Overdose : מינון יתר

4.9 Overdose
Linked to Acetylsalicylic acid:
Symptoms of mild salicylate intoxication include dizziness, tinnitus, deafness, sweating, nausea and vomiting, headache and confusion. These may occur at plasma concentrations of 150 to 300 micrograms/ml. These symptoms can be controlled by reducing the dose, or interrupting the treatment.
More serious intoxication occurs at concentrations above 300 micrograms/ml. The symptoms of severe overdose include hyperventilation, fever, restlessness, ketosis, respiratory alkalosis, and metabolic acidosis. Depression of the CNS may lead to coma. Cardiovascular collapse and respiratory failure may also occur.
Treatment of severe overdose
The patient must be transferred to hospital and the Poison Control Center contacted immediately.
When the patient is suspected of ingesting more than 120 mg/kg salicylate within the last hour, repeated doses of activated charcoal are to be given orally.
Plasma concentrations should be measured in patients having ingested more than 120 mg/kg salicylate, although the severity of the poisoning cannot be determined from these alone. Clinical and biochemical features must equally be taken into account.
In plasma concentrations exceeding 500 micrograms/ml (350 micrograms/ml in children under 5 years of age) the intravenous administration of sodium bicarbonate is effective in removing salicylate from the plasma.
Heamodialysis or haemoperfusion are the methods of choice in cases where the plasma salicylate concentration is more than 700 micrograms/ml, or lower in children and elderly people, or if there is a severe metabolic acidosis.

Linked to Paracetamol:
Overdose (>10 g in total in the adult or >150 mg/kg in one intake) can provoke a hepatic cytolysis which can lead to complete and irreversible necrosis (hepatic failure, metabolic acidosis, renal failure) and eventually to coma and possibly death. Less often renal tubular necrosis may develop.
Early signs of overdose (very commonly nausea, vomiting, anorexia, pallor, lethargy and sweating) generally settle within first 24 hours.

Abdominal pain may be the first indication of liver damage, which is not usually apparent for the first 24 to 48 hours, and may be delayed for up to 4 to 6 days after ingestion. Liver damage is generally at a maximum 72 to 96 hours after ingestion. Abnormalities of glucose metabolism and metabolic acidosis may occur. Acute renal failure with acute tubular necrosis may develop even in the absence of severe liver damage. Cardiac arrhythmias and pancreatitis have been reported.
Patients are considered at high risk when receiving enzyme-inducing medicinal products, such as carbamazepine, phenytoin, phenobarbital, rifampicin, and St John’s wort, or with a history of alcohol abuse, or suffering from malnutrition.
Treatment of overdose:
When the patient is suspected of ingesting more than 150 mg/kg paracetamol within the last hour, repeated doses of activated charcoal are to be given orally. However, if acetylcysteine or methionine is to be given by mouth the charcoal is best cleared from the stomach to prevent it reducing the absorption of the antidote.
Antidotes
N-acetylcysteine should be administered intravenously or orally as soon as possible after ingestion. It is most effective during the first 8 hours after taking the overdose. The effect of the antidote then diminishes progressively after that. Nevertheless it has been shown that treatment up to and beyond 24 hours after ingestion remains beneficial.
Methionine is most effective within the first 10 hours after ingestion of paracetamol overdose.
Hepatic damage is more frequent and severe if treatment with methionine if started more than 10 hours after ingestion.
Oral absorption might be reduced by vomiting or activated charcoal.
Linked to Caffeine:
Common symptoms include anxiety, nervousness, restlessness, insomnia, excitement, muscle twitching, confusion, convulsions. For high intake of caffeine, hyperglycemia could also appear.
Cardiac Symptoms include tachycardia and cardiac arrhythmia. The symptoms are controlled by reducing or stopping caffeine intake.