The counterfeit tablets, packed in four crates and weighing 400 kg, had originated in China, according to Swissmedic, the Swiss Agency for Therapeutic Products.
"Analyses in the Swissmedic laboratory revealed that the drugs, which are prescribed to treat symptoms of acute anxiety, contained no active ingredients whatsoever," Swissmedic said in a statement.
"According to experts, the drugs would be unrecognisable as counterfeits at a first glance."
Xanax is a drug manufactured by Pfizer used to treat severe anxiety or panic disorder. The fake tablets were destroyed.
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According to the WHO, fake drugs range from antibiotics to birth-control medicines, anti-tetanus serums, antimalarials, organ transplant drugs, heart disease and diabetes.
In parts of Asia, Africa and Latin America, fraudulent medicines are thought to amount to as much as 30 per cent of the market, according to the UN drug agency.
Also making up a large part of medicines sold online, fake medicines can contain the wrong dose of active ingredients or toxic substances such as rat poison, according to the UN drug agency.