Duloxetine compliance and its association with healthcare costs among patients with diabetic peripheral neuropathic pain

Epidemiology of Peripheral Neuropathy and Lower Extremity Disease in Diabetes

PURPOSE OF REVIEW

Diabetic peripheral neuropathy eventually affects nearly 50% of adults with diabetes during their lifetime and is associated with substantial morbidity including pain, foot ulcers, and lower limb amputation. This review summarizes the epidemiology, risk factors, and management of diabetic peripheral neuropathy and related lower extremity complications.

RECENT FINDINGS

The prevalence of peripheral neuropathy is estimated to be between 6 and 51% among adults with diabetes depending on age, duration of diabetes, glucose control, and type 1 versus type 2 diabetes. The clinical manifestations are variable, ranging from asymptomatic to painful neuropathic symptoms. Because of the risk of foot ulcer (25%) and amputation associated with diabetic peripheral neuropathy, aggressive screening and treatment in the form of glycemic control, regular foot exams, and pain management are important. There is an emerging focus on lifestyle interventions including weight loss and physical activity as well. The American Diabetes Association has issued multiple recommendation statements pertaining to diabetic neuropathies and the care of the diabetic foot. Given that approximately 50% of adults with diabetes will be affected by peripheral neuropathy in their lifetime, more diligent screening and management are important to reduce the complications and health care burden associated with the disease.

Economic impact of medication non-adherence by disease groups: a systematic review

OBJECTIVE

To determine the economic impact of medication non-adherence across multiple disease groups.

DESIGN

Systematic review.

EVIDENCE REVIEW

A comprehensive literature search was conducted in PubMed and Scopus in September 2017. Studies quantifying the cost of medication non-adherence in relation to economic impact were included. Relevant information was extracted and quality assessed using the Drummond checklist.

RESULTS

Seventy-nine individual studies assessing the cost of medication non-adherence across 14 disease groups were included. Wide-scoping cost variations were reported, with lower levels of adherence generally associated with higher total costs. The annual adjusted disease-specific economic cost of non-adherence per person ranged from $949 to $44 190 (in 2015 US$). Costs attributed to 'all causes' non-adherence ranged from $5271 to $52 341. Medication possession ratio was the metric most used to calculate patient adherence, with varying cut-off points defining non-adherence. The main indicators used to measure the cost of non-adherence were total cost or total healthcare cost (83% of studies), pharmacy costs (70%), inpatient costs (46%), outpatient costs (50%), emergency department visit costs (27%), medical costs (29%) and hospitalisation costs (18%). Drummond quality assessment yielded 10 studies of high quality with all studies performing partial economic evaluations to varying extents.

CONCLUSION

Medication non-adherence places a significant cost burden on healthcare systems. Current research assessing the economic impact of medication non-adherence is limited and of varying quality, failing to provide adaptable data to influence health policy. The correlation between increased non-adherence and higher disease prevalence should be used to inform policymakers to help circumvent avoidable costs to the healthcare system. Differences in methods make the comparison among studies challenging and an accurate estimation of true magnitude of the cost impossible. Standardisation of the metric measures used to estimate medication non-adherence and development of a streamlined approach to quantify costs is required.

PROSPERO REGISTRATION NUMBER

CRD42015027338.

Opioid use in the management of diabetic peripheral neuropathy (DPN) in a large commercially insured population

OBJECTIVE

To examine the proportion of diabetic peripheral neuropathy (DPN) patients receiving pharmacologic DPN treatments and specifically to identify the rates and factors associated with opioid use and first-line opioid use.

METHODS

A 10% sample of IMS-LifeLink claims data from 1998 through 2008 was used. The study population consisted of diabetic patients who met DPN criteria using a validated DPN algorithm. Multivariable logistic regression controlling for demographics, comorbidities, and other clinical characteristics was used to identify factors associated with any DPN pharmacologic treatment, any opioid use, and first-line opioid treatment. Sensitivity analyses were conducted to explore variations in exclusion criteria as well as opioid use definitions.

