Rapid i.v. loading with phenytoin with subsequent dose adaptation using non-steady-state serum levels and a Bayesian...

Area of Science:

• Pharmacology
• Clinical Pharmacy
• Internal Medicine

Background:

• Phenytoin is a critical anticonvulsant medication.
• Optimizing phenytoin dosing is essential for patient safety and efficacy.
• Standardized loading doses may require individual adjustments.

Purpose of the Study:

• Evaluate a phenytoin loading dose regimen's suitability.
• Assess the necessity of dose individualization for phenytoin.
• Investigate Bayesian forecasting for phenytoin dose adaptation using non-steady-state levels.

Main Methods:

• Administered an initial intravenous phenytoin loading dose (15 mg/kg).
• Followed with standardized intravenous maintenance doses every 12 hours for 5 days.
• Individualized the day 5 evening dose based on three serum trough levels (L1, L2, L3).

Main Results:

• 77% (L1) and 68% (L3) of patients achieved therapeutic phenytoin levels (10-20 mg/L).
• Bayesian forecasting prediction error was 3.95 mg/L, with a root mean squared error of 6.27 mg/L.
• 70% of serum levels were within the 68% confidence interval.

Conclusions:

• The rapid intravenous phenytoin loading dose regimen is effective and safe.
• Individualization of phenytoin dosing after day 5 is necessary for optimal patient management.
• Bayesian forecasting shows potential for phenytoin dose adaptation.