Clinical pharmacokinetics of quetiapine: an atypical antipsychotic

Clinical pharmacology of dopamine-modulating agents in Tourette's syndrome

Forty years of research and clinical practice have proved dopamine (DA) receptor antagonists to be effective agents in the treatment of Tourette's syndrome (TS), allowing a significant tic reduction of about 70%. Their main effect seems to be mediated by the blockade of the striatal DA-D2 receptors. Various typical and atypical agents are available and there is still discord between experts about which of them should be considered as first choice. In addition, there are suggestions to use DA receptor agonists such as pergolide or non-DA-modulating agents. The present chapter is focusing on the clinical pharmacology of DA-modulating agents in the treatment of TS. The introduction outlines their clinical relevance and touches on the hypotheses of the role of DA in the pathophysiology of TS. Subsequently, general information about the mechanisms of action and adverse effects are provided. The central part of the chapter forms a systematic review of all DA-modulating agents used in the treatment of TS, including an overview of studies on their effectiveness, and a critical discussion of their specific adverse effects. The present chapter closes with a summary of the body of evidence and a description of the resulting recommendations for the pharmacological treatment of TS.

Psychotropic drug-drug interactions involving P-glycoprotein

Multidrug resistance P-glycoprotein (P-gp; also known as MDR1 and ABCB1) is expressed in the luminal membrane of the small intestine and blood-brain barrier, and the apical membranes of excretory cells such as hepatocytes and kidney proximal tubule epithelia. P-gp regulates the absorption and elimination of a wide range of compounds, such as digoxin, paclitaxel, HIV protease inhibitors and psychotropic drugs. Its substrate specificity is as broad as that of cytochrome P450 (CYP) 3A4, which encompasses up to 50 % of the currently marketed drugs. There has been considerable interest in variations in the ABCB1 gene as predictors of the pharmacokinetics and/or treatment outcomes of several drug classes, including antidepressants and antipsychotics. Moreover, P-gp-mediated transport activity is saturable, and is subject to modulation by inhibition and induction, which can affect the pharmacokinetics, efficacy or safety of P-gp substrates. In addition, many of the P-gp substrates overlap with CYP3A4 substrates, and several psychotropic drugs that are P-gp substrates are also CYP3A4 substrates. Therefore, psychotropic drugs that are P-gp substrates may cause a drug interaction when P-gp inhibitors and inducers are coadministered, or when psychotropic drugs or other medicines that are P-gp substrates are added to a prescription. Hence, it is clinically important to accumulate data about drug interactions through studies on P-gp, in addition to CYP3A4, to assist in the selection of appropriate psychotropic medications and in avoiding inappropriate combinations of therapeutic agents. There is currently insufficient information available on the psychotropic drug interactions related to P-gp, and therefore we summarize the recent clinical data in this review.

Quetiapine fumarate augmentation for patients with a primary anxiety disorder or a mood disorder: a pilot study

BACKGROUND

Comorbid anxiety symptoms,in patients with a primary anxiety disorder or a mood disorder, leads to poor patient outcomes and burdens the healthcare system. This pilot study evaluated the feasibility of extended-release quetiapine fumarate (quetiapine XR) for the treatment of patients with either a primary anxiety disorder or a mood disorder with comorbid anxiety symptoms compared to a placebo, as an adjunct to antidepressant therapy.

METHODS

Thirty-nine patients with a diagnosis of a primary anxiety disorder or a mood disorder with comorbid anxiety symptoms were enrolled in this study. Patients with a stable dose of antidepressant therapy were randomized according to a 2:1 probability of receiving either quetiapine XR or a placebo adjunctive treatment for 8 weeks. The efficacy was assessed by the Hamilton Anxiety Rating Scale (HAM-A) and the Clinical Global Impression of severity (CGI-S) score at baseline, week 1, 4, and 8.

RESULTS

A total of 35 patients were included in this intention-to treat (ITT) population for the efficacy analysis (quetiapine XR: 22 patients; placebo: 13 patients). At week 4, statistically significant differences were observed on both the HAM-A score (p = 0.003) and the CGI-S score (p = 0.025), favouring the quetiapine XR (-13.00 ± 4.14) compared to placebo (-6.63 ± 5.42). However, no statistically significant difference was observed between the two groups with regard to changes from the baseline to week 8 on the HAM-A score (p = 0.332) or the CGI-S score (p = 0.833).

CONCLUSIONS

Augmentation of antidepressant treatment with quetiapine XR did not result in clinical improvement according to the outcome measure of anxiety using the HAM-A and CGI-S scores at week 8, among the patients with either a primary anxiety disorder or a mood disorder with comorbid anxiety symptoms. However, treatment with quetiapine XR as an adjunct to antidepressant therapy appeared to provide a short-term benefit at 4 weeks. Further study is needed with a larger sample size, randomized controlled design and control of the dosage prescribed.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT00912535.

Effects of sustained administration of quetiapine alone and in combination with a serotonin reuptake inhibitor on norepinephrine and serotonin transmission

Quetiapine is now used in the treatment of unipolar and bipolar disorders, both alone and in combination with other medications. In the current study, the sustained administration of quetiapine and N-Desalkyl quetiapine (NQuet) in rats in a 3 : 1 mixture (hQuetiapine (hQuet)) was used to mimic quetiapine exposure in patients because rats do not produce the latter important metabolite of quetiapine. Sustained administration of hQuet for 2 and 14 days, respectively, significantly enhanced the firing rate of norepinephrine (NE) neurons by blocking the cell body α₂-adrenergic autoreceptors on NE neurons, whether it was given alone or with a serotonin (5-HT) reuptake inhibitor. The 14-day regimen of hQuet enhanced the tonic activation of postsynaptic α₂- but not α₁-adrenergic receptors in the hippocampus. This increase in NE transmission was attributable to increased firing of NE neurons, the inhibition of NE reuptake by NQuet, and the attenuated function of terminal α₂-adrenergic receptors on NE terminals. Sustained administration of hQuet for 2 and 14 days, respectively, significantly inhibited the firing rate of 5-HT, whether it was given alone or with a 5-HT reuptake inhibitor, because of the blockade of excitatory α₁-adrenergic receptors on 5-HT neurons. Nevertheless, the 14-day regimen of hQuet enhanced the tonic activation of postsynaptic 5-HT(1A) receptors in the hippocampus. This increase in 5-HT transmission was attributable to the attenuated inhibitory function of the α₂-adrenergic receptors on 5-HT terminals and possibly to direct 5-HT(1A) receptor agonism by NQuet. The enhancement of NE and 5-HT transmission by hQuet may contribute to its antidepressant action in mood disorders.

