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Three Part Question

In [scorpion envenomation] does [antivenom serotherapy] [reduce serum venom concentration]?

Clinical Scenario

A woman has been stung by a scorpion while buying bananas in her local supermarket. She is showing some signs of systemic envenomation and you wonder whether giving her antivenom will reduce her serum venom concentration.

Search Strategy

Medline 1966-11/04 using the OVID interface.
[exp Scorpions OR scorpion.mp OR exp Scorpion Venoms OR scorpion venom.mp OR scorpionism.mp] AND [envenoming.mp OR envenomation.mp] AND [exp Antivenins OR antivenom.mp OR exp Immunization, Passive OR serotherapy.mp OR exp Immunoglobulins, Fab] LIMIT to human AND English language

Search Outcome

Altogether 69 papers were found, only four of which addressed the serum kinetics of scorpion venom after administration of antivenom.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
De Rezende NA et al, 1995, Brazil	18 patients with signs of systemic envenomation	Cohort	Serum venom concentrations measured by ELISA before and after intravenous antivenom treatment	Venom antigens cleared 1 hr after antivenom	No serum venom kinetics in a control group not treated with antivenom.
			Antivenom concentrations measured by ELISA before and after intravenous antivenom treatment	High antivenom titres persisted for 24 hr.
Krifi MN et al, 1999 Tunisia	147 children under 15 years with grade II and III scorpion envenomation, divided into 6 grps according to whether given 1 or 2 doses of antivenom (IM or IV or IM and IV) and no antivenom.	Cohort	Intramuscular administration	No significant effect on toxicokinetic curve or recovery time, when only one dose given	Unclear whether retrospective analysis or prospective study. No apparent blinding.
			Intravenous administration	Rapid clearance of venom and shortened recovery time
Ghalim N et al, 2000, Morocco	275 patients, of which 179 were treated with antivenom. Antivenom administered intramuscularly (77.6%) or subcutaneously (6.2%) or both (16.2%)	Prospective cohort study	Epidemiology of envenomation.	247 showed only grade I symptoms. No patients with grade III symptoms	Venom kinetics not studied in grade II patients as they constituted only 10% of cohort.
			Toxokinetics in grade I envenomation.	Reduction in serum venom concentration. Greater effect of 10ml vs 2-5ml antivenom
			Clinical course	Symptoms improved with antivenom
Hammoudi-Triki D et al, 2004, Algeria	182 patients (adults and children) stung by scorpions. Retrospective review of charts and blood results for those treated with intramuscular antivenom.	Cohort	Epidemiology	No grade III (severe) envenomations	Retrospective review. Intramuscular rather than intravenous route used. Only one dose of antivenom given. Only 40 patients had post immunotherapy blood samples taken. Venom concentrations lower than in Krifi (1999) and Ghalim (2000) studies, although this may be due to ELISA differences.
			Venom kinetics	10 ml of im antivenom did not alter venom kinetics

Comment(s)

The vast majority of patients had only grade I envenomation. Serum venom concentrations were higher in grade II than grade I envenomations. Two studies showed that one dose of antivenom administered intramuscularly was not effective in reducing serum venom concentrations. Intravenous antivenom was effective in reducing serum venom concentrations compared to controls in two studies. Higher doses were more effective. Two studies documented clinical improvements with antivenom treatment.

Clinical Bottom Line

There is good evidence that intravenous administration of antivenom reduces serum venom concentrations. Whether this is clinically relevant is open to question.

References

1. De Rezende NA, Dias MB, Campolina D, et al. Efficacy of antivenom therapy for neutralizing circulating venom antigens in patients stung by Tityus serrulatus scorpions. Am J Trop Med Hyg 1995;52(3):277-80.
2. Krifi MN, Amri F, Kharrat H, et al. Evaluation of antivenom therapy in children severely envenomed by Androctonus australis garzonii (Aag) and Buthus occitans tunetanus (Bot) scorpions. Toxicon 1999;37(11):1627-34.
3. Ghalim N, El-Hafny B, Sebti F, et al. Scorpion envenomation and serotherapy in Morocco. Am J Trop Med Hyg 2000;62(2):277-83.
4. Hammoudi-Triki D, Ferquel E, Robbe-Vincent A, et al. Epidemiological data, clinical admission gradation and biological quantification by ELISA of scorpion envenomation in Algeria: effect of immunotherapy. Trans R Soc Trop Med Hyg 2004;98(4):240-50.