Clinical pharmacokinetics of atypical antipsychotics: a critical review of the relationship between plasma concentrations and clinical response.
ABSTRACT In the past, the information about the dose-clinical effectiveness of typical antipsychotics was not complete and this led to the risk of extrapyramidal adverse effects. This, together with the intention of improving patients' quality of life and therapeutic compliance, resulted in the development of atypical or second-generation antipsychotics (SGAs). This review will concentrate on the pharmacokinetics and metabolism of clozapine, risperidone, olanzapine, quetiapine, amisulpride, ziprasidone, aripiprazole and sertindole, and will discuss the main aspects of their pharmacodynamics. In psychopharmacology, therapeutic drug monitoring studies have generally concentrated on controlling compliance and avoiding adverse effects by keeping long-term exposure to the minimal effective blood concentration. The rationale for using therapeutic drug monitoring in relation to SGAs is still a matter of debate, but there is growing evidence that it can improve efficacy, especially when patients do not respond to therapeutic doses or when they develop adverse effects. Here, we review the literature concerning the relationships between plasma concentrations of SGAs and clinical responses by dividing the studies on the basis of the length of their observation periods. Studies with clozapine evidenced a positive relationship between plasma concentrations and clinical response, with a threshold of 350-420 ng/mL associated with good clinical response. The usefulness of therapeutic drug monitoring is well established because high plasma concentrations of clozapine can increase the risk of epileptic seizures. Plasma clozapine concentrations seem to be influenced by many factors such as altered cytochrome P450 1A4 activity, age, sex and smoking. The pharmacological effects of risperidone depend on the sum of the plasma concentrations of risperidone and its 9-hydroxyrisperidone metabolite, so monitoring the plasma concentrations of the parent compound alone can lead to erroneous interpretations. Despite a large variability in plasma drug concentrations, the lack of studies using fixed dosages, and discrepancies in the results, it seems that monitoring the plasma concentrations of the active moiety may be useful. However, no therapeutic plasma concentration range for risperidone has yet been clearly established. A plasma threshold concentration for parkinsonian side effects has been found to be 74 ng/mL. Moreover, therapeutic drug monitoring may be particularly useful in the switch between the oral and the long-acting injectable form. The reviewed studies on olanzapine strongly indicate a relationship between clinical outcomes and plasma concentrations. Olanzapine therapeutic drug monitoring can be considered very useful in assessing therapeutic efficacy and controlling adverse events. A therapeutic range of 20-50 ng/mL has been found. There is little evidence in favour of the existence of a relationship between plasma quetiapine concentrations and clinical responses, and an optimal therapeutic range has not been identified. Positron emission tomography studies of receptor blockade indicated a discrepancy between the time course of receptor occupancy and plasma quetiapine concentrations. The value of quetiapine plasma concentration monitoring in clinical practice is still controversial. Preliminary data suggested that a therapeutic plasma amisulpride concentration of 367 ng/mL was associated with clinical improvement. A therapeutic range of 100-400 ng/mL is proposed from non-systematic clinical experience. There is no direct evidence concerning optimal plasma concentration ranges of ziprasidone, aripiprazole or sertindole.
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ABSTRACT: Schizophrenia is a chronic illness with a progressive course that can be marked by resistance to antipsychotic treatment. This can make therapeutic support challenging for the practitioner, with results that are partial and unsatisfactory. In the literature, treatment with high-dose olanzapine (N20 mg/day) appears to be a good alter-native to clozapine, the gold standard for treatment-resistant schizophrenia. In the present observational prospective study, we studied the clinical and biological profiles of patients treated with olanzapine doses up to 100 mg/day. In total, 50 patients were clinically and biologically assessed. We found a linear relationship between oral dose and serum concentration (Pearson's r = 0.83, p b 0.001) with effects of tobacco (p b 0.05) and of coffee and tea consumption (p b 0.01). Tolerance seemed to be good regardless of dose. No link was found between concentration and efficiency. Despite a nonexhaustive assessment of pharmacokinetic parame-ters, not least pharmacogenetic data (e.g., genotyping of cytochrome P450-1A2 or glycoprotein P Abcb1a), pharmacokinetic aspects alone cannot account for why the disease may sometimes be resistant to 20 mg of olanzapine but respond to higher doses. A nuclear imaging study exploring brain occupancy by high-dose olanzapine, coupled with the abovementioned pharmacokinetic assessment, may prove a relevant experimental paradigm for studying the pathophysiological mechanisms of resistant schizophrenia.Schizophrenia Research 09/2014; · 4.43 Impact Factor
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ABSTRACT: Insufficient treatment of psychosis often manifests as violent and aggressive behaviors that are dangerous to the patient and others, and that warrant treatment strategies which are not considered first-line, evidence-based practices. Such treatment strategies include both antipsychotic polypharmacy (simultaneous use of 2 antipsychotics) and high-dose antipsychotic monotherapy. Here we discuss the hypothesized neurobiological substrates of various types of violence and aggression, as well as providing arguments for the use of antipsychotic polypharmacy and high-dose monotherapy to target dysfunctional neurocircuitry in the subpopulation of patients that is treatment-resistant, violent, and aggressive. In this review, we focus primarily on the data supporting the use of second-generation, atypical antipsychotics both at high doses and in combination with other antipsychotics.CNS spectrums 08/2014; · 1.30 Impact Factor
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ABSTRACT: Violence is a major management issue for forensic mental health systems. Violence can be approached as a medical syndrome and deconstructed into psychotic, impulsive, and predatory subtypes, which are hypothetically mapped onto corresponding malfunctioning brain circuits. Rational management of violence balances treatment with security, while targeting each subtype of violence with approaches unique to the psychotic, impulsive, and predatory forms of violence.CNS spectrums 10/2014; 19(5):357-65. · 1.30 Impact Factor