Clinical outcome of valproate maintenance treatment in bipolar I disorder at Srinagarind Hospital.

OBJECTIVE

To determine-in a clinical setting-the rate and time to recurrence of any mood episode during valproate maintenance treatment for bipolar I disorder.

MATERIAL AND METHOD

A retrospective cohort based on medical records of both in- and out-patient with bipolar I disorder (DSM-IV-TR) seen at Srinagarind Hospital between January 1, 2009 and December 31, 2010 was done. A recurrence was observed if the patient had fulfilled the remission criteria and valproate was the maintenance drug. Survival analysis and Cox regression analysis were used to analyze the data.

RESULTS

Eighty-five patients with 124 remitted mood episodes met the inclusion criteria. Of the 85 patients, the average age was 41.4 +/- 17.1 years (range, 18-89); 49.4% were males; 48.2% married; 42.4% completed secondary school, 30.6% completed a bachelor degree; 35.3% were unemployed, and 34.1% were government employees. Twenty remitted mood episodes (16.1%) were in maintenance treatment with valproate only. The remaining 104 (83.9%) were in maintenance treatment with valproate in combination with other agents. There were 50 recurrences from 36 patients during the two years of study, the recurrence per a patient ranged from 1 to 3 times. The rate of recurrence was 21%/year or 2.2/100 person-months (95% CI = 1.65-2.93). The average time to recurrence to any mood episode was 33 months (95% CI = 15.06-50.94). With multivariable Cox regression, a statistically significant greater risk for a recurrence was associated with: (a) the previous episode being hospitalized (adjusted hazard ratio = 5.88, 95% CI = 2.76-12.36, p < 0.001); (b) blood valproate concentration during maintenance treatment < 50 microg/mL (adjusted hazard ratio = 3.07, 95% CI = 1.11-8.53, p = 0.03); and (c) time duration (month) of valproate maintenance treatment (adjusted hazard ratio = 0.98, 95% CI = 0.96-0.99, p = 0.001). With the adjusted hazard ratio 0.98, it could be interpreted in the other way that each additional month of taking valproate was associated with a statistically significant protective factor that decreased the risk of recurrence by 2% from the previous month.

CONCLUSION

In the authors'clinical setting, valproate both singly and in combination with other psychotropic agents used for maintenance treatment of bipolar I disorder yielded a recurrence rate of 21% per year or 2.2 per 100 person-months and time to any mood episode recurrence of 33 months. The present result has importance for both clinical treatment decision-making and patient economic status.