Slow dissociation of partial agonists from the D₂ receptor is linked to reduced prolactin release

In this study we investigated the correlation between affinity, efficacy, peripheral receptor occupancy, and kinetic properties of D₂ dopamine receptor ligands with time-course evaluations of prolactin release in rat blood. We profiled typical and atypical antipsychotic antagonists at D₂ receptors, the partial agonist aripiprazole, and four novel partial agonist compounds with different properties. Clozapine and quetiapine revealed lower prolactin release and fast dissociation kinetics, linking fast dissociation and prolactin-sparing properties. Surprisingly, haloperidol, a highly prolactin-releasing antagonist, shared intermediate dissociation properties. Factors other than kinetic properties may thus contribute to prolactin-releasing properties of antagonists. Partial agonists sharing similar efficacies and receptor occupancies differed markedly in their ability to induce hyperprolactinaemia. Aripiprazole moderately released prolactin even at high receptor occupancies, with slow dissociation from D₂ receptors. Other compounds displaying low affinities and fast dissociations released prolactin substantially, although less than haloperidol. The effect augmented after repeated administrations. Compounds with high affinities and slow dissociation rates stimulated moderate prolactin release at high receptor occupancies, reaching a ceiling effect at 50-60% occupancy. Moreover, the effect developed tolerance. In conclusion, we investigated the affinity and kinetic properties of D₂ partial agonists associated with their ability to induce prolactin release in blood. We propose that for D₂ partial agonists, at comparable intrinsic activities and peripheral occupancies, the prolactin-releasing properties are linked to their kinetic rate properties. Differently from D₂ antagonists, partial agonists display slow dissociation and high affinity associated with a low prolactin release profile.

Atypical antipsychotics: trends in analysis and sample preparation of various biological samples

Atypical antipsychotics are increasingly popular and increasingly prescribed. In some countries, they can even be obtained over-the-counter, without a prescription, making their abuse quite easy. Although atypical antipsychotics are thought to be safer than typical antipsychotics, they still have severe side effects. Intoxications are not rare and some of them have a fatal outcome. Drug interactions involving atypical antipsychotics complicate patient management in clinical settings and the determination of the cause of death in fatalities. In view of the above, analytical strategies that can efficiently isolate atypical antipsychotics from a variety of biological samples and quantify them accurately, sensitively and reliably, are of utmost importance both for the clinical, as well as for the forensic toxicologist. In this review, we will present and discuss novel analytical strategies that have been developed from 2004 to the present day for the determination of atypical antipsychotics in various biological samples.

Clinically important differences in the pharmacokinetics of the ten newer "atypical" antipsychotics: part 1

The "atypical" antipsychotics are grouped together by what they are not (i.e., not dopamine-2 selective antagonists like haloperidol). While sharing that characteristic, these agents differ substantially in pharmacokinetics and pharmacodynamics. This column, the first in a series on these agents, reviews the bioavailability and half-life of the 10 newer "atypical" antipsychotics, including the most recently marketed members of this class (asenapine, iloperidone, and lurasidone). Drugs with high oral bioavailability are generally less susceptible to diet or drug-drug interactions affecting first pass metabolism. The converse is true for drugs with lower oral bioavailability (e.g., they may have a food effect in which oral bioavailability is decreased in the fasted versus fed state). The half-life of an antipsychotic agent in large measure determines whether it can be safely and effectively administered once a day, at least in an immediate release formulation. Pharmacokinetic differences among atypical antipsychotics can explain why some individuals may not respond to the usually effective dose of a drug, while others may be especially sensitive to its dose-dependent adverse effects. An understanding of pharmacokinetic differences among the atypical antipsychotics can help clinicians optimize drug selection and dose for specific patients under specific treatment conditions. Subsequent columns in this series on atypical antipsychotics will discuss their metabolism, including the principal enzyme(s) mediating each drug's clearance, effects of co-administration of substantial CYP enzyme inhibitors, effect of hepatic and renal impairment, and the substantial and clinically important pharmacodynamic differences among these agents.

Quetiapine: a review of its use in the management of bipolar depression

Quetiapine (Seroquel®) is an orally administered atypical antipsychotic that is indicated for the treatment of schizophrenia and bipolar disorder, including bipolar depression. An extended-release (XR) formulation of quetiapine is also available. This review summarizes the pharmacological properties, efficacy and tolerability of quetiapine and quetiapine XR in patients with bipolar depression. Quetiapine is an antagonist at both serotonin 5-HT2 and dopamine D2 receptors, and its antipsychotic effects are thought to stem from interactions at these receptors. The antidepressant effects of quetiapine are poorly understood, but may be related to antagonism of 5-HT2A receptors in cortical regions, partial agonism of 5-HT1A in the prefrontal cortex in association with increased extracellular dopamine release in the region, or to reduced synaptic reuptake of noradrenaline resulting from inhibition of the noradrenaline reuptake transporter by the quetiapine metabolite norquetiapine. The efficacy and tolerability of quetiapine was evaluated in five 8-week, randomized, double-blind, placebo-controlled, multicentre or multinational trials in patients with a major depressive episode (MDE) associated with bipolar disorder. Across trials, monotherapy with oral quetiapine 300 or 600 mg/day (or quetiapine XR 300 mg/day) produced significantly greater improvements than placebo in depressive symptoms (primary endpoint), according to the change in the Montgomery-Asberg Depression Rating Scale total score. In general, quetiapine and quetiapine XR were also associated with significantly higher MDE response and remission rates than placebo. Across trials, quetiapine and quetiapine XR produced significantly greater improvements in global severity of illness scores than placebo, according to changes in the Clinical Global Impressions scale score. There were no differences in treatment outcomes between quetiapine 300 mg/day and 600 mg/day dosage groups. Patients with bipolar depression who responded to quetiapine during two 8-week acute treatment trials also benefited from continuing quetiapine therapy for up to 52 weeks. Compared with quetiapine responders randomized to placebo, quetiapine responders who continued quetiapine 300 or 600 mg/day had a significantly reduced risk of recurrence of any mood events and of depression mood events, but not of hypomanic/manic events. In a randomized, double-blind, placebo-controlled trial, quetiapine maintenance therapy for up to 104 weeks was more efficacious than placebo or lithium in prolonging the time to recurrence of any mood event (primary endpoint). Patients in this trial had bipolar I disorder with mania, depression or a mixed episode as the index episode, and the trial included only patients who were responsive to acute phase quetiapine, which may have introduced a positive bias in favour of quetiapine over lithium during maintenance therapy. Quetiapine 300 or 600 mg/day and quetiapine XR 300 mg/day was generally well tolerated in patients with bipolar depression, with most treatment-emergent adverse events being of mild to moderate severity. The most frequent adverse events occurring during the acute treatment phase were dry mouth, sedation, somnolence, dizziness (quetiapine and quetiapine XR), constipation (quetiapine) and increased appetite (quetiapine XR). Extrapyramidal symptoms (EPS) occurred across quetiapine and placebo groups, but there were no significant differences between quetiapine and placebo recipients on objective measures of EPS and akathisia. In some trials, quetiapine recipients experienced significantly greater weight gain than placebo recipients. Across trials, some quetiapine recipients had clinically relevant increases in blood glucose or lipid parameters, although these also occurred in patients from other treatment groups. The clinical significance of these changes is uncertain. In conclusion, quetiapine and quetiapine XR are valuable additions to the first-line treatments for bipolar depression. Further head-to-head trials of quetiapine versus other drug regimens that are effective in bipolar depression would be of considerable interest.