RESULTS

A total of 666 DPN patients met inclusion criteria and pharmacologic treatment was received by 288 patients (43.24%) and of those, 154 (53.47%) had DPN-related opioid use and 96 (33.33%) received opioid as first-line treatment. Persons with diabetic complications were more likely to use opioids (odds ratio=4.53; 95% confidence interval, 1.09-18.92). Food and Drug Administration-approved DPN agents duloxetine 1.04% (n=3) and pregabalin 5.56% (n=16) had much lower rates of use. DPN-related drug use and DPN-related opioid usage increased as we used less restrictive samples in sensitivity analyses.

CONCLUSIONS

Opioids were the most frequently prescribed first-line agents for DPN. More than 50% of DPN patients remained untreated with pharmacologic agents 1 year after a DPN diagnosis.

Duloxetine treatment adherence across mental health and chronic pain conditions

PURPOSE

This study applied a uniform methodology for measuring and comparing duloxetine adherence in the treatment of multiple chronic medical conditions.

MATERIALS AND METHODS

Study patients 18-64 years of age initiating duloxetine therapy during 2008 were identified from a large managed care database. The study was restricted to patients with continuous health plan eligibility for 12 months pre- and post-duloxetine initiation. Study patients had ≥1 medical claim with an inpatient or outpatient diagnosis of one (and only one) of the following conditions: major depressive disorder (MDD); generalized anxiety disorder (GAD); fibromyalgia, diabetic peripheral neuropathic pain; or chronic musculoskeletal pain, as established in studies in patients with osteoarthritis and chronic lower back pain (CLBP). Patients initiating duloxetine who had two or more of the six studied conditions were not included in this study, thereby avoiding the need to differentiate between primary and secondary diagnoses from the claims records. Adherence rate was defined as the percentage of patients with a 365-day medication possession ratio ≥0.8.

RESULTS

A total of 20,490 patients initiated duloxetine treatment during 2008 with a diagnosis of one of the studied conditions during the study period. The adherence rate in our sample was 34.6% and was highest among patients with MDD (37.3%) and lowest for patients with CLBP (29.9%). In general, adherence among patients with MDD and GAD was greater than among those with a chronic pain condition.

CONCLUSION

Adherence among newly initiated duloxetine patients varied modestly across the medical conditions for which it was used. After adjusting for potential confounders, differences between the mental conditions (MDD and GAD) and the chronic pain conditions (CLBP, osteoarthritis, and diabetic peripheral neuropathic pain) were statistically significant. These results may be useful in the determination of expectations of adherence, and how it may differ for each of the conditions studied.

Identification of patients with painful diabetic peripheral neuropathy who have a favorable cost profile with pregabalin treatment

OBJECTIVE

To characterize patient populations with favorable costs after the initiation of pregabalin for the treatment of painful diabetic peripheral neuropathy (pDPN) relative to duloxetine, gabapentin, and amitriptyline.

METHODS

Patients were identified from MarketScan having ≥ 1 claim for pDPN (ICD-9-CM codes 250.6 or 357.2) within 60 days of first prescription (index) for pregabalin, duloxetine, gabapentin, or amitriptyline in 2008 and continuous enrollment 12 months pre- and postindex. Pregabalin patients were propensity-score-matched to each comparator. Using cutoff values ≥ 80% proportion of days covered (PDC) and ≥ 65 years for age, pre- to postindex changes in healthcare costs were estimated for pregabalin vs. comparators.

RESULTS

Of 987 patients initiated on pregabalin, 349 matched to duloxetine; 987 to gabapentin; 276 to amitriptyline. The pre- to postindex changes in total healthcare costs were similar between cohorts: $3272 with pregabalin vs. $2290 with duloxetine (P = 0.5280); $3687 with pregabalin vs. $5498 with amitriptyline (P = 0.5863); $3869 with pregabalin vs. $4106 with gabapentin (P = 0.8303). For the high-age/high-PDC population, the pre- to postindex differences in mean total costs were significantly lower with pregabalin (P < 0.001) relative to comparators ($3573 vs. $8288 for duloxetine; $1423 vs. $3167 for gabapentin; $2285 vs. $6160 for amitriptyline).

