Serum concentrations of clozapine and norclozapine in the prediction of relapse of patients with schizophrenia.

Schizophrenic outpatients (n=102) whose condition had stabilized with clozapine (CLZ) therapy and were being maintained on CLZ were followed for 1 year. Clinical status and concentrations of serum clozapine (CLZ) and its metabolite norclozapine (NCLZ) were evaluated periodically or when relapse occurred. Relapse was defined as a significant exacerbation of psychotic symptoms or hospitalization. Thirty-three patients relapsed and 69 did not. Relapse patients displayed significantly lower serum concentrations of CLZ and a sum of CLZ and NCLZ at endpoint than non-relapses (CLZ: 162 ng/ml vs. 237 ng/ml, p<0.001; CLZ+NCLZ: 225 ng/ml vs. 301 ng/ml, p<0.001). When all subjects were pooled together, a significant inverse correlation was observed between percent increase in the total score on the Brief Psychiatric Rating Scale (BPRS) from baseline and serum levels of CLZ alone (r=0.404, p<0.001) and the sum of CLZ and NCLZ (r=0.364, p<0.001). Relapses and non-relapses were well separated by a threshold CLZ serum concentration of 200 ng/ml with a sensitivity of 73% and a specificity of 80%. The threshold value represented about a 40% lower serum CLZ level than concentration achieved in acute treatment. Survival analysis showed a similarity of the relapse risk over time defined by the CLZ serum threshold and by symptomatic criteria. These results suggest that effective relapse prevention may require maintenance of patients at CLZ serum concentrations above 200 ng/ml and above 60% of the acute-phase level during long-term maintenance treatment of schizophrenia.

Single- and Multiple-Dose Milnacipran Pharmacokinetics in Healthy Han Chinese Volunteers.

BACKGROUND: The pharmacokinetics of milnacipran have been studied in Caucasian subjects but not in Chinese subjects. METHODS: This single-center, open-label study evaluated the pharmacokinetics and safety of oral milnacipran administered as a randomized, three-way crossover, single-dose (25, 50 and 100 mg) and in multiple doses for 8 days (up to 100 mg/day administered as 50 mg twice daily) in Han Chinese healthy volunteers. Both the single- and multiple-dose studies included 12 different adults (six males and six females), respectively. Pharmacokinetic parameters for milnacipran were determined using WinNonlin version 6.3. The safety evaluation included adverse events (AEs) assessed by monitoring, physical examinations, vital signs, and clinical laboratory tests. RESULTS: Plasma concentrations of milnacipran reached a time to maximum concentration (t max) of 1.2-4.3 h after each single dose, and then declined, with a mean half-life (t ½) of 7.0-7.3 h over the dose range of 25-100 mg; the area under the curve (AUC) and maximum concentration (C max) values increased in a dose-proportional manner. After multiple doses, steady state was reached by day 4 and the accumulation was low, with an accumulation index <1.65. No significant sex differences were observed in milnacipran pharmacokinetic parameters and, additionally, no severe AEs were observed in the single- or multiple-dose studies. The most common reported AEs were nausea, vomiting, dizziness and water brash, which appears to be dose-related. CONCLUSION: Milnacipran was safe and well-tolerated in healthy volunteers and displayed linear increase in the C max and AUC values at doses ranging from 25 to 100 mg once daily.

The differential effects of steady-state fluvoxamine on the pharmacokinetics of olanzapine and clozapine in healthy volunteers.

The combination of atypical antipsychotics and selective serotonin reuptake inhibitors is an effective strategy in the treatment of certain psychiatric disorders. However, pharmacokinetic interactions between the two classes of drugs remain to be explored. The present study was designed to determine whether there were different effects of steady-state fluvoxamine on the pharmacokinetics of a single dose of olanzapine and clozapine in healthy male volunteers. One single dose of 10 mg olanzapine (n = 12) or clozapine (n = 9) was administered orally. Following a drug washout of at least 4 weeks, all subjects received fluvoxamine (100 mg/day) for 9 days, and one single dose of 10 mg olanzapine or clozapine was added on day 4. Plasma concentrations of olanzapine, clozapine, and N-desmethylclozapine were assayed at serial time points after the antipsychotics were given alone and when added to fluvoxamine. No bioequivalence was found in olanzapine alone and cotreatment with fluvoxamine for the mean peak plasma concentration (C(max)), the area under the concentration-time curve from time 0 to last sampling time point (AUC(0-t)), and from time 0 to infinity (AUC(0- infinity )). Under the cotreatment, C(max) of olanzapine was significantly elevated by 49%, with a 32% reduced time (t(max)) to C(max), whereas the C(max) and t(max) of clozapine were unaltered. The cotreatment increased the AUC(0-t) and AUC(0- infinity ) of olanzapine by 68% and 76%, respectively, greater than those of clozapine (40% and 41%). The presence of fluvoxamine also prolonged the elimination half-life (t(1/2)) of olanzapine by 40% and, to a much greater extent, clozapine by 370% but reduced the total body clearance (CL/F) of clozapine (78%) more significantly than it did for olanzapine (42%). The apparent volume of distribution (V(d)) was suppressed by 31% in olanzapine combined with fluvoxamine but was unaltered in the clozapine regimen. A significant reduction in the N-desmethylclozapine to clozapine ratio was present in the clozapine with fluvoxamine regimen. The effects of fluvoxamine on different aspects of pharmacokinetics of the two antipsychotics may have implications for clinical therapeutics.