Population pharmacokinetics of orally administered duloxetine in patients: implications for dosing recommendation

Does sex affect the efficacy of systemic pharmacological treatments of pain in knee osteoarthritis? A systematic review

Objective

To determine whether sex influences the analgesic efficacy of systemic pharmacological treatment in patients with knee osteoarthritis.

Design

A systematic review, guided by Cochrane methods, sourced studies from Medline, Cochrane Library, Embase, and CINAHL Plus with Full Text as of October 10, 2022. Eligible studies were double-blind RCTs evaluating systemic pharmacological treatments for knee osteoarthritis in adults, with minimum 30-day treatment duration, reporting sex-specific results or mentioning sex subgroup analysis for analgesic efficacy. The risk of bias was assessed using the Cochrane Risk of Bias tool version 2 (RoB 2).

Results

9 studies (5201 participants) met inclusion criteria, analyzing drugs including duloxetine, etoricoxib, tapentadol, naproxcinod, lutikizumab, and rofecoxib. Only one study reported sex-specific results. Review findings suggested no significant sex-based differences in treatment efficacy, however, data were limited due to a lack of sex-specific reporting or inclusion of sex in subgroup analyses.

Conclusions

Current evidence does not support the existence of sex differences in the analgesic efficacy of systemic knee osteoarthritis treatments. However, this conclusion is substantially limited by the paucity of sex-specific reporting of results or subgroup analyses in most primary studies, emphasizing the need for future research to report on sex-stratified data to allow for comprehensive, personalized treatment strategies.

Population pharmacokinetics of duloxetine in Japanese pediatric patients with major depressive disorder

The objectives of this analysis were to characterize the pharmacokinetics of duloxetine in Japanese pediatric patients aged 9-17 years with major depressive disorder (MDD) and to explore potential intrinsic factors affecting its pharmacokinetics. A population pharmacokinetic (PK) model was developed with plasma steady-state duloxetine concentrations from Japanese pediatric patients with MDD in an open-label long-term extension trial in Japan (ClinicalTrials.gov Identifier: NCT03395353). Duloxetine pharmacokinetics in Japanese pediatric patients was well described by a one-compartment model with first-order absorption. The population mean estimates of CL/F and V/F of duloxetine were 81.4 L/h and 1170 L, respectively. Patient intrinsic factors were assessed for their potential influence on duloxetine apparent clearance (CL/F). Only sex was identified as a statistically significant covariate of duloxetine CL/F. Duloxetine pharmacokinetic parameters and model-predicted duloxetine concentrations at steady state in the Japanese pediatric population were compared with those in Japanese adults. The mean duloxetine CL/F in pediatrics is slightly higher than adults, it is, however, expected that comparable steady-state duloxetine exposure in pediatric patients can be achieved with the approved dose regimen for adults. The population PK model provides useful information to understand the pharmacokinetic characteristics of duloxetine for Japanese pediatric patients with MDD. CLINICALTRIALS.GOV IDENTIFIER: NCT03395353.

Determination of Patient Adherence for Duloxetine in Urine

Duloxetine, known by its brand name, CymbaltaTM, is a selective serotonin and norepinephrine reuptake inhibitor used to treat major depressive disorders. Determination of patient compliance for duloxetine is typically determined through medication possession ratio (MPR) or plasma concentrations. The purpose of this paper was to characterize normal urinary duloxetine concentrations in patients prescribed duloxetine to monitor patient adherence. Patient data collected from routine screens for duloxetine concentrations in urine were included in this study. Inclusion criteria consisted of patients who were prescribed duloxetine and (i) tested positive for duloxetine, (ii) tested negative for illicit substances and (iii) included creatinine, age and duloxetine dose administered. Of the 5,592 patient urines screened, 2,004 of the results fit into the inclusion criteria. Positive urine concentrations of duloxetine ranged from 50 to 2,722 ng/mL. Duloxetine urine concentrations were normalized to creatinine and dose further characterized by sex, age, body mass index (BMI) and dose in milligrams. Sample distribution included urines collected from 1,487 females and 517 males. The age range of the specimen donors was between 15 and 90 years old with an average age of 52. BMI levels ranged from 13.9 (underweight) to 88.1 (obese), with the average BMI being 33.5. The most common dose of duloxetine prescribed was a daily, oral dose of 60 mg. Analysis of the normalized, transformed creatinine concentrations showed that there was a significant statistical difference (P < 0.05) in the urinary duloxetine concentrations by sex and by dose (mg). Female patients further showed a statistical difference in urinary duloxetine concentration in age groups 18-64 and 64 and older. By characterizing urinary duloxetine concentrations in patients prescribed the medication, normalized distributions of data ranges have been established. These data ranges for urinary duloxetine concentrations can be used to determine patient compliance with duloxetine in routine, clinical samples.

