Psychotropic drug interactions with valproate

When, Why and How to Re-challenge Clozapine in Schizophrenia Following Myocarditis

Clozapine-induced myocarditis (CIM) is among the most important adverse events limiting the use of clozapine as the most effective treatment for schizophrenia. CIM necessitates the immediate termination of clozapine, often resulting in its permanent discontinuation with considerable detrimental effects on patients' psychopathology and long-term outcome. Consequently, a clozapine re-challenge after CIM is increasingly regarded as a viable alternative, with published reports indicating a success rate of approximately 60%. However, published cases of re-challenges after CIM remain limited. Here, we provide a narrative review of the current state of research regarding the epidemiology, pathophysiology, risk factors, diagnosis and clinical management of CIM as well as a synthesis of current recommendations for re-challenging patients after CIM. This includes a step-by-step guide for this crucial procedure based on the current evidence regarding the pathophysiology and risk factors for CIM. Slow dose titration regimes and addressing risk factors including concomitant valproate and olanzapine are crucial both to prevent CIM and to ensure a safe and successful re-challenge. Furthermore, we discuss the utility of C-reactive protein, troponin, N-terminal-pro hormone and brain natriuretic peptide, therapeutic drug-monitoring and cardiac magnetic resonance imaging for CIM screening and diagnosis as well as for post-CIM re-challenges.

Predictors of valproic acid steady-state serum levels in adult and pediatric psychiatric inpatients: a comparative analysis

RATIONALE

Valproic acid (VPA) is commonly used as a second-line mood stabilizer or augmentative agent in severe mental illnesses. However, population pharmacokinetic studies specific to psychiatric populations are limited, and clinical predictors for the precision application of VPA remain undefined.

OBJECTIVES

To identify steady-state serum VPA level predictors in pediatric/adolescent and adult psychiatric inpatients.

METHODS

We analyzed data from 634 patients and 1,068 steady-state therapeutic drug monitoring (TDM) data points recorded from 2015 to 2021. Steady-state VPA levels were obtained after tapering during each hospitalization episode. Electronic patient records were screened for routine clinical parameters and co-medication. Generalized additive mixed models were employed to identify independent predictors.

RESULTS

Most TDM episodes involved patients with psychotic disorders, including schizophrenia (29.2%) and schizoaffective disorder (17.3%). Polypharmacy was common, with the most frequent combinations being VPA + quetiapine and VPA + promethazine. Age was significantly associated with VPA levels, with pediatric/adolescent patients (< 18 years) demonstrating higher dose-adjusted serum levels of VPA (β = 7.6±2.34, p < 0.001) after accounting for BMI. Women tended to have higher adjusted VPA serum levels than men (β = 5.08±1.62, p < 0.001). The formulation of VPA (Immediate-release vs. extended-release) showed no association with VPA levels. Co-administration of diazepam exhibited a dose-dependent decrease in VPA levels (F = 15.7, p < 0.001), suggesting a potential pharmacokinetic interaction.

CONCLUSIONS

This study highlights the utility of population-specific pharmacokinetic data for VPA in psychiatric populations. Age, gender, and co-administration of diazepam were identified as predictors of VPA levels. Further research is warranted to establish additional predictors and optimize the precision application of VPA in psychiatric patients.

Targeting the epigenome in malignant melanoma: Facts, challenges and therapeutic promises

Malignant melanoma is the most lethal type of skin cancer with high rates of mortality. Although current treatment options provide a short-clinical benefit, acquired-drug resistance highlights the low 5-year survival rate among patients with advanced stage of the disease. In parallel, the involvement of an aberrant epigenetic landscape, (e.g., alterations in DNA methylation patterns, histone modifications marks and expression of non-coding RNAs), in addition to the genetic background, has been also associated with the onset and progression of melanoma. In this review article, we report on current therapeutic options in melanoma treatment with a focus on distinct epigenetic alterations and how their reversal, by specific drug compounds, can restore a normal phenotype. In particular, we concentrate on how single and/or combinatorial therapeutic approaches have utilized epigenetic drug compounds in being effective against malignant melanoma. Finally, the role of deregulated epigenetic mechanisms in promoting drug resistance to targeted therapies and immune checkpoint inhibitors is presented leading to the development of newly synthesized and/or improved drug compounds capable of targeting the epigenome of malignant melanoma.

