Prolonged haloperidol and reduced haloperidol plasma concentrations after decanoate withdrawal

Pharmacokinetics and efficacy of a direct switch from conventional depot to risperidone long-acting injection in Chinese patients with schizophrenic and schizoaffective disorders

AIMS

This 12-week open-label study was designed to investigate the pharmacokinetics and efficacy of a direct switch from a conventional depot to long-acting injectable risperidone in patients with schizophrenia and schizoaffective disorder.

METHODS

Men or women from 18 to 65 years old with a diagnosis of schizophrenia or schizoaffective disorder were eligible for participation if they had been treated with conventional depot for at least 8 weeks before study entry. Intramuscular long-acting risperidone was administered starting from 25 mg, with the dose flexibly adjusted every two weeks for 12 weeks from week 4.

RESULTS

Of the 25 patients enrolled in this study, 21 completed at least one post-baseline assessment and were thus included in the analysis. The mean serum concentration of risperidone plus 9-hydroxyrisperidone was 29.1 ng/mL at the 12th week after switching, with an average injection dose of 31.25 mg long-acting risperidone every two weeks. The levels of active moiety of risperidone seemed to be higher in Chinese patients compared to those in Caucasian patients. Positive and Negative Syndrome Scale total scores (from 67.5 to 56.4; P = 0.002), scores for negative symptoms (P = 0.006) and general symptoms (P = 0.001) were improved significantly 12 weeks after the switch. Mean Extrapyramidal Symptom Rating Scale scores were improved significantly from 20.1 to 5.5 (P < 0.001). Significantly decreased levels of cholesterol and triglyceride were found at the 12th week. The levels of fasting glucose, low-density lipoprotein, high-density lipoprotein and bodyweight remained unchanged.

CONCLUSIONS

These findings suggest that switching from conventional depot to long-acting risperidone is feasible with the advantage of symptom reduction and side-effect profile decrement.

Haloperidol and reduced haloperidol plasma concentrations after a loading dose regimen with haloperidol decanoate

1. Haloperidol and reduced haloperidol plasma levels were measured in schizophrenic patients who received both oral (10 mg, N=16 and 20 mg, N=4) and depot haloperidol treatment 2. Patients were of Asian ethnicity and were safely and effectively converted from oral to depot therapy using a loading dose regimen using a 100 mg weekly injection interval for 4 weeks, biweekly for one month and then monthly. 3. Significant correlations were found for plasma haloperidol and reduced haloperidol levels and reduced haloperidol/haloperidol ratios between oral and depot therapy in these non-smoking patients. 4. A loading dose regimen is needed due to the long elimination half-life of decanoate of 26 days otherwise steady-state condition will not occur until 34 months of therapy. 5. Patients were maintained on monthly depot treatment for 40 weeks after the loading dose regimen and only one patient relapsed during treatment despite dosage increases. 6. The formation of reduced haloperidol remained consistent for oral and depot haloperidol treatment.

Pharmacoclinical correlations in schizophrenic patients treated with haloperidol decanoate: clinical evaluations, concentrations of plasma and red blood cell haloperidol and its reduced metabolite, and plasma homovanillic acid

1. The aim of this open study was to determine whether a more rational therapeutic approach could be devised for psychotic patients (n = 11) treated for long periods with long-acting (LA) haloperidol. The mean multiplication factor for the transition from the oral formulation to the long-acting one was 12.8 (10.4, standard deviation), lower than the theoretically recommended factor of 20. 2. The best dose (mg/kg)-concentration correlations were found for haloperidol (HAL) and reduced HAL (RHAL) in the red blood cells (RBC) (representative of the free drug fraction) rather than in the plasma of patients that had attained the steady state (at the third cycle and afterwards) 3. Pharmacokinetic analyses were conducted at the same time as clinical evaluations, grading using the BPRS and determinations of plasma levels of total, free and conjugated homovanillic acid (HVA), a marker of central dopaminergic activity. 4. A between groups comparison at the steady state (patients (n = 20) with oral administration and the above patients (n = 11) with long-acting form of HAL), showed that the plasma and RBC RHAL/HAL ratios of long-acting HAL decreased significantly (p < 0,005) in comparison with oral administration, at least by half. 5. Plasma HVA values complete the information provided by plasma and more especially RBC HAL and RHAL levels. All these results taken together, as substantiated by the clinical assessment scales (BPRS), assure a better pharmacoclinical surveillance and can be predictive of a patient's response.