Pharmaceutical giants Roche and GlaxoSmithKline have signed a promotional agreement for weight-loss medication Xenical (orlistat) in the United States, according to a statement issued April 12th.

The pact gives Glaxo exclusive rights to promote prescription Xenical in the United States. Glaxo also acquired the rights to an over-the-counter (OTC) version of the anti-obesity drug in July 2004.

Xenical is the number-one prescription weight-loss medication worldwide but sales of the drug -- which totaled just under $500 million in 2004 -- have been disappointing.

Some patients have been deterred by the fact that the medicine -- which works by hindering the body's ability to absorb fat -- can cause diarrhea when people eat a high-fat meal.

Glaxo hopes that a non-prescription 60 mg dose of the drug -- as opposed to the current 120 mg prescription version -- will produce fewer adverse side effects.