Duloxetine pharmacokinetics in cirrhotics compared with healthy subjects

High-content imaging of human hepatic spheroids for researching the mechanism of duloxetine-induced hepatotoxicity

Duloxetine (DLX) has been approved for the successful treatment of psychiatric diseases, including major depressive disorder, diabetic neuropathy, fibromyalgia and generalized anxiety disorder. However, since the usage of DLX carries a manufacturer warning of hepatotoxicity given its implication in numerous cases of drug-induced liver injuries (DILI), it is not recommended for patients with chronic liver diseases. In our previous study, we developed an enhanced human-simulated hepatic spheroid (EHS) imaging model system for performing drug hepatotoxicity evaluation using the human hepatoma cell line HepaRG and the support of a pulverized liver biomatrix scaffold, which demonstrated much improved hepatic-specific functions. In the current study, we were able to use this robust model to demonstrate that the DLX-DILI is a human CYP450 specific, metabolism-dependent, oxidative stress triggered complex hepatic injury. High-content imaging analysis (HCA) of organoids exposed to DLX showed that the potential toxicophore, naphthyl ring in DLX initiated oxidative stress which ultimately led to mitochondrial dysfunction in the hepatic organoids, and vice versa. Furthermore, DLX-induced hepatic steatosis and cholestasis was also detected in the exposed EHSs. We also discovered that a novel compound S-071031B, which replaced DLX's naphthyl ring with benzodioxole, showed dramatically lower hepatotoxicities through reducing oxidative stress. Thus, we conclusively present the human-relevant EHS model as an ideal, highly competent system for evaluating DLX induced hepatotoxicity and exploring related mechanisms in vitro. Moreover, HCA use on functional hepatic organoids has promising application prospects for guiding compound structural modifications and optimization in order to improve drug development by reducing hepatotoxicity.

Sources of Interindividual Variability

The efficacy, safety, and tolerability of drugs are dependent on numerous factors that influence their disposition. A dose that is efficacious and safe for one individual may result in sub-therapeutic or toxic blood concentrations in others. A significant source of this variability in drug response is drug metabolism, where differences in presystemic and systemic biotransformation efficiency result in variable degrees of systemic exposure (e.g., AUC, C_max, and/or C_min) following administration of a fixed dose.Interindividual differences in drug biotransformation have been studied extensively. It is recognized that both intrinsic factors (e.g., genetics, age, sex, and disease states) and extrinsic factors (e.g., diet , chemical exposures from the environment, and the microbiome) play a significant role. For drug-metabolizing enzymes, genetic variation can result in the complete absence or enhanced expression of a functional enzyme. In addition, upregulation and downregulation of gene expression, in response to an altered cellular environment, can achieve the same range of metabolic function (phenotype), but often in a less predictable and time-dependent manner. Understanding the mechanistic basis for variability in drug disposition and response is essential if we are to move beyond the era of empirical, trial-and-error dose selection and into an age of personalized medicine that will improve outcomes in maintaining health and treating disease.

Antidepressant-lnduced Liver Injury

Objective:

To review principles of drug-induced liver injury (DILI), summarize characteristics of antidepressant-mediated liver Injury, and provide recommendations for monitoring and management.

Data Sources:

A search relating to antidepressant-induced liver injury was performed using MEDLINE (1966–March 2007). Search terms included antidepressant, cholestasis, hepatotoxicity, jaundice, liver injury, toxic hepatitis, and transaminases. Reference citations not Identified in the initial database search were also utilized.

Study Selection and Data Extraction:

All English-language case reports, letters, and review articles identified from the data sources were used. Case reports and letters relating to hepatotoxicity from antidepressant overdose were excluded.

Data Synthesis:

Antidepressant-induced liver injury described in published cases were of the idiopathic type and, by definition, cannot be predicted based on dose or specific risk factors. Paroxetine had the largest number of cases within the selective serotonin-reuptake inhibitor class. Nefazodone, a serotonin–norepinephrine reuptake inhibitor, appeared to have the most serious cases and is the only antidepressant agent that carries a Food and Drug Administration Black Box Warning regarding hepatotoxiciiy. The tricyclic antidepressants and monoamine oxidase Inhibitors are capable of producing hepatotoxicity, but fewer cases with these agents have been reported in the past 15 years, possibly due to a decline in their use. Causality has not been well established in all reports due to the concurrent use of other drugs and/or underlying liver disease.

Conclusions:

Most antidepressant agents have the potential to produce idiopathic liver injury. There is no way to prevent idiopathic DILI, but the severity of the reaction may be minimized with prompt recognition and early withdrawal of the agent. The clinician must be careful to provide ongoing therapy of the underlying depressive disorder and be aware of possible drug discontinuation syndromes should potential hepatotoxicity be suspected.

A Prediction Model of Drug Exposure in Cirrhotic Patients According to Child-Pugh Classification

BACKGROUND AND OBJECTIVE

Prediction of drug clearance in liver cirrhosis patients is currently based on in vitro-in vivo extrapolation and physiologically-based pharmacokinetic models. No static model for this purpose has been described. The objectives of this study were to (1) derive a static model for predicting drug exposure in cirrhotic patients, and (2) to evaluate the model on a large set of published data.

METHODS

The impact of cirrhosis was characterized by the ratio of the total and unbound drug area under the concentration-time curve (AUC) in cirrhotic patients to the AUC measured in healthy subjects These ratios were predicted for Child-Pugh classes A, B, and C. The AUC ratios observed in published data were compared with AUC ratios predicted by the model.

