Last week I had occasion to look into a new generic drug. What I found was somewhat horrific. The generics used a sample of twenty people, ten on the new version and ten on the original. The test lasted a few weeks and the results showed similar drug blood levels between both groups. The results stated that no side effects were seen, but that the sample size and duration was so small that no real results could be given credence. The drug was approved for the NHS with the caveat that side effects should be reported. To add to my confidence, the drug was made in India, but the packaging stated that it was made in the UK! When I think of the lengthy trials that the original maker had to undertake, I am now very suspicious of the quality of any generic.
It is of interest to see the efficacy of Sumatriptan (Immigran) generics reported by various users. Some versions don't work at all and the rest seem less effective than the branded product. I haven't looked at the sumatriptan testing, but have my suspicions. The info is available on the internet if you search the drug approval number printed on the leaflet in the packet.