The safety of treating newly diagnosed epilepsy

INTRODUCTION

Epilepsy is a serious chronic neurological disorder manifested by an enduring symptomatic predisposition to seizures. Newly diagnosed individuals face increased morbidity, mortality, and socioeconomic costs. Anti-epileptic drug therapy is the treatment usually prescribed, which has efficacy in seizure control and mitigating long-term mortality.

AREAS COVERED

Safety of anti-epileptic drug therapy in adults with a focus in newly diagnosed patients. Areas covered include the most commonly experienced adverse drug effects, as well as those with the highest impacts on drug tolerability, quality of life, morbidity and mortality. Evidence was also reviewed to identify clinical strategies to improve the safety of anti-epileptic drug therapy.

EXPERT OPINION

Anti-epileptic drugs (AEDs) are mostly effective and well tolerated. However, a lack of standardised reporting of adverse drug effects in trials and in clinical practice provides an obstacle for evaluation of which adverse drug effects need to be prioritised in management. Improvement in the reporting of cognitive and other effects, as well as improved precision medicine and pharmacogenomics to target the incidence of high-mortality idiosyncratic reactions, will help to reduce the harm of AEDs in people newly diagnosed with epilepsy.

Clozapine toxicity in a CYP2D6 poor metaboliser: Additive effects of haloperidol and valproate on clozapine metabolism

OBJECTIVE:

To illustrate the complexities of clozapine metabolism with the use of therapeutic drug monitoring.

METHODS:

We describe a case of clozapine toxicity in a patient with schizophrenia treated with the combination of clozapine, valproate and haloperidol.

RESULTS:

A 24-year-old CYP2D6 poor metaboliser developed clozapine toxicity corresponding to the additive effects of haloperidol, and increasing clozapine and valproate doses. Saturation of metabolism, evidenced by a high clozapine/norclozapine ratio, was present at this time.

CONCLUSIONS:

Clozapine metabolism is complex and influenced by multiple factors, including interactions with hepatic P450 enzyme inducers/inhibitors, genetic polymorphisms and the potential for saturation of the N-demethylation metabolic pathway.

Infusion of Valproic Acid Into the Renal Medulla Activates Stem Cell Population and Attenuates Salt-Sensitive Hypertension in Dahl S Rats

BACKGROUND

Our previous study has detected a stem cell deficiency in the renal medulla in Dahl salt-sensitive (S) rats. This study determined whether infusion of valproic acid (VA), an agent known to stimulate the stem cell function, attenuated salt-sensitive hypertension in Dahl S rats.

METHODS

Uninephrectomized Dahl S rats were infused with vehicle or VA (50mg/kg/d) into the renal medulla and fed with a low (LS) or high salt diet (HS). Stem cell marker and number were analyzed by immunohistochemistry, Real-time RT-PCR and Western blot. Sodium excretion and blood pressure were measured.

RESULTS

VA significantly increased the mRNA and protein levels of FGF2, a stem cell niche factor, and CD133, a stem cell marker. The number of CD133+ cells was significantly increased in the renal medulla in VA-treated rats. Meanwhile, high salt-induced increases in the mRNA level of proinflammatory factors interleukin-1β and interleukin-6 were blocked in VA-treated rats. Functionally, sodium excretion in response to the blood pressure increase and acute sodium loading was significantly enhanced, sodium retention attenuated, high salt-induced increase of blood pressure reduced in VA-treated rats.

