The effect of coadministration of duloxetine on steady-state serum concentration of risperidone and aripiprazole: a study based on therapeutic drug monitoring data

How Can Drug Metabolism and Transporter Genetics Inform Psychotropic Prescribing?

Many genetic variants in drug metabolizing enzymes and transporters have been shown to be relevant for treating psychiatric disorders. Associations are strong enough to feature on drug labels and for prescribing guidelines based on such data. A range of commercial tests are available; however, there is variability in included genetic variants, methodology, and interpretation. We herein provide relevant background for understanding clinical associations with specific variants, other factors that are relevant to consider when interpreting such data (such as age, gender, drug-drug interactions), and summarize the data relevant to clinical utility of pharmacogenetic testing in psychiatry and the available prescribing guidelines. We also highlight areas for future research focus in this field.

Prevalence and sort of pharmacokinetic drug-drug interactions in hospitalized psychiatric patients

Psychiatric patients are high-risk patients for the development of pharmacokinetic drug-drug interactions (DDIs), leading to highly variable (victim) drug serum concentrations. Avoiding and targeting high-risk drug combinations could reduce preventable adverse drug reactions (ADRs). Pharmacokinetic cytochrome P450 (CYP)-mediated DDIs are often predictable and, therefore, preventable. The retrospective, longitudinal analysis used informations from a large pharmacovigilance study (Optimization of pharmacological treatment in hospitalized psychiatric patients study, study number 01VSF16009, 01/2017), conducted in 10 psychiatric hospitals in Germany. Medication data were examined for the co-prescription of clinically relevant CYP inhibitors or inducers and substrates of these enzymes (victim drugs). In total, data from 27,396 patient cases (45.6% female) with a mean (mean ± standard deviation (SD)) age of 47.3 ± 18.3 years were available for analysis. CYP inhibitors or inducers were at least once prescribed in 14.4% (n = 3946) of the cases. The most frequently prescribed CYP inhibitors were melperone (n = 2504, 28.1%) and duloxetine (n = 1324, 14.9%). Overall, 51.0% of the cases taking melperone were combined with a victim drug (n = 1288). Carbamazepine was the most frequently prescribed CYP inducer (n = 733, 88.8%). Combinations with victim drugs were detected for 58% (n = 427) of cases on medication with carbamazepine. Finally, a DDI was detected in 43.6% of the cases in which a CYP inhibitor or inducer was prescribed. The frequency of CYP-mediated DDI is considerably high in the psychiatric setting. Physicians should be aware of the CYP inhibitory and inducing potential of psychotropic and internistic drugs (especially, melperone).

Treatment With Antipsychotics in Pregnancy: Changes in Drug Disposition

Although pregnancy is known to cause changes in drug pharmacokinetics, little is known about its impact on serum levels of antipsychotics. In this study we retrospectively assessed 201 routine serum antipsychotic therapeutic drug monitoring concentration measurements obtained from a total of 110 pregnancies in 103 women, and 512 measurements from the same women before and after pregnancy. Serum concentrations in the third trimester were significantly lower than baseline for quetiapine (-76%; confidence interval (CI), -83%, -66%; P < 0.001) and aripiprazole (-52%; CI, -62%, -39%; P < 0.001), but not for olanzapine (-9%; CI, -28%, +14%; P = 0.40). For the remaining antipsychotics (perphenazine, haloperidol, ziprasidone, risperidone, and clozapine), our dataset was limited, but it indicates that concentrations may decline at least for perphenazine and possibly also for haloperidol. Even though the clinical consequence of the serum concentrations decline remains to be elucidated, our results warrant close clinical monitoring throughout pregnancy, preferentially supported by therapeutic drug monitoring.

Plasma Methylphenidate Levels in Youths With Attention Deficit Hyperactivity Disorder Treated With OROS Formulation

BACKGROUND

There are limited studies investigating the relationship between oral release osmotic system-methylphenidate (OROS-MPH) doses and plasma methylphenidate (MPH) concentrations in children and adolescents. The aim of this study was to investigate the relationship between the doses of OROS-MPH and the plasma levels of the drug. We also examined the effects of the other drugs including aripiprazole, risperidone, fluoxetine, and sertraline on the levels of the MPH in the plasma.

METHODS

The files of 100 attention deficit hyperactivity disorder (ADHD) subjects (76 male, 24 female) who were diagnosed as ADHD according to the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition criteria, were screened. The ages of subjects were between 6 and 18 years (mean = 11.5 ± 3.8 years). Plasma MPH levels were determined by high-performance liquid chromatography-tandem mass spectrometry assay.

RESULTS

Daily mean OROS-MPH dose used in ADHD children was 0.7 ± 0.2 mg/kg (range: 0.3-1.3 mg/kg). The mean plasma OROS-MPH was 11.6 ± 7.3 ng/mL (range: 0.5-43.4 ng/mL). There was no group difference in the mean plasma MPH and dose-related MPH levels between the groups that used any additional drug including aripiprazole (n = 25), risperidone (n = 10), fluoxetine (n = 16), sertraline (n = 10), and did not use these drugs (P > 0.05). There was a positive correlation between the OROS-MPH doses (mg/kg) and the blood MPH levels (Pearson correlation = 0.40; P < 0.001). The plasma levels of MPH were found to be less than 13 ng/mL in 65% of the subjects.

