Journal of Postgraduate Medicine Medknow Publications and Staff Society of Seth GS Medical College and KEM Hospital, Mumbai, India ISSN: 0022-3859 EISSN: 0972-2823 Vol. 56, Num. 4, 2010, pp. 253-254

Journal of Postgraduate Medicine, Vol. 56, No. 4, October-December, 2010, pp. 253-254

Guest Editorial

Antiscorpion venom scores over other strategies in the treatment of scorpion envenomation

SB Deshpande

Department of Physiology, Institute of Medical Sciences, Banaras Hindu University,Varanasi - 221 005, India

Correspondence Address:S B Deshpande, Department of Physiology, Institute of Medical Sciences, Banaras Hindu University,Varanasi - 221 005, India,desh48@yahoo.com

PMID: 20935392

DOI: 10.4103/0022-3859.70927

The stings due to the Indian red scorpion are a medical emergency. Patients stung with this scorpion present with abnormalities indicative of cardiac, respiratory, autonomic and metabolic changes. Thus, most patients die of multisystem failure. ^[1],[2],[3] The autonomic overactivity, pulmonary edema, acute myocarditis and ischemia-like changes are the most frequent manifestations. The treatment strategies practiced for these patients include prazosin, angiotensin-converting enzyme (ACE) inhibitors, insulin, antiscorpion venom serum (AScVS) and others. ^{[1],[2],[3],[4],[5],[6]}

Prazosin is an alpha adrenoceptor antagonist and thus antagonizes the increased sympathetic (adrenergic) activity. But, the scorpion-stung victims manifest with either hypertension or hypotension. In case of hypotensive manifestations, prazosin further compromises the peripheral circulation. Thus, one should be cautious while using prazosin. ACE inhibitors are antihypertensive agents that decrease the angiotensin-II levels and increase kinins thus decreasing the cardiac after load, which may be of help to the hypertensive patients following scorpion stings. However, it is shown that ACE inhibitors produce augmented visceral reflexes as seen with scorpion venom. ^[7] Thus, the use of ACE inhibitors has to be undertaken judiciously. Further, insulin has been used effectively to reverse the cardiorespiratory abnormalities dramatically. ^[1],[2] The exact mechanisms that are involved in the reversal by insulin are still not clear. Insulin is a general anabolic hormone and regulates cellular glucose homeostasis and utilization. Thus, insulin restores the deranged metabolism following scorpion envenomation. This is further supported by the fact that insulin has been advocated in a number of conditions that are associated with multisystem failure, as in septicemia, irreversible shock syndrome and adult respiratory distress syndrome, to name a few. Thus, use of insulin in multisystem failure is understandable. However, apparently, insulin does not reverse the mechanisms triggered by the venom. Considering the above points with each of the drugs, most treatment regimens are not really focused on neutralizing the venom or its toxin.

A number of toxins have been isolated in the Indian red scorpion venom ^[5] . They include iberiotoxin (lethal toxin), a high-conductance Ca ²⁺ -activated K ⁺ channel blocker; tamulus toxin, a novel K ⁺ channel blocker; lepidopteran-selective toxin, an insect toxin; tamapin, a small conductance Ca ²⁺ -activated K ⁺ channel blocker; BTK-2, an inhibitor of voltage-gated K ⁺ channels; a high-molecular weight lethal polypeptide pulmonary edema-producing toxin (PoTx), ^[8] and the list is expanding. Mechanisms of actions of each of these toxins are different. Thus, it becomes pertinent to neutralize all these toxins.

In light of the presence of a large number of toxins and the involvement of multiple systems, it is expected that the real therapeutic agent for scorpion envenomation should be able to neutralize venom or toxins following scorpion stings. Scorpion venom after sting enters circulation and is distributed in various parts. An article appearing in this issue of the Journal by Natu ^[9] provides evidences for the beneficial effects of AScVS over prazosin. This study compared the efficacy of AScVS with prazosin alone, and in combination. It is shown that patients receiving AScVS reversed the toxicity much earlier than prazosin. Some patients receiving prazosin however did not respond to the drug; rather, their condition deteriorated with the development of complications such as pulmonary edema and severe tachycardia. These patients, when given AScVS, were relieved of the toxicity and were benefited. Administration of AScVS, even at late stages after envenomation, is still able to relieve the patients and restore the abnormalities produced by scorpion envenomation. This is contrary to the belief that AScVS should be given at the earliest possible time after scorpion sting. ^[3],[6] The ability of AScVS thus may neutralize the venom/toxin. However, in vivo neutralization of venom is not shown in this study. ^[9]

