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The economic effect of switching from sildenafil to another phosphodiesterase type 5 inhibitor.

Patients who could benefit from additional education about treatments for erectile dysfunction (ED) may prematurely discontinue or switch ED medications, resulting in unnecessary resource utilization. In a retrospective cohort study using a large, aggregated health claims database, the costs associated with switching from sildenafil to another phosphodiesterase type 5 (PDE-5) inhibitor were compared with those for patients refilling sildenafil. Of the 15,584 patients with an index sildenafil claim, 10,863 had a second PDE-5 inhibitor prescription (10,137 for sildenafil, 726 for vardenafil or tadalafil). Erectile dysfunction?attributable costs in the six-month preindex period were similar (P = .72), but postindex six-month ED costs were higher in patients who initially switched from sildenafil ($173.38) versus patients who refilled sildenafil ($131.51; P < .001). Regression analysis estimated that corrected ED-attributable and overall costs were 41% (P < .001) and 43% (P < .001) higher for patients who switched versus those who refilled sildenafil, respectively.

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Erectile dysfunction (ED) is a condition that affects 20 million to 30 million men in the United States (1) and more than 150 million men worldwide, (2) and the prevalence is expected to increase with an aging population. (2) Sildenafil citrate was the first oral phosphodiesterase type 5 (PDE-5) inhibitor available in the United States for the treatment of ED. It has proven to be efficacious and generally well tolerated. (3-8) The efficacy and tolerability of sildenafil, along with its preferable mode of delivery compared with intracavernosal injection, transurethral pellets, or penile implants, were associated with a dramatic expansion in ED treatment. (9) In 2003, two additional oral PDE-5 inhibitors were approved by the Food and Drug Administration: (1) vardenafil (10) and (2) tadalafil. (11,12)

Evidence suggests that ED is both underdiagnosed and undertreated. (13,14) This is notable, because the prevalence of cardiovascular disease, hypertension, diabetes, dyslipidemia, and depression is increased in men with ED, (15,16) and because of the potential implications for the emotional well-being of men with ED (17,18) and their partners. (19,20) With regard to the former, a diagnosis of ED may lead to the discovery of serious medical conditions. In addition, patients with ED may discontinue medications for comorbidities because of a perceived effect on erectile function. (21)

Sildenafil can be highly efficacious in men with ED with varying cultural backgrounds, (4-8,22,23) comorbidities, (24-30) and ED etiology. (31-33) Moreover, several studies have demonstrated that a substantial number of nonresponders (34,35) or patients who self-identify as poor responders to sildenafil can be successfully treated after reeducation and appropriate dose titration. (34-36) For instance, McCullough and colleagues (34) reported that 54% of 76 sildenafil nonresponders successfully used sildenafil after receiving information on proper usage, titrating up to the maximum dose (100 mg), and making a minimum of eight attempts at sexual activity. Similarly, Atiemo and associates (35) observed a success rate of 41.5% of 236 sildenafil nonresponders after providing information on proper sildenafil usage and instructing patients to titrate to 100 mg after one unsatisfactory attempt with a 50-mg dose. Patients spent an average of 12 minutes with the physician, and 94% of patients maintained responsiveness to sildenafil 26 months later. Jiann and colleagues (36) were able to treat 58.5% of 41 nonresponders after reviewing proper usage instructions and recommending that patients make four attempts at sexual activity with the 100-mg dose. Despite these findings, recent evidence suggests that dose titration is underutilized. (37) Thus, some patients may prematurely discontinue sildenafil or switch to another oral PDE-5 inhibitor, even though no studies have shown other medications to be more effective than sildenafil. (4,10,11) To date, no properly designed, head-to-head efficacy studies that show one PDE-5 inhibitor is superior to another have been conducted. A limited number of head-to-head preference studies have been performed, but these are deeply flawed. (38)

At the time of the current study, no data on costs of switching among oral PDE-5 inhibitors were published. Thus, the cost associated with switching from sildenafil to another oral PDE-5 inhibitor was evaluated by comparing ED-attributable and overall resource utilization for patients who refilled sildenafil versus patients who switched their PDE-5 inhibitor medication.

METHODS

A retrospective cohort study was conducted using Atlanta-based NDCHealth's Intelligent Health Repository (IHR) database to compare the health care costs of patients who switched ED medications with those who refilled sildenafil after receiving their first sildenafil prescription. The IHR database contains pharmacy and medical claims linked by anonymous patient identification numbers. Transaction data from approximately 40,000 U.S. pharmacies representing all 50 states are included in the database, accounting for approximately 40% of all U.S. retail pharmacy transactions. A small percentage (1%-2%) of claims is from mail-order pharmacy. However, no indicator on the IHR claims identify them as such. The IHR database also includes approximately 160 million physician claims per year (approximately 25% of all physician claims) and 72 million hospital claims (20% of all hospital claims).

