Usage
- Medical Conditions: This polyvalent antivenom is used to treat venomous snake bites from the “Big Four” species found in the Indian subcontinent: Cobra ( Naja naja ), Common krait ( Bungarus caeruleus ), Russell’s viper ( Daboia russelii ), and Saw-scaled viper ( Echis carinatus ). It neutralizes the venom, mitigating its systemic effects. While this antivenom also covers Saw-scaled viper, the medicine name provided by the user omits it. A true “Big Four” antivenom would include it.
- Pharmacological Classification: Antivenom, antidote.
- Mechanism of Action: The antivenom contains antibodies (immunoglobulins) raised in horses against the specific venoms of the target snake species. These antibodies bind to venom components in the victim’s bloodstream, neutralizing their toxic effects. This prevents further damage caused by the venom’s components.
Alternate Names
- Anti-snake venom serum (ASV)
- Polyvalent anti-snake venom serum
- Snake venom antiserum
How It Works
- Pharmacodynamics: The antivenom primarily works by binding and neutralizing the venom components circulating in the patient’s blood. It effectively reverses coagulopathy (blood clotting abnormalities) caused by viper venoms and alleviates neurotoxic effects caused by krait and cobra venoms.
- Pharmacokinetics: Administered intravenously, it distributes rapidly throughout the circulatory system. The antibody-venom complex is then cleared from the body, primarily by the reticuloendothelial system. Specific metabolic and elimination pathways are not fully elucidated, but it’s likely that the complexes are broken down and eliminated similarly to other antibody-antigen complexes.
- Mode of Action: Neutralization of venom components occurs through direct binding of antibodies to venom toxins, preventing them from interacting with their target sites in the body. Specific receptor binding or enzyme inhibition studies depend upon the components of the venom. This neutralization interrupts downstream effects such as coagulation disturbances, neurotoxicity, and other systemic effects of envenomation. Elimination is similar to other antigen-antibody complexes, mainly through phagocytic degradation.
Dosage
Standard Dosage
Adults:
- Initial dose: 10-20 vials (100-200 ml), depending on the severity of envenomation. Dilute in 500 ml of normal saline and infuse over 1-2 hours.
- Repeat doses of 5-10 vials (50-100 ml) hourly as needed until symptoms subside and swelling stops progressing.
Children:
- Similar to adult dosing. Children and smaller adults (<40kg) may require up to 50% larger doses based on a higher venom concentration per unit of body weight.
Special Cases:
- Elderly Patients: Dose adjustments are based on clinical assessment and individual patient response.
- Patients with Renal Impairment: Monitor renal function closely. Dose modifications may be necessary based on clinical assessment.
- Patients with Hepatic Dysfunction: Monitor liver function closely. Dose modifications may be necessary based on clinical assessment.
- Patients with Comorbid Conditions: No specific guidelines exist, manage based on clinical assessment.
Clinical Use Cases
- Intubation: Use to treat respiratory paralysis induced by neurotoxic venom.
- Surgical Procedures: May be indicated in severe cases with compartment syndrome or other surgical complications.
- Mechanical Ventilation: Support ventilation if respiratory paralysis develops.
- Intensive Care Unit (ICU) Use: Monitor vital signs, coagulation parameters, and provide supportive care as needed.
- Emergency Situations: Administer antivenom immediately in life-threatening situations.
Dosage Adjustments
Adjustments should be made based on the severity of envenomation and the patient’s clinical response. For severe cases, higher initial doses and more frequent repeat doses might be necessary. For children and smaller adults, increase dosage by up to 50%.
Side Effects
Common Side Effects
- Pyrexia (fever)
- Itching
- Rash
- Nausea and vomiting
Rare but Serious Side Effects
- Anaphylaxis (rare but can be life-threatening)
- Serum sickness (delayed hypersensitivity reaction)
Long-Term Effects
Generally, no long-term effects are associated with antivenom use. However, serum sickness may occur 1-2 weeks after administration, presenting with fever, rash, joint pain, and swollen lymph nodes.
Adverse Drug Reactions (ADR)
Anaphylaxis is a serious ADR and requires immediate management with epinephrine, antihistamines, and corticosteroids.
Contraindications
- Known hypersensitivity to horse serum products.
Drug Interactions
No significant drug interactions have been reported.
Pregnancy and Breastfeeding
Antivenom use is generally considered safe during pregnancy and breastfeeding. The benefits of treating a venomous snake bite outweigh the potential risks to the fetus or neonate.
Drug Profile Summary
- Mechanism of Action: Neutralizes venom toxins through antibody binding.
- Side Effects: Pyrexia, itching, rash, nausea, vomiting; rarely, anaphylaxis and serum sickness.
- Contraindications: Hypersensitivity to horse serum products.
- Drug Interactions: None significant.
- Pregnancy & Breastfeeding: Generally considered safe.
- Dosage: 10-20 vials initially for adults, repeat as needed. Children and smaller adults may require up to 50% higher doses.
- Monitoring Parameters: Vital signs, coagulation profile (especially for viper bites), neurological status (especially for krait and cobra bites), urine output.
Popular Combinations
Antivenom is generally used alone. Other medications might be administered for supportive care (e.g., analgesics, antiemetics, fluids, respiratory support).
Precautions
- Close monitoring for hypersensitivity reactions is essential.
- Premedication with antihistamines and corticosteroids may be considered in patients with a history of allergies.
- Supportive care should be provided as necessary, including management of respiratory complications and coagulopathy.
FAQs
Q1: What is the recommended dosage for Snake Venom Antiserum + Standard Cobra Venom + Standard Russels Viper Venom + Standard common krait Venom?
A: The initial dose is 10-20 vials (100-200 ml) for adults, diluted in normal saline and infused over 1-2 hours. Repeat doses of 5-10 vials (50-100 ml) can be given hourly until the symptoms subside. Children and smaller adults (<40kg) may require up to 50% higher doses.
Q2: How is the antivenom administered?
A: Intravenously, as a slow infusion.
Q3: What are the common side effects of antivenom administration?
A: Common side effects include pyrexia, itching, rash, nausea, and vomiting.
Q4: What is the most serious side effect to watch out for?
A: Anaphylaxis is a rare but serious side effect requiring immediate intervention.
Q5: Are there any contraindications to using this antivenom?
A: Known hypersensitivity to horse serum products is a contraindication.
Q6: Can this antivenom be used during pregnancy?
A: Yes, the benefits generally outweigh the risks in a life-threatening situation.
Q7: How should a patient with a suspected krait bite be managed?
A: Administer 10 vials of antivenom immediately upon observing neurotoxic signs. Monitor closely for respiratory paralysis. Persistence of neuromuscular paralysis is not an indication for repeat dosing.
Q8: How should a patient with a suspected viper bite be managed?
A: Administer antivenom as soon as possible and monitor coagulation parameters (20WBCT). Repeat doses may be necessary if coagulopathy persists.
Q9: Is skin testing recommended before antivenom administration?
A: Skin testing has no predictive value for hypersensitivity reactions and should not be performed.
Q10: How is antivenom stored?
A: Lyophilized (freeze-dried) antivenom should be stored in a cool, dark place. Reconstituted antivenom and liquid antivenom must be refrigerated (+2-8°C) and protected from light. Do not freeze liquid antivenom.