Potential role of a quetiapine metabolite in quetiapine-induced neutropenia and agranulocytosis

Clozapine was the first of the atypical antipsychotics to be developed, but its use has been restricted because of toxicity issues, particularly the risk of potentially life-threatening drug-induced neutropenia and agranulocytosis, which occurs in about 1% of patients. Bioactivation of clozapine by peroxidases forms a reactive nitrenium ion, which covalently adducts to protein and leads to neutrophil toxicity. The current generation of clozapine-inspired atypical antipsychotics has reduced toxicity through improved potency/decreased dose or through structural modification to prevent peroxidase-catalyzed nitrenium ion formation. Through the substitution of sulfur for the bridging nitrogen found in clozapine, quetiapine does not directly form a nitrenium ion when incubated with myeloperoxidase/H(2)O(2). We present evidence that cytochrome P450 2D6 catalyzes the formation of 7-hydroxyquetiapine, which can be oxidized by human myeloperoxidase to form a reactive quinone-imine and a reactive radical, which may account for the continued, although reduced, neutrophil toxicity. In the presence of myeloperoxidase/H(2)O(2) and glutathione, covalent 7-hydroxyquetiapine-glutathione adducts were formed. Bioactivation of quetiapine was verified in vivo in rat where three 7-hydroxyquetiapine-mercaptate adducts and a 7-hydroxyquetiapine-glutathione adduct were detected from bile after oral dosing. The decreased incidence of agranulocytosis with quetiapine over clozapine is postulated to be due to the lower exposure of the toxic precursor, 7-hydroxyquetiapine versus clozapine, respectively.

Update on extended release quetiapine fumarate in schizophrenia and bipolar disorders

The atypical antipsychotic quetiapine fumarate is available both as an immediate release (IR) and as an extended release (XR) formulation allowing flexibility of dosing for individual patients. Approved uses of quetiapine XR include the treatment of schizophrenia (including maintenance therapy for prevention of relapse), the treatment of bipolar disorder (manic and depressive episodes), and the prevention of recurrence in patients with bipolar disorder who respond to quetiapine XR. This narrative review provides an update on quetiapine XR in these indications. The pharmacological profile of quetiapine, including a moderate affinity for dopamine D(2) receptors and higher affinity for serotonin 5-hydroxytryptophan (5-HT)(2A) receptors, may explain its broad efficacy and low propensity for extrapyramidal symptoms (EPS). The XR formulation has similar bioavailability but prolonged plasma levels compared with the IR formulation, allowing for less frequent (once-daily) dosing. Clinical studies have confirmed the efficacy of quetiapine XR in relieving the acute symptoms of schizophrenia during short-term trials, and reducing the risk for relapse in long-term studies. Direct switching from the IR formulation to the same dose of the XR formulation did not reveal any loss of efficacy or tolerability issues, and switching patients to quetiapine XR from conventional or other atypical antipsychotics (for reasons of insufficient efficacy or tolerability) also proved to be beneficial and generally well tolerated. In bipolar disorder, quetiapine XR has also proven effective in relieving acute depressive and manic symptoms. Adverse events with quetiapine XR in patients with either schizophrenia or bipolar disorder are similar to those associated with the IR formulation, the most common being sedation, dry mouth, somnolence, dizziness, and headache. The low propensity for EPS is maintained with the XR formulation. Overall, evidence from clinical trials suggests that quetiapine XR is an effective and generally well-tolerated treatment option in patients with schizophrenia and bipolar disorder.

Lamotrigine is a substrate for OCT1 in brain endothelial cells

The mechanisms that underpin the passage of lamotrigine at the blood-brain barrier to its site of action in the brain is poorly understood. Lamotrigine has been postulated to be delivered to its site of action in the brain favourably despite its physicochemical properties. The aim of this study was to investigate the transport of lamotrigine in an in-vitro model of the BBB. In this study, lamotrigine was found to have a distribution coefficient of 0 at pH 7.4 indicating that it was not highly lipophilic. Human brain endothelial cells (hCMEC/D3) were used to probe the interaction of lamotrigine with drug transporters. The uptake of lamotrigine into hCMEC/D3 cells was found to be an active process (K(m) = 62 ± 14 μM; V(max) = 385 ± 30 pmol/min/million cells). Furthermore, use of a panel of transporter inhibitors indicated that this active uptake was mediated by organic cation transporter 1 (OCT1). OCT1 mRNA and protein were shown to be expressed in hCMEC/D3 cells. KCL22 cells overexpressing OCT1 were then used to validate these findings. Lamotrigine was confirmed to be a substrate and inhibitor in OCT1-transfected KCL22 cells. A putative pharmacokinetic drug-drug interaction (DDI) between quetiapine and lamotrigine was recently reported in patients and we show here that quetiapine is a potent inhibitor of the OCT1-mediated transport of lamotrigine. This is the first time that a specific influx transporter has been shown to transport lamotrigine. The clinical implications of these findings with respect to the efficacy of lamotrigine and its potential for DDI require further investigation.

Possible drug-drug interaction between quetiapine and lamotrigine--evidence from a Swedish TDM database

AIM

The aim of the present study was to investigate a previously proposed interaction between quetiapine and lamotrigine resulting in reduced serum quetiapine concentrations.

