Marketed formulations of extended phenytoin sodium -- long a difficult medication to titrate because of its unique absorption and saturable elimination pharmacokinetics -- may not be bioequivalent ...

Ms. M was also prescribed vitamin K 5 mg by mouth, twice daily, beginning in the third trimester. Initial blood tests showed a subtherapeutic phenytoin level of 6.6 mcg/mL (reference range 10–20 ...