s a tad more complicated than is appropriate for this forum)
There has been a VERY long lived debate about the efficacy of generic vs brand name
meds. For most people, they seem to be able to use either interchangeably with little or no difference in the effectiveness. For other people, they report a BIG difference in the effectiveness of the generic and have to stick with a brand name, sometimes even a specific brand name.
Some meds have more of a reputation for this than others.