Phenytoin Poisoning
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Basics
Description
- Phenytoin follows zero-order pharmacokinetics:
- Small incremental increase in dose can result in a large increase in plasma concentration
- Half-life in overdose prolonged; may be up to 70 hr
- Cardiovascular toxicity from IV administration likely due to the diluent propylene glycol
- Fosphenytoin, a prodrug for parenteral administration, is metabolized to phenytoin, its active moiety
Etiology
- Phenytoin intoxication results from acute, chronic, or acute-on-chronic administration
- If the cause of the intoxication is unclear in a patient receiving chronic phenytoin therapy, consider that there may have been a:
- Change in the brand of phenytoin
- Change in dosage form
- Drug interaction
- Change in serum albumin
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Basics
Description
- Phenytoin follows zero-order pharmacokinetics:
- Small incremental increase in dose can result in a large increase in plasma concentration
- Half-life in overdose prolonged; may be up to 70 hr
- Cardiovascular toxicity from IV administration likely due to the diluent propylene glycol
- Fosphenytoin, a prodrug for parenteral administration, is metabolized to phenytoin, its active moiety
Etiology
- Phenytoin intoxication results from acute, chronic, or acute-on-chronic administration
- If the cause of the intoxication is unclear in a patient receiving chronic phenytoin therapy, consider that there may have been a:
- Change in the brand of phenytoin
- Change in dosage form
- Drug interaction
- Change in serum albumin
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