intravenous paracetamol enters the circulation directly and so has a more rapid onset than its oral or rectal counterparts (Gorocs et al 2009, neal 2009),with onset typically occurring within ten minutes of administration (eMc 2010). The analgesic effects typically last between four and six hours,with peak analgesic effect typically occurring one hour after administration. its oral counterpart has a peak plasma concentration of up to two hours after ingestion and a plasma half life of up to four hours (eMc 2010).