Viva Viagra! Congratulations Pfizer! This year marks the 10th anniversary of the introduction of the world's most famous love drug. Alas, the famous blue pill, which had worldwide sales of US$1.7 billion last year, has also made many counterfeiters wealthy, especially in our part of the world. So, to celebrate the special occasion, the drug company is taking back all unsold four-tablet packages in Hong Kong.

Don't worry, you can still buy them. But the new packs will come with more special security features than banknotes. To check if the pack in your hand is real, just see how the two labels - both with the Pfizer logo - on the box change colours. One goes from blue to purple when you look at it at a 45-degree angle; the other turns green from red, also at the same angle.

The inspection - I can see it now - might get a bit embarrassing in a crowded drugstore. Just imagine guys holding up their packs and turning them this way and that to make sure they turn into the right colours. Woe to those who are colour-blind.