The changing pattern of treatment for latrodectism over time in a toxicology unit: Red-back spider antivenom or standard analgesic therapy: Nothing to RAVE about.

Objective: Red-back spider (RBS) envenoming (latrodectism) can result in local, regional or generalised pain and autonomic overactivity. In 2014, the Australian RAVE-2 study found intravenous RBS-antivenom (RBSAV) was no more effective than placebo in improving pain from envenoming [1]. Anecdotally, RBSAV use appears to have decreased since this study. We aimed to assess the change in frequency of antivenom use, and responses to various treatments for latrodectism in our toxicology unit. Method(s): Retrospective observational study of RBS bite referrals, October 2009 to June 2019. Data extracted included demographics, pain severity (mild 1-3/10, moderate 4-6/10, severe 7+/10), treatment (oral or intravenous analgesia, RBSAV; IM or IV), response to treatment (no response or partial/complete resolution of pain), representation rate, adverse events (allergic reactions, serum sickness), antivenom prescribing frequency over time. Response to treatment was compared between groups using Fisher's exact test. Result(s): There were 252 presentations with latrodectism. Median age 36 (range: 2-91) years, 46% female. Pain was mild in 39%, moderate 19%, and severe 38%. Initial pain not recorded in 4.4%. Patients with mild or no initial pain score were excluded from further analysis, leaving 142 cases. RBSAV was administered as initial treatment to 35% (n= 50), and standard analgesia in 65% (n= 92). RBSAV was administered IM (43%), IV (47%), and IV/IM (10%). Median dose was one vial (range 1-4). Those administered only analgesia received a combination of paracetamol, ibuprofen and oral opioids (52%), paracetamol and ibuprofen (34%), or combination paracetamol, ibuprofen, oral and parenteral opioids (7.5%). In patients receiving antivenom, 91% reported a partial or complete reduction in pain and were discharged home and 94% of patients receiving analgesics had a partial or complete response and were discharged (p= 0.7, OR:0.7 [95% CI:0.16-2.8]). There was no difference in response