Symptomer kan variere fra CNS- depression (sedation, apnoea, nedsat mental årvågenhed, cyanose, koma, kardiovaskulær kollaps) til CNS- stimulation (søvnløshed, hallucination, rysten, kramper) med muligt fatalt udfald.
Symptoms may vary from CNS depression (sedation, apnoea, diminished mental alertness, cyanosis, coma, cardiovascular collapse) to CNS stimulation (insomnia, hallucination, tremors, convulsions) with possible fatal outcome.