From the Research
Antivenin remains effective against viper bites even when administered after 24 hours, and its use should not be counterindicated based solely on the time elapsed since the bite. The decision to administer antivenin should be based on the severity of envenomation and the presence of systemic effects, rather than strictly on the time elapsed since the bite 1. According to a study published in The American Journal of Emergency Medicine, antivenin was observed to be effective in improving hemostasis, and the time to normalization of biologic parameters was similar, whether the treatment was started before or after the 24th hour after the bite 1.
Key points to consider when deciding on antivenin administration include:
- Severity of envenomation
- Presence of systemic effects such as coagulopathy, hypotension, or anaphylaxis
- Extent of local effects such as swelling and pain
- Laboratory values, including complete blood count, coagulation studies, and kidney function tests
The standard treatment involves intravenous administration of species-specific antivenom, typically starting with 4-6 vials diluted in saline and infused over 1 hour, with additional doses based on clinical response 1, 2. While earlier administration is generally preferred, delayed antivenom administration may still be effective in preventing further damage and complications, and may potentially save lives 1, 2. A more recent study published in 2021 supports the use of ViperaTAb antivenom for Vipera berus envenoming, highlighting its effectiveness and safety in clinical practice 2.
In clinical practice, medical professionals should assess the patient's clinical condition and make decisions based on the severity of envenomation, rather than strictly on the time elapsed since the bite. Antivenin should be administered as soon as possible for patients meeting clinical criteria, and patients should be closely monitored for adverse reactions and progression or recurrence of envenoming 2.