Treatment of depression: Are psychotropic drugs appropriately dosed in women and in the elderly? Dosages of psychotropic drugs by sex and age in routine clinical practice

BACKGROUND

Several researchers have shown higher concentration-dose ratios of psychotropic drugs in women and the elderly. Therefore, lower dosages of psychotropic drugs may be recommended in women and the elderly. This study describes sex- and age-related dosage of psychotropic drugs prescribed to patients with major depressive disorder (MDD) in routine clinical practice.

METHOD

Influence of sex and age on dosages are analysed for the 10 most commonly prescribed drugs in our dataset consisting of 32,082 inpatients with MDD. Data stems from the European drug safety program "Arzneimittelsicherheit in der Psychiatrie". The observed sex and age differences in prescriptions are compared to differences described in literature on age- and gender-related pharmacokinetics.

RESULTS

Among patients over 65 years, a statistically significant decrease in dosages with increasing age (between 0.65% and 2.83% for each increasing year of age) was observed, except for zopiclone. However, only slight or no influence of sex-related adjustment of dosage in prescriptions was found.

CONCLUSION

Age appears to influence adjustment of dosage in most psychotropic drugs, but to a lower extent than data on age-related pharmacokinetics suggests. Although literature also suggests that lower dosages of psychotropic drugs may be appropriate for females, this study found women are usually prescribed the same dosage as men.

Duloxetine against symptomatic chemotherapy-induced peripheral neurotoxicity in cancer survivors: a real world, open-label experience

The objective of this observational study was to evaluate the efficacy and safety of duloxetine in a cohort of 100 cancer survivors with chemotherapy-induced peripheral neurotoxicity (CIPN). CIPN was graded employing the TNSc and the NCI-CTCv4. The Patient Global Impression of Change (PGIC) scale measured the efficacy of duloxetine (1: no benefit; to 7: excellent response). A clinically meaningful response was considered a PGIC > 4. Median age was 62 (29-81) years and 42% were male. CIPN was graded as grades 1, 2 and 3 in 20, 66, and 14% of patients, respectively. Median time to duloxetine initiation was 6 (1-63) months after chemotherapy. Fifty-seven patients early dropped out from duloxetine, due to lack of efficacy (20%) or side effects (37%). Male patients more frequently discontinued duloxetine due to lack of efficacy (35.7 vs. 8.6% P = 0.001). PGIC scores were higher in female patients (4 vs. 1, P = 0.001), taxane-treated patients (4 vs. 1, P = 0.042) and with short-lasting (<6 months) CIPN (4 vs. 1, P = 0.008). Patients with long-lasting CIPN had a higher rate of adverse events (47 vs. 27%, P = 0.038) and discontinuation (54.8 vs. 45.1%, P = 0.023). In the multivariate analysis, female gender and short-lasting CIPN were independently associated with a favorable response to duloxetine. Low tolerability, male gender, and long-lasting CIPN significantly limited duloxetine use in daily practice setting. A minority of cancer survivors with CIPN treated with duloxetine had a meaningful CIPN improvement, and tolerability was overall low. Female gender and short-term CIPN were independently associated with a favorable response to duloxetine.

Smoking cessation and duloxetine toxicity: A case report

OBJECTIVE

Psychiatric medications are among the drugs affected by cigarette smoke, and because of the high prevalence of smoking in the psychiatric community, psychiatric patients are particularly at risk when entering the smoke-free environment of a hospital.

CASE SUMMARY

Polycyclic aromatic hydrocarbons present in cigarette smoke are well-known inducers of cytochrome P450 (CYP) enzymes. CYP1A2 induction by cigarette smoking increases metabolic clearance of substrates of this enzyme; smoking cessation results in a decrease in CYP1A2 activity, which causes an increase in serum substrate levels. Although these effects are well documented, the effect of smoking cessation remains a hidden danger, in part, because computerized drug interaction surveillance systems are not designed to alert clinicians when an offending agent is discontinued.

PRACTICE IMPLICATION

To raise awareness and demonstrate the importance of a thorough assessment of smoking status, we present a case in which the temporal relationship of smoking cessation to the emergence of nausea, vomiting, and tachycardia 3 days later (day 3); the development of myoclonic jerks by day 5; and the resolution of symptoms on reduction of duloxetine dosage on day 44 implicates duloxetine toxicity in a patient with ischemic cardiomyopathy awaiting implantation of a left ventricular assist device.

Association between body mass index and response to duloxetine for aromatase inhibitor-associated musculoskeletal symptoms in SWOG S1202

BACKGROUND

Aromatase inhibitor (AI)-associated musculoskeletal symptoms (AIMSS) negatively impact adherence to and persistence with therapy. In SWOG S1202, patients with AIMSS who were treated with duloxetine, a serotonin norepinephrine reuptake inhibitor, reported improvement in pain by 12 weeks compared with placebo. Based on the authors' prior observation that responses to pain interventions differ between obese and nonobese patients, the current study examined whether response to duloxetine therapy differed by obesity status.

