Fluphenazine plasma levels and clinical response

Abstract

We monitored fluphenazine plasma levels in 39 schizophrenic patients who participated in a 2-year double-blind comparison of 5 mg and 25 mg of fluphenazine decanoate (FD) administered every 14 days. We investigated the relationship between log-transformed plasma levels at 3, 6, and 9 months and subsequent psychotic exacerbations with logistic regression and survival analysis. Using logistic regression, the relationship was nonsignificant at 3 months (chi-square = .21, df = 1, p = .65), but significant at 6 months (chi-square = 4.38, df = 1, p = .04) and 9 months (chi-square = 8.98, df = 1, p = .003). Using survival analysis with fluphenazine levels as a covariate (Cox models), we also found significant relationships between the fluphenazine plasma level and the risk of exacerbations at 6 months (chi-square = 3.77, df = 1, p = .052) and 9 months (chi-square = 12.21, df = 1, p = .0005), but not at three months (chi-square = 0.87, df = 1, p = .65). These findings suggest that the measurement of fluphenazine plasma levels may be helpful in decision-making about the dosage of FD.