METHODS

Data on 402 patients subjected to analysis of quetiapine concentration in serum were extracted from a routine therapeutic drug monitoring database. Among these patients, those concomitantly treated with lamotrigine (n= 22) were identified and matched with 22 controls receiving quetiapine while unexposed to lamotrigine. The dose-corrected quetiapine concentrations (C : D ratios) in the two groups were compared in both paired and unpaired analyses.

RESULTS

Patients co-treated with lamotrigine had a lower mean C : D ratio (0.71, 95% CI 0.46, 0.97) compared with controls (1.64, 95% CI 1.00, 2.28). Dose-corrected quetiapine concentrations were 58% lower in patients co-medicated with lamotrigine.

CONCLUSIONS

This study indicates that lamotrigine exposure is associated with substantially reduced serum concentrations of quetiapine, possibly due to induced glucuronidation. These findings need to be confirmed in experimental studies.

Comparison of D₂ dopamine receptor occupancy after oral administration of quetiapine fumarate immediate-release and extended-release formulations in healthy subjects

Quetiapine is an established drug for treatment of schizophrenia, bipolar disorder, and major depressive disorder. While initially manufactured as an immediate-release (IR) formulation, an extended-release (XR) formulation has recently been introduced. Pharmacokinetic studies show that quetiapine XR provides a lower peak and more stable plasma concentration than the IR formulation. This study investigated if the pharmacokinetic differences translate into different time curves for central D₂ dopamine receptor occupancy. Eleven control subjects were examined with positron emission tomography (PET) and the radioligand [11C]raclopride. Eight subjects underwent all of the scheduled PET measurements. After baseline examination, quetiapine XR was administered once-daily for 8 d titrated to 300 mg/d on days 5-8, followed by 300 mg/d quetiapine IR on days 9-12. PET measurements were repeated after the last doses of quetiapine XR and IR at predicted times of peak and trough plasma concentrations. Striatal D₂ receptor occupancy was calculated using the simplified reference tissue model. Peak D₂ receptor occupancy was significantly higher with quetiapine IR than XR in all subjects (50 ± 4% and 32 ± 11%, respectively), consistent with lower peak plasma concentrations for the XR formulation. Trough D₂ receptor occupancy was similarly low for both formulations (IR 7 ± 7%, XR 8 ± 6%). The lower peak receptor occupancy associated with quetiapine XR may explain observed pharmacodynamic differences between the formulations. Assuming that our findings in control subjects are valid for patients with schizophrenia, the study supports the view that quetiapine, like the prototype atypical antipsychotic clozapine, may show antipsychotic effect at lower D₂ receptor occupancy than typical antipsychotics.

Pharmacokinetic variability of quetiapine and the active metabolite N-desalkylquetiapine in psychiatric patients

BACKGROUND

Quetiapine is an atypical antipsychotic drug that was recently also approved for the treatment of uni- and bipolar depression. The antidepressive response is considered to be mediated by the metabolite N-desalkylquetiapine, and the aim of this study was to assess the interindividual pharmacokinetic variability of quetiapine and N-desalkylquetiapine in psychiatric patients based on therapeutic drug monitoring samples.

METHODS

Serum measurements of quetiapine and N-desalkylquetiapine performed between October 2007 and July 2008 were retrospectively included from a routine therapeutic drug monitoring database. Pharmacokinetic variability was expressed as the 5-95 percentile range in dose-adjusted serum concentrations (C/D ratios). The impact of age (65 years or older), gender, and sampling time on the C/D ratios was studied by linear mixed model analysis. Samples from patients comedicated with CYP3A4 inducers or inhibitors were examined separately.

RESULTS

In total, 927 serum samples from 601 patients were included (all using quetiapine immediate-release tablets). The 5-95 percentiles of the C/D ratio ranged 15-fold (0.14-2.1 nmol/L/mg) for quetiapine and fivefold (0.44-2.1 nmol/L/mg) for N-desalkylquetiapine. Elderly (65 years or older) obtained 1.5- and 1.2-fold higher C/D ratios of quetiapine (P = 0.002) and N-desalkylquetiapine (P = 0.03) compared with younger patients, respectively. Sampling time was also found to significantly affect the C/D ratios of quetiapine (P = 0.001), whereas gender was not a significant variable (P > 0.13). In three patients treated with potent CYP3A4 inducers, the observed C/D ratios of quetiapine and N-desalkylquetiapine were 77% and 11% lower than the mean C/D ratio in the study population, respectively.

CONCLUSION

The pharmacokinetic variability was greater for quetiapine compared with N-desalkylquetiapine. Age 65 years or older and comedication with CYP3A4 inducers affected the serum levels of both agents, but the relative impact was greater on quetiapine.

A novel electrochemical sensor for assaying of antipsychotic drug quetiapine

A novel electrochemical sensor based on poly(2-hydroxy-5-[(4-sulfophenyl)azo]benzoic acid) film modified glassy carbon electrode for fast and simple quantification of trace amount of quetiapine fumarate (QF) was developed. It exhibits excellent enhancement effects on the electrooxidation of QF facilitating preconcentration of drug molecules on the electrode surface. Based on its strong adsorptive activity, the concentration of QF in pharmaceutical formulations and biological fluids was determined directly by voltammetry with excellent sensitivity and high selectivity. The introduction of carboxylated and sulfonated functionalities in polymer film improves the uniform selectivity for positively charged target QF molecules. The calibration curve is linear in QF concentration range of 8.0 × 10(-8) to 7.5 × 10(-6)M with detection limit 1.9 × 10(-8) and sensitivity 8.96 × 10(5) μA M(-1). The presented sensor has long term stability and good reproducibility with benefits of fast response time, ease of preparation and regeneration of the surface that makes the proposed method useful in the determination of QF in real samples.

Quetiapine extended release: adjunctive treatment in major depressive disorder

Quetiapine extended release (XR) is a once-daily oral formulation of the atypical antipsychotic quetiapine that is available for use as adjunctive therapy in major depressive disorder (MDD). Systemic quetiapine exposure after orally administered quetiapine XR is similar to that of quetiapine immediate release at the same dosage, although quetiapine XR is absorbed more slowly and plasma concentrations are more stable over time. In two 6-week, randomized, double-blind, placebo-controlled, multinational trials in patients with MDD with an inadequate response to antidepressants, quetiapine XR 300 mg/day adjunctive to antidepressant reduced depressive symptoms significantly more than antidepressant plus placebo, according to changes in Montgomery-Åsberg Depression Rating Scale (MADRS) total scores. In one trial, adjunctive quetiapine XR 150 mg/day also led to significantly greater reductions in MADRS total scores than antidepressant plus placebo. MDD response rates were significantly higher with adjunctive quetiapine XR 300 mg/day (but not 150 mg/day) than with antidepressant plus placebo. The numbers needed to treat to achieve an additional response over antidepressant plus placebo were 11-18 and 8-9 in the quetiapine XR 150 and 300 mg/day dosage groups, respectively. Treatment-emergent adverse events were mostly of mild to moderate severity; 1% of adjunctive quetiapine XR and 1.3% of antidepressant plus placebo recipients reported serious adverse events.