RESULTS

Among 171 drugs examined, 83 published AUC ratios for 45 drugs in cirrhotic patients were available for analysis. The mean ± standard deviation relative prediction error for the total and unbound AUC ratios was 0.22 ± 0.58 and 0.24 ± 0.56, respectively. There were four outliers among the 83 predicted values. Simulations showed that the prediction error was negligible provided that the hepatic extraction coefficient was less than 0.8.

CONCLUSIONS

For mild and moderate cirrhosis (classes A and B), the predicted unbound AUC ratio is typically approximately 2 and 3.5, respectively, for most drugs. In the absence of data in cirrhotic patients, the drug dose might be empirically reduced by these factors. In severe cirrhosis (class C), our model may help clinicians to adjust their prescriptions.

Pharmacokinetics of antidepressants in patients with hepatic impairment

Appropriate use of antidepressant in patients with hepatic impairment requires careful consideration of how the hepatic illness may affect pharmacokinetics. This review aims to analyze pharmacokinetic profile, plasma level variations so as the metabolism of several antidepressants relating to their use in patients with an hepatic impairment. Due to the lack of data regarding hepatic impairment itself, the review is focused mainly on studies investigating pharmacokinetics in hepatic cirrhosis or alcohol-related conditions. More data on reduced hepatic metabolism can be extrapolated by drug studies conducted in elderly populations. Dose adjustment of antidepressants in these patients is important as most of these drugs are predominantly metabolized by the liver and many of them are associated with dose-dependent adverse reactions. As no surrogate parameter is available to predict hepatic metabolism of drugs, dose adjustment according to pharmacokinetic properties of the drugs is proposed. There is a need for a more balanced assessment of the benefits and risks associated with antidepressants use in patients with hepatic impairment, particularly considering pharmacokinetic profile of the drugs to ensure that patients, who would truly benefit from these agents, are not denied appropriate treatment. In conclusion, kinetic studies for centrally acting drugs including antidepressants with predominant hepatic metabolism should be carried out in patients with liver disease to allow precise dose recommendations for enhanced patient safety.

Determination of duloxetine in human plasma with proven lack of influence of the major metabolite 4-hydroxyduloxetine

OBJECTIVES

Minimizing the impact of major or unstable metabolites on the determination of a drug substance represents a leading task in the development and validation of bioanalytical methods. "Incurred samples reanalysis" provides relevant information too late; therefore, carefully selected tests on known metabolites should precede the pharmacokinetic studies.

DESIGN AND METHODS

This paper describes a simple and rapid HPLC-UV method for the determination of duloxetine, a potent serotonin and norepinephrine reuptake inhibitor, in the presence of its major metabolite, i.e. 4-hydroxyduloxetine glucuronide. Analyte and fluoxetine (internal standard) were extracted from human plasma by liquid-liquid extraction.

RESULTS

No influence of the major metabolite was observed on the reliability of the new method. There was also lack of evidence of the major metabolite back-conversion to the parent drug substance. The validation demonstrated high precision of the new method. All validation parameters met the acceptance criteria of bioanalytical regulations.

CONCLUSIONS

The new method enabled the reliable determination of duloxetine in the presence of its major metabolite in the human plasma. The method might be applied to pharmacokinetic studies in humans, including bioequivalence and therapeutic drug monitoring.

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.

A rapid and sensitive liquid chromatography-tandem mass spectrometric assay for duloxetine in human plasma: Its pharmacokinetic application

This paper describes a simple, rapid and sensitive liquid chromatography–tandem mass spectrometry assay for the determination of duloxetine in human plasma. A duloxetine stable labeled isotope (duloxetine d₅) was used as an internal standard. Analyte and the internal standard were extracted from 100 μL of human plasma via solid phase extraction technique using Oasis HLB cartridges. The chromatographic separation was achieved on a C₁₈ column by using a mixture of acetonitrile–5 mM ammonium acetate buffer (83:17, v/v) as the mobile phase at a flow rate of 0.9 mL/min. The calibration curve obtained was linear (r²≥0.99) over the concentration range of 0.05–101 ng/mL. Multiple-reaction monitoring mode (MRM) was used for quantification of ion transitions at m/z 298.3/154.1 and 303.3/159.1 for the drug and the internal standard, respectively. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. A run time of 2.5 min for each sample made it possible to analyze more than 300 plasma samples per day. The proposed method was found to be applicable to clinical studies.

Analgesics in patients with hepatic impairment: pharmacology and clinical implications

The physiological changes that accompany hepatic impairment alter drug disposition. Porto-systemic shunting might decrease the first-pass metabolism of a drug and lead to increased oral bioavailability of highly extracted drugs. Distribution can also be altered as a result of impaired production of drug-binding proteins or changes in body composition. Furthermore, the activity and capacity of hepatic drug metabolizing enzymes might be affected to various degrees in patients with chronic liver disease. These changes would result in increased concentrations and reduced plasma clearance of drugs, which is often difficult to predict. The pharmacology of analgesics is also altered in liver disease. Pain management in hepatically impaired patients is challenging owing to a lack of evidence-based guidelines for the use of analgesics in this population. Complications such as bleeding due to antiplatelet activity, gastrointestinal irritation, and renal failure are more likely to occur with nonsteroidal anti-inflammatory drugs in patients with severe hepatic impairment. Thus, this analgesic class should be avoided in this population. The pharmacokinetic parameters of paracetamol (acetaminophen) are altered in patients with severe liver disease, but the short-term use of this drug at reduced doses (2 grams daily) appears to be safe in patients with non-alcoholic liver disease. The disposition of a large number of opioid drugs is affected in the presence of hepatic impairment. Certain opioids such as codeine or tramadol, for instance, rely on hepatic biotransformation to active metabolites. A possible reduction of their analgesic effect would be the expected pharmacodynamic consequence of hepatic impairment. Some opioids, such as pethidine (meperidine), have toxic metabolites. The slower elimination of these metabolites can result in an increased risk of toxicity in patients with liver disease, and these drugs should be avoided in this population. The drug clearance of a number of opioids, such as morphine, oxycodone, tramadol and alfentanil, might be decreased in moderate or severe hepatic impairment. For the highly excreted morphine, hydromorphone and oxycodone, an important increase in bioavailability occurs after oral administration in patients with hepatic impairment. Lower doses and/or longer administration intervals should be used when these opioids are administered to patients with liver disease to avoid the risk of accumulation and the potential increase of adverse effects. Finally, the pharmacokinetics of phenylpiperidine opioids such as fentanyl, sufentanil and remifentanil appear to be unaffected in hepatic disease. All opioid drugs can precipitate or aggravate hepatic encephalopathy in patients with severe liver disease, thus requiring cautious use and careful monitoring.

