Volume 179 - Issue 8
Latrodectism: a prospective cohort study of bites by formally identified redback spiders
Author: Saul Wiener
Med J Aust 2003; 179 (8): 455-456. || doi: 10.5694/j.1326-5377.2003.tb05640.x
Published online: 20 October 2003
Published online: 20 October 2003
To the Editor: In their study on the effectiveness of antivenom for redback spider bite, Isbister and Gray cast doubt on the current method of administering antivenom intramuscularly.1
Any study on the outcome of treating bites by venomous animals is limited by factors beyond the control of the investigator. These include the variability of the venom content in the animal’s venom apparatus, uncertainty regarding how much and where venom has been injected, and the delay before treatment.
Between 1955 and 1957, I dissected the venom glands of 590 redback spiders for the production of antivenom.2 The yield of freeze dried venom per spider varied from 0.08 mg to 0.32 mg. Based on these findings, and to allow for dilution of antivenom by body fluids, “it was considered that 500 units of antivenene would constitute a suitable initial dose for the treatment of a bite by L. hasseltii”.3 This amount of antivenom will neutralise 5 mg of venom in vitro, and the antivenom is still issued in this strength by CSL Ltd.
No fatalities have occurred from redback spider bite since antivenom became available in 1956,4 and reports from doctors have confirmed its efficacy and safety.5 If symptoms persist after the initial dose, or if diagnosis has been delayed, the initial dose of 500 units may have to be repeated. As Banham et al have wisely stated “treatment should be titrated against response”.6
Because of the risk of anaphylaxis, intramuscular injection, which has stood the test of time, is safer than the intravenous route.
References
- Isbister GK, Gray MR. Latrodectism: a prospective cohort study of bites by formally identified redback spiders. Med J Aust 2003; 179: 88-91.
- Wiener S. The Australian red back spider (Latrodectus hasseltii) I. Preparation of antiserum by the use of venom adsorbed on aluminium phosphate. Med J Aust 1956; 1: 739-742. CACIEDEE
- Wiener S. Red back spider antivenene. Med J Aust 1961; 2: 41-43. CACGGICF
- Sutherland SK. Spider bites in Australia. Med J Aust 1983; 2: 597. CACGIGFG
- Sutherland SK, Trinca KC. Survey of 2144 cases of red-back spider bites. Med J Aust 1978; 2: 620-623. CACDBCBF
- Banham NDG, Jelinek GA, Finch PM. Late treatment with antivenom in prolonged red-back spider envenomation. Med J Aust 1994; 161: 379-381. CACECCDJ
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