CONCLUSIONS

The association of lower total costs among older individuals with pDPN who maintain high adherence to pregabalin therapy relative to key comparators suggests a pharmacoeconomic advantage of pregabalin in this population combined with a need for strategies promoting adherence.

Use of select medications prior to duloxetine initiation among commercially-insured patients

BACKGROUND

The purpose of this study was to assess select medication utilization prior to duloxetine initiation among patients with major depressive disorder, generalized anxiety disorder, diabetic peripheral neuropathic pain, fibromyalgia, and musculoskeletal pain associated with osteoarthritis or low back pain.

METHODS

Commercially insured duloxetine initiators between January 1, 2007 and March 31, 2010 were identified from a large US administrative claims database. Disease subgroups were constructed based on diagnosis from medical claims during the 12 months prior to duloxetine initiation. Prior use of antidepressants, anticonvulsants, opioids, nonsteroidal anti-inflammatory drugs, and muscle relaxants was assessed during the 12-month preinitiation period.

RESULTS

This study identified 56,845 (2007), 44,838 (2008), and 65,840 (January 2009 to March 2010) duloxetine initiators. Among the 2009 initiators, utilization patterns were similar for patients with major depressive disorder and generalized anxiety disorder, with antidepressants being the most used (84% and 80%, respectively), followed by opioids (58% and 55%, respectively). Patients across pain-related conditions also had similar utilization patterns, with opioid use being the highest (76%-82%), followed by antidepressants (65%-72%). Use of other medication classes was common (29%-63%) but less frequent, and over 50% of the patients used any antidepressants, 70% used any antidepressants or anticonvulsants, and 90% used any antidepressants, anticonvulsants, or opioids. Trends in the use of these select medications were similar between 2007 and 2009.

CONCLUSION

Patients used several types of medications over the 12 months prior to initiating duloxetine across disease states, with antidepressants and opioids being the most frequently used medications. Trends of select medication use were similar over time.

Dosing pattern comparison between duloxetine and pregabalin among patients with diabetic peripheral neuropathic pain

OBJECTIVE

To compare medication dosing patterns of duloxetine and pregabalin among patients with diabetic peripheral neuropathic pain (DPNP).

METHODS

Applying a retrospective cohort study design on a large U.S. healthcare claims database, we examined the dosing patterns of duloxetine and pregabalin among commercially insured patients with DPNP aged 18 to 64 who initiated (a 90-day medication gap) duloxetine or pregabalin therapy in 2006. Selected patients had continuous enrollment during the 12-month pre- and post-index periods. The index mediation was used to classified individuals into the duloxetine or pregabalin cohorts. Initial daily dose, average daily dose over the first post-index year, and average daily dose of the first several prescriptions were estimated and compared across the cohorts.

RESULTS

The study sample included 828 duloxetine and 1934 pregabalin-treated patients with a mean age of 50 years. Cardiovascular diseases, neuropathic pain other than DPNP, osteoarthritis, and diabetic retinopathy were the most common comorbid conditions. The average initial daily doses were 54.3 and 171.8 mg for duloxetine and pregabalin, respectively. The average daily dose over the first post-index year was 55.2 mg for duloxetine and 173.8 mg for pregabalin. The average daily dose for the first 10 duloxetine prescriptions ranged between 54.3 and 61.9 mg, but increased from 171.8 to 264.3 mg for pregabalin.

CONCLUSIONS

The commercially insured patients with DPNP who initiated duloxetine or pregabalin therapy had different dosing patterns. The average daily dose for duloxetine was relatively stable over time, while pregabalin-treated patients had significant dose increase over the 12-month post-index period.

