generic drug price variation for heart failure drugs

Most of us, I believe, usually prescribe generic medications to patients, especially for patients who have limited or no insurance and have large out-of-pocket medication costs. A recent study looked at the variability of 3 generic drugs used for heart failure finding dramatic differences within similar geographical areas (see generic drug cost variability jamaintmed2016 in dropbox, or doi:10.1001/jamainternmed.2016.6955). Details:

-- data reflect 153 chain and 22 independent pharmacies in a 2-state region (Missouri and Illinois), across 55 zipcodes
-- they compared the cost for uninsured patients of low and high dose digoxin (0.125 and 0.25 mg/d), lisinopril (10 and 40 mg/d), and carvedilol (6.25 and 25 mg bid) for 30– and 90–day supplies.
-- They also correlated the costs with the annual income by zipcode

results:
-- median annual income within pharmacy zipcodes was $53,122, with a range of $10,491 – $112,017
-- the number of manufacturers was about 8 for each drug
-- only one chain had consistent pricing across its stores
-- for a 90-day supply of the highest dose of the meds:
    --digoxin 0.25mg varied from $10 to $910.99, with median $114.99
    ​--lisinopril 40mg varied from $6.75 to $223.95, with median $34.25
    ​--carvedilol 25mg varied from $6 to $208.44, with median $41.23
    ​--and, for all 3, $30 to $1,144.98, with median $180.46
-- only 1.7% of pharmacies charged less than $25 for 30-day supply and 5.3% less than $100 for 90-day supply.
-- overall, they found:
    -- pharmacy type (chain vs. independent) was not significantly associated with pricing
    -- pharmacy pricing did not vary by median annual income of the area, whether median income was $85,883, $59,347 or $31,032
    ​-- pricing did not vary significantly by state, or clustering by zipcode (review of their figure showed very close proximity of pharmacies with very high and very low price drugs)

commentary:
-- so, pretty shocking differences in generic drug pricing, independent of the income of the neighborhood, the type of pharmacy, or drug dose/duration of therapy.
-- And, it is clear from several studies that the cost of medications does correlate with medication adherence.
-- We do seem to have a counterintuitive (and counterproductive) system in the US: patients without insurance, often those with the least income, have to pay much more for medications than insurance companies negotiate (ie, the above prices are likely much higher than an insurer would pay, even with the patient co-pay added).
--This study only looked at 3 drugs, and though more data is needed on other meds, my own experience is that there is large variability in pricing for other drugs as well
So, bottom line: I think the study reinforces that patients without insurance really should call around to different pharmacies to check pricing. Patient should understand that there are potentially huge variations in drug costs from one pharmacy to another, even in the same neighborhood. And we really should move to a more transparent and consistent system of drug pricing in this country.