or any of their measures). They only difference was a mild skin hypersensitivity that occurred in 4 of 112 patients in the antivenom group with none in the placebo group.
It has always been my practice (and teaching) to use redback/black widow antivenom sparingly. I would only recommend it in very severe cases as it can cause significant allergic reactions and patients recover just fine without it.
Isbister GK, Page CB, Buckley NA, Fatovich DM, Pascu O, MacDonald SP, Calver LA, Brown SG; RAVE Investigators.Randomized Controlled Trial of Intravenous Antivenom Versus Placebo for Latrodectism: The Second Redback Antivenom Evaluation (RAVE-II) Study. Ann Emerg Med. 2014 Jul 3.