Duloxetine in the management of diabetic peripheral neuropathic pain

Diabetic neuropathy affects up to 70% of diabetics, and diabetic peripheral neuropathic pain (DPNP) is the most common and debilitating of the diabetic neuropathies. DPNP significantly reduces quality of life and increases management costs in affected patients. Despite the impact of DPNP, management is poor with one-quarter of patients receiving no treatment and many treated with medications having little or no efficacy in managing DPNP. Duloxetine is one of two drugs approved by the United States Food and Drug Administration for DPNP management. Duloxetine is a serotonin and norepinephrine reuptake inhibitor (SNRI) proven safe, effective, and cost-saving in reducing DPNP symptoms at a dose of 60 mg/day. Duloxetine doses greater than 60 mg/day for DPNP management are not recommended since they are no more efficacious and associated with more side effects; addition of pregabalin or gabapentin for these patients may be beneficial. Side effects of duloxetine are generally mild and typical for the SNRI class including nausea, dizziness, somnolence, fatigue, sweating, dry mouth, constipation, and diarrhea. Given its other indications, duloxetine is a particularly good choice for DPNP treatment in patients with coexisting depression, anxiety, fibromyalgia, or chronic musculoskeletal pain. Duloxetine treatment had no clinically significant effect on glycemic control and did not increase the risk of cardiovascular events in diabetes patients. However, duloxetine use should be avoided in patients with hepatic disease or severe renal impairment. Given its safety, efficacy, and tolerability, duloxetine is an excellent choice for DPNP treatment in many patients.

Opioid utilization and health-care costs among patients with diabetic peripheral neuropathic pain treated with duloxetine vs. other therapies

OBJECTIVE

This retrospective cohort study assessed subsequent opioid utilization and health-care costs among patients with diabetic peripheral neuropathic pain (DPNP) who initiated duloxetine vs. other standard of care (SOC) treatments.

METHODS

Medical and pharmacy claims were analyzed for commercially-insured individuals aged 18-64. Two study cohorts were constructed from DPNP patients who initiated duloxetine or SOC medications (tricyclic antidepressants, venlafaxine, gabapentin, pregabalin) between March 1, 2005 and December 31, 2005. Initiation was defined as a prior 90-day period without access of the medication. The dispense date of the first initiation was denoted as the index date. Patients with opioids dispensed in the prior 90 days were excluded. Opioid utilization including total days, number of prescriptions filled, and morphine equivalent dosage was assessed for overall, long-acting, and short-acting opioids. Health-care costs and opioid use in the 12-month post-index period were examined via multivariate regression analyses.

RESULTS

Four hundred and ninety-nine DPNP patients (272 duloxetine, 227 SOC) were identified. SOC patients had higher prevalence of comorbidities and pre-index health-care costs than duloxetine patients. Controlling for cross-cohort differences, duloxetine patients were significantly less likely to use any opioids than SOC patients. Also, duloxetine patients had 20 fewer adjusted opioid supply days (largely due to the use of short-acting opioids, P < 0.05) and significantly lower adjusted total costs ($8,088, P < 0.05) and diabetes-related costs ($3,092, P < 0.05) in the 12-month post-index period, with most of the cost differences from lower outpatient costs.

CONCLUSIONS

DPNP patients who initiated duloxetine therapy were less likely to have subsequent opioid use and had lower health-care costs than SOC patients.

The relationship between average daily dose, medication adherence, and health-care costs among diabetic peripheral neuropathic pain patients initiated on duloxetine therapy

OBJECTIVE

To examine the relationship between average daily dose (ADD) of duloxetine, adherence to therapy, and health-care costs among patients with diabetic peripheral neuropathic pain (DPNP).

METHODS

A retrospective analysis of commercially insured DPNP patients was conducted among those aged 18 to 64 years who initiated duloxetine therapy between Ocotober 1, 2004 and December 31, 2006. The dispense date of the first duloxetine prescription was defined as the index date. All duloxetine prescriptions over the 12-month post-index period were used to assess ADD and adherence. Four study cohorts were constructed based on ADD: 30 mg, 31 to 59 mg, 60 mg; and >60 mg. High adherence was defined as having a medication possession ratio for duloxetine of ≥0.8. Health-care costs over 12-month post-index period were estimated. Multiple regression models were used to examine the association between ADD, adherence, and health-care costs.