Duloxetine in the treatment of stress urinary incontinence

This manuscript reviews the pharmacodynamics and pharmacokinetics of duloxetine and its efficacy and safety in women with stress urinary incontinence. Duloxetine is a selective inhibitor of neuronal serotonin and norepinephrine uptake which increases urethral striated muscle activity and bladder capacity. Duloxetine is readily absorbed and extensively metabolized; cytochrome P450 1A2 (CYP1A2) inhibiting drugs can markedly increase duloxetine exposure. The clinical efficacy of duloxetine has consistently been demonstrated in several randomized, double-blind studies in women with moderate-to-severe stress urinary incontinence, but the additional benefit relative to placebo was moderate. Duloxetine treatment is frequently associated with adverse events such as nausea, dry mouth, fatigue, insomnia and constipation, but serious adverse events are rare. Therefore, duloxetine appears suitable for the treatment of stress urinary incontinence.

Duloxetine in the acute and continuation treatment of major depressive disorder

Duloxetine is a serotonin-noradrenaline reuptake inhibitor with indications for use in the short term, continuation and maintenance treatment of major depression. Although clinicians currently have access to a range of medications for the treatment of depression, a significant number of patients fail to respond or remit from their illness despite adequate trials of treatment with multiple agents. A developing concept is that antidepressant strategies that combine multiple mechanisms of action may have advantages over agents with single mechanisms (i.e., selective serotonin reuptake inhibitors). As a dual-acting agent, duloxetine offers the promise of advantages in terms of efficacy over selective serotonin reuptake inhibitors while retaining a favorable safety and tolerability profile in comparison to older agents. Likewise, duloxetine is of interest in the treatment of certain conditions commonly seen in conjunction with major depression, particularly anxiety and pain, both of which may respond more favorably to agents that act on both serotonin and noradrenaline neurotransmitter systems.

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.

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.

Pharmacological and clinical profile of newer antidepressants: implications for the treatment of elderly patients

The pharmacological treatment of older adults with major depressive disorder presents a variety of challenges, including a relative lack of high quality studies designed to measure the efficacy and safety of antidepressants specific to this patient population. Gaining a clear understanding of how to use antidepressants in elderly patients with depression, especially new and widely used agents, would provide valuable insight to clinicians. The purpose of the current article is to review the pharmacology, efficacy and safety of newer antidepressants (i.e. escitalopram, duloxetine and desvenlafaxine) in the treatment of late-life depression. To accomplish this goal, a MEDLINE and PubMed search (1966 - February 2010) was conducted for relevant articles. Animal and human studies have clearly demonstrated the effects of desvenlafaxine, duloxetine and escitalopram on monoamine reuptake transporters. The serotonergic and noradrenergic actions of desvenlafaxine and duloxetine may provide for a faster onset of antidepressant activity in the elderly, but more definitive data are needed and the clinical effects of the possible faster onset of action need to be elucidated. Duloxetine and escitalopram are extensively metabolized via cytochrome P450 (CYP) enzymes and the decreased hepatic metabolism present in many older adults should be taken into account when prescribing these medications. Duloxetine possesses the greatest likelihood of producing clinically relevant drug-drug interactions because of its inhibition of CYP2D6. All three agents must also be used cautiously in older adults with poor renal function. In terms of clinical efficacy, 14 prospective published trials involving escitalopram (n = 8) and duloxetine (n = 6) in the treatment of older adults with major depressive disorder were identified. No such studies involving desvenlafaxine were found. Of the five randomized, double-blind, controlled trials, 46% and 37% of antidepressant-treated patients were considered responders and remitters, respectively. In contrast to escitalopram, duloxetine-treated patients experienced improvements in depressive symptoms that more consistently differentiated themselves from the symptoms of placebo-treated patients. Escitalopram and duloxetine were generally well tolerated, but 5-20% and 10-27% of patients, respectively, dropped out because of medication-related adverse effects. Adverse effects experienced by older adults were generally similar to those experienced by younger adults, although indirect comparisons suggest that older adults are more likely to experience dry mouth and constipation with duloxetine and escitalopram, while orthostasis may be more common in older adults prescribed desvenlafaxine. Overall, duloxetine and escitalopram represent modestly effective treatments for late-life depression that are generally well tolerated but do produce a variety of adverse effects. Conclusions regarding desvenlafaxine cannot be made at this time because of a lack of geriatric-specific data.

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.

