There seems to be a consensus about Cosmelan. The good news is that it really does seem to work on  stubborn age spots and for those with dark complexions. The bad news is that patients and doctors report that the new formulation, introduced by Cosmelan in 2007, doesn't work anywhere near as well as the original one.

Cosmelan is a pack of prescription-only topical creams. The initial treatment with Cosmelan is always carried out by a dermatologist. After cleansing the skin with aqua and an acetone product to remove dead cells and debris, Cosmelan 1
is applied. This is a mask with azelaic acid, kojic acid, phytic acid, ascorbic acid, arbutine and titanium dioxide. Take a good book with you because it is left on for a total of 4-8 hours depending on
your skin type. Following this, you will be allowed to go home (with the
mask on, so don't opt for mass transit).

After cleansing, you apply Mesoestetic Hydra-vital factor K (hydroviton, vItamin K, vitamin E, amniotic fluid, glycerine, silicone oil). The at-home routine continues with daily application of Cosmelan 2 cream. The cream (titanium dioxide, kojic acid, phytic acid, ascorbic acid)
is applied two to three times a day, for the first two weeks, then once a day.

One dermatologist reports trying different age spot treatments for years without success - until he came across Cosmelan. He says Cosmelan 2 is the only thing that works. Patients who have recently used it are less happy. This seems to be because they are being given the 'new' Cosmelan. The mask causes less redness and irritation than the 'old' version. But there is no gain without pain and it simply doesn't work as well as the original.

If you decide to look into this, make sure your doctor can get hold of the 'old' Cosmelan. You will, during the initial weeks, peel and flake like a well-weathered paint job. But, by all accounts, you will lose the hyperpigmentation.