METHODS

In SWOG S1202, a total of 299 AI-treated postmenopausal women with stage I to III (AJCC 7th Edition) breast cancer who developed new or worsening average pain were enrolled, randomized to duloxetine or placebo, and treated for 12 weeks. Patient-reported outcomes were obtained at baseline and through 12 weeks. Patients were categorized into nonobese (body mass index [BMI] <30 kg/m² ) or obese (BMI ≥30 kg/m² ). The authors tested the interaction between intervention and obesity with respect to average pain at 12 weeks in the 289 eligible patients, using a P value of .05 to indicate statistical significance.

RESULTS

In approximately 54% of evaluable patients with a BMI ≥30 kg/m² , the reduction in the mean average pain score between baseline and 12 weeks was statistically significantly greater for patients treated with duloxetine compared with those receiving placebo (-2.73 vs -1.64 points; P = .003). Conversely, in the nonobese patients, the reduction in the mean average pain score was similar in the 2 cohorts (-2.46 vs -2.34 points; P = .75). The P value for interaction was .02, thereby meeting the threshold criteria of the current study. Similar findings were evident for other pain-related patient-reported outcomes.

CONCLUSIONS

In this trial, obese patients with AIMSS obtained more analgesic benefit from duloxetine compared with nonobese patients. Additional studies are warranted to determine the biologic basis for these findings.

Smoking and antidepressants pharmacokinetics: a systematic review

BACKGROUND

Despite an increasingly recognized relationship between depression and smoking, little is known about how smoking influences antidepressant response and treatment outcomes. The aim of this study was to systematically review the evidence of the impact of smoking on new-generation antidepressants with an emphasis on the pharmacokinetic perspective.

METHODS

We present a systematic review of clinical trials comparing the serum levels of new-generation antidepressants in smokers and nonsmokers. Data were obtained from MEDLINE/PubMed, Embase, and other sources. Risk of bias was assessed for selection, performance, detection, attrition, and reporting of individual studies.

RESULTS

Twenty-one studies met inclusion criteria; seven involved fluvoxamine, two evaluated fluoxetine, sertraline, venlafaxine, duloxetine or mirtazapine, and escitalopram, citalopram, trazodone and bupropion were the subject of a single study. No trials were found involving other common antidepressants such as paroxetine or agomelatine. Serum levels of fluvoxamine, duloxetine, mirtazapine and trazodone were significantly higher in nonsmokers compared with smokers.

CONCLUSIONS

There is evidence showing a reduction in the concentration of serum levels of fluvoxamine, duloxetine, mirtazapine and trazodone in smoking patients as compared to nonsmokers. The evidence regarding other commonly used antidepressants is scarce. Nonetheless, smoking status should be considered when choosing an antidepressant treatment, given the risk of pharmacokinetic interactions.

Pharmacokinetics of orally administered duloxetine in children and adolescents with major depressive disorder

BACKGROUND

Duloxetine, a selective serotonin (5-hydroxytryptamine) and norepinephrine reuptake inhibitor, has been approved since 2004 for the treatment of adults with major depressive disorder (MDD). It is currently not approved for use in pediatric patients (aged <18 years) with MDD. The clinical development program for duloxetine in the pediatric MDD population, which consisted of three clinical studies, provided extensive data on the safety, tolerability, and pharmacokinetics of duloxetine across a wide dose range in pediatric patients of differing ages, sex, body weights, and sexual maturation.

OBJECTIVES

The objectives were to characterize the pharmacokinetics of duloxetine based on population modeling following daily oral administration in children and adolescents aged 7-17 years diagnosed with MDD; to estimate the magnitude of between- and within-patient variability; to identify potential patient factors affecting duloxetine pharmacokinetics, and to compare duloxetine pharmacokinetics in the pediatric population with those characterized in adults.

METHODS

The analyses meta-dataset was created from pharmacokinetic and demographic data available from one phase II (open-label) and two phase III (randomized, double-blind) clinical trials of duloxetine in children and adolescents. Patients received 20-120 mg of oral duloxetine once daily. Duloxetine concentrations (a total of 1,581 concentrations) were obtained from 428 patients: 34% were children (aged 7-11 years) and 66% were adolescents (aged 12-18 years). Population modeling analyses were performed using nonlinear mixed-effects modeling and the first-order conditional estimation method with interaction. Patient factors were assessed for their potential influence on duloxetine apparent clearance (CL/F) and apparent volume of distribution (V d/F). Duloxetine pharmacokinetic parameters and model-predicted duloxetine concentrations at steady state in the pediatric population were compared with those in adults.

