Women have easier and quicker access to the morning-after pill since the Food and Drug Administration ruled that the medication could be sold to adults without a prescription, a survey of pharmacies in three large US cities shows.

In 2006, the FDA approved "behind the counter" status for Plan B — meaning that people aged 18 and older can buy the emergency contraceptive over the counter, while younger people need a prescription from a doctor. The medication consists of a high dose of progesterone, and works by preventing the ovaries from releasing an egg, or delaying this release. Unlike the "abortion pill," RU-146, it will not affect an existing pregnancy.

"The sooner you take it the more effective it is, which is why availability is so important," Dr. Rebekah E. Gee of the University of Pennsylvania School of Medicine in Philadelphia, the lead researcher on the study, told Reuters Health. Plan B works best if it is taken within 24 hours of unprotected sex, she added.

To investigate whether the rule change had any effect on the drug's availability, Gee and her colleagues surveyed pharmacies in Atlanta, Boston, and Philadelphia in 2005 and 2007. The first round of the survey included 1,087 pharmacies, while the second included 795.

In 2005, Gee and her team found, 23 percent of pharmacies reported being unable to dispense Plan B within 24 hours. Two years later, just 8 percent did. And 2 percent of the pharmacists surveyed in 2007 said they would refuse to dispense the drug, compared to 4 percent in 2005.

In Atlanta, where state law permits pharmacists to refuse to dispense emergency contraception if it conflicts with their moral or religious beliefs, the rate of refusal was 9 percent in 2005 and fell to 2 percent in 2007. The percentage of pharmacies that were unable to dispense the drug within 24 hours fell from 35 percent to 14 percent.

Philadelphia has no laws on the books regarding whether a pharmacist can refuse to dispense emergency contraception or requiring pharmacies to stock commonly used medications. In that city, the percentage of pharmacies reporting being unable to dispense the drug fell from 23 percent in 2005 to 10 percent in 2007, while refusal rates were 3 percent in 2005 and 4 percent in 2007.

In Boston, which has laws requiring pharmacies to stock all commonly available medications, rates of being unable to dispense Plan B or refusing to do so were low at both time points.

Plan B is extremely safe, Gee noted, with nausea being the most common side effect. She said she believes it should be available without a prescription to younger people as well. "There's no evidence that use of Plan B leads to more intercourse or riskier behavior, even though some of its opponents have claimed that," she added. "The data definitely show that that's not true."

The US has the highest rate of unplanned pregnancies in the industrial world, Gee pointed out, while 1 in 3 US women will have an abortion. Plan B does not reduce rates of unplanned pregnancy in the population at large, she added; she and her colleagues say that this is because it isn't a replacement for routine contraception. "Only through increased access to more effective methods of contraception and by empowering women to be educated about their reproductive health will we likely see a change in unintended pregnancy rates," they wrote.