Yes, I think changing generics can make a big difference in how you feel. We've had the issue here with a couple different meds and now stick to filling any generics we use by the same manufacturer each month. As posted above this can be a HUGE issue with something like seizure meds (we found this out the hard way- if Emily doesn't get the gabapentin manufactured by Greenstone, she is in BIG trouble!) But I can see how it would be an issue with abx, too- when getting tobra levels checked they were SO precise with the dosage, and when Emily needed a dose change it was adjusted in very small increments. Switching mfr's that could vary in formulations a dramatic amount just doesn't seem safe to me.<br><br>According to the regulations governing the production of generic medications (the Hatch Waxman act), they are given what is imo an INSANE amount of leeway in the manufacturing process. For a generic to be approved, it has to be proven 'therapeutically equivalent' to the branded version. Equivalent, at least to ME, would imply 'the same'. However, that is not the case. Active ingredient can be dramatically different (and inactive ingredients can be different as well.)<br><br>Here is a good overview of the act: <a target="_blank" title="" href="http://www.regulatorypro.com/FDLI%20-%20Overview%20of%20Hatch-Waxman%20Act%201984.pdf">http://www.regulatorypro.com/FDLI%20-%20Overview%20of%20Hatch-Waxman%20Act%201984.pdf</a> <br>quote from above link:<br><div class="FTQUOTE"><begin quote>A number of assumptions were made in enacting Hatch-Waxman. One major assumption underlying the Hatch-Waxman Act was that duplicates of pioneer drugs would be the same as the innovator's drug. FDA still uses the plus-or-minus-twenty percent test to determine blood serum bioavailability (i.e., the amount of active ingredient in the blood over a period of time has to come within plus-or-minus twenty percent of that which is observed when the innovator's drug is ingested). Twenty percent is a fairly good margin, and many medical professionals believe that for drugs that have a wide index of tolerance, twenty percent is not important at all; in such instances, twice as much or half as much of the active ingredient in a generic product will still work. <br><br>For drugs where there is a very narrow therapeutic band, for example, where a patient gets antiseizure medication, plus-or-minus twenty percent may not be appropriate. This is true particularly if a drug is at that higher end of bioavailability and a patient is titrated on the higher end (plus twenty percent) and then a second generic is dispensed where the active ingredient was at the lower end (minus twenty percent); mathematically, that is a fifty percent swing and may not be safe or effective. It is a curious thing that FDA has not altered its regulatory approach to this situation. With the advances in modern pharmaceutics, those standards could be tightened. Although such tightening might not be to the advantage of the brand name companies, it could be to the advantage of patients.</end quote></div><br><br>to add: this paper was published around 1997 I believe, from what I could find in the references. There has since been further legislation refining some parts of the act, but I couldn't find anything indicating that the standards of manufacture have changed. <br>