RESULTS

The study sample included 1,351 DPNP patients (mean age: 55 years; male: 41%). Twelve percent of patients had a duloxetine ADD of 30 mg, 17% of 31 to 59 mg, 56% of 60 mg, and 15% of >60 mg. Patients with ADD of 30 mg (>60 mg) were significantly less (more) likely to adhere to duloxetine therapy compared with those in the 60 mg cohort. Controlling for cross-cohort demographic and clinical differences, patients with ADD of 30 mg, 31 to 59 mg, or >60 mg had significantly higher total health-care costs than those with ADD of 60 mg (adjusted differences: $6,090, $6,320, $6,466 for 30 mg, 31 to 59 mg, >60 mg, respectively, all P < 0.05).

CONCLUSION

The findings suggest that having an ADD of 60 mg for duloxetine among commercially insured DPNP patients is associated with improved medication adherence and lower health-care costs.

Factors associated with pain medication selection among patients diagnosed with diabetic peripheral neuropathic pain: a retrospective study

OBJECTIVE

To assess the demographic and clinical characteristics associated with initiation of duloxetine therapy compared with other pharmacologic therapies for treatment of diabetic peripheral neuropathic pain (DPNP).

METHODS

This study used administrative claims databases for commercially-insured individuals aged 18-64 years to examine factors associated with treatment among DPNP patients who initiated duloxetine versus tricyclic antidepressants (TCAs), venlafaxine, gabapentin, pregabalin, or opioids between 7/1/2005 and 12/31/2007. Treatment initiation was defined as no pill coverage of the same medication over the previous 90 days. Multiple logistic regression models were estimated to assess factors associated with initiating duloxetine versus each of the other DPNP therapies.

RESULTS

The study included 11,060 DPNP patients with average age of 55 years old. Cardiovascular disease (63-70%), cerebrovascular/peripheral vascular disease (26-33%), low back pain (24-39%), and osteoarthritis (17-26%) were the most common diabetes- and pain-related comorbidities. Controlling for demographic and clinical characteristics, patients who received duloxetine or pregabalin in the prior 12-month period were more likely to initiate duloxetine. Patients from other DPNP treatment cohorts, except for those in the pregabalin cohort, were more likely to re-initiate the same prior therapy than begin treatment with duloxetine (all p<0.05). A history of anxiety disorder was significantly associated with initiation of all DPNP treatments other than duloxetine (all p<0.05), except for TCAs. Patients with low back pain were more likely to initiate duloxetine than TCAs or venlafaxine, but less likely to initiate duloxetine than pregabalin or opioids. Patients with infections related to diabetes were less likely to initiate duloxetine than venlafaxine, gabapentin, or opioids.

LIMITATIONS

Because a retrospective administrative claims database was used, this study is subject to selection bias due to unobservable confounders, inability to measure prescriber preferences or characteristics or disease severity.

CONCLUSIONS

Among commercially-insured DPNP patients, those with prior use of duloxetine or pregabalin were more likely to initiate duloxetine than other treatments. The presence of select comorbidities was also associated with specific medication initiation.

Opioid use and healthcare costs among patients with DPNP initiating duloxetine versus other treatments

OBJECTIVE

To compare opioid utilization and healthcare costs over a 1-year period following the initiation with duloxetine versus other standard of care (SOC) treatments among patients with diabetic peripheral neuropathic pain (DPNP).

METHODS

This retrospective cohort study assessed commercially-insured DPNP patients between 18 and 64 years old who initiated duloxetine or other SOC treatments (tricyclic antidepressants, venlafaxine, gabapentin, pregabalin) between 3/1/2005 and 12/31/2005. Initiation was defined as a 90-day period without available study medication. The first dispense date of the study medication was denoted as the index date. Selected patients had no opioid pill coverage during the 90 days prior to initiation. Duloxetine and SOC patients were matched via propensity scoring (1:1 ratio), controlling for demographics, comorbidities, prior healthcare utilization and costs, and prior medication history. Opioid utilization and healthcare costs over the 12-month post-index period were compared between study cohorts.

