Discussions that mention phenytoin

Pain Management board


It took some digging but here it is.
According to the Food and Drug Administration (FDA), a generic drug is identical or bioequivalent to its brand-name counterpart in dosage form, safety, strength, route of administration, quality, performance characteristics and intended use. The current FDA criterion for bioequivalence for both branded and generic drugs is a 0.8 to 1.2 confidence interval. Tighter confidence intervals would result in many branded and generic products not being bioequivalent to themselves.

But are generic and branded drugs interchangeable in the case of narrow-therapeutic-ratio (NTR) drugs? These drugs (such as warfarin, quinidine, procainamide, theophylline, lithium, phenytoin, carbamazepine and valproic acid) are used in clinical situations where small variations in tissue levels might result in sub-therapeutic or toxic clinical outcomes. The FDA makes no distinctions between standard and NTR drugs when it comes to interchangeability. NTR drugs do require frequent adjustments and careful patient monitoring, regardless of whether a brand-name or generic product is being used. However, the FDA does not recommend that physicians perform additional testing when switching NTR drugs or any other drugs, whether from branded to generic, generic to branded, or generic to generic.4

I was wrong too, the allowable confidence interval is -20 and +20% or
.8 and 1.2 .
.8X10mg =8mgs and considered bioequivalent
Take care, Dave