Pharmacies across much of Canada are sifting through their stocks of Alysena 28 birth control pills, after it was discovered that one batch did not contain enough contraceptive tablets.

In a recall notice, Apotex Inc. said Alysena pill packs in the affected batch – LF01899A – may contain only two weeks’ worth of the contraceptive instead of three, which could lead to unplanned pregnancies.

The packs are supposed to contain 21 active pills and seven placebo pills, meant to remind women to keep taking them until the next cycle. But due to a packaging mistake, the lot may instead contain 14 active tablets and 14 placebos.

 “The first three rows of the package are the hormones, which are pink pills. And the last row contains the placebo pills, which are white,” said Nova Scotia pharmacist Darlene George.

“The recall was on a package that had two rows of white pills, instead of one row of white.”

Apotex issued an Alysena 28 recall last week, but it wasn’t until Monday – five days later -- that Health Canada upgraded the recall, warning pill users to use a back-up method of birth control “as an interim measure until you speak with your physician and obtain medical advice.”

Dr. Supriya Sharma, a senior medical advisor with Health Canada, said the agency was notified of the Apotex recall “very quickly,” but needed time to sort through the information and issue an upgraded recall notice.

“We are going to be following up with the company to find out if the recall was done appropriately and certainly we need to follow up with the company to find out why this issue occurred in the first place,” she told CTV News.

Alysena 28 is sold in British Columbia, New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island and Quebec.

The mix-up could have “devastating effects” for women who have taken pills from the affected batch, said Louise MacDonald, executive director of Every Woman’s Centre in Sydney, N.S.  

“It really is hard to imagine that could happen in this day and age,” she told CTV Atlantic.

Pharmacists are now in the process of trying to contact the women who may have been given packs from the faulty batches of Alysena.

One pharmacy chain, British Columbia-based London Drugs, is even offering free pregnancy tests to women who may have taken the pills.

Apotex said Tuesday that it’s co-operating with the Health Canada investigation. It also noted that the birth control pills originate in a factory in Spain.

With a report from CTV’s medical specialist Avis Favaro and producer Elizabeth St. Philip