"Ovine polyvalent crotalidae" refers to a type of antivenom used to treat snakebites from various species of venomous snakes in the Crotalidae family, which includes pit vipers such as rattlesnakes, copperheads, and cottonmouths/water moccasins. "Ovine" means derived from sheep, so ovine polyvalent crotalidae antivenom is produced using antibodies from sheep that have been exposed to the venoms of multiple species of snakes within the Crotalidae family.

Polyvalent antivenoms are designed to neutralize the venoms of multiple species of snakes, making them useful in regions where there is a variety of venomous snakes present. This type of antivenom can help counteract the effects of venomous snakebites and is often administered in hospitals or emergency settings following a snakebite.

Antivenom for North and South American crotalid snakes made from serum sheep is called CroFab.

CroFab (Ovine polyvalent crotalidae) Uses:

• Crotalid envenomation:
  • Treatment of adults and children with envenomations from North American crotalid snakes
  • See Coral Snake Antivenom.

Ovine polyvalent crotalidae Dose in Adults

CroFab Antivenom Dose in the therapy of Crotalid envenomation:

Initial Dose:

• When the person first gets to the hospital, they might receive 4 to 6 vials of the medicine through an IV.
• It's important to start treatment as soon as possible, ideally within 6 hours of the snakebite.
• Doctors will watch the person closely for about an hour after giving the medicine to see if it's working. They're looking for signs that the snake's venom isn't causing more harm.
• If the person's condition is very serious, like if they're in shock or have severe bleeding, doctors might give them a higher initial dose, usually 8 to 12 vials.

Additional Doses:

• If the first dose doesn't control the effects of the snakebite, doctors might give another 4 to 6 vials.
• They'll keep giving these doses until the person's symptoms start getting better and tests show that their blood is clotting normally again.
• The most medicine someone would get in the beginning is 12 vials.

Maintenance Dose:

• After the person's condition stabilizes, they might get 2 vials of the medicine every 6 hours for up to 18 hours.
• Doctors aren't sure if it's helpful to keep giving the medicine after 18 hours, but they might continue if the person still needs it based on how they're doing.

Ovine polyvalent crotalidae Dose in Children

CroFab Antivenom Dose in the therapy of Crotalid envenomation:

When treating children and adolescents for snakebites with ovine polyvalent crotalidae, the dosage and administration are adjusted accordingly:

Initial Dose:

• For children and adolescents, the initial dose is typically 4 to 6 vials of the medication given through an IV.
• It's important to start treatment as soon as possible after the snakebite, preferably within 6 hours.
• Doctors will watch the child closely for about an hour after giving the medicine to see if it's working. They're looking for signs that the snake's venom isn't causing more harm.
• If the child's condition is very serious, like if they're in shock or have difficulty breathing, doctors might give them a higher initial dose, usually 8 to 12 vials.
• If the initial dose doesn't control the effects of the snakebite, additional doses of 4 to 6 vials may be given until the symptoms improve and tests show that the venom is no longer causing problems.

Maintenance Dose:

• After the child's condition stabilizes, they might receive 2 vials of the medicine every 6 hours through an IV for up to 18 hours.
• Doctors aren't sure if it's helpful to keep giving the medicine after 18 hours, but they might continue if the child still needs it based on how they're doing.

CroFab Pregnancy Risk Category: C

• Information about using crotalidae polyvalent immune FAB (ovine) during pregnancy is limited.
• Generally, when a pregnant woman needs medication like this to treat a snakebite, doctors consider her health first.
• If there's a clear reason to use the medicine, they'll give it, even if they're worried about possible harm to the baby.
• Antivenom treatment is often necessary for serious snakebites or when other treatments haven't worked, but doctors will closely monitor both the mother and the baby afterward to make sure everything is okay.

Use of polyvalent crotalidae from Ovines during breastfeeding

• It's uncertain if crotalidae polyvalent immune FAB (ovine) is found in breast milk.
• The manufacturer advises being careful if giving it to a breastfeeding mother.
• This means doctors should consider the potential risks and benefits before deciding if it's safe for a breastfeeding woman to receive this medication.

CroFab Dose in Kidney Disease:

• The manufacturer's instructions do not include any specific adjustments in dosage for individuals with renal impairment.
• This means that the usual dose of the medication should be used regardless of kidney function.

CroFab Dose in Liver Disease:

• The manufacturer's labeling does not specify any dosage adjustments for individuals with hepatic impairment.
• Therefore, the standard dosage prescribed for patients without hepatic impairment should be followed.

CroFab antivenom Side effects:

• Gastrointestinal:
  • Anorexia
  • Nausea
• Central Nervous System:
  • Chills
• Cardiovascular:
  • Hypotension
• Dermatologic:
  • Pruritus
  • Skin Rash
  • Urticaria
• Miscellaneous:
  • Fever
• Hypersensitivity:
  • Hypersensitivity Reaction
  • Serum Sickness
  • Anaphylactoid Reaction
  • Anaphylaxis
• Respiratory:
  • Asthma
  • Cough
  • Dyspnea
  • Wheezing

Contraindications to CroFab (Ovine polyvalent crotalidae):

• If someone has a known hypersensitivity to any component of the formulation of the medication, including papaya or papain, it's typically not recommended to use it unless the benefits outweigh the risks.
• In such cases, it's crucial to have appropriate management available for anaphylaxis, a severe allergic reaction.

