Optimizing a Phenytoin Dosage Regimen

At the clinic you have a new patient (S.V.), age 62 years and weight 45 kg. An initial dose of 260 mg/day was recommended. The patient was instructed to take this dose each day for a few weeks and return for a plasma sample. This plasma sample was found to contain 7.5 mg/L phenytoin. This was somewhat low so you need to calculate a new dose per day with the aim of achieving an average plasma concentration of 15 mg/L. For this calculation you can assume that the patient has a Km value of 4 mg/L (a population average value).

A useful equation

Equation 31.1.1 Dose Rate equals Rate of Elimination

Last update: Sat 16 Sep 2006 07:42:00 pm

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