Clinical outcome and tolerability of duloxetine in the treatment of major depressive disorder: a 12-week study with plasma levels

Duloxetine (DLX) is a dual serotonin and norepinephrine reuptake inhibitor that has been recently approved for the treatment of major depressive disorder (MDD). However, little is known about the relationship between DLX plasma levels and clinical response. The aims of this open-label study were 1) to assess clinical outcome and tolerability of DLX by means of clinician and patient assessments and 2) to evaluate the value of plasma DLX levels as predictors of clinical response and tolerability. This was a naturalistic, open-label study of 45 outpatients affected with MDD (16 men and 29 women), who received DLX at doses of 30-120 mg/day and were evaluated at baseline (T0) and after 2, 4 and 12 weeks (T1-3). The assessments included the Hamilton Rating Scales for Depression (HRSD) and Anxiety (HRSA), Clinical Global Impression-Severity (CGI-S), Beck's Depression Inventory (BDI) and a mood visual analogue scale (VAS). Compared with T0, there were significant improvements in HRSD at T1, T2 and T3 (P < 0.001), in HRSA, CGI-S and the self-administered BDI at T2 and T3 (P < 0.001), and in the VAS scores shown at T3 (P = 0.01). DLX treatment was safe and well tolerated. Plasma DLX levels at T2 ranged from 5 to 135 ng/mL (mean +/- SD = 53.56 +/- 39.45) and correlated almost significantly with the DLX dose (r = 0.35; P = 0.069). There was a significant curvilinear quadratic relationship between the improvement of HRSA scores and plasma DLX levels (R(2) = 0.27; P = 0.02). The incidence of anxiety or irritability was associated with the highest plasma levels. Our findings suggest that monitoring plasma DLX levels may be helpful in predicting better treatment responses and tolerability. The present data seem to suggest an optimal anxiolytic efficacy of DLX at intermediate plasma levels.

Duloxetine: in patients with fibromyalgia

Duloxetine is a selective serotonin and norepinephrine reuptake inhibitor available in delayed-release capsules for oral use. Duloxetine 60 mg/day, compared with placebo, was associated with a greater reduction from baseline in the Brief Pain Inventory (BPI) average pain severity score, a greater improvement in the patient-rated global impression of improvement (PGI-I) scale in patients with fibromyalgia, with or without major depressive disorder, in two 12- and 15-week phase III studies. In a 27-week, phase III trial, there was no significant difference between duloxetine (60 or 120 mg/day) and placebo for the least squares mean change from baseline to endpoint in BPI average pain scores and the PGI-I score. The significant improvements in efficacy that occurred in patients with fibromyalgia during 8 weeks of open-label treatment with duloxetine 60 mg/day were generally maintained during 52 weeks of subsequent blinded treatment at the same dosage in a phase III trial. Nonresponders during treatment with open-label duloxetine 60 mg/day, demonstrated no increased ability to respond if the duloxetine dosage was up-titrated to 120 mg/day than those who remained on the same dosage during the subsequent 52-week, double-blind phase. Duloxetine was generally well tolerated in studies of up to 1 year in duration, with nausea being the most frequent adverse event and main cause for discontinuing therapy.

Duloxetine: a review of its use in the treatment of generalized anxiety disorder

Duloxetine (Cymbalta(R)) is a potent serotonin and noradrenaline (norepinephrine) reuptake inhibitor (SNRI) in the CNS. It is indicated for the treatment of generalized anxiety disorder (GAD) as well as other indications. In patients with GAD of at least moderate severity, oral duloxetine 60-120 mg once daily was effective with regard to improvement from baseline in assessments of anxiety and functional impairment, and numerous other clinical endpoints. Longer-term duloxetine 60-120 mg once daily also demonstrated efficacy in preventing or delaying relapse in responders among patients with GAD. In addition, duloxetine was generally well tolerated, with most adverse events being of mild to moderate severity in patients with GAD in short- and longer-term trials. Additional comparative and pharmacoeconomic studies are required to position duloxetine among other selective serotonin reuptake inhibitors and SNRIs. However, available clinical data, and current treatment guidelines, indicate that duloxetine is an effective first-line treatment option for the management of GAD. Duloxetine is a potent and selective inhibitor of serotonin and noradrenaline transporters, and a weak inhibitor of dopamine transporters. It has a low affinity for neuronal receptors, such as alpha(1)- and alpha(2)-adrenergic, dopamine D(2), histamine H(1), muscarinic, opioid and serotonin receptors, as well as ion channel binding sites and other neurotransmitter transporters, such as choline and GABA transporters. It does not inhibit monoamine oxidase types A or B. The pharmacokinetics of duloxetine in healthy volunteers were dose proportional over the range of 40-120 mg once daily. Steady state was typically reached by day 3 of administration. Duloxetine may be administered without regard to food or time of day. Duloxetine is highly protein bound and is widely distributed throughout tissues. It is rapidly and extensively metabolized in the liver by cytochrome P450 (CYP) 1A2 and 2D6, and its numerous metabolites, which are inactive, are mainly excreted in the urine. The mean elimination half-life of duloxetine is approximately 12 hours. Duloxetine is a substrate for CYP1A2 and CYP2D6 and a moderate inhibitor of CYP2D6. Concomitant use of duloxetine and potent CYP1A2 inhibitors should be avoided and duloxetine should be used with caution in patients receiving drugs that are extensively metabolized by CYP2D6, particularly those with a narrow therapeutic index. Duloxetine was effective in the short-term treatment of patients with primary GAD of at least moderate severity. In four randomized, double-blind, placebo-controlled, multicentre, phase III trials, duloxetine 60-120 mg once daily for 9 or 10 weeks was significantly more effective than placebo with regard to the primary endpoint of mean change in Hamilton Anxiety Rating Scale (HAM-A) total score from baseline to study endpoint. In addition, all other endpoints were generally improved from baseline to a greater extent with duloxetine 60-120 mg once daily than with placebo. Duloxetine also improved patient role functioning (assessed using Sheehan Disability Scale global impairment functioning scores), health-related quality of life and patient well-being compared with placebo. Duloxetine was effective in patients with GAD who were aged >/=65 years. Pooled results of data from the two short-term efficacy trials that also included an active comparator arm showed that the mean change in HAM-A scores with duloxetine relative to placebo were of the same magnitude as those with venlafaxine extended release versus placebo. Duloxetine 60-120 mg once daily was also more effective than placebo in preventing or delaying relapse in responders to duloxetine in a longer-term study. In this study, patients with GAD received duloxetine during a 26-week, open-label, acute treatment phase and responders were then randomized to continue on duloxetine or receive placebo during a 26-week, double-blind, continuation phase. Time to relapse was significantly longer in duloxetine recipients than in placebo recipients. In addition, significantly fewer duloxetine recipients than placebo recipients relapsed during the double-blind phase of the trial and more duloxetine recipients achieved remission. Short- (9-10 weeks) and longer-term (52 weeks) treatment with duloxetine 60-120 mg once daily was generally well tolerated in patients with GAD, with the majority of adverse events being of mild to moderate severity. Nausea, dry mouth, headache, constipation, dizziness and fatigue were among the most common treatment-emergent adverse events. The adverse event profile of duloxetine did not differ with dose or treatment duration. Significantly more patients receiving short-term duloxetine than placebo discontinued treatment because of an adverse event, with nausea being the only event that resulted in significantly more treatment discontinuations in duloxetine recipients than in placebo recipients. Serious adverse events were uncommon with both short- and longer-term duloxetine treatment. Two episodes of attempted suicide and one episode of completed suicide occurred in duloxetine recipients during the 24-week open-label phase of a longer-term trial. No deaths or suicides were reported in any of the short-term trials. Discontinuation-emergent adverse events, most commonly nausea and dizziness, occurred in up to one-third of duloxetine recipients in the short-term trials.