Men at least 18 years of age with an initial prescription claim for sildenafil between November 2003 and March 2004 were identified from the IHR database. The date of the initial sildenafil claim was defined as the index date. Patients with prescription or medical claims activity (for any reason) in the IHR database at least six months before and at least six months after their index date were eligible for the study. Patients with zero total charges in the preindex period were excluded, and patients were required to have at least one medical claim during either the six-month preindex or postindex period. Prescription activity during the six-month postindex period was used to categorize patients according to whether their second prescription was for sildenafil (i.e., refilled) or another oral PDE-5 inhibitor (i.e., switched). Overall costs and those attributable to ED were evaluated in the six-month preindex and postindex sildenafil periods. Costs were defined as all medical and pharmacy expenses incurred by patients that were covered by payers and all patient out-of-pocket expenses, including copays and charges for items and services not covered by insurance providers. Costs attributed to ED were based on claims for International Classification of Diseases, 9th Edition, Clinical Modification (ICD-9-CM) codes (302.70, 302.71, 302.72, 302.9, V41.7, and 607.84) as well as NDC codes for sildenafil, tadalafil, and vardenafil (Appendix). Overall costs included ED-attributable and non-ED-attributable ("all other") costs. Preindex and postindex costs of patients who initially switched to a different oral PDE-5 inhibitor were compared with the respective costs of patients who refilled sildenafil. Analysis of the ICD-9-CM codes identified comorbidities of interest, including hypertension (401.xx), dyslipidemia (272.xx), depression (296.22, 296.3, 311.xx), and diabetes (250.xx), in addition to medications associated with these comorbidities using NDC codes (Appendix).

Statistical Analysis. Differences in demographic characteristics and costs between patients who switched to an alternative oral PDE-5 inhibitor and those who refilled their sildenafil prescription were evaluated using t tests and chi-square tests. Differences in ED-attributable and overall costs were further evaluated using ordinary linear regression, for which costs were log transformed. The following covariates were included in the model: patient age, presence of other chronic conditions, index sildenafil cost, and preindex costs. Statistical analyses were performed using SAS/STAT Version 8.2 (SAS Institute, Cary, NC).

RESULTS

A total of 15,584 patients had their first claim for sildenafil during the study period, of which 10,863 had a second prescription for a PDE-5 inhibitor (10,137 sildenafil, 726 vardenafil or tadalafil). Patient characteristics for those who initially refilled sildenafil and those who immediately switched to another PDE-5 inhibitor are presented in Table I.

Although preindex costs attributable to ED were similar between those who initially refilled ($19.32) and those who switched ($20.81) from sildenafil (P = .72), postindex ED costs were significantly higher (P < .001) in patients who switched ($173.38) relative to patients who refilled their sildenafil prescription ($131.51) (Figure 1). Pharmacy ($116.43 vs. $146.73, P < .0001) and medical ($15.08 vs. $26.65, P = .016) costs were lower for those who did not switch their PDE-5 inhibitor. Overall costs during the postindex period were not significantly higher among patients who initially switched ED medications than among those who refilled ($757.31 vs. $648.40, respectively, P = .087), which was consistent with differences in preindex costs ($794.91 vs. $636.48, respectively, P = .061) (Figure 2).

Controlling for differences in age, comorbidities, preindex costs, and index sildenafil cost, ordinary linear regression revealed the ED-attributable costs incurred during the postindex period by patients who switched medications were approximately 41% greater than the ED-attributable costs incurred by patients who refilled their prescription for sildenafil (P < .001; Table II). In addition to medication switching, the regression analysis revealed that index sildenafil cost, preindex costs (P < .001, all comparisons), and patient age (P = .002) were significantly associated with higher ED-attributable costs during the postindex period. The presence of diabetes and depression (P < .001, all comparisons) was significantly associated with lower ED-attributable costs (Table II). Medication switching, index sildenafil cost, presence of dyslipidemia, presence of hypertension, preindex costs (P < .001, all comparisons), age (P = .007), presence of diabetes (P = .0057), and presence of depression (P < .001) were associated with significantly higher overall health care costs during the postindex period (Table II).

DISCUSSION

Oral PDE-5 inhibitors are currently the first-line treatment for ED, owing to their efficacy, tolerability, and ease of use. (39) However, one of the major challenges of successful ED treatment in clinical practice is the lack of patient education and appropriate dosage titration. (40) These difficulties may result in patients prematurely switching medications and incurring additional costs.

