AScVS and/ or Prazosin for Scorpion Envenomation
Condition: Scorpion Envenomation
MeSH terms: Poisoning; Scorpion Stings
Study type: Interventional
Phase: Phase 3

Summary: 
      The data available for the efficacy of AScVS and prazosin is generated through different
      trials done in different clinical setting. Hence it was felt worthwhile to confirm the
      documented efficacy of AScVS and prazosin in terms of time taken for clinical recovery in a
      clinical trial. Along with this, effects of both the therapies on various biochemical
      parameters will be recorded and compared with. It was also felt necessary to study the effect
      of combination on the clinical outcome.
    

Detailed description: 
      Red Scorpion (Mesobuthus Tamulus Concanesis Pocock) sting is a common medical emergency in
      the coastal regions of India and is a cause for considerable morbidity and mortality.

      Signs and symptoms show either cholinergic or adrenergic predominance. Cholinergic symptoms
      are profuse sweating, priapism, bradycardia, increased salivary and bronchial secretions and
      vomiting. Adrenergic symptoms are transient hypertension followed by hypotension,
      tachycardia, tachypnoea, pulmonary edema and circulatory failure in later stages. Scorpion
      venom blocks voltage dependent inactivation of sodium channels, resulting in intense
      persistent voltage depolarization of autonomic nerves with massive release of catecholamines
      from adrenal medulla and parasympathetic and sympathetic nerve endings.

      Prazosin a selective alpha-1 blocker is used as the treatment for scorpion sting, which can
      only counteract the manifestations of sympathetic over-activity. Experimentally and
      clinically it is seen that scorpion venom stays in the body for 24-36 hours, as Prazosin does
      not neutralize the venom, 3 hourly round the clock doses of prazosin and continuous I.C.U.
      monitoring is necessary with alpha blocker therapy. However, ideal treatment modality remains
      neutralization of venom in the systemic circulation.

      Since 1997 enzyme refined AScVS ( Monovalent Anti-scorpion venom serum against Mesobuthus
      tamulus concanesis Pocock.) has been made available by Haffkine Biopharmaceuticals, Mumbai
      for field use. Throughout the konkan(western coastal Maharashtra, India) area the same
      species of scorpions responsible for fatal envenomation is found.

      From 1997-2002, 48 patients of serious scorpion envenomation were treated with AScVS(1).
      Based on this experience a clinical scoring system for dose requirement was evolved based on
      sweating, pulse rate, respiratory rate, blood pressure, CNS effects and presence of priapism.
      In our experience computed doses given as intravenous bolus are more effective and
      successfully ameliorated signs and symptoms in all patients. Subsequently 16 patients were
      given treatment with either AScVS (n=8), Prazosin (n=5) and a combination of both (n=3) so as
      to compare the effects of these available treatment modalities. It was found that the
      patients receiving either AScVs or a combination showed a complete recovery approximately
      within 4 hours of onset of therapy as against patients receiving Prazosin, who required 16
      hours for recovery. There was no mortality in any of the group. There was not a single
      incidence of anaphylaxis after administration of AScVS. Release of adrenaline in the systemic
      circulation by scorpion sting itself appears to be protective against the danger of
      anaphylaxis. The label on the AScVS vials states that the maximum dose is 3 vials, which can
      be given either intramuscular or by intravenous route. However we used AScVS as slow bolus
      intravenously and dose was decided clinically depending upon the severity of the patient
      condition. (maximum 10-15vials.) Based on this experience, an open labeled, randomized
      controlled parallel group clinical trial has been initiated. Eighty-three patients have been
      recruited so far, 28 patients each, in AScVS and AScVS + prazosin group and 27 patients in
      Prazosin group, two patients out of 27 in Prazosin group were withdrawn as both the pediatric
      patients (around 12 years old) developed pulmonary edema after few hours, so AScVS had to be
      given. The onset of relief (based on composite score) with AScVS or combination of AScVS with
      prazosin was early and complete recovery occurred at 4.14+/- 1.6 hrs. and 3.46+/- 1.10hours.
      However, in patients receiving only prazosin, the clinical score was found to worsen
      initially, followed by a gradual improvement and subsequent complete recovery, at 19.28 +/-
      5.03 hrs. (p<0.001 vs AScVS). Recovery time with AScVS is much shorter because after complete
      neutralization of venom, fresh secretion of catecholamines stop and adrenaline and
      nor-adrenaline which are already in circulation have action as short as 1 to 2 minutes. These
      findings appear consistent with our clinical experience and indicate that in the near future
      AScVS would evolve as a safe, efficacious and life saving treatment modality for patients
      with severe scorpion envenomation. Use of clinical scoring system can enable the clinician to
      select the optimum dose of AScVS to be administered.

      Neutralization of venom is thus proved to be better than therapy for complications, akin to
      the dictum 'prevention is better than cure'.

      References:

      1. Natu VS, Murthy RKK, Deodhar KP. Efficacy of species specific Antiscorpion venom serum
      (AScVS) against severe, serious scorpion stings (mesobuthus tamulus concanesis pocock.)-An
      experience from rural hospital in western Maharashtra. JAPI, 2006; 54: 283-7.
    

Intervention name(s): Antiscorpion venom serum(AScVS).; T.Prazosin; AScVS + Prazosin
Intervention type(s): Drug; Drug; Drug
Intervention description(s): AScVS therapy group
If the score is 5 and if the patient belongs to pediatric group(>12-14): 1 vial AScVS as i.v. slow bolus after test dose If the score is 5 and if the patient is adult: 2 vials of AScVS as i.v. slow bolus after test dose. For injection, 1 vial will be dissolved in 10 ml distilled water and given over a period of 4 to 5 minutes.
According to the scores 1 vial for pediatric and 2 vials for adult patient will be increased as shown below:
Vials of AScVS Composite score Child Adult 5-10 2 4 > 10-15 3 6 >15- 21 4 8; Prazosin therapy Prazosin (30 micrograms/Kg/dose): 500 micrograms for pediatric patient, and 1mg for adult patients) will be given every 3 hourly orally till complete recovery.; Combination AScVS and Prazosin therapy In this group, AScVS therapy will be given as mentioned in AScVS therapy group and in addition, prazosin(500 micrograms for pediatric patient and 1mg for adult patients,30 micrograms/Kg/dose) every 3 hourly will be given.
Other intervention name(s): AScVS(Haffkine); T.Prazosin (sun pharma); AScVS (Haffkine); T. Prazosin (sun pharma)
Intervention MeSH terms: Prazosin
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Red Scorpion envenomation; Composite clinical scoring system; AScVS; Prazosin; Superiority