CONCLUSIONS

Our findings point to the fact that plasma levels of MPH show a wide range of changes at similar doses, correlate positively with the doses and, as expected, are not affected by using risperidone, sertraline, fluoxetine, and aripiprazole. Therapeutic drug monitoring may help to optimize MPH dose in patients not responding to treatment or in those experiencing serious side effects, but not in routine clinical practice. The presence of intermediate dose formulations such as 45-mg tablets for OROS-MPH may contribute to the optimization.

Clinically relevant interactions between newer antidepressants and second-generation antipsychotics

INTRODUCTION

Combinations of newer antidepressants and second-generation antipsychotics (SGAs) are frequently used by clinicians. Pharmacokinetic drug interaction (PK DI) and poorly understood pharmacodynamic (PD) drug interaction (PD DI) can occur between them.

AREAS COVERED

This paper comprehensively reviews PD DI and PK DI studies.

EXPERT OPINION

More PK DI studies are needed to better establish dose correction factors after adding fluoxetine and paroxetine to aripiprazole, iloperidone and risperidone. Further PK DI studies and case reports are also needed to better establish the need for dose correction factors after adding i) fluoxetine to clozapine, lurasidone, quetiapine and olanzapine; ii) paroxetine to olanzapine; iii) fluvoxamine to asenapine, aripiprazole, iloperidone, lurasidone, olanzapine, quetiapine and risperidone; iv) high sertraline doses to aripiprazole, clozapine, iloperidone and risperidone: v) bupropion and duloxetine to aripiprazole, clozapine, iloperidone and risperidone; and vi) asenapine to paroxetine and venlafaxine. Possible beneficial PD DI effects occur after adding SGAs to newer antidepressants for treatment-resistant major depressive and obsessive-compulsive disorders. The lack of studies combining newer antidepressants and SGAs in psychotic depression is worrisome. PD DIs between newer antidepressants and SGAs may be more likely for mirtazapine and bupropion. Adding selective serotonin reuptake inhibitors and SGAs may increase QTc interval and may very rarely contribute to torsades de pointes.

When to start aripiprazole therapy in patients with bipolar mania

Aripiprazole is a third generation atypical antipsychotic with compelling evidence as a highly effective treatment option in the management of acute manic and mixed episodes of bipolar I disorders. It has a unique mode of action, acting as a partial agonist at dopamine D2 and D3, and serotonin 5-HT1A; and exhibiting antagonistic action at the 5-HT2A and H1 receptors. Overall, it has a favorable safety and tolerability profile, with low potential for clinically significant weight gain and metabolic effects, especially compared to other well-established treatments. It also has a superior tolerability profile when used as maintenance treatment. Side effects like headache, insomnia, and extrapyramidal side effects (EPSEs), such as tremor and akathisia may be treatment limiting in some cases. It is efficacious in both acute mania and mixed states, and in the long-term prevention of manic relapses. Aripiprazole therefore, is a significant player in the current portfolio of anti-manic pharmacological treatments. The data sources for this article are from EMBASE, MEDLINE, and the clinical trial database searches for all the literature published between January 2003 and September 2013. The key search terms were "aripiprazole" combined with "bipolar disorder", "mania", "antipsychotics", "mood stabilizer", "randomized controlled trial", and "pharmacology". Abstracts and proceedings from national and international psychiatric meetings were also reviewed, along with reviews of the reference lists of relevant articles.

Clinically significant drug interactions with atypical antipsychotics

Atypical antipsychotics [also known as second-generation antipsychotics (SGAs)] have become a mainstay therapeutic treatment intervention for patients with schizophrenia, bipolar disorders and other psychotic conditions. These agents are commonly used with other medications--most notably, antidepressants and antiepileptic drugs. Drug interactions can take place by various pharmacokinetic, pharmacodynamic and pharmaceutical mechanisms. The pharmacokinetic profile of each SGA, especially with phase I and phase II metabolism, can allow for potentially significant drug interactions. Pharmacodynamic interactions arise when agents have comparable receptor site activity, which can lead to additive or competitive effects without alterations in measured plasma drug concentrations. Additionally, the role of drug transporters in drug interactions continues to evolve and may effect both pharmacokinetic and pharmacodynamic interactions. Pharmaceutical interactions occur when physical incompatibilities take place between agents prior to drug absorption. Approximate therapeutic plasma concentration ranges have been suggested for a number of SGAs. Drug interactions that markedly increase or decrease the concentrations of these agents beyond their ranges can lead to adverse events or diminished clinical efficacy. Most clinically significant drug interactions with SGAs occur via the cytochrome P450 (CYP) system. Many but not all drug interactions with SGAs are identified during drug discovery and pre-clinical development by employing a series of standardized in vitro and in vivo studies with known CYP inducers and inhibitors. Later therapeutic drug monitoring programmes, clinical studies and case reports offer methods to identify additional clinically significant drug interactions. Some commonly co-administered drugs with a significant potential for drug-drug interactions with selected SGAs include some SSRIs. Antiepileptic mood stabilizers such as carbamazepine and valproate, as well as other antiepileptic drugs such as phenobarbital and phenytoin, may decrease plasma SGA concentrations. Some anti-infective agents such as protease inhibitors and fluoroquinolones are of concern as well. Two additional important factors that influence drug interactions with SGAs are dose and time dependence. Smoking is very common among psychiatric patients and can induce CYP1A2 enzymes, thereby lowering expected plasma levels of certain SGAs. It is recommended that ziprasidone and lurasidone are taken with food to promote drug absorption, otherwise their bioavailability can be reduced. Clinicians must be aware of the variety of factors that can increase the likelihood of clinically significant drug interactions with SGAs, and must carefully monitor patients to maximize treatment efficacy while minimizing adverse events.

