tapentadol

introduction

synthetic opiate-like analgesic similar to tramadol invented in the late 1980's and approved by TGA in Australia in 2010 as an S8 controlled drug
as with tramadol it has a dual mode of action as an agonist of the μ-opioid receptor and as a norepinephrine reuptake inhibitor (NRI)
analgesic efficacy comparable to that of oxycodone despite an alleged lower incidence of side effects
100mg immediate release tapentadol appears to have similar analgesia to 15mg oxycodone but with less N/V although more somnolence
100-250mg SR tapentadol bd appears to equate to 20-50mg SR oxycodone bd for analgesia

the tapentadol dose is 5x the dose of oxycodone
- hence if the patient is on 15-20mg oxycodone, a reasonable new dose for tapentadol is 100mg

only 1/3rd of dose makes it past 1st pass hepatic metabolism
onset of action after oral administration is around 30min
duration of action of immediate release oral form is 4-6hrs
cleared mainly via hepatic metabolism
those who are rapid or ultra rapid metabolizers for the CYP2C9, CYP2C19, and CYP2D6 enzymes may not respond adequately to tapentadol therapy

epilepsy or in those prone to seizures as lowers seizure threshold
raises intracranial pressure so avoid in head injuries, patients with brain tumours, etc
patients at risk of respiratory depression eg. COPD, OSA, other resp. depressant medications
patients with low BP as may cause further lowering of BP
biliary disease or pancreatitis as may cause spasms of the sphincter of Oddi
liver disease as risk of reduced clearance and toxicity
patients on monoamine oxidase inhibitors (MAOIs) as risk of adrenergic storm
patients taking anti-muscarinic anticholinergic agents as risk of urinary retention