How a new weight-loss drug may cause more harm than good

Weight-loss drug ‘orlistat’, known by the brand names ‘Xenical’ and ‘Alli’, inhibits a key enzyme that may lead to “severe toxicity of internal organs such as the liver and kidney. The inhibition is irreversible and can be caused by a low level of the drug.

This drug alters efficacy of medicines, and particularly limits the effectiveness of some anti-cancer drugs.

‘Orlistat’, has been the most commonly used medicine to treat obesity for more than a decade.

Since it has been available over-the-counter, there has been a drastic increase of toxicity among patients using the drug.  It has been linked to severe liver failure, acute pancreatic failure and acute renal (kidney) failure.

‘Orlistat’ works in the intestinal tract by preventing fat from being absorbed by the body. It is generally accepted that ‘orlistat’ remains in the intestine and that the body does not absorb it.

‘Orlistat’ is reportedly absorbed and certainly internal organs such as the liver and kidney are exposed to this drug upon absorption. This drug is a potent inhibitor of carboxylesterase-2, which is a major detoxification enzyme in the liver, kidney and gastrointestinal track. When the activity of this enzyme drop in those organs, toxicity increases or the efficacy of some drugs are altered

The enzyme is known to metabolise a wide range of medicines including aspirin and the cancer drugs ‘irinotecan’ and ‘pentyl carbamate’ of ‘p-aminobenzyl carbamate’ of ‘doxazolidine’.

The drug ‘orlistat’ profoundly alters the therapeutic potential of the anti-cancer drugs.  In the case of the anti-cancer drugs, it weakens their effectiveness.

It increases the therapeutic potential of aspirin, which may increase the tendency of bleeding.

Alli-based interactions can be key factors in the efficacy of medicines.

Anti-viral drug Tamiflu would be rendered ineffective in patients also taking the anti-clotting drug Plavix.

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