The world's largest drugmaker recalled 14 lots of Lo/Ovral-28 and 14 lots of the generic counterpart Norgestrel and Ethinyl Estradiol late on Tuesday, prompting panicked exchanges on social media like Twitter.

Litigators began soliciting new clients who may have suffered health problems or unplanned pregnancy as a result.

"Unfortunately, this manufacturing error diminishes people's confidence in an extremely important and safe method of contraception," said Dr. Vanessa Cullins, vice president for external medical affairs at Planned Parenthood Federation of America.

Cullins noted this version of birth control has been in use for decades and remains safe and effective.

Pfizer said on Wednesday that the error may have been limited to 30 packets of the birth control pills, in which the "placebo" tablets taken at the beginning of a woman's menstrual cycle were placed in the wrong order with the pills that contain the contraceptive's active ingredient.

The placebo pills, which are different color from the active tablets, were placed in the blister pack out of order during the automated packaging process in a few random packets manufactured throughout 2011, company spokeswoman Kristen Neese said.

Pfizer was alerted to the problem when a consumer noticed a discolored pill in the middle of a pack, she said. All lots possibly affected were recalled, the problem was fixed and prevention measures are now in place, she said.

The company is now using social media and video messages on its own website to notify women of the recall.

But even if the error was more limited, women who took pills from any of the recalled lots should use a non-hormonal form of birth control immediately, experts said.

"If pills come from those lots, she should consider those pills ineffective from the standpoint of preventing pregnancy," Cullins said. "She is at risk of ovulation, of eggs being released and of becoming pregnant."

Pfizer manufactures and packages the birth control pill, but it is sold by Akrimax Pharmaceuticals.

The pills were distributed nationwide with no specific geographic concentration, Pfizer said. Expiration dates on the affected packs range from July 2013 to March 2014.

Dr. Natasha Johnson, a gynecologist at Brigham and Women's Hospital, a teaching affiliate of Harvard Medical School, said most women these days take generic forms of birth control pills.

She called the affected brands "fairly popular, well tolerated pills."

The Pfizer recall comes on the heels of increased attention surrounding birth control and possible health risks.

In recent months, U.S. health advisers have recommended stricter labels on a more widely used, newer generation of birth control pills, based on data showing they may put women at a higher risk of dangerous blood clots. They include Bayer AG's popular Yaz and Yasmin tablets.

A new federal rule requiring religious universities and other affiliated institutions to provide free birth control coverage has also drawn fresh opposition from religious groups.

(Editing by Michele Gershberg and Greg McCune)

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