Any drug, regardless of how benign and well tolerated, is potentially toxic. The toxicity may be due to (1) dosage; (2) the size of the patient; (3) drug interaction; (4) drug specificity for the disease; (5) the nature of the disease for which the drug is used; and (6) the mode and frequency of medication.
DOSE OF ANTICONVULSANT
Dose of anficonvulsant is very important (Table I). Any anticonvulsant in higher than therapeutic doses has toxic potential. It is well known that anticonvulsants in large enough doses can act as convulsants. This is especially true for diphenylhydantoin, benzodiazepines, and lidocaine.
THE SIZE OF THE PATIENT
The size of the patient should be considered in dosage. It is safer and more accurate to adjust dosage to body surface than to weight (Table I). As the child grows, there may be a need to gradually increase the dose of anticonvulsants if seizure control is poor, or if the serum level of the anticonvulsant starts to decline.
DRUG INTERACTION
The relationship. of multiple drug therapy and its toxic effects on the brain is quite complicated, and many forms of toxicity can result.
Toxicity may be the result of a combination of pharmacologically similar drugs. Such a combination may enhance the side effects of drowsiness and ataxia. The patient may suffer from these side effects without attaining therapeutic levels of individual anticonvulsants in the blood. In other words, a combination of drugs such as phenobarbital and primidone may result in severe ataxia and drowsiness.
Relationship of Ketamine's Plasma Metabolites with Response, Diagnosis, and Side Effects in Major Depression