Overdose : מינון יתר

4.9 Overdose
Symptoms of overdose
Acute overdoses will probably lead initially to dipyridamole-induced cardiovascular symptoms, foll- owed by dose-dependent symptoms of ASA intoxication.

Dipyridamole
A feeling of warmth, facial flushing, sweating, accelerated pulse, restlessness, feelings of weakness and dizziness, a fall in blood pressure and anginal symptoms may occur.
ASA
A distinction is made between chronic intoxication ("salicylism"), in which CNS symptoms such as light-headedness, dizziness or nausea predominate, and acute intoxication.
The most prominent feature of acute intoxication is a severe disturbance of acid-base balance. Resp- iratory alkalosis due to hyperpnoea occurs even at therapeutic doses. It is compensated by increased renal excretion of bicarbonate, which normalises blood pH. After toxic doses, compensation becomes insufficient and blood pH and bicarbonate concentrations fall. Plasma PCO2 may be temporarily nor- 
mal, suggesting metabolic acidosis, whereas a combination of respiratory and metabolic acidosis is in fact present.

Symptoms of acute intoxication
Symptoms of mild acute intoxication (associated with plasma levels of 200 - 400 g/ml): Hyperventilation, tinnitus, nausea, vomiting, impaired vision and hearing, headache, dizziness and confusional states may occur in addition to disturbances of acid-base balance or electrolyte balance (e.g. potassium loss).

Symptoms of severe intoxication (associated with plasma levels of 400 µg/ml) may include delirium, tremor, dyspnoea, sweating, dehydration, hyperthermia and coma. In cases of fatal intoxication, death normally results from respiratory failure.

Treatment of overdose

Dipyridamole
Gastric emptying should be considered. Administration of xanthine derivatives such as aminophylline may abolish the haemodynamic effect of dipyridamole.
Owing to its wide distribution in tissues and its predominantly hepatic elimination, dipyridamole is not likely to be accessible to enhanced removal procedures.

ASA
Treatment of ASA intoxication is guided by the extent, stage and clinical symptoms of the intoxicat- ion. It encompasses the usual measures for reducing absorption of ASA, monitoring and correcting water and electrolyte balance and restoring normal temperature regulation and respiration.

Treatment consists chiefly of measures to accelerate excretion and to restore the acid-base and electro- lyte balance. Diuretics are given in addition to infusions of sodium bicarbonate and potassium chlori- de. The urine should be alkalinised in order to increase salicylate ionisation and thus reduce salicylate reabsorption into the renal tubules.
It is highly advisable to monitor blood parameters such as pH, PCO2, bicarbonate and potassium. In severe cases, haemodialysis may be necessary.