Atypical absorption of morphine sulphate through oral mucosa: an unusual case of acute opioid poisoning.

Abstract

An unusual case of probable opioid poisoning due to atypical absorption of morphine sulphate through the oral mucosa is reported. A patient with advanced laryngeal cancer, who was unable to swallow, became stuporous, bradypneic, and cyanotic and had pinpoint pupils 1 hour after taking a controlled-release tablet of morphine sulphate 30 mg. Intravenous naloxone 0.4 mg induced prompt reversal of the clinical picture. The tablet of morphine, in advanced stage of decomposition, was found in the patient's mouth, the mucosa of which was inflamed and extensively ulcerated because of the long-standing stagnation of food residuals. Usually morphine is not amenable to transmucosal absorption, because of its low lipid solubility. In this case, the retention of the tablet of morphine in the mouth and the breakdown of oral mucosa integrity could have provoked a quick transmucosal absorption of the drug, with by-pass of hepatic first-pass metabolism. This may have induced a peak in drug concentration much higher than that usually resulting from the enteric absorption of controlled-release tablets of morphine.