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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 4 of 4. This is the beginning of the thread.
Posted by sam123 on August 24, 2007, at 9:27:24
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=12860486&dopt=AbstractPlus
The bioequivalence and therapeutic efficacy of generic versus brand-name psychoactive drugs.
Borgheini G.Neurological and Psychiatric Department, University of Padua, and Casa di Cura Parco dei Tigli, Padua, Italy. g.borgherini@gpnet.it
BACKGROUND: For the purposes of drug approval, the interchangeability of a generic drug and the corresponding brand-name drug is based on the criterion of "essential similarity," which requires that the generic drug have the same amount and type of active principle, the same route of administration, and the same therapeutic effectiveness as the original drug, as demonstrated by a bioequivalence study. However, bioequivalence and therapeutic effectiveness are not necessarily the same. OBJECTIVE: This review summarizes available data comparing the bioequivalence and therapeutic efficacy of brand-name psychoactive drugs with those of the corresponding generic products. METHODS: Relevant information was identified through searches of MEDLINE, Current Contents/Clinical Medicine, and EMBASE for English-language articles and English abstracts of articles in other languages published between 1975 and the present. The search terms used were generic drug, branded drug, safety, toxicity, adverse events, clinical efficacy, bioequivalence, bioavailability, psychoactive drugs, and excipients. RESULTS: Few publications compared the bioequivalence and efficacy of brand-name and generic psychoactive drugs. Those that were identified revealed differences in the efficacy and tolerability of brand-name and generic psychoactive drugs that had not been noted in the original bioequivalence studies. Specifically, l study found that plasma levels of phenytoin were 31% lower after a switch from a brand-name to a generic product. Several controlled studies of carbamazepine showed a recurrence of convulsions after the shift to a generic formulation. After a sudden recurrence of seizures when generic valproic acid was substituted for the brand-name product, an investigation by the US Food and Drug Administration found a difference in bioavailability between the 2 formulations. Statistically significant differences in pharmacokinetic variables have been reported in favor of brand-name versus generic diazepam (P < 0.001). Finally, a case report involving paroxetine mesylate cast doubt on the tolerability and efficacy of the generic formulation. CONCLUSION: The essential-similarity requirement should be extended to include more rigorous analyses of tolerability and efficacy in actual patients as well as in healthy subjects.
PMID: 12860486 [PubMed - indexed for MEDLINE]
Posted by Phillipa on August 24, 2007, at 10:15:46
In reply to bioequivalence of generics not always same, posted by sam123 on August 24, 2007, at 9:27:24
Thought they had to be within 20% of original formulation . Of course this doesn't account for different fillers, dyes. I know synthroid is going generic end of year but the endos say it will not differ by more than 5%. So there are not formal studies? Could this account for TRD? And other disorders. Frightening about the dilantin. Thanks. Phillipa
Posted by Bob on August 24, 2007, at 12:13:32
In reply to Re: bioequivalence of generics not always same » sam123, posted by Phillipa on August 24, 2007, at 10:15:46
I learned this the hard way with Clonazepam. I switched from the brand name the generic, and had many problems. Of course, most health professionals would dismiss this as hogwash, but my primary psych said that differences in bioavailability can exist because of the fillers and other supposedly inert compounds present in the drug. General availability and rates of absorption can be affected.
Posted by Phillipa on August 24, 2007, at 20:06:16
In reply to Re: bioequivalence of generics not always same, posted by Bob on August 24, 2007, at 12:13:32
I did too with xanax but found greenstone is the same med made by the same company my pharmacist couldn't understand why I was paying for brand and clued me in on it. Others have also found this to be true. Phillipa
This is the end of the thread.
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