CONCLUSION

Activation of stem cell function by VA inhibits the activation of proinflammatory factors and attenuates salt-sensitive hypertension in Dahl S rats.

Three patients needing high doses of valproic Acid to get therapeutic concentrations

Valproic acid (VPA) can autoinduce its own metabolism. Cases requiring VPA doses >4000 mg/day to obtain therapeutic plasma concentrations, such as these 3 cases, have never been published. Case 1 received VPA for seizures and schizophrenia and had >50 VPA concentrations in 4 years. A high dose of 5,250 mg/day of VPA concentrate was prescribed for years but this dose led to an intoxication when switched to the enterocoated divalproex sodium formulation, requiring a normal dose of 2000 mg/day. VPA metabolic capacity was significantly higher (t = −9.6; df = 6.3, p < 0.001) during the VPA concentrate therapy, possibly due to autoinduction in that formulation. Case 2 had VPA for schizoaffective psychosis with 10 VPA concentrations during an 8-week admission. To maintain a VPA level ≥50 μg/mL, VPA doses increased from 1500 to 4000 mg/day. Case 3 had tuberous sclerosis and epilepsy and was followed up for >4 years with 137 VPA concentrations. To maintain VPA concentrations ≥50 μg/mL, VPA doses increased from 3,375 to 10,500 mg/day. In Cases 2 and 3, the duration of admission and the VPA dose were strongly correlated (r around 0.90; p < 0.001) with almost no change after controlling for VPA concentrations, indicating progressive autoinduction that increased with time.

A case of a potential drug interaction between clobazam and etravirine-based antiretroviral therapy

The cytochrome P450 isoforms primarily involved in clobazam metabolism are CYP3A4 and 2C19. Drugs that modulate these enzymes would then be expected to alter the exposure of clobazam and its major metabolites. Etravirine, a second-generation non-nucleoside reverse transcriptase inhibitor has been shown to induce CYP3A4, while inhibiting CYP2C9 and CYP2C19. We report a case in which a potential drug interaction between clobazam and etravirine may have led to increased concentrations of clobazam and its pharmacologically active metabolite, N-desmethylclobazam, causing neurotoxic symptoms.

The impact of dosage of sustained-release formulation on valproate clearance and plasma concentration in psychiatric patients: analysis based on routine therapeutic drug monitoring data

Pharmacokinetic parameters were compared between 2 dosages of valproic acid (VPA) sustained-release (SR) formulation in psychiatric patients. A total of 66 psychiatric patients (21 women and 45 men; age range, 18-60 years) receiving 500 mg/d (n = 28) or 1000 mg/d (n = 38) of VPA SR for at least 4 weeks were recruited into the study. A 5-mL blood sample was collected into a plain tube and immediately centrifuged for plasma. Separation of free VPA was further done using Centrifree micropartition devices. Both total and free VPA concentrations (C(total) and C(free)) were analyzed by TDx analyzer with fluorescence polarization immunoassay technique. The patients' characteristics and pharmacokinetic parameters were compared between the 2 dosage groups using independent t test or χ² test where appropriate. The results show that the increment in C(total) (mg/mL) for every milligram-per-kilogram increment in dosage was decreased from 7 ± 3 to 4 ± 1 (mg/L) / (mg/kg) when the total VPA clearance (CL(total)) increased from 6.1 ± 2.6 to 9.0 ± 3.1 mL/kg per hour with the increasing dose in the 500 mg/d and 1000 mg/d groups, respectively (P < 0.05). The increment in C(free) [0.6 ± 0.3 vs 0.5 ± 0.2 (mg/L) / (mg/kg)] and CL(free) (80.4 ± 41.5 vs 92.2 ± 47.6 ml/kg per hour) were not significantly different. Owing to the saturation of protein binding, percent free VPA was significantly increased from 8 ± 3 to 11 ± 3 when the dose was increased from 500 to 1000 mg/d (P < 0.05). In conclusion, an increase in the VPA dose resulted in a disproportional increase between dosage and C(total), whereas a proportional increase between dosage and C(free) still existed. Therefore, our study suggests that the therapeutic range of C(free) is 4 to 12 mg/L based on the therapeutic range of C(total) (45-100 mg/L) for general psychiatric conditions.