RESULTS

Duloxetine pharmacokinetics in pediatric patients was described by a one-compartmental model. Typical values of CL/F, V d/F, and half-life (t 1/2) at 60 mg/day of duloxetine were 79.7 L/h, 1,200 L, and 10.4 h, respectively. The between-patient variability in CL/F and V d/F was 68 and 87%, respectively, while within-patient variability was 57% (proportional error) and 2.04 ng/mL (additive error). Body surface area (BSA), dose, and race had a statistically significant effect on duloxetine pharmacokinetics. With a 2.2-fold increase in BSA, the CL/F increased about twofold. A sixfold increase in dose (20 to 120 mg) decreased CL/F by 32%. In American Indian patients, V d/F was 131% higher than the other races combined. Age, sex, body mass index, serum creatinine, cytochrome P450 2D6 predicted phenotype, and menarche status did not have a statistically significant effect. Estimates of CL/F and V d/F were higher in the pediatric population than in adults; subsequently, the average steady-state duloxetine concentration was approximately 30% lower in the pediatric population than in adults.

CONCLUSIONS

Duloxetine pharmacokinetics was similar in children and adolescents with MDD. The statistically significant effects of dose, BSA, and race on duloxetine pharmacokinetics in pediatric patients did not appear to be clinically meaningful. At a given dose, the typical steady-state duloxetine concentrations in the pediatric population were lower than in adults, and the distribution of steady-state duloxetine concentrations in pediatric patients were typically in the lower range of concentrations in adults.

Emerging areas of research in the assessment of pharmacokinetics in patients with chronic kidney disease

Chronic kidney disease (CKD) has been shown to alter the pharmacokinetics of drugs that are eliminated not only via the renal pathway but also by nonrenal clearance and transport. Dosing recommendations in subjects with CKD have historically come from small pharmacokinetic (PK) studies, which have been insulated from the broader clinical development strategy. Opportunities for prospective strategic integration of both preclinical and clinical data on drug clearance mechanisms, model-based approaches, and clinical knowledge of therapeutic index are therefore often missed in designing and analyzing the results of PK studies in subjects with CKD, and eventually providing dosing recommendations. These considerations are valuable in designing informative PK studies in subjects with CKD, as well as for guiding kidney function-related inclusion/exclusion criteria in the broader clinical program and ultimately defining dosing guidelines that optimize benefit-risk balance for these special patient populations based on all available data. This paper offers points to consider for drug developers to increase adoption of a contemporary multidisciplinary approach, which includes key considerations on study design and conduct, methodologies for analysis (population PK and physiologically based PK modeling), and a roadmap to interpret the effect of kidney function on the overall benefit-risk profile of drugs in development.

Handling missing data in a duloxetine population pharmacokinetic/pharmacodynamic model - imputation methods and selection models

PURPOSE

In pharmacokinetic (PK)/pharmacodynamic (PD) modelling and simulations (M&S), omitting dropouts can cause inaccuracies in parameter estimation and clinical trial simulations (CTS). This study examines the impact of different imputation methods for missing data on the interpretation of model results, as well as develops a selection model (where dropout and efficacy are jointly modelled) for use in CTS.

METHODS

Missing data were imputed using single and multiple imputation and pattern mixtures methods for a previously reported duloxetine PK/PD model. The probability of dropout was described in the selection model and CTS was conducted with a hypothetical drug to examine the impact of dropout on trial results.

RESULTS

The study completion rate was 75% and dropouts were not random. Model parameters obtained with different imputation methods were mostly within 40% (range 0 to 63%) compared to the model without dropouts. CTS showed 0.3 points lower median pain scores and 3% lower coefficient of variation over the 12-week simulations when dropout was included.

CONCLUSIONS

Missing data had little impact on the original population PK/PD analyses. Sensitivity analyses for dropouts should be conducted in M&S exercises. The utility of selection models in CTS was explored via a hypothetical case study.

Pharmacotherapy for mood disorders in pregnancy: a review of pharmacokinetic changes and clinical recommendations for therapeutic drug monitoring

OBJECTIVE

Pharmacotherapy for mood disorders during pregnancy is often complicated by pregnancy-related pharmacokinetic changes and the need for dose adjustments. The objectives of this review are to summarize the evidence for change in perinatal pharmacokinetics of commonly used pharmacotherapies for mood disorders, discuss the implications for clinical and therapeutic drug monitoring (TDM), and make clinical recommendations.

METHODS

The English-language literature indexed on MEDLINE/PubMed was searched for original observational studies (controlled and uncontrolled, prospective and retrospective), case reports, and case series that evaluated or described pharmacokinetic changes or TDM during pregnancy or the postpartum period.

RESULTS

Pregnancy-associated changes in absorption, distribution, metabolism, and elimination may result in lowered psychotropic drug levels and possible treatment effects, particularly in late pregnancy. Mechanisms include changes in both phase 1 hepatic cytochrome P450 and phase 2 uridine diphosphate glucuronosyltransferase enzyme activities, changes in hepatic and renal blood flow, and glomerular filtration rate. Therapeutic drug monitoring, in combination with clinical monitoring, is indicated for tricyclic antidepressants and mood stabilizers during the perinatal period.

