Mylan Pharmaceuticals is recalling its oral contraceptive Freya-28 from the Canadian market, after a pharmacy found a package in which a placebo pill was in place of an active one.

Packages of Freya-28 have three rows of white, active pills, along with one row of green, placebo pills. Women typically take 21 active pills, followed by seven placebo pills during their menstrual period.

Health Canada, which is monitoring the voluntary recall, says missing one or more of the active pills could result in reduced effectiveness of the contraception and risks the possibility of an unplanned pregnancy.

“If you are missing one pill, it can increase your chances of getting pregnant but that depends on when that pill is taken or when you are having unprotected sex,” Dr. Supriya Sharma, a senior medical advisor at Health Canada, told CTV News Channel Wednesday.

Two Freya-28 lots were affected: 3739F001B and 3739F002B. The company’s other product, Freya-21, which contains only 21 active pills, are not part of the recall.

Almost 76,300 packages from the affected Freya-28 lots have been distributed in nine Canadian provinces since May 10 -- meaning that potentially thousands of women are affected.

The drug is packaged for Mylan by a Mumbai, India-based pharmaceutical company called Famy Care Ltd. The maker says so far, no one has reported any surprise pregnancies, but a full investigation is underway.

Unopened packages should be returned to the pharmacies where they were purchased, Health Canada says.

Health Canada also recommends that users of the pills use a non-hormonal method of birth control, such as condoms, spermicidal foam or gel, until another oral contraceptive can be obtained.

Consumers are also being asked to report to Health Canada any problems they might have potentially related to recalled pills, by visiting MedEffect Canada's webpage on Adverse Reaction Reporting.

The recall comes just four months after another similar birth-control pill recall, involving a brand called Alysena 28. One lot of that product contained too little active drug and too much placebo. About 50,000 faulty packets were distributed across Canada before the problem was discovered.

A law firm in Thunder Bay, Ont. launched an $800-million class action lawsuit against Alysena’s maker, Apotex, after more than 100 women came forward to say they had become pregnant while taking Alysena or endured undue stress.

Dr. David Juurlink, a former pharmacist and current drug safety researcher, says these incidents underscore the reality that the drug manufacturing industry is not perfect.

“But no process is perfect and I don’t think we can expect it to be. I mean there are millions upon millions of tablets and capsules made and dispensed every years in Canada and periodically, there are going to be mix-ups,” he told CTV News.

“Drug manufacturers have an obligation to consumers to make the process as close to perfect as they can, and I think consumers should realize that the process simply can’t be perfect.”

Consumers with any further concerns should contact their healthcare practitioners. Users of the pills can also contact Health Canada's toll-free line at 1-800-267-9675 with questions or complaints.