Fewer than 2% of people taking high doses of prescription opioids have filled a prescription for the opioid overdose antidote naloxone, a new study suggests.

The percentage of filled naloxone prescriptions was no higher among people who had survived an overdose or who had been diagnosed with opioid use disorder, the researchers reported in the Journal of General Internal Medicine.

The Centers for Disease Control and Prevention (CDC) recommends that patients who take high doses of opioid painkillers receive a prescription for naloxone, according to HealthDay. Anyone who has other major overdose risk factors, such as a history of opioid use disorder or opioid overdose, also should receive a naloxone prescription, the CDC says.

“The vast majority of naloxone prescribing is to patients who have received opioid prescriptions, but there are other groups at high risk for overdose but not receiving prescription opioids, including people using only street drugs, that warrant further attention,” lead researcher Lewei (Allison) Lin, M.D., M.Sc., said in a news release.