Troopers did not identify the drug involved in a brief mention on the agency's Web site.
However, trooper spokeswoman Megan Peters said late Friday in a news release that the charges were in connection to the drug OxyContin, a strong prescription painkiller.
Johnston is the mother of 18-year-old Levi Johnston. Alaska Gov. Sarah Palin, the GOP nominee for vice president, announced in September that her 18-year-old daughter, Bristol, was pregnant and Johnston was the father.
Sherry Johnston was released from jail in Palmer on $5,000 bail. She was not scheduled to be immediately arraigned.
Peters said no one else had been charged. Few details could be released Friday because the investigation was ongoing, she said.
Palmer District Attorney Roman Kalytiak said information on the case had not yet been forwarded to his office.