 As a polar compound, it has a limited ability to cross the blood–brain barrier, but kidney failure may lead to its accumulation and result in seizures.Probenecid and inhibitors of P-glycoprotein can enhance uptake of morphine-3-glucuronide and, to a lesser extent, morphine-6-glucuronide.Reported side effects related to the accumulation of this metabolite include convulsions, agitation, hallucinations, hyperalgesia, and coma.