Poisoning opioids

Antidotes that act pharmacologically e.g. naloxone used in opioid poisoning. 

Supportive therapy for acute opioid poisoning may be performed first by stomach wash, and then laxative and intensive supportive therapy to treat respiratory failure and shock. Further, naloxone may be given to treat severe respiratory depression and coma. However, intravenous infusions are preferred if the toxicity is the result of a long-acting opioid. The treatment of adverse effects itself may cause withdrawal symptoms.32... 

Acute opioid poisoning involves marked CNS depression, with drowsiness, loss of consciousness, and coma. Other prominent features are a reduced respiratory rate, hypotension, and sjmmetrical pinpoint pupils (unless the patient has been hjrpoxic for some time, in which case the pupils can be dilated). Reduced urine output, hypothermia, flaccid skeletal muscles, and pulmonary edema can also be present. Convulsions have occurred in children. 

The triad of coma, pinpoint pupils, and depressed respiration strongly suggests opioid poisoning. 

It is inactive orally because of high first pass metabolism in liver. Metabolised by glucuronidation in liver. The main use of naloxone is in the treatment of acute opioid overdose (acute morphine poisoning). It also precipitates withdrawal syndrome when administered to morphine addicts. The constricted pupils of addicts dilate after administration of naloxone. This has been used as a diagnostic tool for opioid addiction. 

Abdominal examination may reveal ileus, which is typical of poisoning with antimuscarinic, opioid, and sedative drugs. Hyperactive bowel sounds, abdominal cramping, and diarrhea are common in poisoning with organophosphates, iron, arsenic, theophylline, A phalloides, and A muscaria. 

The major application of naloxone is in the treatment of acute opioid overdose (see also Chapter 59 Management of the Poisoned Patient). It is very important that the relatively short duration of action of naloxone be borne in mind, because a severely depressed patient may recover after a single dose of naloxone and appear normal, only to relapse into coma after 12 hours. 

Although methadone is used for the management of opioid dependence, symptoms of overdose are similar to those of morphine poisoning. 

Action on receptors provides numerous examples. Beneficial interactions are sought in overdose, as with the use of naloxone for morphine overdose (opioid receptor), of atropine for anticholinesterase, i.e. insecticide poisoning (acetylcholine receptor), of isoproterelol (isoprenaline) for overdose with a P-adrenoceptor blocker (p-adrenoceptor), of phentolamine for the monoamine oxidase inhibitor-sympathomimetic interaction (a-adrenoceptor). 

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