The U.S. Food and Drug Administration said the only over-the-counter asthma inhaler sold in the US will no longer be available after December 31, 2011.

The action was taken because Primatene Mist uses chlorofluorocarbons (CFCs), which deplete the ozone layer, to propel the medication and the U.S. signed an international agreement to phase out their use.

Then-President Ronald Reagan signed the agreement, called the Montreal Protocol on Substances the Deplete the Ozone Layer, in 1987.

Many other drug makers that had used CFCs have replaced them with hydrofluoroalkane, which is safer for the environment.

The FDA emphasized there are other medications that are safe and effective for treating asthma symptoms and suggested sufferers who use Primatene Mist should seek medical help to find a replacement.