Select one or more newsletters to continue. Unbound phenytoin concentrations may be more useful.-Elderly patients: A lower loading dose and/or infusion rate, and lower or less frequent maintenance dosing may be required. a mini phenytoin loading dose of 10mg/kg based on AdBW of 83kg Leave maintenance the same as it is only day #2 of therapy (not at steady state) On day #5, the total level is reported as 9 mcg/mL.

Applies to the following strengths: 50 mg/mL; 50 mg; 100 mg; 30 mg; 25 mg/mL; 200 mg; 300 mg; sodiumDue to an increased fraction of unbound phenytoin in patients with renal disease, the interpretation of total phenytoin plasma concentrations should be made with caution. Maintenance intravenousphenytoin therapy of 3-5mg/kg/day in three divided doses (normally 100mg THREE TIMES A DAY) should be commenced 12 – 24 hours after loading dose. A phenytoin tolerance test was devised with the intention of predicting a more adequate daily dose for such a patient. Administration of phenytoin via enteral feeding tubes is not recommended due to variable absorption of phenytoin.

*0 I I I 0 10 20 30 Serumphenytoin concentration(pg/mi) Fig. Unbound phenytoin concentrations may be more useful.Due to an increased fraction of unbound phenytoin in patients with hepatic disease, the interpretation of total phenytoin plasma concentrations should be made with caution.

A phenytoin tolerance test was devised with the intention of predicting a more adequate daily dose for such a patient.Fifteen patients were each given an oral test dose of 600 mg phenytoin sodium and the serum concentration of phenytoin was measured at intervals over 48 h; the concentration rose during the first 4 h and decayed between 12–48 h as an almost linear function of time.The serum concentration/time curves were fitted by an iterative computer program based on the Michaelis‐Menten equatioa The mean saturated rate of elimination of phenytoin was 435 mg/day and the serum concentration (The Michaelis‐Menten principle was used to predict steady state serum phenytoin concentrations in individual patients receiving daily doses of phenytoin sodium adjusted by steps of 100 mg. A rough guide to making an adjustment to the daily dose that should increase a serum level without leading to supratherapeutic / toxic levels is: If the phenytoin concentration is < 7 mcg/mL, the dose may be increased by 100 mg/day. Currently available data are described in

Unbound phenytoin concentrations may be more useful.

Phenytoin concentrations increase disproportionately with dose; toxicity may occur if the maintenance dose is increased by more than 25 to 50mg per day. Only use intravenous administration when oral administration is not feasible and where cardiac monitoring is available.Phenytoin is highly protein bound but only the unbound concentration is active. We comply with the HONcode standard for trustworthy health information - Based on the patient's current dose and the measured concentration (columns 1 and 2), column 3 gives a rough guide to interpretation of the result and possible dosage adjustment. and you may need to create a new Wiley Online Library account.Enter your email address below and we will send you your usernameIf the address matches an existing account you will receive an email with instructions to retrieve your username Renal Dose Adjustments Due to an increased fraction of unbound phenytoin in patients with renal disease, the interpretation of total phenytoin plasma concentrations should be made with caution.