Botox has become a front-line weapon in cosmetic medicine for erasing wrinkles -- while therapeutic applications of the drug are being used to help a wide variety of disorders from swallowing problems to muscle spasms.

"If I knew (how big it would become), I would have never given it to the drug company Allergan in 1991," Dr Alan Scott told the Times of India in an interview published on Monday.

"At present Botox is being used for over 100 disorders besides aesthetic applications," Scott said in New Delhi where he was en route to a conference in southern India.

The San Francisco opthalmologist said he got around $4.5 million for handing over the rights to the drug to the California-based company Allergan which "was then a satisfactory deal."

"But if I had held on to Botox, maybe I could have made a billion dollars a year now," Scott said.

Botox, which makes muscles relax, is a purified form of a nerve poison produced by a bacteria that causes a disease that paralyses muscles and can be fatal.

Botox was first approved in 1989 to treat two eye muscle disorders -- uncontrollable blinking and misaligned eyes.

"Initially when I developed it, I knew it could do wonders for neurological disorders. However, I had absolutely no idea it could work so well as a cosmetic agent," said Scott, who initially called the drug Oculinum.

The big cosmetic breakthrough came when Canadian ophthalmologist Dr. Jean Carruthers noticed her patients were starting to lose their frown lines and published a study in 1992.

A decade later Botox was approved as a frown fixer by the US Food and Drug Administration and now it is used in 80 countries.

Does Scott worry about any side-effects from the widespread use of Botox?

"It is not clear what will happen after decades of use. Maybe the facial muscles will weaken and sag. But we know that it works in reducing facial wrinkles," he said.

"Most women don't care what will happen years later. They just want the wrinkles to disappear now." (AFP)