Can income-based co-payment rates improve disparity? The case of the choice between brand-name and generic drugs

Table 1 Summary statistics on patients for Top 5 drugs in terms of number of prescriptions

	rebamipide 100 mg		amlodipine 5 mg		lansoprazole OD 15 mg		sennoside 12 mg		etizolam 0.5 mg
	Copayment rate		Copayment rate		Copayment rate		Copayment rate		Copayment rate
	10%	30%	10%	30%	10%	30%	10%	30%	10%	30%
Number of prescriptions	1,018,112	135,815	922,264	127,108	851,256	117,551	787,883	88,352	714,066	95,195
Generic dispensed	46.4%	44.1%^e	50.8%	47.7%^e	41.7%	38.3%^e	49.0%	39.0%^e	26.5%	23.1%^e
Age, year
Mean	82.9	82.3	83.2	82.4	84.5	83.7	85.3	84.8	83.3	82.5
Std. Dev.	5.3	5.1	5.5	5.2	5.9	5.6	6.0	5.7	5.3	5.1
Female	72.2%	56.5%	66.5%	48.1%	69.3%	51.3%	71.2%	51.0%	77.3%	61.8%
Amount^a, tablets/capsules
Mean	51.6	52.0	31.2	34.7	28.9	31.9	43.8	48.3	38.2	41.5
Std. Dev.	41.3	44.3	19.7	22.3	19.3	21.4	40.6	41.4	31.5	34.4
Medical spending^{b, c}, JPY/month
Mean	27,358	28,883	20,837	21,279	27,507	31,314	25,014	31,681	24,379	25,244
Std. Dev.	24,623	27,106	21,421	23,105	26,470	30,274	25,793	29,529	23,459	25,662
Spending on other drugs^{b, d}, JPY/month
Mean	25,534	25,637	21,258	21,745	27,723	29,779	23,400	26,886	23,949	24,410
Std. Dev.	23,669	26,258	19,538	21,628	25,276	28,081	25,458	28,794	22,327	23,813

Notes: Std. Dev. stands for standard deviation, OD stands for orally disintegrating tablet. We present summary statistics for top 5 prescribed drugs in number of prescriptions in our data. Statistics are calculated at the prescription level. The observation period is from October 2013 to September 2014. ^aAmount is the total number of tablets/capsules within each prescription. ^b“Medical spending” and “Spending on other drugs” are represented in Japanese yen (JPY) per month. 100 JPY is approximately 1 USD. Each spending is calculated as the sum of spending by the patient and the insurer. ^cWe exclude spending on drugs to calculate “Medical spending”. ^dWe exclude the drug to be analyzed in calculation of “Spending on other drugs”. ^eThe proportion of generic drugs dispensed was statistically smaller in the 30% copayment group (high-income group) than in the 10% copayment group (general-income group) (p < 0.01 for each of the 5 drugs)

ISSN: 1472-6963