Cytochrome P450 and ABCB1 genetics: association with quetiapine and norquetiapine plasma and cerebrospinal fluid concentrations and with clinical response in patients suffering from schizophrenia. A pilot study

Variability in response to atypical antipsychotic drugs is due to genetic and environmental factors. Cytochrome P450 (CYP) isoforms are implicated in the metabolism of drugs, while the P-glycoprotein transporter (P-gp), encoded by the ABCB1 gene, may influence both the blood and brain drug concentrations. This study aimed to identify the possible associations of CYP and ABCB1 genetic polymorphisms with quetiapine and norquetiapine plasma and cerebrospinal fluid (CSF) concentrations and with response to treatment. Twenty-two patients with schizophrenia receiving 600 mg of quetiapine daily were genotyped for four CYP isoforms and ABCB1 polymorphisms. Quetiapine and norquetiapine peak plasma and CSF concentrations were measured after 4 weeks of treatment. Stepwise multiple regression analysis revealed that ABCB1 3435C > T (rs1045642), 2677G > T (rs2032582) and 1236C > T (rs1128503) polymorphisms predicted plasma quetiapine concentrations, explaining 41% of the variability (p = 0.001). Furthermore, the ABCB1 polymorphisms predicted 48% (p = 0.024) of the variability of the Δ PANSS total score, with the non-carriers of the 3435TT showing higher changes in the score. These results suggest that ABCB1 genetic polymorphisms may be a predictive marker of quetiapine treatment in schizophrenia.

Mood stabilizers for patients with bipolar disorder: the state of the art

Bipolar disorder (BD) is a prevalent and disabling condition, often comorbid with other medical and psychiatric conditions and frequently misdiagnosed. International treatment guidelines for BD recommend the use of mood stabilizers - either in monotherapy or in association - as the gold standard in both acute and long-term therapy. Commonly used in the clinical practice of BD, mood stabilizers have represented an evolving field over the last few years. The concept of stabilization, in fact, has been stressed as the ultimate objective of the treatment of BD, given the chronic and recurrent nature of the illness, which accounts for its significant levels of impairment and disability. To date, different compounds are included within the broad class of mood stabilizers, with lithium, anticonvulsants and, more recently, atypical antipsychotics being the most representative agents. This article is aimed at providing an updated review of the available literature in relation to the role of mood stabilizers in BD, with particular emphasis on their mechanism of action, main clinical aspects and specific use in the different phases of BD treatment, according to the most recently published international treatment guidelines.

Multiple intracerebral hemorrhages in an elderly patient after adding quetiapine to a stable warfarin regimen

The efficacy of antipsychotics in patients with dementia exhibiting psychiatric symptoms has been overshadowed by safety concerns in recent years. Evidence suggests that the long-term use of antipsychotics in older adults is associated with a greater risk of cerebrovascular adverse events than accrues with short-term use (less than 30 days) [J Clin Psychiatry. 2010;71(6):689-98]. Here, we present an elderly male patient with dementia who developed multiple intracerebral hemorrhages (ICHs) 3 days after the addition of quetiapine to his stable warfarin regimen. To our knowledge, this is the second case of possible interaction between quetiapine and warfarin. We suggest mechanisms that may account for the patient's clinical presentation and highlight that combining treatment with quetiapine and warfarin may cause serious complications in patients with risk factors for ICH.

Atypical Antipsychotics for the Treatment of ICU Delirium

Delirium is commonly described in critically ill patients as 1 factor contributing to increased length of intensive care unit and hospital stay, secondary complications, and increased mortality. Initial screening tools for delirium in hospitalized patients are generally easy to use; however, many centers have struggled with implementing these tools in a consistent and systematic manner. Haloperidol has traditionally been prescribed as the primary agent of choice for the treatment of delirium in critically ill patients. Clinicians have been challenged to consider alternative agents due to adverse effects such as extrapyramidal symptoms, QTc prolongation, and possible torsades de pointes with haloperidol use. The atypical antipsychotics are attractive alternatives to haloperidol with improved safety profiles but are flawed by limited data to support dosing and efficacy in this patient population. Future studies that provide large, prospective, double-blinded, placebo-controlled data to support the implementation of these agents as standard therapy over haloperidol are needed.

Pharmacokinetic drug interactions and adverse consequences between psychotropic medications and pharmacotherapy for the treatment of opioid dependence

BACKGROUND

Psychiatric comorbidities among opioid-dependent patients are common. Many medications used to treat both conditions are metabolized through complimentary cytochrome P450 isoenzymes. When medication-assisted treatment for opioid dependence is concurrently used with psychotropic medications, problematic pharmacokinetic drug interactions may occur.

METHODS

We reviewed relevant English language articles identified through the MedLine, Scopus, and Embase databases from 1950 to December 2009 using the specific generic names of medications and keywords such as pharmacokinetics and drug interactions with buprenorphine, methadone, and naltrexone. Selected references from these articles were reviewed. Additionally, a review was conducted of abstracts and conference proceedings from national and international meetings from 1990 to 2009. A total of 60 studies were identified and reviewed.

RESULTS

Clinical case series and carefully controlled pharmacokinetic interaction studies have been conducted between methadone, buprenorphine, or naltrexone and some psychoactive medications. Important pharmacokinetic drug interactions have been demonstrated within each class of medications affecting either methadone and buprenorphine or psychoactive drugs. Few studies, however, have been conducted with naltrexone.

CONCLUSIONS

Several interactions between methadone, buprenorphine, or naltrexone and psychoactive medications are described and may have important clinical consequences. To optimize care, clinicians must be alerted to these interactions.

Serotonin2A receptor blockade and clinical effect in first-episode schizophrenia patients treated with quetiapine

RATIONALE

We have previously reported decreased frontal cortical serotonin2A receptor binding in 30 antipsychotic naïve first-episode schizophrenic patients and a relationship between this binding and positive psychotic symptoms. Until now, no longitudinal studies of serotonin2A receptor in first-episode antipsychotic-naïve schizophrenia patients have reported on the relationship between serotonin2A receptor occupancy and treatment effect after sustained treatment with a specific atypical antipsychotic compound.

