@zhulaoye: You are pretty much correct. I have experienced most of what you have related. Ignore @Alien, he/she is either negative (don't do this), or clueless, "I don't understand anything about the theory behind it and what I do understand makes no real sense to me," or is flat dispensing misinformation based on what makes common sense but not connected to the China reality.
Before I committed to living in China I researched my meds and all were available in Beijing and Shanghai. Silly me, because I had no problems buying them in BJ and SHA, I thought, wrongly, I could easily get them elsewhere.
I buy Aspirin, Tylenol, Vitamin C, and Zinc from Amazon.com, have them sent to my son. He remails them to me. Even with the airmail costs, it is much much cheaper that way.
Kirkland (Costco) Vitamin C, 500 1000mg tablets cost about $35 USD to get to me. To get the same amount of Vitamin C in a domestic brand would take more than 420 bottles and cost more than $7,000 USD.
Aspirin in China is usually 40mg/pill. Standard US pill is 325mg, so, you need to take 16+ Chinese aspirins to equal two US aspirins.
Chinese either say Western medicine doesn't work or is too strong. I get the doesn't work because I find the effective ingredient is usually a fraction, less than 25%, of the western dose. I don't get the too strong idea but think you have the answer.
If you buy medicines or food supplements in China, you need to be very aware of what you are taking. Read the labels, understand the effective dosage. Check the expiry dates on EVERY bottle.
@Alien: Before you inject yourself into this conversation you should know I was Controller for a food supplement company so I am quite familiar with the production of such items. Also know I brought together a Taiwan Chinese, a mainland Chinese (with a USA PhD) and a Vietnamese to make and sell US made food supplements in China. They paid me for 10 years for each and every bit of product shipped to China. That is why you can find US made supplements in China.