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

OBJECTIVES

The objectives of this analysis were to characterize the pharmacokinetics of duloxetine at steady state in patients, estimate the variability, identify significant covariates that may influence duloxetine pharmacokinetics and provide appropriate dosing recommendations for patients on duloxetine treatment.

METHODS

The pharmacokinetic meta-analysis dataset was created from one open-label clinical study and four double-blind, placebo-controlled clinical studies. Duloxetine concentrations (N = 2002) were obtained from 594 patients diagnosed with major depressive disorder (n = 223), diabetic peripheral neuropathic pain (n = 112), stress urinary incontinence (n = 128) and fibromyalgia (n = 131). Patients were given 20-60 mg/day of oral duloxetine once or twice daily (the highest dose studied was 120 mg/day). A population pharmacokinetic model was developed using a nonlinear mixed-effects modelling method. Covariates including bodyweight, age, sex, ethnicity, smoking status, disease condition, dose, dosing regimen and creatinine clearance were tested for their influence on duloxetine pharmacokinetics. The final model was used to predict steady-state duloxetine concentration-time profiles in various patient subgroups.

RESULTS

Duloxetine pharmacokinetics in patients were described by a one-compartmental pharmacokinetic model. The interpatient variability in apparent oral clearance (CL/F) was 59% and the interpatient variability in the apparent volume of distribution after oral administration (V(d)/F) was 97%. The residual error was 31%. Sex, smoking status, age and dose had a statistically significant effect on CL/F, whereas the V(d)/F was influenced by ethnicity. CL/F was 40% lower in females than in males and 30% lower in nonsmokers than in smokers. CL/F decreased with increasing dose and age. The V(d)/F in Hispanic patients was twice that of non-Hispanic patients. Simulations showed a considerable overlap in duloxetine exposure between the identified patient subgroups.

CONCLUSION

Given the clinically insignificant change in the magnitude of duloxetine steady-state exposure and the considerable overlap in duloxetine exposure between the patient subgroups, specific dose recommendations based on sex, smoking status, age, dose and ethnicity are not warranted.

Duloxetine in the treatment of generalized anxiety disorder

Duloxetine, a medication with effects on both serotonin and noradrenaline transporter molecules, has recently been approved for the treatment of generalized anxiety disorder. The evidence for its efficacy lies in a limited number of double blind, placebo controlled comparisons. Statistically significant improvements in the Hamilton Anxiety Rating Scale from baseline were demonstrated in all studies at doses of 60 to 120 mg per day. The significance of such changes in terms of clinical improvements compared to placebo is less certain, particularly when the effect size of the change is calculated. In comparative trials with venlafaxine, duloxetine was as effective in providing relief of anxiety symptoms. In addition to improvements in clinical symptoms duloxetine has also been associated with restitution of role function as measured by disability scales. Duloxetine use is associated with nausea, dizziness, dry mouth, constipation, insomnia, somnolence, hyperhidrosis, decreased libido and vomiting. These treatment emergent side effects were generally of mild to moderate severity and were tolerated over time. Using a tapered withdrawal schedule over two weeks in the clinical trials, duloxetine was associated with only a mild withdrawal syndrome in up to about 30% of patients compared to about 17% in placebo treated patients. Duloxetine in doses of up to 200 mg twice daily did not prolong the QTc interval in healthy volunteers. Like other agents with dual neurotransmitter actions duloxetine reduces the symptoms of generalized anxiety disorder in short term treatments. Further evidence for its efficacy and safety in long term treatment is required.

The hepatic safety profile of duloxetine: a review

BACKGROUND

Hepatotoxicity related to the use of duloxetine resulted in rewording of the US product insert.

OBJECTIVE

To characterize the hepatic safety profile of duloxetine.

METHODS

We conducted a PubMed search of all English-language articles published between January 1990 and December 2007 and contacted the manufacturer (Eli Lilly, Inc.).

