Naloxon for injections, 0,4 mg/ml. Naloxone belongs to a group of medicines known as opioids antagonists. Opioid medicines are strong painkillers such as morphine and codeine. In high doses these painkillers can result in side effects which cause difficulty in breathing and drowsiness. These effects can be reversed by an opioid antagonist (blocks the effects of opioids). Naloxone Injection may be used: - to treat the breathing problems caused by these opioid painkillers. - to help determine whether a patient has taken or received an overdose of opioid drugs. - to reverse the depressant effects on breathing and on other parts of the brain and spinal cord in newborn infants (resulting from the use of opioid painkillers in the mother during childbirth).