Patients worry that generic drugs are not the equivalent of the original brand-name drugs which many of them were first given when the drug came on the market.
Well, it's hard to gainsay what people feel unless there are stats to say otherwise. There's a lot riding on this, for patients, physicians and drug companies. So what are the stats to date? Let's take different groups of drugs:

Beta Blockers.. in randomized controlled trials (the gold standard) clinical outcomes (=how did the patients do?) were NO better with brand names versus generics. (7 out of 7 clinical trials)

Diuretics.. 10 out of 11 clinical trials showed no difference between brand names vs generics.

Calcium channel blockers.. same again, 5 out of 7 clinical trials.

Warfarin preparations.. no difference in clinical outcomes 5 out of 5 times.

P.P.I's.. (Omeprazole a.k.a. Prilosec, Losec and others)...not clinical trials comparing efficacy, but... was the rate of dissolution the same for generics as with the brand names?... well the FDA studies on omeprazole showed that the dissolution rates were the same...i.e. the drug was available just as quickly from either source.

Thyroid drugs. In the past there have been problems with Levothyroxine preparations because this drug is inherently unstable and affected by heat and light. After a lot of complaints the FDA tightened the regs about the stability of these compounds and the generics are closer to the original brand name compound... which is now very stable.

Anti epileptic drugs... Looking backwards... retrospectively... it seems that people who switch from brand name to generic drugs have more serious epileptic events than people who did not switch. But retrospective studies are not the best way of checking this kind of thing and no PROSPECTIVE study has shown that generics are worse than brand name.

So what's the bottom line here? Probably that if you can afford it... stay with the drugs you started with... brand name or generic.. if they are working okay. No study has shown convincingly that generics are worse. If you have to switch from brand name to generic this seems to be less of a problem than has been said...but people know what they feel and I've learnt never to disregard a patient's feelings.
John Bart