Overdose : מינון יתר

4.9   Overdose
Salicylate toxicity can result from chronic, therapeutic overdose or potentially life- threatening acute poisoning (overdose due to inadvertent intake by children including accidental intoxication).

Chronic salicylate poisoning
Chronic salicylate poisoning can be problematic, as the signs and symptoms are non- specific. Mild salicylate poisoning generally occurs following repeated intake of high doses (> 100/mg/kg/day over 2 days can be toxic). Symptoms include drowsiness, dizziness, tinnitus, hearing impairment, sweating, nausea and vomiting, headache and confusion and can be controlled by reducing the dose.

Acute salicylate poisoning
The main manifestation of acute poisoning is a severe disturbance in the acid-base balance, which can vary with age and the degree of poisoning. The most common sign of acute poisoning in children is metabolic acidosis. The severity of poisoning cannot be estimated from the plasma concentrations alone. The absorption of acetylsalicylic acid may be delayed by slowing of gastric emptying, concrement formation in the stomach or as a result of taking gastro-resistant medicinal products. Tinnitus can occur at plasma levels of 150 to 300 µg/mL. Further severe adverse effects can occur at concentrations over 300 µg/mL.

The pathophysiological effects of salicylate poisoning are complex.

Mild to moderate poisoning manifests as nausea, vomiting, tachypnoea, hyperventilation, respiratory alkalosis and diaphoresis.

Signs of moderate to severe poisoning include respiratory alkalosis with compensatory metabolic acidosis, hyperpyrexia, impaired glucose metabolism and ketosis, tinnitus, deafness, gastrointestinal bleeding, respiratory disorders (from hyperventilation up to respiratory arrest), cardiovascular disorders (from arrhythmia up to cardiovascular shock), water and electrolyte disturbances (from dehydration up to kidney failure), haematological disorders (from inhibition of platelet function up to coagulopathy), toxic encephalopathy and CNS depression (from lethargy up to coma and seizures).

Treatment of acetylsalicylic acid poisoning is guided by the extent, severity and clinical symptoms corresponding to standard measures to manage poisoning. The first emergency measures must be to accelerate the excretion of the drug and to restore the electrolyte and acid-base balance.