The current study demonstrates that ED-attributable costs in patients receiving an initial prescription for sildenafil are significantly lower among patients who refill their sildenafil prescription compared with patients who switch to another PDE-5 inhibitor agent. Specifically, patients who refilled their sildenafil prescription incurred an average of $131.51 in health care costs attributable to ED during the six-month postindex period, compared with an average of $173.38 among patients who switched ED medications. The difference in ED costs was primarily attributed to an additional $30 in pharmacy costs, which was accompanied by an additional $12 in medical costs for patients who switched.

No significant differences were noted in the prevalence of comorbidities, and preindex overall costs were not significantly higher in the switch cohort. Patients who switched were slightly older and had a higher index sildenafil cost. Thus, regression was used to correct for differences in age, comorbidities, preindex costs, and index sildenafil cost. The regression analysis revealed that ED-attributable health care costs were approximately 41% lower among those who refilled their sildenafil prescription compared with those who switched. The regression analysis for overall costs was consistent with this finding, indicating 43% higher costs in patients who switched medications. However, this was not a surprise because preindex costs were also numerically higher for the switch cohort.

Index sildenafil cost, patient age, and preindex costs were significantly associated with higher ED-attributable and overall costs in the regression models. As expected, depression and diabetes were associated with higher overall costs; however, these comorbidities were also connected to lower ED-attributable costs. This may be related to a potential negative effect of depression and diabetes on ED treatment success, resulting in discontinuation of PDE-5 medications and subsequently lower ED-attributable costs. Although the presence of dyslipidemia and hypertension was not significantly associated with ED-attributable costs, overall costs were significantly higher for patients with these comorbidities.

Limitations. The results of this study should be interpreted in the context of its limitations. First, costs were only examined in patients whose initial prescription claim was for sildenafil. Furthermore, the IHR does not contain indicators for prescriptions from mail-order pharmacy. It is possible that for socially sensitive medical conditions, such as ED, mail-order services may be used more often than for other types of medical conditions. Although this may have an effect on pharmacy costs, mail-order pharmacy accounts for only 1% to 2% of prescriptions in the IHR. There is no reason to assume that the distribution of mail-order prescriptions differed across the study comparator groups, which were derived from a cohort of patients who filled their first PDE-5 inhibitor prescription for sildenafil.

Although a retrospective study using a claims database has the advantage of reflecting real-world patient experience, it lacks the control of a properly conducted clinical trial. Moreover, such data may be subject to miscoding or undercoding and cannot account for the distribution of medication samples by physicians, a practice that could influence a patient's propensity to switch their medications.

Another important limitation of this analysis is that the data were culled from patients who received their index prescription for sildenafil between November 2003 and March 2004. Both vardenafil and tadalafil were approved in 2003 and thus were relatively new to the market at the beginning of the study period. This may have contributed to the minimal switching observed in this study and subsequent underestimation of the costs of switching.

CONCLUSIONS

The present study suggests that patients who switch to another PDE-5 inhibitor agent after receiving an initial prescription for sildenafil incur greater ED-attributable and overall costs than patients who refill their sildenafil prescription. Although the influence of physician communication about ED was not evaluated in this study, perhaps additional discussion with patients about appropriate use and expectations for ED treatment, including potential need for dose titration, may prevent switching and associated additional costs.
APPENDIX: ICD-9-CM AND NATIONAL DRUG CODES

