(Associated Press)

Right now, Plan B is available to teenagers under 17 by prescription, while older women must request it from a pharmacist. The decision to leave those regulations in place, my colleague Rob Stein reports, is “a surprise move and a stunning blow to some doctors, health advocates, family-planning activists, members of Congress and others to help women prevent unwanted pregnancies.”

It’s surprising to see such a public clash of opinions between two federal agencies over a drug’s availability. But in a way, it’s not. Plan B has, for over a decade now, had an incredibly complex path toward obtaining federal approvals. It’s been marked by multiple administrations’ officials resignations and created a complicated web of regulations around the contraceptive.

It started in 1999, when the FDA approved Plan B as a prescription emergency contraceptive. Four years later, its manufacturer asked FDA to make the drug available over the counter but that request was rejected, citing a lack of data on how it affects women under 16. Two FDA officials resigned in 2005 after the FDA announced it would indefinitely postpone any further review of providing Plan B over the counter. Although just a year later, the agency decided it would allow women over 18 to purchase the drug over the counter.

That has put Plan B in a very small category of medications with a two-tiered, age-based system: Over the counter for adults but by prescription for minors. Others include Sudafed, because it can be made into methamphetamine, and aids to quit smoking (since it’s illegal for minors to buy cigarettes).

Had this change been approved, as Stein explains, “The pill would have moved out from behind pharmacists’ counters, eliminating the requirement that women produce a prescription or prove that they are at least 17 years old to get it without a doctor’s order.”

But the change was not approved. Plan B will remain behind the counter, and its complex political history now includes another, surprising twist.