Analgesic Effect of IV Acetaminophen in Tonsillectomies

Acetaminophen (paracetamol) is a first-line antipyretic and analgesic for mild and moderate pain for pediatric patients. Its common use (particularly in oral form) is underscored by its wide therapeutic window, safety profile, over the counter accessibility, lack of adverse systemic effects (as compared with NSAIDS and opioids) when given in appropriate doses. Although the exact anti-nociceptive mechanisms of acetaminophen continue to be elucidated, these mechanisms appear to be multi-factorial and include central inhibition of the cyclo-oxygenase (COX) enzyme leading to decreased production of prostaglandins from arachidonic acid, interference with serotonergic descending pain pathways, indirect activation of cannabinoid 1 (CB1) receptors and inhibition of nitric oxide pathways through N-methyl-D-aspartate (NMDA) or substance P. Of the above mechanisms, the most commonly known is that of central inhibition of COX enzymes by which the decreased production of prostaglandins diminish the release of excitatory transmitters of substance P and glutamate which are both involved in nociceptive transmission (Anderson, 2008; Smith, 2011). To date, several studies have shown acetaminophen's opioid sparing effect in the pediatric population when given by the rectal or intravenous routes (Korpela et al, 1999; Dashti et al, 2009; Hong et al, 2010).