ADHD patients may experience a drug shortage of Adderall as some pharmacies across the U.S. are having difficulties securing the prescription drug due to supply chain issues.

Adderall is a commonly used medication for treating attention-deficit/hyperactivity disorder (ADHD). CVS Health and Walgreens have had to tell patients that Adderall was out of stock with wait times of more than a week, according to a report from Bloomberg.

Walgreens confirmed the Adderall supply disruption, with company spokesperson Rebekah Pajak telling the news outlet, “There are supply chain challenges with this drug. The issues are affecting both instant-release and extended-release Adderall.”

CVS spokesperson Matthew Blanchette also said, “in most cases,” it is able to fill Adderall prescriptions.

The supply chain problems for Adderall are being seen by drugmakers Teva Pharmaceutical, Amneal Pharmaceuticals, Rhodes Pharmaceuticals, and Novartis, which have had the drug on back order, according to the report.

The need for Adderall has accelerated during the COVID pandemic as more patients are receiving the drug, which was prescribed more frequently due to telehealth appointments. While more patients have received Adderall for ADHD diagnosis, the drug itself has been scrutinized over “aggressive prescribing practices,” Bloomberg said.

Despite reports that Adderall is in short supply, the Food and Drug Administration (FDA) has not added it to its official list of drug shortages, saying on its website it reports shortages when “it has confirmed that overall market demand is not being met by the manufacturers of the product.”

The FDA suggests patients continue to watch its website for updates or contact the drug manufacturers directly for more information, agency spokesperson Cherie Duvall-Jones said in the report.

Because Adderall is a Schedule II controlled substance, patients are prevented from picking up more than a month’s supply at one time due to its potential for abuse. Some patients told Bloomberg they have to call around to several pharmacies to find one that has Adderall in stock, and some have considered buying the drug illegally.

A survey from the National Community Pharmacists Association said that 64% of pharmacies are struggling to secure a supply of Adderall.