EVERETT, Mass. -- An Everett teenager was recovering Friday after he ingested high-blood pressure pills that a local pharmacy accidentally put in his sleeping pill prescription.

NewsCenter 5's Sean Kelly reported that Chris Stopford's father, Robert, noticed that his son was ill Wednesday after the teen took what should have been Ambien sleeping pills.

"I said, 'Chris, are you all right?' And he was lying on the couch, and he started shaking," Robert Stopford said.

He said that he recalled seeing reports on NewsCenter 5 about several CVS drugstores that accidentally mixed up prescriptions. He thought that the same mistake could have happened at the Glendale Square Walgreens, where he picked up his son's medication.

"I looked at the prescription, and I opened it up, and pulled (out the pills), and when I was looking at them I saw a few different ones that were smaller,"

A Walgreens pharmacist later determined that the bottle had high-blood pressure medication mixed in with the sleeping pills. Robert Stopford said that he thinks his son may have taken three of the wrong pills within 24 hours.

"The most fear I had was when I thought I was going to lose my son -- my only son. That's the only thing I live for," Robert Stopford said.

A Walgreens spokesperson said that there are a number of checkpoints they go through when a pharmacist fills a prescription.

"Errors are rare and we take them very seriously. We are investigating what happened and what can be done to prevent it from happening again," Walgreens said in a statement.

The company said that they made a phone call to the Stopford family to apologize, but Robert Stopford said that he has not heard from anyone at Walgreens.