We have two drugs that are serotonin reuptake inhibitors (SRIs) and which have varying side effects. They also have different costs, one being available as a generic drug ($180 annual co-pay), and the other being fairly new and still under patent ($360 annual co-pay). The new drug tends to be more effective in lowering the risk of suicide but also to have a more profound impact on the personality of the patient, which some patients find disturbing. Both of the drugs are prescribed only for patients who underwent at least one severe depressive episode during the past year requiring 3-day hospitalization due to suicide risk. The following table gives the known information about both drugs

Drug	Annual Co-Pay	Life Expectancy ( (expressed as months/years f free of suicide risk)	EQ-5D Quality of Life Index (self-report)
SRI # 1	$180.00	7 months or 0.583 years	0.85
SRI #2	$360.00	11.5 months or 0.958 years	0.65

Question 1: Finding the Quality Adjusted Life Years (QALY) for each drug

The EQ-5D index is calibrated so that the index numbers can be used as simple multipliers to find Quality Adjusted Life Years.

Step 1: Multiply the index number for SRI#1 by its Life Expectancy expressed as a fraction of a year. What is the Quality Adjust Life Year for SRI #1? (Note that it will be a fraction of a year. Calculate to third decimal place)

Step 2: Multiply the index number for SRI#2 by its Life Expectancy expressed as a fraction of a year. What is the Quality Adjust Life Year for SRI #2? (Note that it will be a fraction of a year. Calculate to third decimal place)

Question 2: Finding the Opportunity Cost of the Newer Drug

The cost-utility ratio answers the question: How much more do I pay for each additional unit of benefit? Our benefit in this case is the increase in Quality Adjusted Life Years, so we want to find the increase in cost and in benefit when we adopt the newer drug.

Step 1: Subtract the Annual Co-Pay of SRI #1 from the Annual Co-Pay of SRI #2.

Step 2: Subtract the QALY that you found for SRI #1 in Question 1 from the QALY that you found for SRI #2 in Question 1. (To get the difference between QALY)