CONCLUSIONS

Substantial pharmacokinetic changes can occur during pregnancy in a number of commonly used antidepressants and mood stabilizers. Dose increases may be indicated for antidepressants including citalopram, clomipramine, imipramine, fluoxetine, fluvoxamine, nortriptyline, paroxetine, and sertraline, especially late in pregnancy. Antenatal dose increases may also be needed for lithium, lamotrigine, and valproic acid because of perinatal changes in metabolism. Close clinical monitoring of perinatal mood disorders and TDM of tricyclic antidepressants and mood stabilizers are recommended.

Effects of duloxetine on norepinephrine and serotonin transporter activity in healthy subjects

Duloxetine selectively inhibits the serotonin (5-HT) and norepinephrine (NE) transporters (5-HTT and NET, respectively), as demonstrated in vitro and in preclinical studies; however, transporter inhibition has not been fully assessed in vivo at the approved dose of 60 mg/d. Here, the in vivo effects of dosing with duloxetine 60 mg once daily for 11 days in healthy subjects were assessed in 2 studies: (1) centrally (n = 11), by measuring concentrations of 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylglycol (DHPG), and NE in cerebrospinal fluid, and (2) versus escitalopram 20 mg/d (n = 32) in a 2-period crossover study by assessing the ΔDHPG/ΔNE ratio in plasma during orthostatic testing and by pharmacokinetic/pharmacodynamic modeling of reuptake inhibition using subjects' serum in cell lines expressing cloned human 5-HTT or NET. At steady state, duloxetine significantly reduced concentrations of DHPG and 5-hydroxyindoleacetic acid (P < 0.05), but not NE, in cerebrospinal fluid; DHPG was also decreased in plasma and urine. The ΔDHPG/ΔNE ratio in plasma decreased significantly more with duloxetine than escitalopram (65% and 21%, respectively; P < 0.0001). Ex vivo reuptake inhibition of 5-HTT was comparable (EC50 = 44.5 nM) for duloxetine and escitalopram, but duloxetine inhibited NET more potently (EC50 = 116 nM and 1044 nM, respectively). Maximal predicted reuptake inhibition for 5-HTT was 84% for duloxetine and 80% for escitalopram, and that for NET was 67% and 14%, respectively. In summary, duloxetine significantly affected 5-HT and NE turnover in the central nervous system and periphery; these effects presumably occurred via inhibition of reuptake by the 5-HTT and NET, as indicated by effects on functional reuptake inhibition ex vivo.

Duloxetine: a review of its use in the management of major depressive disorder in older adults

Duloxetine (Cymbalta(®)) is a selective serotonin norepinephrine reuptake inhibitor indicated for the treatment of major depressive disorder (MDD). This article reviews the therapeutic efficacy and tolerability of duloxetine in older adults with MDD and summarizes its pharmacological properties. Treatment with duloxetine significantly improved several measures of cognition, depression, anxiety, pain and health-related quality-of-life (HR-QOL) in older adults with MDD in two 8-week, double-blind, placebo-controlled trials. However, no significant improvements in measures of depression were observed at week 12 (primary endpoint) of a 24-week, double-blind trial, although symptoms of depression did improve significantly at earlier timepoints. Benefit of treatment was also observed during continued therapy in the 24-week study (i.e. after the 12-week primary endpoint) and in an open-label, 52-week study, with improvements being observed in some measures of depression, pain and HR-QOL. Duloxetine was generally well tolerated in these studies, with nausea, dizziness and adverse events reflecting noradrenergic activity (e.g. dry mouth, constipation) being the most common treatment-emergent adverse events during treatment for up to 52 weeks. Duloxetine therapy had little effect on cardiovascular parameters and bodyweight. Although further well designed and long-term studies in this patient population are required to confirm the efficacy of duloxetine and to compare it with that of other antidepressants, current evidence suggests that treatment with duloxetine may be beneficial in older adults with MDD.

Pharmacometric Analyses to Support Early Development Decisions for LY2878735: A Novel Serotonin Norepinephrine Reuptake Inhibitor

LY2878735 is a novel dual serotonin (5-hydroxytryptamine (5-HT)) and norepinephrine (NE) reuptake inhibitor (SNRI) in development for chronic pain indications. In vitro profile suggests a more balanced profile as compared with other SNRI's, which is expected to confer superior clinical efficacy. LY2878735 is metabolized partly by the genetically polymorphic cytochrome P450 (CYP) 2D6 pathway, raising pharmacokinetic (PK) variability concerns. Phase 1 PK and biomarker data were analyzed by pharmacometric methods to characterize the balance between dual-target engagement and adverse effects on heart rate (HR) and blood pressure (BP). A narrow range of plasma LY2878735 levels was associated with an acceptable balance. As compared with poor metabolizers (PM), CYP2D6 extensive metabolizers (EM) have 21- and threefold higher clearance and distribution volume, respectively. Even with a CYP2D6-based dosing paradigm, a superior therapeutic index comparable to duloxetine, a widely used SNRI, was not achievable and LY2878735 development was thus terminated. Model-based approach effectively synthesizes PK-pharmacodynamic (PD) relationships, enabling efficient early development decisions.

