BOSTON (CBS) — Anyone who has waited in a drug store for a prescription knows a pharmacy counter can be a busy place.

“It’s a high-pace, high-stress environment,” a former CVS pharmacy technician told the I-Team.

She did not want to be identified, but she believes that stress leads to mistakes.

“Somebody gets the wrong strength of medication, somebody gets the wrong number of pills,” she said.

The I-Team obtained documents detailing prescription drug errors reported to the State Department of Public Health. Since 2010, pharmacies reported 194 serious drug errors. In one case, an allergy drug was given to a patient instead of a high blood pressure medication. In another case, a patient got something for acid reflux instead of an anti-depressant, and an arthritis drug was given to someone who needed a medicine for seizures.

The pharmacy technician believes a growing trend in pharmacies is behind all that stress and the errors. It is called performance metrics, a system used to measure how many prescriptions a pharmacist fills and how fast. It also counts flu shots and phone calls pharmacists make to patients urging them to fill prescriptions. If the pharmacist falls behind, she says, they’ll hear about. “You didn’t make all of your 50 phone calls. I want you to write an action plan to tell me how tomorrow you are going to get all of your prescriptions filled, get your phone calls made plus give out x number of flu shots,” she said describing what pharmacists she worked with were told.

CVS would not talk to us on camera, and would not allow our cameras inside their stores, but they did invite the I-Team inside a store to see how the system works. Company representatives told us if metrics contributed to mistakes they would change the system. They insist it does not.

In a written statement the company said: “The health and safety of our customers is our number one priority and we have comprehensive policies and procedures in place to ensure prescription safety.”

In spite of those assurances, pharmacists are starting to speak out against metrics. Susan Holden is the president of the Massachusetts Association of Pharmacists. She worked under a metrics system at a different drug store chain. “It was very nerve-wracking, very stressful, sometimes tearful,” she recalled. Holden now works as a hospital pharmacist and she says metrics puts too much stress on pharmacists. “Ultimately, I was afraid of harming a patient,” she said.

A survey of nearly 700 pharmacists conducted by the institute for safe medication practices found that more than 83 percent believed performance metrics contributed to dispensing errors.

Susan Holden believes if something doesn’t change, the problem could get worse. “The worst case scenario, it could be a very dangerous prescription error. I think anybody could draw a conclusion about what could happen,” she said.

The National Association of Boards of Pharmacy is urging states to restrict the use of metrics that are proven to compromise safety. The Massachusetts Board of Pharmacy has taken no action.