Original Research
Utilization, price, and spending trends for antidepressants in the US Medicaid program

https://doi.org/10.1016/j.sapharm.2007.06.019Get rights and content

Abstract

Background

Antidepressants are often used in the treatment of major depressive disorder and other mental illnesses, and constitute one of the most widely prescribed and costly medication classes in the US Medicaid Program. However, antidepressant utilization and price patterns within this market have not yet been adequately characterized.

Objectives

This study was undertaken to analyze antidepressant drug utilization and price trends and to quantify market-share competition in Medicaid.

Methods

Quarterly utilization and payment data were retrieved from the national Medicaid pharmacy claims files provided by the Centers for Medicare & Medicaid Services. Quarterly per-prescription prices were estimated by dividing the payment amounts by the number of prescriptions. Descriptive time series analysis was conducted to assess the trends of utilization, expenditures, market shares, and prices from January 1991 through December 2005, for 3 major antidepressant subclasses—Selective Serotonin Reuptake Inhibitors (SSRIs), Tricyclic Antidepressants, and Other Antidepressants—as well as for individual agents within these subclasses. Using exponential smoothing models, 3-year market-share forecasts were produced.

Results

From 1991 to 2005, the total number of antidepressant prescriptions rose 380% from 6.82 million to 32.72 million. Total expenditures on antidepressants increased from $159 million in1991 to $2.26 billion in 2004, then decreased to $1.99 billion in 2005, following the entry of lower-priced generic fluoxetine in 2001 and generic paroxetine in 2003. The payment market share for the SSRIs increased from 40% in 1991 to 82% in 1997, then decreased to 64% in 2005. It is projected to be 64% (95% confidence interval [CI]: 51-77%) in 2008 quarter 4.

Conclusions

Increases in antidepressant drug expenditures were primarily because of rising utilization; however, there was also some increase in average price per prescription for many of the antidepressants studied. Switching to generic drugs may offer significant cost-saving potential.

Introduction

Depression is among the most prevalent major mental health disorders, as 8-10% of the US population suffer from depression.1 Depression may be associated with a patient's family history or medical illness such as stroke, heart attack, cancer, Parkinson's disease, or a hormonal disorder.2 Depression is particularly prevalent among Medicaid recipients, and Medicaid enrollees experience a higher rate and severity of depression than privately insured individuals.3 In a 10-state Substance Abuse and Mental Health Services Administration Medicaid study, 17% of adult enrollees were treated for major depression and 32% for minor depression and anxiety disorders.4 In another study, claims data were analyzed for 6500 adults who were eligible for services in both a Health-Maintenance Organization (Colorado Access) and a behavioral health carve-out. Nine hundred and fifty individuals (14.6%) had a depressive disorder diagnosis.5 A 2003 review of data from the National Comorbidity Survey and the National Household Survey on Drug Abuse reported depression prevalence estimates for Medicaid enrollees ranging from 18% to 20%.1 In conjunction with high prevalence rates, depression is associated with a significant economic burden on society. The annual cost of depression in the United States was estimated at $83 billion in 2000, including $26 billion in the direct costs of depression treatment, $51 billion in productivity loss, and $6 billion in suicide-related costs.6

Antidepressant medications are widely used in the treatment of depression. Available antidepressants are generally categorized into 3 subclasses: Selective Serotonin Reuptake Inhibitors (SSRIs), Tricyclic Antidepressants (TCAs), and Other Antidepressants, a category which includes Monoamine Oxidase Inhibitors (MAOIs), Heterocyclic Agents (HCAs), and several other antidepressants. The SSRIs, TCAs, and HCAs are all commonly used for the treatment of depression. TCAs have additional indications besides depression; for example, clomipramine was the first drug approved by the US Food and Drug Administration (FDA) for obsessive-compulsive disorder (OCD). Patents on the branded TCAs have expired, and all TCAs are currently produced by generic manufacturers.7 SSRIs are considered a major advancement in the treatment of depression, as this antidepressant subclass provides for improved dosing, safety, and tolerability compared with the TCAs and MAOIs.8, 9, 10 With a better understanding of the role of serotonin in other psychiatric disorders, the use of SSRIs expanded beyond mood disorders into the treatment for alcoholism, anorexia nervosa, borderline personality disorder, bulimia nervosa, hot flashes, OCD, panic disorder, posttraumatic stress disorder, premature ejaculation, premenstrual syndrome, and social anxiety disorder.11, 12, 13, 14, 15 Finally, a number of Other Antidepressants have been approved by the FDA between 1961 and 2004 for the treatment of major depressive disorder. Like the other subclasses, the use of these antidepressants has expanded into other indications. For example, in June 2006, extended-release bupropion became the first drug to be approved by the FDA for patients with seasonal affective disorder.16

