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Analgesic Poisoning
By Sadia Saeed (PMC)

INTRODUCTION:
Analgesics are among the most widely used of all drugs and poisoning with these agents is a universal problem.

CLASSIFICATION OF ANALGESIC DRUGS

Features:
Many popular analgesics combinations contain narcotic analgesics whose respiratory depressant effect represents a particular hazard when taken as an overdose .one such combination contains “PARACETAMOL” and “DEXTROPROPOXYPHENE” and is particularly dangerous as it can rapidly cause fatal respiratory depression.

OVERDOSE WITH ASPRIN AND THE SALICYTES:
An intentional overdose with asprin is the most common cause of salicylate intoxication; overdose may be with methylsalicylate.
Poisoning may also occur as a result of transdermal absorption from skin ointments containing salicylate. The elimination of salicylate is highly doze dependent and “therapeutic” salicylate intoxication is not uncommon. When a small doze of salicylate is taken, it is rapidly conjugated with glycine to form salicyluric acid, which is then removed by renal excretion. 

CLINICAL FEATURES:
Serious complications are mostly limited to severe poisoning, but young children and the elderly are particularly vulnerable. 

BIOCHEMICAL ABNORMALITIES:
· Disturbance of fluid, acid base and electolyte imbalances.
· Dehydration may develop as a result of vomiting, sweating and hyperventilation.
· Respiratory alkalosis due to hyperventilation.
· Accumulation of organic acid causes metabolic acidosis.
· Pulmonary oedema due to the decrease in ionization of salicylate which tend to increase the tissue distribution.

MANAGEMENT:
Methods to decrease absorption:
Gastric lavage is recommended up to twelve hours after ingestion. Salicylate absorption may also be delayed and prolonged after the ingetion of enteric coated asprin.

Other procedures:
Salicylate intoxication include the corrections of dehydration, electrolyte imbalance, and most importantly acidosis. 

Method to increase elimination:
The simple method for the elimination of salicylate is the repeated oral administration of activated charcoal.
Dose:
50-100 grams for every four hours until recovery. 

Forced alkaline diuresis:
It is established treatment for symptomatic intoxication with plasma salicylate concentration above 500 mg/ liter.
The relation between the renal clearance of salicylate and the pH of the urine is logarithmic, and it is more important to make the urine alkaline (pH8).

Haemodialysis and haemoperfusion:
In the case of very severe poisoning, with plasma salicylate concentration above 1000 mg/liter, haemodialysis and haemoperfusion may be necessary.


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