RESULTS

Elevations of alanine aminotransferase to three times the upper limit of normal occurs in 0.9-1.7% of duloxetine-treated patients versus 0.0-0.3% of placebo-treated patients. Hepatocellular, cholestatic and mixed hepatocellular-cholestatic forms of hepatic injury have been described.

CONCLUSION

Duloxetine does not appear to pose a greater hazard for hepatic toxicity when compared to other conventional antidepressants. Systematic monitoring of liver aminotransferases does not appear to be warranted with routine duloxetine use.

In vitro and in vivo evaluations of cytochrome P450 1A2 interactions with duloxetine

OBJECTIVE

To determine whether duloxetine is a substrate, inhibitor or inducer of cytochrome P450 (CYP) 1A2 enzyme, using in vitro and in vivo studies in humans.

METHODS

Human liver microsomes or cells with expressed CYP enzymes and specific CYP inhibitors were used to identify which CYP enzymes catalyse the initial oxidation steps in the metabolism of duloxetine. The potential of duloxetine to inhibit CYP1A2 activity was determined using incubations with human liver microsomes and phenacetin, the CYP1A2 substrate. The potential for duloxetine to induce CYP1A2 activity was determined using human primary hepatocytes treated with duloxetine for 72 hours. Studies in humans were conducted using fluvoxamine, a potent CYP1A2 inhibitor, and theophylline, a CYP1A2 substrate, as probes. The subjects were healthy men and women aged 18-65 years. Single-dose duloxetine was administered either intravenously as a 10-mg infusion over 30 minutes or orally as a 60-mg dose in the presence or absence of steady-state fluvoxamine (100 mg orally once daily). Single-dose theophylline was given as 30-minute intravenous infusions of aminophylline 250 mg in the presence or absence of steady-state duloxetine (60 mg orally twice daily). Plasma concentrations of duloxetine, its metabolites and theophylline were determined using liquid chromatography with tandem mass spectrometry. Pharmacokinetic parameters were estimated using noncompartmental methods and evaluated using mixed-effects ANOVA. Safety measurements included vital signs, clinical laboratory tests, a physical examination, ECG readings and adverse event reports.

RESULTS

The in vitro results indicated that duloxetine is metabolized by CYP1A2; however, duloxetine was predicted not to be an inhibitor or inducer of CYP1A2 in humans. Following oral administration in the presence of fluvoxamine, the duloxetine area under the plasma concentration-time curve from time zero to infinity (AUC(infinity)) and the maximum plasma drug concentration (C(max)) significantly increased by 460% (90% CI 359, 584) and 141% (90% CI 93, 200), respectively. In the presence of fluvoxamine, the oral bioavailability of duloxetine increased from 42.8% to 81.9%. In the presence of duloxetine, the theophylline AUC(infinity) and C(max) increased by only 13% (90% CI 7, 18) and 7% (90% CI 2, 14), respectively. Coadministration of duloxetine with fluvoxamine or theophylline did not result in any clinically important safety concerns, and these combinations were generally well tolerated.

CONCLUSION

Duloxetine is metabolized primarily by CYP1A2; therefore, coadministration of duloxetine with potent CYP1A2 inhibitors should be avoided. Duloxetine does not seem to be a clinically significant inhibitor or inducer of CYP1A2; therefore, dose adjustment of CYP1A2 substrates may not be necessary when they are coadministered with duloxetine.

Duloxetine: a review of its use in the treatment of major depressive disorder

Duloxetine (Cymbalta) is an orally administered, selective serotonin and noradrenaline reuptake inhibitor (SNRI) that has been approved for the treatment of major depressive disorder (MDD). Based on a considerable body of evidence, duloxetine at dosages ranging from 40 to 120 mg/day was effective in the short- and long-term treatment of MDD. Significant improvements versus placebo in core emotional symptoms as well as painful physical symptoms associated with depression, were seen in most, but not all, appropriately designed studies; results of meta-analyses suggested that improvements in these efficacy measures were apparent after 1-2 weeks' treatment with the highest recommended dosage of 60 mg once daily. Short-term (< or =15 weeks) administration of duloxetine at fixed or flexible dosages between 60 and 120 mg/day was noninferior to paroxetine 20 mg once daily, noninferior or inferior to escitalopram 10-20mg once daily, and had a similar global benefit-risk (GBR) profile to that of venlafaxine extended-release (XR) 150-225 mg/day in the treatment of MDD. Longer-term (6-8 months) treatment with duloxetine was similar in efficacy to paroxetine and escitalopram. Duloxetine is generally well tolerated, although it may be appropriate to avoid initiating treatment with the 60 mg/day dosage, as this has been associated with a higher discontinuation rate due to adverse events in some (but not all) comparative studies with escitalopram and venlafaxine XR. Definitive comparisons are awaited, although duloxetine seemingly provides a useful alternative to SSRIs and other SNRIs for the treatment of MDD. It also appears to be an attractive option for MDD patients presenting with painful physical symptoms.

QT effects of duloxetine at supratherapeutic doses: a placebo and positive controlled study

BACKGROUND

The electrophysiological effects of duloxetine at supratherapeutic exposures were evaluated to ensure compliance with regulatory criteria and to assess the QT prolongation potential.

METHODS

Electrocardiograms were collected in a multicenter, double-blind, randomized, placebo-controlled, crossover study that enrolled 117 healthy female subjects aged 19 to 74 years. Duloxetine dosages escalated from 60 mg twice daily to 200 mg twice daily; a single moxifloxacin 400 mg dose was used as a positive control. Data were analyzed using 3 QT interval correction methods: mixed-effect analysis of covariance model with RR interval change from baseline as the covariate, the QT Fridericia's correction method, and the individual QT correction method. Concentrations of duloxetine and its 2 major metabolites were measured.