RESULTS

The matched sample included 117 patients in each of the duloxetine and SOC cohorts. Compared with SOC-treated patients, duloxetine-treated patients were less likely to use any opioids (52.1 vs. 84.6%, p < 0.05) over the 12-month post-index period. Duloxetine-treated patients, on average, had two fewer opioid prescriptions dispensed, 27 fewer days on opioids, 121 days greater delay in subsequent opioid use, and 1815 mg lower morphine equivalent dosage than SOC-treated patients (all p < 0.05). Also, duloxetine-treated patients had significantly lower total ($18,623 vs. 30,602, p < 0.05) and outpatient costs ($7371 vs. 15,343, p < 0.05). Due to the use of a retrospective administrative claims database, limitations of this study include the potential for selection bias between study cohorts, and inability to measure unobservable confounding and disease severity and/or duration.

CONCLUSIONS

Among commercially-insured DPNP patients, duloxetine-treated patients had delayed and reduced opioid use and lower healthcare costs than SOC-treated patients.

Changes in opioid use and healthcare costs among U.S. patients with diabetic peripheral neuropathic pain treated with duloxetine compared with other therapies

OBJECTIVE

To examine changes in opioid use and healthcare costs among commercially insured patients with diabetic peripheral neuropathic pain (DPNP) who initiated duloxetine versus other standard of care (SOC) medications (tricyclic antidepressants, venlafaxine, gabapentin, pregabalin).

RESEARCH DESIGN AND METHODS

Using an administrative claims database, patients with DPNP aged 18-64 who initiated duloxetine or SOC between March 1, 2005 and December 31, 2005 were identified. Initiation was defined as a 90-day clean period without the available study medication. Selected patients had 12 months of continuous enrollment before and after the index date, and at least one opioid dispensed in the prior 90 days. Duloxetine and SOC patients were further classified into continuous and non-continuous users based on whether the medication possession ratio was > or =0.8. Total opioid days, number of opioid prescriptions dispensed, and cumulative morphine equivalents were examined over the 12-month pre- and post-index periods. Multivariate regressions were applied to assess the changes (pre-index minus post-index) in opioid use (total, short-acting vs. long-acting) and healthcare costs, controlling for demographic and clinical characteristics.

RESULTS

The study sample included 1281 patients: 98 duloxetine continuous, 243 duloxetine non-continuous, 195 SOC continuous, and 745 SOC non-continuous users. Controlling for demographic and clinical characteristics, duloxetine non-continuous and SOC (continuous and non-continuous) patients had significantly less reduction in total opioid days (-24.4, -23.7, -18.5, respectively, all p < 0.05) from the 12-month pre-index to the post-index period than duloxetine continuous patients. Compared with duloxetine non-continuous, SOC continuous, and SOC non-continuous users, duloxetine continuous users had a greater reduction in short-acting hydrocodone use (difference between the 12 month pre-index and post-index periods) in terms of the total number of prescriptions dispensed (adjusted differences: 1.5, 1.7, 1.7, respectively, all p < 0.05), total supply days (adjusted differences: 28.1, 27.3, 29.7, respectively, all p < 0.05), and morphine equivalent dosage (adjusted differences: 1290 mg, 1132 mg, 1127 mg, respectively, all p < 0.05). Duloxetine non-continuous patients had significantly higher adjusted total ($12,729, p < 0.05) and inpatient costs ($14,993, p < 0.05) than duloxetine continuous patients.

LIMITATIONS

Due to the use of a retrospective administrative claims database, this study is subject to selection bias between study cohorts, misidentification of DPNP and/or other comorbidities, and an inability to confirm adherence to therapy or assess indirect costs and costs of over-the-counter medications.

CONCLUSIONS

Among commercially insured patients with DPNP, continuous treatment with duloxetine was associated with a reduction in opioid use between the 12-month pre- and post-index periods compared with treatment with SOC or non-continuous treatment with duloxetine. Duloxetine continuous patients also incurred lower subsequent healthcare costs than non-continuous duloxetine patients.