A patient comes with sudden respiratory distress, on examination, b/l miosis ,bilateral basal crepts are present over chest suggestive of pulmonary edema with normal alveoler wedge pressure.The likely cause is-

The presentation involves shallow and slow respirations,pupillary miosis (mydriasis does not occur until significant brain anoxia supervenes), bradycardia, hypothermia, and stupor or coma. If naloxone is not administered, progression to respiratory and cardiovascular collapse leading to death occurs. At autopsy, cerebral edema and sometimes frothy pulmonary edema are generally found, but those pulmonary effects are most likely from allergic reactions to adulterants mixed with the heroin. Opiates generally do not produce seizures except for unusual cases of mixed drug abuse with the opiate meperidine or with high doses of tramadol. ref : Harrison&;s principle of internal medicine, 20th edition,pg no.3554