OBJECTIVES

Here, we measured serotonin2A receptor occupancy with [(18)F]altanserin PET in 15 first-episode antipsychotic-naïve schizophrenia patients before and after 6 months of quetiapine treatment. Moreover, we investigated possible relationships between clinical efficacy, oral dose, and plasma levels of quetiapine

RESULTS

Significant nonlinear relationships were found between serotonin2A receptor occupancy, quetiapine dose, and plasma concentration. There was a modest effect on positive symptoms up until a serotonin2A receptor occupancy level of approximately 60%. A receptor occupancy level between 60% and 70% appeared to exert the optimal serotonin2A receptor related treatment effect on positive symptoms whereas no additional serotonin2A receptor associated treatment effect was obtained above a receptor occupancy of 70%.

CONCLUSIONS

Taken together, the data point to a therapeutic role of the serotonin2A receptor in the treatment of subgroups of patients with schizophrenia. Specifically, the study indicates a serotonin2A receptor associated therapeutic window on positive symptoms in responding patients in the range between 60% and 70% occupancy in antipsychotic-naïve first-episode schizophrenia. We speculate that non-responding patients need higher dopamine D(2) receptor blockade. Future studies with concurrent measurement of interactions with the dopamine system are, however, warranted to clarify this.

Development and validation of a stability indicating RP-UPLC method for determination of quetiapine in pharmaceutical dosage form

The present work reports a stability indicating reversed phase ultra performance liquid chromatography (RP-UPLC) method for the quantitative determination of quetiapine in pharmaceutical dosage form. The chromatographic separation is performed on an Agilent Eclipse Plus C18, RRHD 1.8 μm (50 mm x 2.1 mm) column using gradient elution. The optimized mobile phase consists of 0.1 % aqueous triethylamine (pH 7.2) as a solvent-A and 80:20 v/v mixture of acetonitrile and methanol as solvent-B. The eluted compounds are monitored at 252 nm wavelength using a UV detector. The developed method separates quetiapine from its five impurities/degradation products within a run time of 5 min. Stability indicating capability of the developed method is established by analyzing forced degradation samples in which the spectral purity of quetiapine is ascertained along with the separation of degradation products from analyte peak. The developed RP-UPLC method is validated as per International Conference on Harmonization (ICH) guidelines with respect to system suitability, specificity, precision, accuracy, linearity, robustness and filter compatibility.

The management of schizophrenia: focus on extended-release quetiapine fumarate

Effective management of schizophrenia remains a significant clinical challenge. While antipsychotic medications have proven efficacy in this disease, there remains an opportunity to further improve symptom control and long-term relapse prevention. Also, a number of factors, including tolerability and complex dosing regimens, can result in nonadherence to medication. Quetiapine is an atypical antipsychotic with proven efficacy and an established tolerability profile in schizophrenia. The once-daily extended-release formulation (quetiapine XR) offers a simplified dosing regimen and titration schedule. Short-term clinical studies have shown that quetiapine XR (400-800 mg/d) is efficacious in the acute treatment of schizophrenia, while a long-term study has shown that quetiapine XR was significantly more effective than placebo at preventing relapse. Furthermore, an investigation in which stable patients switched from the immediate-release formulation (quetiapine IR) to quetiapine XR showed that quetiapine XR is generally well tolerated and has no loss of efficacy compared with quetiapine IR. In patients who experienced insufficient efficacy or poor tolerability on their previous antipsychotic, switching to quetiapine XR significantly improved efficacy compared with the previous treatment. In conclusion, quetiapine XR is an effective and generally well tolerated treatment for schizophrenia. Furthermore, once-daily dosing may improve patient adherence, which may impact positively on patient outcomes.

Antipsychotic occupancy of dopamine receptors in schizophrenia

Antipsychotic drugs were introduced in the early 50s on the basis of clinical observations in patients with schizophrenia. Experimental studies later revealed that antagonism at the D(2) dopamine receptor is a common characteristic of all antipsychotic drugs. In the 80s, the advent of brain imaging technologies such as positron emission tomography (PET) allowed for direct noninvasive studies of drug binding in treated patients. The concept receptor occupancy is defined as the fraction (%) of a receptor population that is occupied during treatment with an unlabelled drug. With regard to antipsychotic drugs, the radioligand [(11) C]-raclopride has been the most widely used for binding to the D(2) /D(3) -dopamine receptors. The present review discusses the contribution from molecular imaging to the current understanding of mechanism of action (MoA) of antipsychotic drugs. Consistent initial PET-findings of high D2-receptor occupancy in the striatum of patients responding to different antipsychotic drug treatments provided clinical support for the dopamine hypothesis of antipsychotic drug action. It has subsequently been demonstrated that patients with extrapyramidal syndromes (EPS) have higher occupancy (above 80%) than patients with good response but no EPS (65-80%). The PET-defined interval for optimal antipsychotic drug treatment has been implemented in the evolvement of dose recommendations for classical as well as more recently developed drugs. Another consistent finding is lower D(2) -occupancy during treatment with the prototype atypical antipsychotic clozapine. The MoA of clozapine remains to be fully understood and may include nondopaminergic mechanisms. A general limitation is that currently available PET-radioligands are not selective for any of the five dopamine receptor subtypes. Current attempts at developing such ligands may provide the tools required to refine further the MoA of antipsychotic drugs.

A pooled analysis of two randomised, placebo-controlled studies of extended release quetiapine fumarate adjunctive to antidepressant therapy in patients with major depressive disorder

BACKGROUND

Two positive studies evaluated adjunctive extended release quetiapine fumarate (quetiapine XR) in patients with major depressive disorder (MDD) showing inadequate response to antidepressant treatment. This preplanned, pooled analysis provides an opportunity for subgroup analyses investigating the influence of demographic and disease-related factors on observed responses. Additional post hoc analyses examined the efficacy of quetiapine XR against specific depressive symptoms including sleep.

METHODS

Data were analysed from two 6-week, multicentre, double-blind, randomised, placebo-controlled studies, prospectively designed to be pooled. Patients received once-daily quetiapineXR 150mg/day (n=309), 300mg/day (n=307) or placebo (n=303) adjunctive to ongoing antidepressant therapy. The primary endpoint was change from randomisation to Week 6 in MADRS total score. Other assessments included MADRS response (≥50% decrease in total score) and remission (total score≤8), change from randomisation in HAM-D, HAM-A, PSQI global and CGI-S scores.

