Pfizer said on Tuesday it was recalling about 1 million packets of birth control pills in the United States because they may not contain enough contraceptive to prevent pregnancy.
Pfizer said the birth control pills posed no health threat to women but it urged consumers affected by the recall to "begin using a non-hormonal form of contraception immediately."
The drugmaker said the issue involved 14 lots of Lo/Ovral-28 tablets and 14 lots of Norgestrel and Ethinyl Estradiol tablets.
It said an investigation had found that some blister packs of the oral contraceptive might contain an inexact count of inert or active ingredients in the tablets.
The pills were manufactured by Pfizer and marketed by Akrimax Pharmaceuticals and shipped to warehouses, clinics and retail pharmacies nationwide, the company said.