PK-Merz Overdosage

Overdose and Treatment: The possibility of multiple intoxication must always be considered, for example ingestion of more than one drug with suicidal intention.
Symptoms of overdose: Acute intoxication is characterised by nausea, vomiting, hyperexcitability, tremor, ataxia, blurred vision, lethargy, depression, dysarthria and cerebral seizures; a malignant cardiac arrhythmia has been reported in one case.
Acute toxic psychoses in the form of states of confusion with visual hallucinations sometimes including coma and myoclonus have been observed after simultaneous administration of amantadine and other antiparkinsonian drugs.
Management of overdose: There is no known specific drug treatment or antidote. In the event of intoxication with film-coated tablets, vomiting should be induced and/or gastric lavage performed.
In the event of life-threatening intoxication, intensive care is necessary additionally.
Therapeutic measures to be considered include fluid intake and acidification of the urine for more rapid excretion of the substance, and possibly sedation, anticonvulsive measures, and antiarrhythmic agents (lidocaine i.v.).
For the treatment of neurotoxic symptoms (such as those described previously), intravenous administration of physostigmine can be tried in adults at a dose of 1-2 mg every 2 hours and in children 2×0.5 mg at intervals of 5-10 minutes up to a maximum dose of 2 mg. Because of the low dialysability of amantadine (approx. 5%), haemodialysis is not an option.
It is advisable to monitor patients particularly closely for possible QT prolongation and for factors that promote the occurrence of torsade de pointes, e.g. electrolyte imbalances (particularly hypokalaemia and hypomagnesaemia) or bradycardia.