It's been a rough couple of days for GlaxoSmithKline, with the pharmaceutical giant recalling all bottles of the weight loss drug Alli from the U.S. and Puerto Rican shelves. The drug, a non-prescription weight loss aid, has reportedly been compromised, with customers finding other medications in several sealed bottles. 

The discovery of contaminated bottles came to light on Wednesday, with the company promptly pulling Alli from all pharmaceutical outlets. GSK, a British company, is collaborating with the U.S. Food and Drug Administration (FDA) to coordinate the domestic recall.

GSK responded to concerns from customers in seven different states reporting different pills in Alli bottles, as well as inauthentic tamper-evidence seals. Overall, 20 tampered bottles have been noted so far, though it's unclear how the different pills made their way to the bottles. GSK hasn't disclosed how many bottles are currently on shelves. 

"The investigation is ongoing. We've asked people to return bottles to us, so we can examine them very closely ... we don't have any theories at this point," a GSK spokeswoman said.

Colin McKenzie, GSK's North American consumer healthcare group president, offered similar platitudes. "Safety is our first priority and we are asking retailers and pharmacies to remove all Alli from their shelves immediately," he said.

Alli is easily recognized, sold as a turquoise capsule with a darker blue ring imprinted with the words '60 Orlistat.' It works by stopping fat from being absorbed by the stomach, and is best used in conjunction with a low-fat diet and exercise regime. It's the only FDA-approved weight loss drug that's sold without a prescription, and was expected to attract booming sales when it was first released. However, its early promise is yet to be fulfilled, with disappointing sales putting a dent in GSK's earlier ambitions. An unrelated supply issue in 2012 is also thought to be an reason for Alli's struggle to gain traction as common weight loss option. 

However, GSK remains optimistic for the future of Alli. Though the company hasn't disclosed recent sales figures, it's known that around $337 million in revenue was generated in 2009, before temporarily halting sales in 2012. In February this year, GSK reported a steep jump in sales throughout 2013, prompting the company to continue throwing its weight behind the product.