Usage
- Snake Venom Antiserum (SVA) is prescribed for the treatment of envenomation caused by venomous snake bites, specifically those from cobras (Naja naja), common kraits (Bungarus caeruleus), Russell’s vipers (Vipera russelli), and saw-scaled vipers (Echis carinatus).
- Pharmacological classification: Antivenom, antidote.
- Mechanism of Action: SVA contains antibodies that neutralize venom toxins by binding to them and preventing their interaction with target tissues. This reduces the toxic effects of the venom.
Alternate Names
- Anti-snake Venom Serum (ASV)
- Antivenom
- Snake Antivenin
How It Works
- Pharmacodynamics: SVA primarily works by neutralizing venom components. It counteracts the systemic effects of envenomation, such as coagulopathy, neurotoxicity, and hemolysis, depending on the type of snake venom.
- Pharmacokinetics: Administered intravenously, SVA is rapidly distributed in the bloodstream. The antibodies bind to venom toxins, forming complexes that are then eliminated from the body, mainly through the reticuloendothelial system. Specific details on metabolism and elimination pathways are not readily available.
- Mode of Action: SVA exerts its effects through antibody-antigen interactions. The antibodies in SVA specifically target venom toxins, preventing the toxins from binding to their physiological targets, such as receptors, enzymes, or other molecules.
- Elimination pathways: Primarily eliminated through the reticuloendothelial system.
Dosage
Dosage is based on the severity of envenomation, not the patient’s age or weight. Children and smaller adults (<40 kg) may require up to 50% higher doses due to the relatively higher venom concentration per unit of body weight.
Standard Dosage
Adults & Children:
- Minimal Envenomation: 5 vials (50 ml) IV.
- Moderate Envenomation: 5-10 vials (50-100 ml) IV.
- Severe Envenomation: 10-20 vials (100-200 ml) or more IV.
Administer via slow intravenous infusion, either undiluted at a rate not exceeding 2 ml/minute or diluted in 250-500ml of normal saline or 5% dextrose solution over 1-2 hours. Repeat infusions hourly as needed, based on clinical response.
Clinical Use Cases
The clinical use cases are the same across all settings and are based on the degree of envenomation following a venomous snake bite.
Dosage Adjustments
- Repeat doses hourly until symptoms improve.
Side Effects
Common Side Effects
- Early reactions (within 30 mins): urticaria, facial edema, cough, dyspnea, cyanosis, vomiting, collapse.
- Late reactions: serum sickness (5-24 days post-administration), fever, urticaria, edema, nausea, vomiting, neurological manifestations (pain and muscle weakness).
- Injection site reactions: pain, redness, and swelling.
Rare but Serious Side Effects
Long-Term Effects
- Serum sickness (can persist for days or weeks)
Adverse Drug Reactions (ADR)
- Anaphylaxis requires immediate treatment with epinephrine and supportive measures.
Contraindications
- Hypersensitivity to horse serum or any component of the antivenom.
Drug Interactions
- May potentiate anaphylaxis with beta-blockers.
- May increase respiratory depression with opioids.
- Immunoglobulins may interfere with live vaccine responses.
Pregnancy and Breastfeeding
Pregnancy and breastfeeding are not contraindications. Administer SVA if clinically indicated, considering the risk-benefit ratio. The effects on the fetus and excretion in breast milk are not well established.
Drug Profile Summary
- Mechanism of Action: Neutralizes snake venom toxins.
- Side Effects: Early reactions (anaphylaxis), late reactions (serum sickness), injection site reactions.
- Contraindications: Hypersensitivity to horse serum.
- Drug Interactions: Beta-blockers, opioids, live vaccines.
- Pregnancy & Breastfeeding: Use with caution if benefits outweigh risks.
- Dosage: See detailed dosage section above.
- Monitoring Parameters: Coagulation tests, respiratory function, urine output, signs of envenomation and hypersensitivity.
Popular Combinations
No specific drug combinations are explicitly highlighted in the sources, but supportive care medications may include:
- Epinephrine for anaphylaxis
- Antihistamines and corticosteroids for allergic reactions
- Analgesics for pain management
- Fluids for hydration
- Antibiotics to prevent secondary infection
- Tetanus toxoid for prophylaxis
Precautions
- Screen for allergies to horse serum.
- Premedication with adrenaline may be considered.
- Monitor for hypersensitivity reactions.
- Avoid IM injections in haemotoxic envenomation until coagulopathy is corrected.
- Release tourniquets slowly after starting SVA.
- Have adrenaline and supportive measures available.
FAQs
Q1: What is the recommended dosage for Snake Venom Antiserum?
A: See detailed dosage guidelines above. The dosage depends on the severity of envenomation (minimal, moderate, or severe), not the patient’s age or weight.
Q2: How is SVA administered?
A: SVA is administered intravenously, either undiluted by slow infusion (max 2ml/min) or diluted in normal saline or 5% dextrose.
Q3: What are the signs of anaphylaxis after SVA administration?
A: Urticaria, edema of the face, tongue, and throat, cough, dyspnea, cyanosis, vomiting, and collapse.
Q4: What is serum sickness, and how is it treated?
A: Serum sickness is a delayed hypersensitivity reaction that can occur 5-24 days after ASV administration. Symptoms include fever, rash, joint pain, and itching. Treatment may involve antihistamines and corticosteroids.
Q5: Can SVA be given to pregnant or breastfeeding women?
A: Yes, if the benefits outweigh the risks. Pregnancy and breastfeeding are not absolute contraindications.
Q6: Are there any drug interactions with SVA?
A: SVA can potentiate anaphylaxis with beta-blockers and increase respiratory depression with opioids. It may also interfere with live vaccine responses.
Q7: What are the common side effects of SVA?
A: Common side effects include early reactions (like anaphylaxis), late reactions (serum sickness), and injection site reactions.
Q8: What precautions should be taken before administering SVA?
A: Screen for horse serum allergies, consider premedication with epinephrine, and have resuscitation equipment readily available.
Q9: Can ASV be administered intramuscularly?
A: Intravenous administration is preferred. Intramuscular administration is generally avoided, especially in cases of haemotoxic bites, to prevent hematoma formation.
Q10: How should a tourniquet be managed in a snake bite victim?
A: If a tourniquet is applied, release it slowly only after starting SVA administration.