A validated UHPLC–diode array detector method for the bioanalysis of atypical antipsychotics in whole blood, urine and cerebrospinal fluid following SPE

Background: Risperidone, quetiapine, amisulpride and aripiprazole are atypical antipsychotics increasingly prescribed in Greece. Results: We have developed and validated a UHPLC–diode array detector method for the determination of these drugs in whole blood, urine and cerebrospinal fluid, following SPE. The separation was achieved within 7 min. Validation was performed in terms of linearity, selectivity, accuracy, precision and stability. Following validation, the method was applied to post-mortem blood, urine and cerebrospinal fluid samples. Conclusion: The method proved fast and simple for the determination of four atypical antipsychotic drugs in whole blood, urine and cerebrospinal fluid. To the best of our knowledge, this is the only available method for the simultaneous determination of these drugs in cerebrospinal fluid.

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 relevant drug interactions in anxiety disorders

OBJECTIVE

Certain drugs used in the treatment of patients with anxiety disorders can interact with other psychotropic drugs and with pharmacological treatments for physical illnesses. There is a need for an updated comparative review of clinically relevant drug interactions in this area.

DESIGN

Relevant literature on drug interactions with medications used in the treatment of anxiety disorders was identified through a search in MEDLINE and EMBASE.

RESULTS

Drug interactions involving medications used to treat anxiety disorders may be pharmacokinetic, such as enzyme inhibition or induction in the cytochrome P450 system and transporter-mediated drug interactions, or pharmacodynamic, such as additive effects in causing drowsiness or additive effects at neurotransmitter receptors. Certain selective serotonin reuptake inhibitors (fluoxetine, fluvoxamine, and paroxetine) are particularly liable to be potentially involved in untoward pharmacokinetic interactions.

CONCLUSIONS

The potential for drug interactions with medications used in anxiety disorders should be the cause of clinical concern, particularly in elderly individuals. However, the liability for harmful drug interactions may be anticipated, and the risk reduced. Although not all interactions are clinically relevant, careful monitoring of clinical response and possible interactions is essential.

Clinically significant drug interactions with newer antidepressants

After the introduction of selective serotonin reuptake inhibitors (SSRIs), other newer antidepressants with different mechanisms of action have been introduced in clinical practice. Because antidepressants are commonly prescribed in combination with other medications used to treat co-morbid psychiatric or somatic disorders, they are likely to be involved in clinically significant drug interactions. This review examines the drug interaction profiles of the following newer antidepressants: escitalopram, venlafaxine, desvenlafaxine, duloxetine, milnacipran, mirtazapine, reboxetine, bupropion, agomelatine and vilazodone. In general, by virtue of a more selective mechanism of action and receptor profile, newer antidepressants carry a relatively low risk for pharmacodynamic drug interactions, at least as compared with first-generation antidepressants, i.e. monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants (TCAs). On the other hand, they are susceptible to pharmacokinetic drug interactions. All new antidepressants are extensively metabolized in the liver by cytochrome P450 (CYP) isoenzymes, and therefore may be the target of metabolically based drug interactions. Concomitant administration of inhibitors or inducers of the CYP isoenzymes involved in the biotransformation of specific antidepressants may cause changes in their plasma concentrations. However, due to their relatively wide margin of safety, the consequences of such kinetic modifications are usually not clinically relevant. Conversely, some newer antidepressants may cause pharmacokinetic interactions through their ability to inhibit specific CYPs. With regard to this, duloxetine and bupropion are moderate inhibitors of CYP2D6. Therefore, potentially harmful drug interactions may occur when they are coadministered with substrates of these isoforms, especially compounds with a narrow therapeutic index. The other new antidepressants are only weak inhibitors or are not inhibitors of CYP isoforms at usual therapeutic concentrations and are not expected to affect the disposition of concomitantly administered medications. Although drug interactions with newer antidepressants are potentially, but rarely, clinically significant, the use of antidepressants with a more favourable drug interaction profile is advisable. Knowledge of the interaction potential of individual antidepressants is essential for safe prescribing and may help clinicians to predict and eventually avoid certain drug combinations.