As the death toll from opioids — both prescription and nonprescription — spiked to an estimated 33,000 in 2015, counties across the United States were filling dramatically different numbers of opioid prescriptions. In 1 in 5 U.S. counties, the number of prescriptions increased by more than 10 percent over five years, from 2010 to 2015. Half of all counties experienced reductions in prescriptions over that same time period.

The data was previously described in a July report from the Centers for Disease Control and Prevention and made available by The Associated Press last week. Quintiles IMS, a health technology company, provided the raw retail prescription data based on 59,000 pharmacies representing 88 percent of all U.S. prescriptions.

The numbers reflect the amount of opioids prescribed using a standardized unit of measurement, morphine milligram equivalents, not the number of doctors’ prescriptions filled. The prescriptions are also shown in the county where they were filled, not where a patient lives. This could affect the numbers by, for example, making prescriptions look particularly high in counties located next to a county without a pharmacy.

The data shows that changes in the amount of opioids being prescribed over the five-year span varied greatly by place. In 80 percent of Florida counties, some of which contained clinics unofficially labelled as “pill mills” (the name refers to the ease with which people could buy prescription pain medication), prescriptions dropped from 2010 to 2015. By 2015, many of these counties’ numbers were in line with the national average. Meanwhile, in the heart of Appalachia, the number of opioid prescriptions filled per capita dropped in many counties — even though numbers remained higher than figures in most of the U.S.

In general, the places with the largest number of prescriptions filled tended to have more white residents and higher rates of poverty and unemployment, the CDC found in its study. Maps of the per capita opioid prescriptions by county and the change in those prescriptions over time reveal regional variations as well. Prescriptions are low and decreasing in much of the middle of the country. Ohio and Kentucky, two of the states that have been hit hardest by the opioid epidemic, have made some changes to curb inappropriate prescribing, according to the CDC. Those include mandating that doctors review a state database of prescribing data to monitor patients’ prescriptions and changing regulations on pain management clinics. Both states saw declines in prescriptions in a majority of counties.

CORRECTION (Aug. 7, 1:10 p.m.): A previous version of this article misstated the annual number of drug overdose deaths that involve a prescription or non-prescription opioid. It is approximately 33,000, not 60,000.

CORRECTION (Aug. 2, 11:07 a.m.): A previous version of this article incorrectly described U.S. opioid deaths. An estimated 60,000 people die each year from prescription and non-prescription opioids, not just prescription opioids.