 Medical
 Codes Pharmaceuticals

ED 302.70, 302.71, Viagra, Cialis, Levitra
 302.72, 302.9,
 V41.7, 607.84

Hypertension 401.xx Accupril, Accuretic, acebutolol,
 Aceon, Adalat CC, Afeditab CR,
 Altace, Atacand, Atacand HCT,
 atenolol, atenolol/chlorthalidone,
 Avalide, Avapro, benazepril, benaze-
 pril HCTZ, Benicar, Benicar HCT,
 Betachron, Betapace, Betapace AF,
 betaxolol, bisoprolol fumarate,
 bisoprolol fumarate/HCTZ, Blocadren,
 Calan, Calan SR, Capoten, Capozide,
 captopril, captopril/HCTZ, Cardene,
 Cardene SR, Cardizem, Cardizem CD,
 Cardizem LA, Cardizem SR, Cardura,
 Cartia XT, Cartrol, Catapres,
 Catapres-TTS 1, Catapres-TTS 2,
 Catapres-TTS 3, clonidine, Clorpres,
 Coreg, Corgard, Corzide, Covera-HS,
 Cozaar, Dilacor XR, Dilt-XR, Diltia
 XT, diltiazem, diltiazem XR, Diovan,
 Diovan HCT, Diutensen-R, doxazosin
 mesylate, Dynacirc, Dynacirc CR,
 enalapril maleate, enalapril maleate/
 HCTZ, Enduronyl, Enduronyl Forte,
 fosinopril sodium, guanabenz acetate,
 guanfacine, HCTZ/reserpine/
 hydralazine, Hydra-Zide, hydralazine,
 Hytrin, Hyzaar, Inderal, Inderal LA,
 Inderide-40/25, Innopran XL, Isoptin
 SR, Kerlone, Labetalol, Levatol,
 Lexxel, Lisinopril, Lisinopril/HCTZ,
 Loniten, Lopressor, Lopressor HCT,
 Lotensin, Lotensin HCT, Lotrel, Mavik,
 methyldopa, methyldopa/HCTZ,
 metoprolol tartrate, Micardis,
 Micardis HCT, Minipress, Minizide 1,
 minoxidil, moexipril, Monopril,
 Monopril HCT, nadolol, nicardipine,
 Nifediac CC, Nifedical XL,
 nifedipine, nifedipine ER, Nimotop,
 Normodyne, Norvasc, pindolol,
 Plendil, prazosin, Prinivil, Prinzide,
 Procardia, Procardia XL, propranolol,
 propranolol w/HCTZ, Quinaretic,
 reserpine, Sectral, Sorine, sotalol,
 sotalol AF, sotalol, Sular, Tarka,
 Taztia XT, Tenex, Tenoretic 100,
 Tenoretic 50, Tenormin, terazosin,
 Teveten, Teveten HCT, Tiazac,
 Timolide, timolol maleate, Toprol XL,
 Trandate, Uniretic, Univasc, Vascor,
 Vaseretic, Vasotec, verapamil,
 Verelan, Verelan PM, Visken, Wytensin,
 Zebeta, Zestoretic, Zestril, Ziac

Dyslipidemia 272.xx Advicor, Altocor, Altoprev, Caduet,
 cholestyramine, cholestyramine light,
 Colestid, Crestor, fenofibrate,
 gemfibrozil, Lescol, Lescol XL,
 Lipitor, Locholest, Lofibra, Lopid,
 lovastatin, Mevacor, Niaspan,
 Pravachol, Pravigard PAC, Prevalite,
 Questran, Questran Light, Tricor,
 Welchol, Zetia, Zocor

Depression 296.22, 296.3, Amitriptyline, amoxapine, Anafranil,
 311.xx Aventyl, Budeprion SR, bupropion,
 Celexa, clomipramine, desipramine,
 Desyrel, Effexor, Effexor XR, Elavil,
 Emitrip, fluoxetine, fluvoxamine
 maleate, imipramine, Lexapro,
 Ludiomil, Luvox, maprotiline,
 mirtazapine, nefazodone, Norpramin,
 nortriptyline, Pamelor, paroxetine,
 Paxil, Paxil CR, Pexeva, Prozac,
 Prozac Weekly, Remeron, Serzone,
 Surmontil, Tofranil, Tofranil-PM,
 Trazodone, Vivactil, Wellbutrin,
 Wellbutrin SR, Wellbutrin XL, Zoloft

Diabetes 250.xx Actos, Amaryl, Avandamet, Avandia,
 chlorpropamide, Diabeta, Diabinese,
 Fortamet, Glipizide, Glipizide ER,
 Glipizide XL,Glucophage, Glucophage
 XR, Glucotrol, Glucotrol XL,
 Glucovance, glyburide, glyburide
 micronized, glyburide-metformin,
 Glynase, Glyset, Humalog, Humalog Mix
 75/25, Humulin 50/50, Humulin 70/30,
 Humulin L, Humulin N, Humulin R,
 Humulin U, Iletin II Lente Pork,
 Iletin II NPH Pork, Iletin II Regular
 Pork, Iletin NPH, Lantus, Metaglip,
 metformin, metformin ER, Micronase,
 Novolin 70/30, Novolin L, Novolin N,
 Novolin R, Novolog, Novolog Mix
 70/30, Prandin, Precose, Riomet,
 Starlix, tolazamide, tolbutamide,
 Tolinase, Velosulin Human BR

ED = Erectile dysfunction; ICD-9-CM = International Classification of
Diseases, 9th Edition, Clinical Modification; HCTZ =
hydrochlorothiazide.


