E-drug: Re: Bioequivalence of generics and brand name drugs (contd)
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In addition to the statement by FDA mentioned by Joel Lexchin, an article
from Drug and Therapeutics Bulletin (1997;35(2):9-11) called Generic
medicines - can quality be assured? is worth mentioning. In countries with
regulatory measures that ensures that licensed medicines are safe, effective
and of adequate quality
patients should be confident that branded and generic versions with the same
ingredient in the same strength and in the same dosage form should provide the
same therapeutic response. Manufacturers of generic equivalents are required to
show 'essential similarity' to the first branded drug, i.e. that the product
is of the same pharmaceutical form and has the same quality and quantity of
active ingredient. A debate has been going on in EU concerning a definition
of 'essentially similar'. There is also some differences in opinion as to
whether tablets and capsules are 'essentially similar'. The manufacturer is
also required to show that the preparation is bioequivalent (absorbed at the
same rate and to the same extent) as the first brand. Typically, tests of
bioequivalence are done in groups of 12 to 24 young, healthy volunteers.
Products are tested in a crossover design and usually in single-dose studies.
Now all this has certain limitations of course and as mentioned in my note
to Joel's most recent posting, regulatory authorities may have different
limits for what is regarded as 'essentially similar' e.g. an acceptable
deviation of + - 20% in plasma levels.
The day after posting Joel's question, I was reading the Pharmaceutical
Journal and came across an advertisement with the heading: Epilepsy: An
exception to the generic rule. This advert - for sodium valproate from
Sanofi Winthrop provides references for a claim that switching should not
occur: (please note that this is an advert in favour of one drug)
Crawford P et al. Generic prescribing for epilepsy. Is it safe? Seizure
1996;5(1):1-5
Phillips G. Prescribing of anticonvulsant medicine (letter). Pharmaceutical
Journal 1996;257:658
Phillips G. Prescribing in epilepsy (letter). Pharmaceutical Journal 1997;258:18
Chappel B, Crawford P. Generic prescribing (letter). Pharmaceutical Journal
1997;258:446
Chappel B. The threat of medicine substitution - the patient's viewpoint Not
What the Doctor Ordered. Queen's University, Belfast 1993:71-80
Therapeutics and Technology Assessment Subcommittee of the American Academy
of Neurology Assessment: Generic substitution for anti-epileptic medication.
Neurology 1990;40:1641-3
New Zealand Medical Assosiation: A warning re anticonvulsant drugs. New
Zealand Medical Association Newsletter in New Zealand Medicine 23rd March
1994:10
Kirsten
Kirsten Myhr
Bygdoy alle 58B
0265 Oslo, Norway
myhr@online.no
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