RESULTS

Quetiapine XR (150 and 300mg/day) reduced MADRS total scores vs placebo at every assessment including Week 6 (-14.5, -14.8, -12.0; p<0.001 each dose) and Week 1 (-7.8,-7.3,-5.1; p<0.001 each dose). For quetiapineXR 150 and 300mg/day and placebo, respectively at Week 6: MADRS response 53.7% (p=0.063), 58.3% (p<0.01) and 46.2%; MADRS remission 35.6% (p<0.01), 36.5% (p<0.001) and 24.1%. QuetiapineXR 150 and 300mg/day significantly improved HAM-D, HAM-A, PSQI and CGI-S scores at Week 6 vs placebo. Quetiapine XR demonstrated broad efficacy, independent of factors including concomitant antidepressant.

LIMITATIONS

Fixed dosing; lack of active comparator.

CONCLUSIONS

Adjunctive quetiapine XR is effective in patients with MDD and an inadequate response to antidepressant therapy, with improvement in depressive symptoms seen as early as Week 1.

Prescribing patterns and the use of therapeutic drug monitoring of psychotropic medication in a psychiatric high-security unit

The aim of this study was to investigate the use of psychotropic medication and therapeutic drug monitoring in a high-security psychiatric unit and to compare the doses and serum concentrations both with the recommended intervals and with the doses and serum concentrations in a control group. One hundred thirty-two patients were admitted in the period from January 2000 to December 2005. All available samples were used when comparing serum concentrations and doses with the recommended ranges. For the comparison of doses and serum concentration-to-dose (C:D) ratios with the control group only 1 sample from each patient was used. A total of 459 analyses of 27 different drugs in samples from 8 women and 73 men were included. The median number of therapeutic drug monitoring analyses per patient was 4 (range 1-29). Thirty-seven of the 81 patients (46%) used 2 or more antipsychotics at the same time. Clozapine, lamotrigine, olanzapine, quetiapine, ziprasidone, and zuclopenthixol were often given in doses above the recommended. The serum levels were frequently above those recommended for clozapine, olanzapine, quetiapine, risperidone, ziprasidone, and zuclopenthixol. The serum levels were significantly higher in the study group than in the control group for clozapine, lamotrigine, quetiapine, and zuclopenthixol. The given dose was significantly higher in the study group than in the control group for clozapine, lamotrigine and zuclopenthixol. The C:D ratio was significantly lower in the study group than in the control group for olanzapine but higher for quetiapine. The non-evidence based practice of high-dose polypharmacy with several antipsychotics is widely used in this unit. The use of higher doses in the study group than in the control group was not due to differences in metabolism or adherence to treatment between the 2 groups. The frequent use of therapeutic drug monitoring did not seem to have a great impact on the prescribed doses.

Patient adherence and efficacy of quetiapine treatment in schizophrenia: results of a multicentre, naturalistic 6-month follow-up study

The aim of the study was to evaluate the adherence and efficacy of quetiapine treatment in a 6-month, multicentre, noninterventional naturalistic design. Overall, 710 schizophrenia patients using quetiapine or who had switched to quetiapine were included. The continuation rate for quetiapine treatment during 6-month follow-up period was 69%. Adherence improved with each subsequent visit for continued patients, 92.9% at the second visit to 96.1% at the last. Treatment adherence was correlated to improvement of symptoms, though not significantly. Patients having lower clinical global impression severity scores at the beginning were twice as likely to improve compared with patients with higher clinical global impression scores. Schizophrenia patients with antisocial behaviour problems had two and a half times higher drop-out rates. In conclusion, this naturalistic study showed that adherence to quetiapine treatment was high, and treatment was effective in schizophrenia patients during long-term treatment. Remission of symptoms in schizophrenia is much related to severity of symptoms at baseline, treatment adherence and characteristics of patients such as antisocial behavioural patterns.

Quetiapine and norquetiapine in plasma and cerebrospinal fluid of schizophrenic patients treated with quetiapine: correlations to clinical outcome and HVA, 5-HIAA, and MHPG in CSF

This study investigated concentrations of quetiapine and norquetiapine in plasma and cerebrospinal fluid (CSF) in 22 schizophrenic patients after 4-week treatment with quetiapine (600 mg/d), which was preceded by a 3-week washout period. Blood and CSF samples were obtained on days 1 and 28, and CSF levels of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) concentrations were measured at baseline and after 4 weeks of quetiapine, allowing calculations of differences in HVA (ΔHVA), 5-HIAA (Δ5-HIAA), and MHPG (ΔMHPG) concentrations. Patients were assessed clinically, using the Positive and Negative Syndrome Scale (PANSS) and Clinical Global Impression Scale at baseline and then at weekly intervals. Plasma levels of quetiapine and norquetiapine were 1110 ± 608 and 444 ± 226 ng/mL, and the corresponding CSF levels were 29 ± 18 and 5 ± 2 ng/mL, respectively. After the treatment, the levels of HVA, 5-HIAA, and MHPG were increased by 33%, 35%, and 33%, respectively (P < 0.001). A negative correlation was found between the decrease in PANSS positive subscale scores and CSF ΔHVA (r(rho) = -0.690, P < 0.01), and the decrease in PANSS negative subscale scores both with CSF Δ5-HIAA (r(rho) = -0.619, P = 0.02) and ΔMHPG (r(rho) = -0.484, P = 0.038). Because, unfortunately, schizophrenic patients experience relapses even with the best available treatments, monitoring of CSF drug and metabolite levels might prove to be useful in tailoring individually adjusted treatments.

