ASSESSING THE ECONOMIC VALUE OF A NEW ANTIDEPRESSANT - A WILLINGNESS-TO-PAY APPROACH

Using the method of willingness to pay (WTP), this study assesses the value of a new antidepressant, moclobemide, relative to that of tricyc lic antidepressants (TCAs), which have equivalent efficacy but less fa vourable adverse effect profiles. From a published meta-analysis of co ntrolled clinical trials, we identified 7 adverse effects, the risk of which differed significantly between moclobemide and TCAs. We obtaine d risk reduction data and descriptions of adverse effects from intervi ews with 95 individuals who had mild to moderate depression and who ha d been taking one or more TCAs in the previous year. Using a visual an alogue scale, respondents ranked and rated each adverse effect. Partic ipants were then asked (using the scenario of additional out-of-pocket drug payment) to quantify the maximum amount that they would pay for a new drug that reduced each adverse effect by the specified probabili ty. Blurred vision and tremor were ranked and rated as the most bother some adverse effects, with dry mouth being the least bothersome. On av erage, respondents were willing to pay an additional $Can22 per month [95% confidence interval (CI) 16-28] to reduce the risk of blurred vis ion from 10 to 5%. The lowest WTP value was for reducing the risk of d ry mouth from 40 to 15%, at $Can11 per month (95% CI 8-15). Although n ot measured directly, we derived 2 estimates of WTP for multiple (i.e, all 7) risk reductions. We obtained upper and lower WTP limits of $Ca n118 and $Can36 per month, respectively, depending upon aggregation as sumptions. Compared with the TCAs amitriptyline and imipramine, the ne t cost of moclobemide is greater, but the overall net benefit (WTP min us cost) is ambiguous given uncertainty about WTP aggregation over adv erse effects. However, compared with the TCAs desipramine and clomipra mine, the net benefit of moclobemide is unambiguously positive. We con clude that the WTP approach is a potentially valuable tool that requir es more development for use in healthcare economic evaluation.