Moclobemide monotherapy vs. combined therapy with valproic acid or carbamazepine in depressive patients: a pharmacokinetic interaction study

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Moclobemide (MCB) undergoes extensive both presystemic and systemic metabolism that can be affected by concomitant drugs. Valproic acid (VPA) and carbamazepine (CBZ) have been found to interact with psychotropic medications of all classes and many other drugs; VPA acts as a broad-spectrum inhibitor, and CBZ as a potent inducer of a variety of drug-metabolizing enzymes. There have been no previous studies designed to investigate a potential pharmacokinetic (PK) interaction between MCB and VPA or CBZ; however, these agents are likely to be used concomitantly for the treatment of depressive disorders.

WHAT THIS STUDY ADDS

VPA does not significantly affect PK or metabolism of MCB at steady state. CBZ significantly decreases MCB exposure. This effect is time-dependent, being more pronounced after 3-5 weeks of co-administration.

AIM

To assess the impact of valproic acid (VPA) and carbamazepine (CBZ) on moclobemide (MCB) pharmacokinetics (PK) and metabolism at steady state in depressive patients.

METHODS

Twenty-one inpatients with recurrent endogenous depression received MCB (150 mg t.i.d.), either as monotherapy or in combination with VPA (500 mg b.i.d.) or CBZ (200 mg b.i.d.) in a nonrandomized manner. Steady-state plasma PK parameters of MCB and its two metabolites, Ro 12-8095 and Ro 12-5637, were derived. Clinical assessments of treatment efficacy were performed weekly using standard depression rating scales.

RESULTS

CBZ, but not VPA, was associated with decreases in the MCB AUC by 35% [from 7.794 to 5.038 mg h l(-1); 95% confidence interval (CI) -4.84863, -0.66194; P = 0.01] and C(max) by 28% (from 1.911 to 1.383 mg l(-1); 95% CI -0.98197, -0.07518; P < 0.05), and an increase in its oral clearance by 41% (from 0.323 to 0.454 l h(-1) kg(-1); 95% CI 0.00086, 0.26171; P < 0.05) after 4 weeks of co-administration. MCB through concentrations were also decreased, on average by 41% (from 0.950 to 0.559 mg l(-1); 95% CI -0.77479, -0.03301; P < 0.05). However, the efficacy in this group of patients was not inferior to the controls, for several possible reasons. Overall tolerability of all study medications was good.

CONCLUSIONS

VPA does not significantly affect PK or metabolism of MCB, whereas CBZ time-dependently decreases MCB exposure, probably by inducing metabolism of MCB and its major plasma metabolite. The actual clinical relevance of the observed MCB-CBZ PK interaction needs to be further evaluated in a more comprehensive study.

Differential pharmacological regulation of drug efflux and pharmacoresistant schizophrenia

Pharmacoresistant schizophrenia is a significant impediment to the successful management of the disease. The expression and function of P-glycoprotein (P-gp) has recently been implicated in this phenomenon. P-gp is a multidrug efflux transporter that prevents drug substrates from crossing the blood-brain barrier (BBB). Although the direct interaction between individual antipsychotic agents and P-gp has been demonstrated, the effect of antipsychotic drug combinations used in disease management on P-gp transport function remains to be elucidated. This could have important clinical implications in some individuals as dosage adjustments based on plasma drug concentration changes may not always be appropriate if drug-drug interactions and the resulting changes in drug concentration in the brain are not considered. This paper introduces the potential impact that combination antipsychotic therapy may have on P-gp function at the BBB and discusses the consequences of this in the prevention and circumvention of unfavourable therapeutic response in schizophrenic disorders.

