A 25-year-old woman with known peanut allergy collapses at a café after accidental exposure. On arrival, the GP finds her pale, hypotensive (BP 80/40 mmHg), tachycardic (HR 120 beats/min), wheezy with widespread urticaria. She weighs approximately 60 kg. According to Australian anaphylaxis guidelines, what is the most appropriate initial dose of intramuscular adrenaline (1:1000) to administer?