Shoppers Drug Mart has issued an apology for dispensing expired birth control medication to about 100 women in Western Canada.

The retailer confirmed that expired Alesse 21 was given to customers in British Columbia, Alberta, Saskatchewan and Manitoba between March 16 and April 1.

“We deeply regret this occurrence and apologize unreservedly to all those affected,” Shoppers said in a statement on its website.

Shoppers is blaming its blunder on a data entry error at a distribution centre in Calgary, which resulted in the expired birth control being shipped to various stores. The Alesse 21 was sold in packages of 21 tables with lot number G73720 and an expiry date of Sept. 2014.

Women in Alberta who bought that brand of birth control from Shoppers during the listed dates are urged to check the expiry date on their medication immediately and contact their pharmacy.

The retailer has already reached out to affected customers in all other provinces directly, and offered to replace their medication and provide information and counselling.

“The care of all our patients and their health is the utmost priority for us at Shoppers. Our pharmacists take their professional responsibility to dispense medications very seriously,” it said.

Shoppers has promised to conduct a review of internal protocols to determine how to prevent similar problems in the future.