An open-label safety and pharmacokinetics study of duloxetine in pediatric patients with major depression

OBJECTIVE

This preliminary, 32-week study assessed the safety, tolerability, and pharmacokinetics of duloxetine in pediatric patients (aged 7-17 years) with major depressive disorder.

METHODS

Patients received flexible duloxetine doses of 20-120 mg once daily, with dose changes made based on clinical improvement and tolerability. Pharmacokinetic samples were collected across all duloxetine doses, and data were analyzed using population modeling. Primary outcome measures included treatment-emergent adverse events (TEAEs), vital signs, and Columbia-Suicide Severity Rating Scale (C-SSRS).

RESULTS

Of the 72 enrolled patients, 48 (66.7%) completed acute treatment (18 weeks) and 42 (58.3%) completed extended treatment. Most patients (55/72; 76%) required doses ≥ 60 mg once daily to optimize efficacy based on investigator judgment and Clinical Global Impressions-Severity score. Body weight and age did not significantly affect duloxetine pharmacokinetic parameters. Typical duloxetine clearance in pediatric patients was ≈ 42%-60% higher than that in adults. Four patients (5.6%) discontinued due to TEAEs. Many (36/72, 50%) patients experienced potentially clinically significant (PCS) elevations in blood pressure, with most cases (21/36, 58%) being transient. As assessed via C-SSRS, one nonfatal suicidal attempt occurred, two patients (2.8%) experienced worsening of suicidal ideation, and among the 19 patients reporting suicidal ideation at baseline, 17 (90%) reported improvement in suicidal ideation.

CONCLUSION

Results suggested that pediatric patients generally tolerated duloxetine doses of 30 to 120 mg once daily, although transient PCS elevations in blood pressure were observed in many patients. Pharmacokinetic results suggested that adjustment of total daily dose based on body weight or age is not warranted for pediatric patients and different total daily doses may not be warranted for pediatric patients relative to adults.

Exploratory translational modeling approach in drug development to predict human brain pharmacokinetics and pharmacologically relevant clinical doses

The central nervous system (CNS) pharmacokinetics (PK) of drugs that have pharmacological targets in the brain are not often understood during drug development, and this gap in knowledge is a limitation in providing a quantitative framework for translating nonclinical pharmacologic data to the clinical patient population. A focus of translational sciences is to improve the efficiency of clinical trial design via a more judicious selection of clinical doses on the basis of nonclinical data. We hypothesize that this can be achieved for CNS-acting drugs based on knowledge of CNS PK and brain target engagement obtained in nonclinical studies. Translating CNS PK models from rat to human can allow for the prediction of human brain PK and the human dose-brain exposure relationship, which can provide insight on the clinical dose(s) having potential brain activity and target engagement. In this study, we explored the potential utility of this translational approach using rat brain microdialysis and PK modeling techniques to predict human brain extracellular fluid PK of atomoxetine and duloxetine. The results show that this translational approach merits consideration as a means to support the clinical development of CNS-mediated drug candidates by enhancing the ability to predict pharmacologically relevant doses in humans in the absence of or in association with other biomarker approaches.

Duloxetine: clinical pharmacokinetics and drug interactions

Duloxetine, a potent reuptake inhibitor of serotonin (5-HT) and norepinephrine, is effective for the treatment of major depressive disorder, diabetic neuropathic pain, stress urinary incontinence, generalized anxiety disorder and fibromyalgia. Duloxetine achieves a maximum plasma concentration (C(max)) of approximately 47 ng/mL (40 mg twice-daily dosing) to 110 ng/mL (80 mg twice-daily dosing) approximately 6 hours after dosing. The elimination half-life of duloxetine is approximately 10-12 hours and the volume of distribution is approximately 1640 L. The goal of this paper is to provide a review of the literature on intrinsic and extrinsic factors that may impact the pharmacokinetics of duloxetine with a focus on concomitant medications and their clinical implications. Patient demographic characteristics found to influence the pharmacokinetics of duloxetine include sex, smoking status, age, ethnicity, cytochrome P450 (CYP) 2D6 genotype, hepatic function and renal function. Of these, only impaired hepatic function or severely impaired renal function warrant specific warnings or dose recommendations. Pharmacokinetic results from drug interaction studies show that activated charcoal decreases duloxetine exposure, and that CYP1A2 inhibition increases duloxetine exposure to a clinically significant degree. Specifically, following oral administration in the presence of fluvoxamine, the area under the plasma concentration-time curve and C(max) of duloxetine significantly increased by 460% (90% CI 359, 584) and 141% (90% CI 93, 200), respectively. In addition, smoking is associated with a 30% decrease in duloxetine concentration. The exposure of duloxetine with CYP2D6 inhibitors or in CYP2D6 poor metabolizers is increased to a lesser extent than that observed with CYP1A2 inhibition and does not require a dose adjustment. In addition, duloxetine increases the exposure of drugs that are metabolized by CYP2D6, but not CYP1A2. Pharmacodynamic study results indicate that duloxetine may enhance the effects of benzodiazepines, but not alcohol or warfarin. An increase in gastric pH produced by histamine H(2)-receptor antagonists or antacids did not impact the absorption of duloxetine. While duloxetine is generally well tolerated, it is important to be knowledgeable about the potential for pharmacokinetic interactions between duloxetine and drugs that inhibit CYP1A2 or drugs that are metabolized by CYP2D6 enzymes.

