Table 2.

Characteristics of included studies for meta-analyses

Studies and parameters	Comments
Comparison	Antivenom vs. standard therapy (new world scorpions)
Boyer et al. 2009 [20]
Methods	Randomized double blind study
Participants	Children and adults aged between 6 months and 18 years admitted to a paediatric intensive care unit within 5 h since a scorpion sting
Interventions	The test group (n = 8) received scorpion antivenom against Centruroides sp. while the control group (n = 7) received a placebo. Dose: three vials diluted in 50 ml of saline. Both groups received similar supportive care.
Outcomes	Resolution of clinical syndrome within 4 h of antivenom administration, cumulative midazolam dose required for sedation and serum venom levels up to 4 h post admission, adverse events
Study location	Arizona, USA
Boyer et al. 2013 [19]
Methods	Controlled study with trial arm recruited prospectively and compared with a retrospective control group
Participants	Children and adults aged between 6 months and 18 years admitted to a paediatric intensive care unit within 5 h since a scorpion sting
Interventions	The prospectively recruited subjects (n = 78) received scorpion antivenom against Centruroides sp. while the control group (n = 97) had been managed without antivenom. Three vials of antivenom were administered within 10 min diluted in 50 ml of saline. Two additional vials were administered at the discretion of the physician if symptoms had not resolved at 1 or 2 h since the initial dose.
Outcomes	Resolution of clinical syndrome within 4 h of antivenom administration, serum venom levels up to 4 h post admission (in prospective group only), adverse events
Study location	Arizona, USA and Morelos, Mexico
LoVecchio et al. 2003 [18]
Methods	Observational study without randomization
Participants	Children aged less than 2 years with either a witnessed scorpion sting or signs and symptoms consistent with scorpion envenoming
Interventions	Severity was graded on a scale of I–IV with grades III and IV having systemic envenoming. A subset of patients with grade III and IV envenoming had received anti-Centruroides antivenom (1 vial diluted in 50 ml of saline, n = 86). Another 46 children did not receive antivenom despite having grade III and IV envenoming. Criteria for administration of antivenom are not clear.
Outcomes	Meantime for resolution/improvement of systemic envenoming, adverse events, deaths
Study location	Arizona, USA
Comparison	Antivenom vs. standard therapy (old world scorpions)
Abroug et al. 1999 [15]
Methods	Prospective randomized controlled trial
Participants	Patients with scorpion stings older than 10 years. A total of 825 patients were randomly allocated to test (n = 412) and control arms (n = 413)
Interventions	The test group received 20 ml of bivalent (A. australis and B. occitanus) scorpion antivenom. Both groups received supportive care with steroids, fluid replacement, antihistamines and life-supporting measures for systemic envenoming as required.
Outcomes	Severity was graded as I (no systemic envenoming) and II (systemic envenoming). Prevention was defined as non-progression from grade I to II, and cure was defined as reversal of symptoms from grade II. Outcomes were defined after 4 h since administration of antivenom or admission. Other monitored outcomes were death, complications of envenoming and adverse effects attributable to antivenom.
Study location	Tunisia
Belghith et al. 1999 [16]
Methods	Retrospective analysis of a sub-population of patients enrolled for a clinical trial. Control group selected prospectively
Participants	Patients with scorpion stings older than 10 years. One hundred and thirty five patients who were administered bivalent antivenom for scorpion during a previous trial had their records re-examined and matched with controls on a pair-match basis.
Interventions	No prospective intervention. Controls did not receive antivenom.
Outcomes	Severity was graded as I (no systemic envenoming) and II (systemic envenoming). Prevention was defined as non-progression from grade I to II, and cure was defined as reversal of symptoms from grade II. Outcomes were defined after 4 h since administration of antivenom or admission. Other monitored outcomes were death, complications of envenoming and adverse effects attributable to antivenom.
Study location	Tunisia
Comparison	Antivenom plus prazosin vs. prazosin
Bawaskar et al. 2011 [23]
Methods	Randomised open label clinical trial
Participants	Patients older than 6 months, reporting to hospital within 6 h of the sting and of grade II clinical severity (systemic autonomic symptoms without shock). A total of 70 patients were randomized, 35 each to test and control groups.
Interventions	The test group received Haffkine Biopharma monovalent scorpion antivenom (against M. tamulus) 30 ml dissolved in 100 ml of normal saline and infused over 30 min. Both groups received either 250 μg (under 18 years of age) or 500 μg of oral prazosin at 3 hourly intervals until the extremities were cold (resolution of peripheral vasodilatation).
Outcomes	Primary endpoint: resolution of grade II clinical syndrome at 10 h and prevention of progression to a higher grade (III, IV characterized by autonomic symptoms plus shock, pulmonary oedema) Secondary endpoints: time to total resolution of clinical syndrome, total dose of prazosin required within 10 h and adverse events
Study location	Maharashtra, India
Natu et al. 2010 [22]
Methods	Prospective open label clinical trial
Participants	Patients aged 12–70 with a confirmed scorpion sting. The authors developed a composite clinical score based (minimum and maximum scores were 0 and 25, respectively) on pulse rate, blood pressure, presence of priapism, sweating, pain and neurological symptoms. Scores between 5 and 21 were included in the study. The enrolled were randomized into three trial arms: prazosin alone (n = 25), prazosin and antivenom (n = 28) and antivenom alone (n = 28).
Interventions	Haffkine monovalent antivenom was administered dissolved in distilled water (1:1) over 5–7 min intravenously. The total dose of antivenom was decided based on composite clinical score and patient’s age. The doses varied between 20 and 80 ml. Prazosin was administered orally at 3 hourly intervals at a dose of 500 μg (<20 kg body wt) or 1 mg (>20 kg body wt).
Outcomes	Primary endpoint: time to resolution of clinical symptoms
Study location	Maharashtra, India
Pandi et al. 2014 [24]
Methods	Randomized controlled trial
Participants	Children aged less than 13 years were randomized into test (n = 25) and control (n = 25) groups. Grading of severity of sting was as according to Bawaskar et al.
Interventions	The test group received monovalent Haffkine antivenom according to protocol described by Bawaskar et al. Both groups received prazosin at a dose of 30 μg/kg/dose at 3 hourly intervals until resolution of the clinical syndrome.
Outcomes	Primary endpoint: time to resolution of clinical syndrome Secondary endpoints: total dose of prazosin required, adverse events, prevention of worsening of clinical syndrome and duration of hospital stay
Study location	Pondicherry, India