Overdose can lead to headache, tinnitus, numbness and tingling around the mouth and tongue, convulsions, inability to breathe, and decreased heart function.
en.wikipedia.org Activation of receptors by an agonist ligand may induce hallucinogenic effects and also may be responsible for the paradoxical convulsions sometimes seen in opiate overdose.
en.wikipedia.org However, evidence from non-fatal oxygen convulsions indicates that most convulsions are not preceded by any warning symptoms at all.
en.wikipedia.org Symptoms of exposure may include drowsiness, rhinorrhea (runny nose), sore throat, coughing, confusion, nausea, vomiting, edema, loss of consciousness, convulsions, paralysis, and death.
en.wikipedia.org Symptoms that suggest the presence of metastatic disease include weight loss, bone pain and neurological symptoms (headaches, fainting, convulsions, or limb weakness).
en.wikipedia.org