Acetaminophen
"Administered an IV bolus of 600mg of Paracetamol to a patient in severe to moderate pain and patient suddenly started sleeping off but that was not expected so I checked and found the pulse unrecordable and BP not measurable. Quickly gave and IV bolus of saline and restored vitals and subsequently monitored patient for the next six hours. I think the effect of rapid administration IV should be hammered on."