Warnings and precautions

Hypersensitivity reactions

• Hypersensitivity reactions can occur with the use of this medication, which is derived from sheep plasma.
• Anaphylaxis and anaphylactoid reactions are possible, particularly in patients with known allergies to sheep protein.
• It's important to have immediate treatment available, such as epinephrine, for such reactions before administering the medication.
• If acute hypersensitivity reactions occur, including anaphylaxis, the infusion should be stopped immediately, and appropriate emergency treatment should be given.
• It's worth noting that the incidence of these reactions might be lower than previously believed.
• This product differs from older equine-derived ones as it lacks certain immunogenic fragments and proteins.
• However, sensitization may still happen with repeated doses.
• Additionally, since it's processed with papain, patients allergic to papaya or related substances like bromelain may also experience hypersensitivity reactions.
• Cross-allergenicity with dust mite and latex allergens is also possible.

Crotalid Envenomation

• In the treatment of crotalid envenomation, it's crucial to administer antivenom as soon as possible, ideally within 4 to 6 hours of the snakebite, to prevent worsening symptoms and coagulation problems caused by the snake venom.
• Even if treatment is delayed, antivenom can still be beneficial.
• Coagulation abnormalities, which are directly caused by the venom interfering with the body's blood clotting process, are common and can persist for a week or more.
• About half of patients may experience recurrent coagulopathy, with a higher likelihood if it occurs within the first 12 hours after antivenom treatment.
• Repeat doses of antivenom may be needed in some cases.
• Patients should be closely monitored for at least a week and evaluated for any other conditions that might affect their ability to clot blood.
• Severe envenomations can also lead to a decrease in platelets, which can last for hours to several days.
• Blood products are generally not effective as they are quickly used up by the venom circulating in the body.

Monitoring Parameters:

• Vital Signs: Check temperature, heart rate, blood pressure, and respiratory rate regularly.
• Blood Tests: Monitor CBC (Complete Blood Count), platelet count, prothrombin time, activated partial thromboplastin time (aPTT), fibrinogen levels, fibrin split products, clot retraction, bleeding and coagulation times, BUN (blood urea nitrogen), electrolytes, and bilirubin.
• Bite Area Size: Measure the size of the snakebite area every 15 to 30 minutes to track any changes.
• Fluid Balance: Keep track of fluid intake and output to ensure proper hydration.
• Allergic Reactions: Watch for signs and symptoms of anaphylaxis or allergic reactions, such as difficulty breathing, swelling, or itching.
• Delayed Reactions: Look out for delayed allergic reactions or serum sickness, which may include rash, fever, muscle pain, or joint pain.
• Repeated Blood Tests: Evaluate CBC, platelet counts, and clotting studies every 6 hours until the patient's condition stabilizes.

How to administer CroFab (Ovine polyvalent crotalidae)?

• Initial Rate: Administer IV medication over 60 minutes. Begin at a slow rate of 25 to 50 mL/hour for the first 10 minutes.
• Increase Rate: If no allergic reaction is observed during the initial period, increase the infusion rate to 250 mL/hour. Monitor the patient closely for any signs of adverse reactions.
• Anaphylaxis Preparedness: Have immediate treatment available for anaphylactoid and/or hypersensitivity reactions ready during the entire infusion process.
• Managing Adverse Effects: If infusion-related adverse effects like fever, low back pain, wheezing, or nausea occur, consider decreasing the rate of infusion to help control these symptoms.

Following these IV administration guidelines ensures the safe and effective delivery of the medication while minimizing the risk of adverse reactions.

Mechanism of action of CroFab (Ovine polyvalent crotalidae):

• The venom-specific fragment of IgG is a specialized part of the immune system that recognizes and attaches to venom toxins.
• Once attached, it neutralizes the toxins, which helps remove them from the affected tissue and eliminates them from the body.
• Essentially, it acts like a targeted defense mechanism against the venom, helping to counteract its harmful effects and aid in the healing process.

Onset of Action:

• Stability of the patient or reduction in symptoms may be observed within 1 hour of administration of the medication.

Distribution:

• The unbound Fab portion of the medication has a distribution volume of 110 mL/kg.

Half-life Elimination:

• The half-life of elimination for the medication ranges from 12 to 23 hours based on limited data.

Excretion:

• Excretion of the venom-antibody complex is believed to occur via the reticuloendothelial system.

Clearance:

• The clearance rate of the unbound Fab portion is approximately 5.9 mL/h/kg.

International Brands of Ovine polyvalent crotalidae:

• CroFab

Ovine polyvalent crotalidae Brand Names in Pakistan:

No Brands Available in Pakistan.