RESULTS

Compared with placebo, the mean change from baseline in QTc decreased with duloxetine 200 mg twice daily. The upper limits of the 2-sided 90% confidence intervals for duloxetine vs. placebo were <0 msec at each time point by any correction method. No subject had absolute QT Fridericia's correction values >445 msec with duloxetine, and the change in QT Fridericia's correction from baseline with duloxetine did not exceed 36 msec. No relationship was detected between QTc change and plasma concentrations of duloxetine or its metabolites even though average duloxetine concentrations ranged to more than 5 times those achieved at therapeutic doses. Moxifloxacin significantly prolonged QTc at all time points, regardless of correction method.

CONCLUSIONS

Duloxetine does not affect ventricular repolarization as assessed by both mean changes and outliers in QT corrected by any method.

Duloxetine in the treatment of major depressive disorder

Since depression impacts all body systems, antidepressant treatments should relieve both the emotional and physical symptoms of depression. Duloxetine demonstrated antidepressant efficacy at a dose of 60 mg qd in two placebo-controlled, randomized, double-blind studies and significantly improved remission rates compared with placebo. Duloxetine-treated patients had significant reduction in severity of the symptoms of depression as assessed by the HAM-D(17), anxious symptoms as measured by the HAM-A and quality of life measures compared to placebo. Duloxetine also improved somatic symptoms, particularly painful symptoms which may have contributed to significantly improved remission rates compared to placebo. Approximately 10% of the 1139 patients with major depressive disorder in placebo-controlled trials discontinued treatment due to an adverse event, compared to 4% of the 777 patients receiving placebo. In addition to nausea (1.4% incidence), which was the most common reason for discontinuation, dizziness, somnolence, and fatigue were the most common AEs reported as reasons for discontinuation and all were considered drug-related. Duloxetine treatment lacks effects on ECG, increases heart rate, and has little effect on blood pressure or weight.

Development and validation of a liquid chromatography-tandem mass spectrometric method for the determination of the major metabolites of duloxetine in human plasma

A sensitive bioanalytical method for the measurement of two major circulating metabolites of duloxetine [4-hydroxy duloxetine glucuronide (LY550408) and 5-hydroxy-6-methoxy duloxetine sulfate (LY581920)] in plasma is reported. This method produced acceptable precision and accuracy over the validation range of 1-1000 ng/mL. Several issues had to be addressed in order to develop an LC/MS/MS assay for these metabolites. First, 4-hydroxy duloxetine glucuronide required chromatographic resolution from the 5-, and 6-hydroxy duloxetine glucuronide isomers. Second, the glucuronide conjugate is readily ionized under positive ESI conditions, while the sulfate conjugate required negative ESI conditions to obtain adequate sensitivity. Finally, the chromatographic conditions needed to separate the glucuronide isomers were not suitable for the analysis of the sulfate conjugate. The present method addressed these challenges, and was successfully applied to multiple human pharmacokinetic studies in which subjects received oral doses of duloxetine hydrochloride.

Determination of duloxetine in human plasma via LC/MS and subsequent application to a pharmacokinetic study in healthy Chinese volunteers

BACKGROUND

The pharmacokinetics of duloxetine hydrochloride have been well studied after its approval for clinical use. However, few such data have been reported in the English language literature. We developed a method to determine the pharmacokinetics of duloxetine enteric-coated capsules in healthy Chinese volunteers.

METHODS

A rapid and sensitive liquid chromatography-mass spectrometric (LC/MS) method for the determination of duloxetine in human plasma using flupentixol as the internal standard (I.S.) was developed and validated. Sample preparation of the plasma involved deproteination with acetonitrile twice, repeatedly. Samples were then analyzed by HPLC on a Thermo Hypersil-Hypurity C18 column (150 x 2.1 mm, 5 microm). A single-quadrupole mass spectrometer with an electrospray interface was operated in the selected-ion monitoring mode to detect the [M+H](+) ions at 298 m/z for duloxetine and at 435 m/z for the internal standard.

RESULTS

Pharmacokinetics were measured in 12 healthy Chinese male volunteers (6 males and 6 females) who received a single regimen with 3 different dosages at 22.4, 44.8 and 67.2 mg of duloxetine enteric-coated capsules.

CONCLUSION

A sensitive and specific method for quantifying duloxetine levels in human plasma has been devised and successfully applied to a clinic pharmacokinetic study of an enteric-coated capsule of duloxetine hydrochloride administered as a single oral dose.

Duloxetine in the treatment of diabetic peripheral neuropathic pain

Diabetic peripheral neuropathic pain is a common complication of diabetes mellitus that adversely affects the quality of life of these patients. Many antidepressants and anticonvulsants are effective in relieving diabetic peripheral neuropathic pain. Duloxetine, a dual serotonin and norepinephrine reuptake inhibitor, was very effective in reducing diabetic peripheral neuropathic pain and improving quality of life and was the first antidepressant approved by regulatory authorities for the treatment of diabetic peripheral neuropathic pain. Safety was evaluated in 1074 diabetic peripheral neuropathic pain patients representing 472 patient-years exposure. More duloxetine-treated (79/568, 13.9%) than placebo-treated (16/223, 7.2%; p = 0.008) patients discontinued owing to adverse events. Duloxetine should be used with similar cautions to the newer antidepressants. In addition, rare duloxetine-induced hepatic enzyme elevations should result in discontinuation of duloxetine therapy. Duloxetine should prove effective in other painful conditions and might provide additional relief when used with anticonvulsants in neuropathic conditions.