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DISCLOSURE

Dr. Harnett and Dr. Russell disclosed they are employees of Pfizer Inc. Dr. Mulhall acknowledged that he received grant/research support from and was on the speaker's bureau for Pfizer, and was a consultant/advisory board member for Pfizer, Eli Lilly, Auxillium, and Johnson & Johnson.

Address for correspondence: James P. Harnett, PharmD, MS, U.S. Outcomes Research, Pfizer Inc, 235 East 42nd Street, New York, New York 10017. E-mail: james. harnett@pfizer.com.

To obtain reprints, please contact Kevin Chamberlain at (914) 337-7878, ext. 202 or visit our website at www.medicomint.com. Copyright 2006 by Medicom International. All rights reserved.

Dr. Harnett is Director of Outcomes Research and Dr. Russell is Senior Director, Regional Medical & Research Specialist, U.S. Outcomes Research, Pfizer Inc, New York City. Dr. McLaughlin is Director, Clinical Analytics and Outcomes, Quality Improvement and Patient Safety, Stanford University Medical Center, Stanford, California. Mr. McLean is Programmer, Statistician, NDCHealth, Phoenix. Dr. Mulhall is Associate Professor of Medicine, Department of Urology, Weill Medical College of Cornell University, New York Presbyterian Hospital, and Memorial Sloan Kettering Cancer Center, New York City.

This research was supported by Pfizer Inc.
TABLE I: DEMOGRAPHIC CHARACTERISTICS

 Refilled
Characteristic (N = 10,137)

Mean Age (yr) * 56.4 [+ or -] 11.1
Comorbidities of Interest ([dagger]) (N)
 Dyslipidemia 4,920 (49%)
 Hypertension 6,048 (60%)
 Diabetes 2,015 (20%)
 Depression 2,804 (28%)
Mean Index Sildenafil Cost * $24.80 [+ or -] $37.38

 Switched
Characteristic (N = 726)

Mean Age (yr) * 58.5 [+ or -] 10.8
Comorbidities of Interest ([dagger]) (N)
 Dyslipidemia 354 (49%)
 Hypertension 425 (59%)
 Diabetes 157 (22%)
 Depression 207 (29%)
Mean Index Sildenafil Cost * $29.47 [+ or -] $43.21

Characteristic P Value

Mean Age (yr) * < .001
Comorbidities of Interest ([dagger]) (N)
 Dyslipidemia .907
 Hypertension .552
 Diabetes .621
 Depression .255
Mean Index Sildenafil Cost * .005

* Mean [+ or -] standard deviation.

([dagger]) See Appendix for ICD-9-CM codes.

N = Number; ICD-9-CM = International Classification of Diseases,
9th Edition, Clinical Modification.

TABLE II: REGRESSION ANALYSES OF POSTINDEX COSTS

 Costs Attributable to ED
Variable Coefficient * P Value

Medication Switching 0.4076 < .001
Index Sildenafil Cost 0.0149 < .001
Age 0.0052 .002
Dyslipidemia 0.0595 .113
Hypertension -0.0540 .162
Depression -0.3115 < .001
Diabetes -0.1958 < .001
Preindex Cost 0.0958 < .001

 Overall Costs
Variable Coefficient P Value

Medication Switching 0.4294 < .001
Index Sildenafil Cost 0.0081 < .001
Age 0.0043 .007
Dyslipidemia 0.2614 < .001
Hypertension 0.2536 < .001
Depression 0.1335 < .001
Diabetes 0.1179 .006
Preindex Cost 0.2222 < .001

* The coefficient, or partial regression coefficient, represents
the importance of the covariant to the costs.

ED = Erectile dysfunction.

Figure 1. Preindex and postindex costs contributable to
erectile dysfunction for patients who refilled their sildenafil
prescription compared with those who switched to another
phosphodiesterase type 5 (PDE-5) inhibitor. * P < .001.

 Refill sildenafil Switch to another PDE-5
 inhibitor

Preindex $19.32 $20.81

Postindex $131.51 $173.38

Note: Table made from bar graph.

Figure 2. Preindex and postindex overall health care costs for
patients who refilled their sildenafil prescription compared with
those who switched to another phosphodiesterase type 5 (PDE-5)
inhibitor.

 Refill sildenafil Switch to another PDE-5
 inhibitor

Preindex $636.48 $794.91

Postindex $648.40 $757.31

Note: Table made from bar graph.
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Article Details
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Title Annotation:Health Economics
Author:Harnett, James P.; McLaughlin, Trent P.; Mulhall, John P.; Russell, David; McLean, Sean
Publication:Managed Care Interface
Geographic Code:1USA
Date:Nov 1, 2006
Words:4349
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