When a generic is available, I'm generally open to trying it. I've had very few bad experiences overall.
One medication gave me migraine headaches in its generic version, but not in the brand name -- migraines are a known side effect of this medication in both forms, so maybe I just got lucky with the brand name. In that case, the generic was consistent, so I was pretty sure it was responsible.
More recently I switched from a brand name blood pressure medication to the very recent generic equivalent. My blood pressure had been pretty stable since I'd started on the brand name version several years ago so I foolishly failed to check my blood pressure more frequently when I made the switch. I'd been checking it about once a week. I picked up the new prescription on a Friday and had an appointment with my physician the following Wednesday. By the time I arrived at the office, my blood pressure had reverted to my pre-medication levels. Not a good thing at all.
I've had an issue with intermittent white-coat hypertension with this doc. ONLY this doc. Every one else gets normal readings. As one of her partners says, "She's so intimidating."
NOT. She's very soft-spoken and I have no idea why this happens. She asked me to start checking more often at home and let her know the results. I kept taking the generic version for about another week with blood pressure readings that were inconsistent. One day 116/60, the next 140/70.
Finally the light bulb went on. I called the pharmacist who offered to replace the remaining generic tablets with the brand name version. 2 days later I haven't had a high reading. That's not long enough to be certain, so I'll be monitoring daily (at least) for the next month or so. If my blood pressure stays down, I'll have to assume that the generic just doesn't do the job for me.
Update: It's not the generic. It's not the doc. I'm pretty sure it's not the meter. Rats. God bless the pharmacist for letting me try though.