Duloxetine in the management of depression

Duloxetine is a serotonin and noradrenalin reuptake inhibitor, and is hence in the same pharmacological class as venlafaxine. Randomized controlled trials have demonstrated it to be effective in the treatment of depression and also that it has analgesic properties in diabetic neuropathic pain, fibromyalgia and depressed patients with pain. To date, there is limited published data comparing duloxetine with other antidepressants. However, what data are available suggest that duloxetine is more effective than selective serotonin reuptake inhibitors in severely depressed patients (although the magnitude of this difference is uncertain) and equally effective as venlafaxine. While, theoretically, a serotonin and noradrenalin reuptake inhibitor may be more effective than a selective serotonin reuptake inhibitor in depressed patients with pain, there are no randomized, controlled trial data to support this hypothesis. Generally, duloxetine is well tolerated and there is no suggestion of the recent concerns of cardiotoxicity and toxicity in overdose that have been raised over venlafaxine. Duloxetine is an appropriate drug to consider for second-line treatment, after a selective serotonin reuptake inhibitor, for the management of depression.

Case report: fulminant hepatic failure involving duloxetine hydrochloride

BACKGROUND AND AIMS

Duloxetine hydrochloride was approved by the Food and Drug Administration in August 2004 for the treatment of major depressive disorder and diabetic peripheral neuropathic pain. Initial product labeling contained a precaution regarding the risk for increases in liver function test results. Recently, postmarketing research has revealed episodes of cholestatic jaundice and increases in transaminase levels to greater than 20 times normal in patients with chronic liver disease.

METHODS

In this case report, we describe a patient with non-Hodgkin's lymphoma in remission and depression treated with duloxetine and mirtazapine.

RESULTS

Approximately 6 weeks after increasing her duloxetine dose from 30 to 60 mg daily, she became jaundiced and presented with fulminant hepatic failure. Liver function tests immediately before initiating duloxetine were not available, although the patient carried no prior history of chronic liver disease. A complete work-up for alternate causes failed to reveal another explanation for the patient's clinical presentation. A liver biopsy examination showed histologic changes of subacute injury and the patient's clinical course was consistent with drug-induced liver injury. Despite aggressive measures, the patient's condition deteriorated and the decision was made to withdraw care.

CONCLUSIONS

This report shows a case of fulminant hepatic failure and death involving duloxetine use. Given recent reports of severe hepatotoxicity associated with the use of duloxetine in patients with pre-existing liver disease, further investigation into the safety of this compound is warranted.

Adjunctive pharmacological management of persistent, nonmalignant pain in older individuals

Chronic or persistent pain is a common comorbidity of aging, primarily due to the relatively high frequency of pain-associated disorders in this population (e.g., inflammatory and noninflammatory musculoskeletal disease, zoster infection, diabetes, stroke, and peripheral and central neurological diseases). Acetaminophen, nonsteroidal anti-inflammatory drugs and opioids are important long-term analgesics in this age group. However, adjunctive agents are also important in the management of persistent pain in the elderly, especially neuropathic pain. Oral antiepileptic drugs, mexiletine, baclofen, tricyclic antidepressants, selective serotonin–norepinephrine dual reuptake inhibitors and intranasal/injectable calcitonin are the subjects of this review of the management of persistent, nonmalignant pain in the elderly. While some of these agents are considered narrow-spectrum analgesics (e.g., baclofen in trigeminal neuralgia and calcitonin in bone pain), most are broad-spectrum analgesics, useful in neuropathic pain syndromes of multiple etiologies. Within the antiepileptic drug class, gabapentin and carbamazepine can be considered first-line agents, followed by lamotrigine and pregabalin as second-line agents, and the other most recently approved drugs as third-line or ‘salvage’ agents. The tricyclic antidepressants have numerous precautions/contraindications and tolerability issues in this population, thus reducing their utility. Duloxetine and venlafaxine are the only useful analgesics among the modern antidepressants. Challenges for the future include not only the search for more effective and less toxic adjunctive analgesics for the elderly, but also translating our knowledge of current and future analgesics into effective therapies in the ‘real world’ community and institutional settings where elderly people live. There is no justification in our society today for anyone to live with untreated or undertreated persistent pain.

Duloxetine hydrochloride: A new dual-acting medication for the treatment of major depressive disorder

BACKGROUND

Duloxetine hydrochloride has recently been approved by the US Food and Drug Administration for the treatment of major depressive disorder (MDD). Duloxetine is a potent inhibitor of serotonin and norepinephrine reuptake, with weak effects on dopamine reuptake.

OBJECTIVE

This article reviews the literature on duloxetine with regard to its pharmacodynamics, pharmacokinetics, clinical efficacy, and tolerability.

METHODS

A comprehensive search of MEDLINE was performed using the terms duloxetine, Cymbalta, and major depressive disorder, with no restriction on year. The Eli Lilly and Company clinical trial registry, and abstracts and posters from recent American Psychiatric Association meetings were also reviewed.

RESULTS

Duloxetine exhibits linear, dose-dependent pharmacokinetics across the approved oral dosage range of 40 to 60 mg/d. No dose adjustment appears to be needed based on age. Duloxetine has shown efficacy in reducing depressive symptoms compared with placebo, and duloxetine recipients have shown significant improvements in global functioning compared with placebo (both, P < 0.05). Response and remission rates have been comparable to or greater than those seen with fluoxetine or paroxetine. Duloxetine is generally well tolerated, with nausea, dry mouth, and fatigue being the most common treatment-emergent adverse effects. Cardiovascular adverse effects do not appear to result in sustained blood pressure elevations, QTc-interval prolongation, or other electrocardiographic changes.

CONCLUSIONS

Based on the available evidence, duloxetine is a well-tolerated and effective treatment for MDD in adults. Randomized head-to-head comparisons against established antidepressants are needed to determine the relative safety and efficacy of duloxetine.