Obagi Products for South Asians?

Yes, you can use the Obagi products and it will work for your skin type. You should start slowly by using small amounts. If you don't use sunscreen regulalry then any brown spots removed by these products will return.
Also keep in mind that these products contain hydroquinone which has been found harmful in some people after long term use.
My advice would be to use the products to achieve the results over a short period of time and after that stick to sunscreen. Karachi is pretty sunny, so avoiding sun is going to be your biggest challenge.
Regards

Having worked directly with Dr. Obagi in his Beverly Hills Skin Health Institute, and in my own practice in Los Angeles, I have helped treat hundreds, if not thousands of patients with the Obagi Nuderm system.
South Asian skin is ideal for treatment with the Obagi Nuderm system and has been proven effective in this skin type.