Authors’ Reply to Liedgens and Henske: “Cost-Utility Analysis of Duloxetine in Osteoarthritis: A US Private Payer Perspective”

Abstract

Thank you for giving us the opportunity to respond to the letter from Liedgens and Henske [1] concerning our costutility analysis of duloxetine in osteoarthritis (OA) [2]. Our analysis spanned multiple drug classes, including nonsteroidal anti-inflammatory drugs (NSAIDs), opioids and an antidepressant. We were surprised by the reaction of Dr. Liedgens and Henske and are pleased to address their concerns. We do so below, using the same order and numbering as those used in their letter. 1) In their letter, Liedgens and Henske focus on pain levels. The basis of the treatment-specific utilities in our model was Western Ontario and McMaster Universities Arthritis Index (WOMAC) total scores, not exclusively pain scores. Total WOMAC scores incorporate function and stiffness, as well as pain. WOMAC scores have been mapped to health-related quality of life utilities by several studies [3–5] and have been used in pharmacoeconomic models such as that produced for the UK National Institute for Health and Clinical Excellence OA guideline [6]. The inclusion criteria for nearly all OA trials, regardless of treatment, specify pain of at least 4 on a 0–10 scale, i.e. at least moderate pain. Moreover, tapentadol trials have not reported baseline WOMAC scores, so there is no basis to assume that the severity of OA in those trials was greater than that in trials of other treatments. We believe that the continuum of treatments from NSAIDs to opioids represent relevant comparators to duloxetine and therefore they are appropriately represented in our analysis. 2) Liedgens and Henske note that our article did not make it clear which formulation of tapentadol was being compared. We concede that we could have been more specific; however, the assumptions we made for tapentadol were not made to enhance the position of duloxetine, but were made because of the unclear reporting of WOMAC scores in tapentadol trials (see response #9 below) and to be conservative in our estimation of the cost of tapentadol. The makers of tapentadol have conducted clinical trials of both immediate release (IR) [7] and extended release (ER) [8–10] formulations of tapentadol in OA populations. To be conservative in our analysis, the tapentadol IR formulation was used for costing because it is cheaper in the USA. Therefore, tapentadol IR dosing was also used. 3) Liedgens and Henske incorrectly state that an oxycodone daily dose of 10–30 mg was used in our model. The model’s dosage was 10–30 mg twice daily (see Table 1 in our article) [2]. The range of tapentadol dosing in the model was the same as that in the tapentadol IR study conducted by Hale et al. [7]. The average tapentadol IR daily dose used in the model was 450 mg, not the 600 mg stated by Liedgens and Henske. 4) Liedgens and Henske incorrectly state that the utility for tapentadol in our model was the same as that for tramadol. In fact, tapentadol was assigned the same utility as oxycodone—the highest efficacy-based, treatment-specific utility assigned in the model (see Table 1 in our article). In addition, the initial 3-month discontinuation rates for tapentadol IR and ER are very similar (44.0 % for tapentadol ER in the analysis performed by Lange et al. [11] This reply refers to the article available at doi:10.1007/s40258-0130031-3 and doi:10.1007/s40258-013-0048-7.