An anti-hypertensive in scorpion envenomination

Q: Which of the following anti-hypertensives is found to be of benefit in scorpion envenomation?

A) Amlodipine

B) Losartan

C) Metoprolol

D) Hydrochlorothiazide

E) Prazosin

Answer: E

Antivenom for scorpion bites is not readily available, and when available, it is usually species-specific. It is almost an art to know the right venom for the right scorpion species. Interestingly, a simple antihypertensive, prazosin, has been found to be of value in Grade II* or higher scorpion envenomation, particularly with Hottentotta (Mesobuthus) species. It may reduce the risk of death from scorpion envenomation from 25 percent to almost nil. Also, it may expedite the recovery by preventing cardiogenic pulmonary edema. 

Due to its relatively few side effects, it is recommended as an adjuvant treatment in almost all venomations, including those involving Androctonus, Buthus, Leiurus, or Tityus species. Prazosin works by mitigating excessive catecholamine release and progression to cardiotoxicity! The recommended prazosin dose is 0.5 mg every three hours until systemic toxicity resolves.

#toxicity

* There are four grades, as per escalation of toxicity severity

References:

1. Bawaskar HS, Bawaskar PH. Scorpion sting: update. J Assoc Physicians India 2012; 60:46.

2. Gupta V. Prazosin: a pharmacological antidote for scorpion envenomation. J Trop Pediatr 2006; 52:150.

3. Al-Asmari AK, Al-Seif AA, Hassen MA, Abdulmaksood NA. Role of prazosin on cardiovascular manifestations and pulmonary edema following severe scorpion stings in Saudi Arabia. Saudi Med J 2008; 29:299.