Relationship between dopamine D2 receptor occupancy, clinical response, and drug and monoamine metabolites levels in plasma and cerebrospinal fluid. A pilot study in patients suffering from first-episode schizophrenia treated with quetiapine

Combining measurements of the monoamine metabolites in the cerebrospinal fluid (CSF) and neuroimaging can increase efficiency of drug discovery for treatment of brain disorders. To address this question, we examined five drug-naïve patients suffering from schizophrenic disorder. Patients were assessed clinically, using the Positive and Negative Syndrome Scale (PANSS): at baseline and then at weekly intervals. Plasma and CSF levels of quetiapine and norquetiapine as well CSF 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxyindole-acetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) were obtained at baseline and again after at least a 4 week medication trail with 600 mg/day quetiapine. CSF monoamine metabolites levels were compared with dopamine D(2) receptor occupancy (DA-D(2)) using [(18)F]fallypride and positron emission tomography (PET). Quetiapine produced preferential occupancy of parietal cortex vs. putamenal DA-D(2), 41.4% (p<0.05, corrected for multiple comparisons). DA-D(2) receptor occupancies in the occipital and parietal cortex were correlated with CSF quetiapine and norquetiapine levels (p<0.01 and p<0.05, respectively). CSF monoamine metabolites were significantly increased after treatment and correlated with regional receptor occupancies in the putamen [DOPAC: (p<0.01) and HVA: (p<0.05)], caudate nucleus [HVA: (p<0.01)], thalamus [MHPG: (p<0.05)] and in the temporal cortex [HVA: (p<0.05) and 5-HIAA: (p<0.05)]. This suggests that CSF monoamine metabolites levels reflect the effects of quetiapine treatment on neurotransmitters in vivo and indicates that monitoring plasma and CSF quetiapine and norquetiapine levels may be of clinical relevance.

Why do patients with schizophrenia smoke?

PURPOSE OF REVIEW

Among the mentally ill, smoking prevalence is highest in patients with schizophrenia ( approximately 70-80%). This can impose a significant financial burden on patients, not to speak of increased smoking-related morbidity and mortality. Therefore, it is critical for clinicians to understand why patients with schizophrenia smoke in order to adapt treatment schemes. Understanding the reasons may also help to develop new drugs that target the nicotinic system in the brain as well as smoking cessation programs that are specifically designed for this particular patient population.

RECENT FINDINGS

So far, several reasons have been identified which are believed to explain tobacco consumption in patients with schizophrenia. Originally, it was widely believed that patients with schizophrenia smoke to increase hepatic clearance and to restore the dopamine blockade of certain antipsychotic drugs to diminish their side effects. However, more recently it became obvious that cigarette smoking may also be reinforcing for patients because it improves psychiatric symptoms, most notably negative and cognitive symptoms. The underlying molecular mechanisms of these nicotine effects are currently under intensive investigation.

SUMMARY

Heavy smoking in schizophrenia cannot simply be viewed as a 'bad habit'. Rather, self-medication of clinical symptoms and side effects of antipsychotic drugs appear to play a major role.

Role of CYP pharmacogenetics and drug-drug interactions in the efficacy and safety of atypical and other antipsychotic agents

Cytochrome P450 (CYP) drug oxidases play a pivotal role in the elimination of antipsychotic agents, and therefore influence the toxicity and efficacy of these drugs. Factors that affect CYP function and expression have a major impact on treatment outcomes with antipsychotic agents. In particular, aspects of CYP pharmacogenetics, and the processes of CYP induction and inhibition all influence in-vivo rates of drug elimination. Certain CYPs that mediate the oxidation of antipsychotic drugs exhibit genetic variants that may influence in-vivo activity. Thus, single nucleotide polymorphisms (SNPs) in CYP genes have been shown to encode enzymes that have decreased drug oxidation capacity. Additionally, psychopharmacotherapy has the potential for drug-drug inhibitory interactions involving CYPs, as well as drug-mediated CYP induction. Literature evidence supports a role for CYP1A2 in the clearance of the atypical antipsychotics clozapine and olanzapine; CYP1A2 is inducible by certain drugs and environmental chemicals. Recent studies have suggested that specific CYP1A2 variants possessing individual SNPs, and possibly also SNP combinations (haplotypes), in the 5′-regulatory regions may respond differently to inducing chemicals. CYP2D6 is an important catalyst of the oxidation of chlorpromazine, thioridazine, risperidone and haloperidol. Certain CYP2D6 allelic variants that encode enzymes with decreased drug oxidation capacity are more common in particular ethnic groups, which may lead to adverse effects with standard doses of psychoactive drugs. Thus, genotyping may be useful for dose optimization with certain psychoactive drugs that are substrates for CYP2D6. However, genotyping for inducible CYPs is unlikely to be sufficient to direct therapy with all antipsychotic agents. In-vivo CYP phenotyping with cocktails of drug substrates may assist at the commencement of therapy, but this approach could be complicated by pharmacokinetic interactions if applied when an antipsychotic drug regimen is ongoing.

Intoxication after extreme oral overdose of quetiapine to attempt suicide: pharmacological concerns of side effects

Quetiapine is an atypical antipsychotic approved for the treatment of patients with psychotic disorders. Since approvement several case reports about intoxication with quetiapine were linked mainly with tachycardia, QT_c-prolongation, somnolence, and hyperglycemia. Here, we present the first case report of an intoxication with an extreme overdose of quetiapine (36 g), ingested by a 32-year-old female (62 kg bodyweight) to attempt suicide. Symptoms associated with intoxication were coma without arterial hypotension, persistent tachycardia, hyperglycemia, and transient hypothyreoidism. QT_c-interval was moderately extended. Management consisted of intubation for airway protection, gastric lavage, the use of activated charcoal, i.v. saline, and observation for 17 hours on an intensive care unit. Despite the extremely high dose of quetiapine, the patient recovered completely without residual symptoms.

Psychotropic drugs and renal failure: translating the evidence for clinical practice

INTRODUCTION

The kidney is a primary route of drug elimination; abnormal kidney function is predicted to alter the pharmacokinetics of agents metabolized and/or excreted predominantly through this route. The high prevalence of mental disorders associated with psychotropic drug use in individuals with deteriorating renal function suggests there is a need to investigate the effects of renal failure on psychotropic pharmacokinetics. The aim of this review is to provide a clinically accessible overview of the effect of chronic renal failure on the pharmacokinetics for each of the major classes of prescribed psychotropic agents.

METHODS

All English language articles published between 1977 and 2008 were searched through PubMed, using the following keywords: "renal," "kidney," "pharmacokinetics," "renal impairment," "renal insufficiency," and "renal failure." Each of these search words was cross-referenced with the non-proprietary name of each psychotropic agent. The manufacturer's product insert was also reviewed for some agents for updated dosing. Owing to the lack of adequately powered studies, an inclusive manner was used.

RESULTS

Chronic renal failure variably affects the pharmacokinetic parameters of psychotropic drugs. A review of each psychotropic drug is provided, with an emphasis on the individual pharmacokinetic parameters and recommended dosing.

CONCLUSIONS

The adjudication of safe and effective doses for any psychotropic agent needs to be individualized. Tactics including dosage adjustment, slow titration, and careful monitoring for serious adverse events should be incorporated into practice.