The venoms of some snakes (vipers, cobras) can cause recurrent or persistent envenomation, even after administration of antivenom.
Some components of venom are stable and can form depots in soft tissue that can slowly enter the circulation. Once the serum concentration of antivenom drops after 2-3 half-lives sufficient venom may be present to cause symptoms.
Risk factors for recurrent or persistent envenomation:
(1) large amount of venom injected
(2) insufficient dose of the antivenom
(3) failure to administer multiple doses of antivenom over time
(4) antivenom with no or limited activity against the snake venom
(5) antivenom with a short half-life
Clinical findings of envenomation can occur up to 2 weeks after the snakebite, so a patient should be followed.
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