Funnel-Web Spider Antivenom

Indication:

• Clinical evidence of systemic envenomation e.g. sudden onset perioral tingling, tongue fasciculations, salivation, sweating and lacrimation. This can progress to muscle twitching, tachycardia, hypertension, pulmonary oedema and eventually death.

Contraindication:

• No absolute
• Increased Risk of anaphylaxis in patients previously treated with antivenom or those who are suspected of lapine sera allergy

Administration:

• Place the patient in a monitored area where anaphylaxis can be managed.
• Reconstitute the freeze-dried antivenom in 10ml of sterile water. Administer 2 ampoules diluted in 100ml of 0.9% saline intravenous over 20 minutes. If severe envenomation is present give 4 ampoules.
• Repeat doses of 2 ampoules are given every 2 hours until clinical features of envenomation have resolved.
• Adult and paediatric doses are the same.

Adverse drug reactions:

• Anaphylaxis: Cease antivenom infusion, treat as per anaphylaxis with oxygen, IV fluids and IM adrenaline. Recommence antivenom infusion when anaphylaxis has resolved. Rarely will ongoing administration of adrenaline be required to complete the antivenom infusion.
• Serum Sickness: A benign and self limiting complication occurs 5-10 days after antivenom, symptoms include fever, rash, arthralgia and myalgia. Oral steroids for 5 days may ameliorate symptoms (e.g. prednisolone 50mg/day in adults and 1mg/kg in children). All patients should be warned about this complication who receive antivenom.