Effectiveness of therapeutic drug monitoring (TDM) of phenytoin and valproic acid in adult patients / Nurul Izzati Hairussam

The study aim to describe the effectiveness of therapeutic drug monitoring (TDM) of phenytoin and valproic acid in the control of seizures in adult patients. The data was collected from Hospital Tengku Ampuan Rahimah, Klang. A total of 233 forms were reviewed of which 98 patients are females and 135 of them are males. The patients' demographics, renal profile and pharmacokinetics were analyzed to examine the pattern correlation to phenytoin and valproic acid. The data was best describes by a one­ compartment model. The analysis has shown that there is a strong correlation between total daily dose and clearance (L/day) in phenytoin polytherapy with R2 value is 0.3031. The mean of serum level, dose per kg and clearance ofphenytoin monotherapy are (9.97 ± 7.02 mg/L), (6 ± 3.59 mg/kg) and (0.362 ± 0.13 L/kg/hr) respectively. The mean of serum level, dose per kg and clearance of patients on phenytoin polytherapy are (9.14 ± 6.67 mg/L), (5.5 ± 4.18 mg/kg) and (0.36 ± 0.147 L/kg/hr) respectively. The mean of serum level, dose per kg and clearance of patients on valproic acid monotherapy are (52.12 ± 11.06 mg/L), (15 ± 5.64 mg/kg) and (10.57 ± 4.6 ml/kg.hr) respectively. Meanwhile, the mean of serum level, dose per kg and clearance of patients on valproic acid polytherapy are (38.49 ± 8.93 mg/L), (16 ± 6.03 mg/kg) and (11.68 ± 4.66 ml/kg/hr) respectively. The COV value (more than 10%) has shown high inter-patient variability in terms of pharmacokinetics. In short, the population pharmacokinetics of hospitalized adults prescribed with phenytoin and valproic acid has high intra and inter­ patient variability in gender, races and drug therapy. Finally, it is necessary to monitor the patients individually and regularly in order to avoid toxicities and achieve the optimum level of therapeutic range.