ER visits, hospital admissions, hospital lengths of stay (problem?), and/or medical expenditures (compared to patients taking older drugs)?
“Too often,” says Robert Seidman, chief pharmacy officer at health insurer WellPoint, “we're choosing the newer, pricier drug without considering whether older drugs would get the job done just as well”
Lipitor: $612/180 20mg tablets
Zocor: $799/180 20mg tablets but soon generics
Mevacor: $228.31/180 20mg tablets
Number of hospital bed-days declined most rapidly for those diagnoses with the greatest change in the total number of drugs prescribed and greatest change in the distribution of drugs (proxy for novelty)
Patients who consume newer drugs experience fewer work-loss days than patients who consume older drugs; and the former tend to have lower non-drug expenditures, reducing total expenditures
With larger dataset, and 3 years instead of 1 year of observation, Lichtenberg argues that a reduction in the age of drugs decreased non-drug expenditures 7.2 times as much as it increased drug expenditures. (8.3 times for Medicare population)
Effect of the launch of new drugs: Average 1 week increase in life expectancy in the entire population
Empirical question: Estimation of Average Treatment Effect
Are the high cost of new drugs justified based on their health outcome impact?
Lichtenberg studies do not address selection bias in treatment
Atorvastatin (Lipitor): Clinical Research
Collaborative Atorvastatin Diabetes Study (CARDS),
2,800 patients with type-2 diabetes, no history of heart disease, and relatively-low levels of cholesterol,
Positive Health outcome:
patients who took Lipitor had a 37 percent reduction in major cardiovascular events
which included heart attacks, stroke, chest pain that required hospitalization, cardiac resuscitation, and coronary revascularization procedures.
overall mortality rate for Lipitor patients was 27 percent lower than for those on placebo.
But: Study Sponsored by Pfizer / No comparison with older drugs / Relatively Healthy Population
Atorvastatin (Lipitor) Clinical Research - Hypertension
LIPITOR significantly reduced the rate of coronary events
either fatal coronary heart disease (46 events in the placebo group vs 40 events in the LIPITOR group)
or nonfatal MI (108 events in the placebo group vs 60 events in the LIPITOR group)]
relative risk reduction of 36% (based on incidences of 1.9% for LIPITOR vs 3.0% for placebo), p=0.0005
The risk reduction was consistent regardless of age, smoking status, obesity or presence of renal dysfunction. The effect of LIPITOR was seen regardless of baseline LDL levels. Due to the small number of events, results for women were inconclusive.
N = 10,305 (Anglo-Scandinavian Cardiac Outcomes Trial)
Mixed Results for Lipitor Vs. Zocor By THERESA AGOVINO, AP Business Writer Tuesday, November 15, 2005 06 57 PM
High doses of the cholesterol-lowering drug Lipitor were no better at preventing major heart problems than regular doses of rival Zocor, according to the latest study on efforts to aggressively treat the conditions released Tuesday.
Lipitor outperformed Zocor on several fronts such as lowering cholesterol and preventing nonfatal heart attacks. The findings will continue to give it an advantage in the market even if generic Zocor is less expensive, some doctors said.
But: HIGH DOSE OF LIPITOR vs. REGULAR DOSE OF ZOCOR
What about LIPITOR vs. MEVACOR, PRAVACHOL, LESCOL, CRESTOR
Naïve Fixed Effects Regression
Threats to Identification
Selection for treatment most likely not random
Selection Bias in Treatment
Perhaps physicians assign nonrandom populations to treatment
Perhaps patients seek physicians who prescribe new drugs (e.g., Lipitor)
Correction for Selection Bias
Instrumental Variable Approach
Gives internally valid causal effects for individuals whose treatment status is manipulable by the instrument
Candidates: the combination of covariates from Chapter 2 as an instrument for the treatment (i.e., use of new drug, such as Lipitor)
With patient’s pre-adoption status in the instruments to avoid patient self-selection
However, may reduce statistical power
Note: we can see if patients actually self-select into treatment
But: instruments (predicts adoption) may also affect the dependent variable (measures for health outcome)?
Correction for Selection Bias
Selection on Observables
Propensity Score Matching
Analysis of the Effects of Unobservables?
Lipitor Costs (Taiwan NHID formulary 2004, in USD):
$1.04 per 10 mg tablet; $1.40 per 20 mg; $1.75 per 40 mg
What are the cost savings?
If new drug reduces emergency and hospital services
Savings = reduced cost in emergency and hospital services – increased drug costs
What are the additional costs?
If new drug has not health outcome impact?
Additional cost = difference in price of new and old drugs
Distribution of new Lipitor takers
“Treatment” vs. “Non-Treatment”
Graphical Evidence – ER visits No adjustment for selection bias
Graphical Evidence – ER visits (1009 Lipitor takers)
Graphical Evidence – Smoothed ER visits (1009 Lipitor takers)
Graphical Evidence – ER visits (656 consistent takers)
Graphical Evidence – Smoothed ER visits (656 consistent takers)