Age and gender effects on olanzapine and risperidone plasma concentrations in children and adolescents

BACKGROUND

Risperidone and olanzapine are second-generation antipsychotics that are increasingly used in child and adolescent psychiatry. So far, little is known about plasma concentrations and concentration-to-dose (C/D) ratios of these agents in children and adolescents compared to adults.

METHOD

This study investigated whether age and gender influence risperidone and olanzapine plasma concentration by determining risperidone and olanzapine plasma levels by tandem mass spectrometry in 162 Caucasian patients (98 risperidone and 64 olanzapine).

RESULTS

For risperidone and 9-hydroxyrisperidone, the C(total)/D ratio was almost identical in both age groups (10-18 and 19-45 years, respectively). In the younger age group, females exhibited significantly higher total plasma levels than males while receiving similar doses of risperidone. For olanzapine, in adolescents significantly higher C/D ratios were detected by an average of 43% (after adjustment for weight: 34%) compared to adults.

CONCLUSION

This study demonstrates an age effect for olanzapine but not for risperidone resulting in higher olanzapine plasma levels in younger patients. For risperidone, we found a gender effect as female adolescent patients had significantly higher risperidone plasma concentrations than male adolescent patients. Future prospective studies are necessary to clarify whether the prescribed dosage should be different in young and older patients.

High-performance liquid chromatographic method for the determination of moclobemide and its two major metabolites in human plasma

A selective, sensitive, and simple high-performance liquid chromatographic (HPLC) method was developed for the determination of moclobemide and its two major metabolites, Ro 12-5637 and Ro 12-8095, in human plasma. Sample preparation (0.5 ml of plasma) involved solid-phase extraction (SPE) using Speedisk H(2)O-Philic DVB columns. Separations were performed on a Waters XTerra RP18 column (5 microm, 150 mm x 4.6 mm). The mobile phase consisted of 10 mM KH(2)PO(4) with 1% triethylamine (pH 3.9) and acetonitrile (83:17, v/v), and a flow-rate was 1.2 ml/min. The total run time was 13 min. UV detection was performed at 240 nm. Mean absolute recoveries were > or =90% and the limit of quantification (LOQ) for all analytes was 0.02 mg/l. Calibration curves were linear (r>0.995) over a wide range of the analyte concentrations in plasma; thus, the method is suitable for different clinical studies when large variations in the drug/metabolites concentrations are observed. During a 5-day assay validation procedure the accuracy and precision were tested and proven (relative errors (RE)< or =13%; intra-day coefficient of variation (CV)< or =7%; inter-day CV< or =13%). Many drugs frequently used in the target patient population were evaluated for potential interference in order method selectivity to be ensured. The assay has been used in a clinical pharmacokinetic study to assess steady-state pharmacokinetics of moclobemide and two metabolites in depressive patients on mono- and combined therapy.

Therapeutic monitoring of valproate in psychiatry: how far have we progressed?

Valproate (VPA) is a well-established anticonvulsant drug that has found increasing use as a psychotherapeutic agent. The drug is currently used in the management of bipolar, depressive, anxiety, and psychotic disorders; alcohol withdrawal and dependence; agitation associated with dementia; and borderline personality disorder. Despite such widespread use, studies focusing on the concentration-response relationship of VPA in psychiatry are limited. This article examines the rationale for therapeutic monitoring of VPA in psychiatric disorders and reviews reports of VPA concentrations measured during efficacy studies of this drug in psychiatry. Most studies have been open-labeled and uncontrolled, and have not placed the determination of a target concentration range as a primary objective. Furthermore, most studies have used the therapeutic range (50-100 mg/L) for seizure disorders to guide dosage in the psychiatric disorders, although study outcomes have suggested the need to redefine a threshold concentration in the different psychiatric conditions. With the increasing popularity of VPA as a psychotropic agent, it is clear that further investigation of the plasma concentration range associated with efficacy in psychiatric conditions is warranted.