Evaluation of duloxetine for chronic pain conditions

Summary Duloxetine hydrochloride (duloxetine) is used as a nonopioid analgesic for the treatment of certain chronic pain conditions. It is a serotonin and norepinephrine reuptake inhibitor and has been approved in the USA for the management of both diabetic peripheral neuropathic pain and fibromyalgia. In addition, based on several studies demonstrating that duloxetine was efficacious in the management of chronic low back pain and chronic pain caused by osteoarthritis, duloxetine was approved for the management of chronic musculoskeletal pain. Effect sizes in studies of each of the aforementioned chronic pain conditions are comparable with other commonly used pain medications. Treatment-emergent adverse events are generally mild to moderate in severity, and tend to occur early and transiently.

Prediction of repeat-dose occupancy from single-dose data: characterisation of the relationship between plasma pharmacokinetics and brain target occupancy

Positron emission tomography (PET) is used in drug development to assist dose selection and to establish the relationship between blood and tissue pharmacokinetics (PKs). We present a new biomathematical approach that allows prediction of repeat-dose (RD) brain target occupancy (TO) using occupancy data obtained after administration of a single dose (SD). A PET study incorporating a sequential adaptive design was conducted in 10 healthy male adults who underwent 4 PET scans with [(11)C]DASB ([(11)C]N,N-dimethyl-2-(2-amino-4-cyanophenylthio) benzylamine): 1 at baseline, 2 after 20 mg SD of the 5-hydroxytryptamine transporter (5-HTT) inhibitor duloxetine, and 1 after 4 days daily administration of 20 mg duloxetine. An adaptive design was used to select optimal times after SD for measurement of occupancy. Both direct and indirect PK/TO models were fitted to the SD data to characterise the model parameters and then applied to a predicted RD duloxetine plasma time course to predict the 5-HTT occupancy after RD. Repeat-dose prediction from the indirect model (OC(50)=2.62±0.93 ng/mL) was significantly better (P<0.05) than that from the direct model (OC(50)=2.29±1.11 ng/mL). This approach increases the value of SD occupancy studies that are performed as part of first time in human drug development programmes by providing an estimate of the dose required to achieve the desired TO at RD.

Effects of varying degrees of renal impairment on the pharmacokinetics of duloxetine: analysis of a single-dose phase I study and pooled steady-state data from phase II/III trials

BACKGROUND

Duloxetine is indicated for patients with a variety of conditions, and some of these patients may have mild to moderate degrees of renal impairment. Renal impairment may affect the pharmacokinetics of a drug by causing changes in absorption, distribution, protein binding, renal excretion or nonrenal clearance. As duloxetine is highly bound to plasma proteins and its metabolites are renally excreted, it is prudent to evaluate the effect of renal insufficiency on exposure to duloxetine and its metabolites in the systemic circulation.

OBJECTIVE

The aim of this study was to evaluate the effects of varying degrees of renal impairment on duloxetine pharmacokinetics in a single-dose phase I study and using pooled steady-state pharmacokinetic data from phase II/III trials.

METHODS

In the phase I study, a single oral dose of duloxetine 60 mg was given to 12 subjects with end-stage renal disease (ESRD) and 12 matched healthy control subjects. In the phase II/III trials (n = 463 patients), duloxetine 20-60 mg was given as once- or twice-daily doses. Duloxetine and metabolite concentrations in plasma were determined using liquid chromatography with tandem mass spectrometry. Noncompartmental methods (phase I: duloxetine and its metabolites) and population modelling methods (phase II/III: duloxetine) were used to analyse the pharmacokinetic data.

RESULTS

The maximum plasma concentration (C(max)) and the area under the plasma concentration-time curve (AUC) of duloxetine were approximately 2-fold higher in subjects with ESRD than in healthy subjects, which appeared to reflect an increase in oral bioavailability. The C(max) and AUC of two major inactive conjugated metabolites were as much as 2- and 9-fold higher, respectively, reflecting reduced renal clearance of these metabolites. Population pharmacokinetic results indicated that mild or moderate renal impairment, assessed by creatinine clearance (CL(CR)) calculated according to the Cockcroft-Gault formula, did not have a statistically significant effect on pharmacokinetic parameters of duloxetine. Values for the apparent total body clearance of duloxetine from plasma after oral administration (CL/F) in subjects with ESRD were similar to CL/F values in patients with normal renal function or with mild or moderate renal impairment.

