Distribution Rapidly distributed in the body and readily crosses the placenta. Plasma protein binding is relatively weak.
Metabolism Metabolized in the liver primarily by glucuronidation (major metabolite naloxone-3-glucuronide).
Elimination In adults the t ½ ranges from 30 to 81 min, while in neonates the t ½ is about 3 h. Approximately 25% to 40% is excreted as metabolites in the urine within 6 h, about 50% in 24 h, and 60% to 70% in 72 h.
Onset Following IV administration, the onset of action is usually apparent within 2 min.
Duration Duration of effect is more prolonged after IM injection compared with IV administration.
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