In a recent report that appeared in New England Journal of Medicine, ^[10] it was shown that critically ill children with neurotoxic effects of scorpion envenomation and intravenous administration of scorpion-specific F(ab′)2 antivenom resolved the clinical syndrome within 4 h and also reduced the need for additional supportive treatment, as shown in the report appearing in this issue. Further, they have shown the reduction in the levels of circulating unbound venom. Thus, AScVS has a clear advantage over other therapies. In both the studies, ^[9],[10] it is noteworthy that anaphylactic reactions were not observed after antiscorpion antivenom. However, the number of patients recruited in these studies is too small to make a definitive conclusion.

In summary, it is recommended that AScVS is likely to be the first choice in management as it neutralizes the venom and reverses the toxic effects. However, the availability of AScVS in rural settings is difficult to ensure. In such situations, the easily available cost-effective drugs like prazosin or insulin can be used in order to restore the peripheral circulation or metabolic derangements in addition or as an alternative to AScVS. In order to achieve successful treatment, the AScVS should be made available easily in the area where these stings are common. Further, it is necessary to develop species-specific antiserum or toxin-specific antiserum. The paper by Natu ^[9] is not randomized and hence placebo-controlled double-blind studies with a much larger sample size are required to confirm or refute the findings.

References

1.	Murthy KR, Shenoy R, Vaidyanathan P, Kelkar K, Sharma N, Birevar N, et al. Insulin reverses haemodynamic changes and pulmonary edema in children stung by the Indian red scorpion Mesobuthus tamulus concanesis, Pocock. Ann Trop Med Parasitol 1991;85:651-7.   Back to cited text no. 1
2.	Yugandhar B, Murthy KR, Sattar SA. Insulin administration in severe scorpion envenoming. J Venom Anim Toxins 1999;5:200-19.  Back to cited text no. 2
3.	Bawaskar HS, Bawaskar PH. Utility of scorpion antivenin in the management of severe Mesobuthus tamulus (Indian red scorpion) envenoming at rural setting. J Assoc Physicians India 2007;55:14-21.  Back to cited text no. 3  [PUBMED]
4.	Krishnan A, Sonawane RV, Karnad DR. Captopril in the treatment of cardiovascular manifestations of Indian red scorpion (Mesobuthus tamulus concanesis Pocock) envenomation. J Assoc Physicians India 2007;55:22-6.  Back to cited text no. 4  [PUBMED]
5.	Deshpande SB, Pandey R, Tiwari AK. Pathophysiological approach to the management of scorpion envenomation. Indian J Physiol Pharmacol 2008;52:311-4.  Back to cited text no. 5  [PUBMED]
6.	Bagchi S, Deshpande SB. Indian red scorpion (Buthus tamulus) venom-induced augmentation of cardiac reflexes is mediated through the mechanisms involving kinins in urethane anesthetized rats. Toxicon 1998;36:309-20.  Back to cited text no. 6  [PUBMED]  [FULLTEXT]
7.	Deshpande SB, Alex AB, Jagannadham MV, Rao GR, Tiwari AK. Identification of a novel pulmonary oedema producing toxin from Indian red scorpion (Mesobuthus tamulus) venom. Toxicon 2005;45:735-43.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]
8.	Natu VS, Murthy KR, Deodhar KP. Efficacy of species specific Anti-scorpion venom serum (AScVS) against severe, serious scorpion stings (Mesobuthus tamulus concanesis Pocock): An experience from rural hospital in Western Maharashtra. J Assoc Physicians India 2006;54:283-7.  Back to cited text no. 8  [PUBMED]
9.	Natu VS. Efficacy of anti-scorpion venom serum over prazosin in the management of severe scorpion envenomation. J Postgrad Med 2010;56:275-80.  Back to cited text no. 9  [PUBMED]
10.	Boyer LV, Theodorou AA, Berg RA, Mallie J; Arizona Envenomation Investigators, Chαvez-Mιndez A, et al. Antivenom for critically ill children with neurotoxicity from scorpion stings. N Engl J Med 2009;360:2090-8.  Back to cited text no. 10

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