During much of the 1990s, antidepressants were the most widely prescribed medications in the United States.17, 18 For the Ohio Medicaid Program, this category ranked number 1 during each of the years 1997-2001.19 Not surprisingly, in parallel with high utilization, expenditures on antidepressants have been extremely high. In 2001, a total of $12 billion was spent on antidepressants in the United States, representing approximately 8% of total US prescription retail sales.20 In 2005, Medicaid (all state programs combined) was spending approximately $2 billion per year on antidepressants, about 5% of its total pharmaceutical budget.21

To understand the underlying causes of this expenditure increase, it is important to determine the specific roles of utilization and price in this context. One study across drug classes, which was based on US national retail sales data, found that the overall rise in drug spending was accounted for by utilization increase (39% of the rise in spending was because of rising drug use), price increases (37%), and switching from traditional to newer medications (24%).22, 23 Similarly, in this study, which focuses specifically on antidepressants, we aim to analyze utilization and price trends and to quantify market-share competition in Medicaid. By doing so, this study may provide policy makers and physicians, who are interested in cost containment, a real scenario to understand better the specific causes of increased cost. Furthermore, from the assessment of the market shares across 3 major subclasses of antidepressants, we can highlight the dynamic character of the antidepressant market as newer SSRIs and Other Antidepressants have generally replaced the older MAOIs and TCAs over time. Finally, because we examine individual drugs within the antidepressant subclasses, we are able to describe competition between antidepressant drug manufacturers and shed light on whether the Medicaid Program can take advantage of such competition in designing cost-containment initiatives.

Section snippets

Methods

Using the national Medicaid pharmacy claims database from the Centers for Medicare & Medicaid Services (CMS), which covers 49 states (all states except Arizona) and the District of Columbia,24 utilization and payment data from 1991 quarter 1 through 2005 quarter 4 were collected for each of the antidepressants listed in Table 1. CMS data were collected for individual national drug code (NDC) drug forms. The national files are large databases representing aggregation across all the states and

Results

The total number of antidepressant prescriptions increased substantially from 1991 to 2004 (from 6.8 million to 35.0 million scripts, over a 400% increase), but then fell in 2005 to 32.7 million prescriptions (Table 2). Total US Medicaid expenditure on antidepressants also increased from $159 million in 1991 to $2.23 billion in 2003 (an increase of approximately 1300% over this 13-year period). In 2004, spending remained at about the same level ($2.26 billion) as in 2003, while in 2005,

Discussion

Our findings indicate that increasing Medicaid expenditures on antidepressants over the past decade can be explained by both rising utilization and prices. First, the total number of prescriptions for antidepressants rose dramatically over this period. Second, there was a shift in prescribing to SSRIs and Other Antidepressants and away from TCAs, although TCAs still accounted for over 10% of the prescriptions in 2005. Because drugs in the former 2 categories were significantly more expensive

Conclusions

Increases in antidepressant drug expenditures from 1991 to 2005 were primarily because of rising utilization of antidepressants. This rise was accompanied by increased use of more expensive SSRIs and the expanded use of antidepressants for various psychiatric disorders. Nevertheless, as seen over the past couple of years, switching to generic drugs may offer significant cost-saving potential.

Medicaid accounts for much of the spending in the United States on antidepressants, as seen, for

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    This study was presented at the 10th Annual Meeting for the International Society for Pharmacoeconomics and Outcomes Research (ISPOR), Arlington, VA, USA, May 2005, and at the 2nd Asia-Pacific ISPOR Conference, Shanghai, China, March 2006, where it received the Best Poster Presentation Award.

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