CONCLUSION

Dose adjustments for duloxetine are not necessary for patients with mild or moderate renal impairment (CL(CR) > or =30 mL/min). For patients with ESRD or severe renal impairment (CL(CR) <30 mL/min), exposures of duloxetine and its metabolites are expected to increase; therefore, duloxetine is not generally recommended for these patients.

Getting the balance right: Established and emerging therapies for major depressive disorders

Major depressive disorder (MDD) is a common and serious illness of our times, associated with monoamine deficiency in the brain. Moreover, increased levels of cortisol, possibly caused by stress, may be related to depression. In the treatment of MDD, the use of older antidepressants such as monoamine oxidase inhibitors and tricyclic antidepressants is decreasing rapidly, mainly due to their adverse effect profiles. In contrast, the use of serotonin reuptake inhibitors and newer antidepressants, which have dual modes of action such as inhibition of the serotonin and noradrenaline or dopamine reuptake, is increasing. Novel antidepressants have additive modes of action such as agomelatine, a potent agonist of melatonin receptors. Drugs in development for treatment of MDD include triple reuptake inhibitors, dual-acting serotonin reuptake inhibitors and histamine antagonists, and many more. Newer antidepressants have similar efficacy and in general good tolerability profiles. Nevertheless, compliance with treatment for MDD is poor and may contribute to treatment failure. Despite the broad spectrum of available antidepressants, there are still at least 30% of depressive patients who do not benefit from treatment. Therefore, new approaches in drug development are necessary and, according to current research developments, the future of antidepressant treatment may be promising.

Duloxetine for the treatment of fibromyalgia

This article presents a brief review of the physiologic abnormalities seen in fibromyalgia, current theories of widespread pain, and treatment options, including emerging therapeutics, with a focus on the use of duloxetine to manage fibromyalgia symptoms. Major clinical trials that examine the efficacy and effectiveness of duloxetine to date are reviewed, and safety issues are discussed.

New and emerging therapeutic agents for the treatment of fibromyalgia: an update

Fibromyalgia (FM) is a chronic widespread pain condition that is estimated to affect 5 million US adults. Several molecular pathophysiologies are thought to contribute to the symptoms of FM, complicating the development of effective clinical management techniques. It is now known that abnormalities in both nociceptive and central pain processing systems are necessary (but perhaps not sufficient) to condition the onset and maintenance of FM, producing associated neuropsychologic symptoms such as pronounced fatigue, sleep abnormalities, cognitive difficulties, stress sensitivity, anxiety, and depression. Current treatment strategies are focused primarily on correcting the pathophysiologic mechanisms underlying these nervous system abnormalities. Clinical studies demonstrate the safety and efficacy of three drugs recently approved for the treatment of FM: pregabalin (an alpha-2-delta ligand), and duloxetine and milnacipran (serotonin/norepinephrine reuptake inhibitors). This review describes these pharmaceuticals in detail and discusses their current roles in FM management.

Duloxetine 60 mg/day for the prevention of depressive recurrences: post hoc analyses from a recurrence prevention study

OBJECTIVE

To assess the efficacy of duloxetine 60 mg/day in the prevention of depressive recurrence in patients with major depressive disorder (MDD).

METHODS

Patients having at least three episodes of MDD in the past 5 years received open-label (OL) duloxetine 60-120 mg/day for up to 34 weeks. Patients meeting response criteria were then randomised to either duloxetine or placebo for up to 52 weeks of double-blind maintenance treatment. Only patients taking duloxetine 60 mg/day during the OL phase, and randomised to either duloxetine (remained on 60 mg/day dose) or placebo, were included in this post hoc analysis. The primary outcome measure was time to recurrence of a major depressive episode. The 17-item Hamilton Rating Scale for Depression (HAMD(17)) was used to evaluate depressive symptomatology. Global and physical functioning and pain were also assessed. Safety and tolerability were assessed via analysis of treatment-emergent adverse events (TEAEs), vital signs and weight.

RESULTS

A total of 124 patients were randomised to duloxetine 60 mg/day (n = 64) or placebo (n = 60). Time to depressive recurrence was significantly longer in duloxetine-treated patients compared with placebo-treated patients (p = 0.001). During the double-blind maintenance phase, 31.7% of placebo-treated patients experienced a depressive recurrence compared with 12.5% of duloxetine-treated patients (p = 0.004). The HAMD(17) total score and most of its subscales as well as the Clinical Global Impression of Severity (CGI-S), significantly worsened in the placebo group compared with the duloxetine 60 mg/day group. There were no significant differences between treatment groups in TEAEs, discontinuations because of adverse events, vital signs or weight.

CONCLUSIONS

Treatment with duloxetine 60 mg/day was associated with a longer time to depressive recurrence and a significantly lower recurrence rate compared with placebo.