Whats peoples opinions on the various manufacturers of the same drug, for example I take Mirtazipine, but so far have had two manufacturers, one seemed to work the second not so.

I have had many different manufacturers of Citrolapram and noticed no difference between them.

So is it possible that the quality of the ingredients makes a difference, or does the fact that its made by different manufacturers make no difference.

My reckoning is that chemists must go for the cheapest one, and hence if one manufacturer is cheaper than the other, quality of ingredients must come into play.

Thoughts?