Rate of Serum Valproate Concentration Monitoring in Patients with Bipolar Disorder Type I at Srinagarind Hospital Outpatient Clinic.

OBJECTIVE

Determine in the out-patient setting the rate and the purpose of serum valproate concentration monitoring during treatment with valproate, either single valproate or valproate in combination with other psychotropics in patients with bipolar disorder type I (BD-I), to determine the rate of recording valproate associated adverse effects, the rate of the follow-up and the length (days) that the patients were in the condition of full remission/recovery and symptomatic.

MATERIAL AND METHOD

The present study was a retrospective descriptive study done between January 1, 2007 and December 31, 2008. The data were from the medical records of DSM-IV-TR BD-I out-patients at Srinagarind Hospital, Khon Kaen who were treated either by single valproate or valproate in combination with other drugs for at least six weeks long. The studied variable included the annual rate and the reason that psychiatrist requested serum valproate concentration (SVC) monitoring per patient, the annual rate that psychiatrist recorded the valproate associated adverse effects, the annual rate that the patient returned to have a follow-up visit, and the length (days) that the patient was in full remission/recovery and symptomatic.

RESULTS

During the study period, of the 199 patients with BD-I, only 57 patients (28.6%) that were treated with valproate had complete records. The SVC monitoring occurred 17 times from 13 patients (22.8%). The mean SVC was 76.4 microgram/ml (SD = 31.8). The mean value +SD and range of SVC during the remission/recovery period were 75.1+17.5 μg/ml and 43.5-96.8 μg/ml, which was not significantly different from the symptomatic period, which was 77.1+39.9 μg/ml and 0.7 to 124.9 μg/ml. However, the oral dosage of valproate during the remission/recovery period (944.7+275.4 mg/day, median 1,000 mg/day) was significantly higher than during the symptomatic period (699.0+592.5 mg/day, 1,000 mg/day) (t = 2.7, df = 104 and p = 0.009). Of all the SVC monitoring, 58.8% occurred during the symptomatic period and most of the monitoring was due to the emergence of adverse effects. The causes for requesting the SVC determination were the emergence of adverse effects (29.4%), no reason specified (29.4%), and to monitor the clinical response (11.8%). The rate of valproate associated adverse effects recording was 1.1 times/person/year, which was 18.6% of the average rate of follow-up visits (6.6 times/person/year). The most frequent adverse effect was sedation. The treatment of BD-I by valproate or in combination with other psychotropics resulted in the remission/recovery period lasting 470.2 days (SD 256.8, median 517.0) while the symptomatic period lasted 176.1 days (SD 157.5, median 139.5).

CONCLUSION

During treatment of BD-I, the rate of serum valproate concentration monitoring was very few. However, when determination was requested, the SVC was within the therapeutic range. In addition, rate of recording of valproate associated adverse effects was very low and the most frequent adverse effect was mild. The reason for monitoring the clinical response was rarely found. Valproate seems to be easily administered. The dosage can be adjusted using only clinical response and adverse effects. Therefore, valproate was effective and safe in treatment of BD-I.