Re: So much for Bio-'equivalent'...

[Guest guest]

,

Bioequivalence means they adjust the concentration of the T4 molecule so

that each labeled pill has the exact same potency as the same labeled

Synthroid dosage. Since the incipients are different, they might

dissolve or be absorbed a little differently, so the FDA makes them

standardize the amount based on the biological effect, hence

bioequivalence.

This has nothing to do with " bioidentical. " In every case, the T4 has

the exact same molecular structure as that in your thyroid gland.

Incidentally, Forest also has to adjust Armour to get a consistent ratio

of T3/T4. That is also a bioequivalence issue.

Chuck

>

> Check this out...from the FDA...hmmmmmm...?

>

>

> This is from the FDA's Electronic Orange Book...the link will take you

> directly to the levothyroxine listing...if not, just click on 'Search

> by Active Ingredient', then type 'levothyroxine' into the search space.

>

> http://www.accessdata.fda.gov/scripts/cder/ob/docs/tempai.cfm

> <http://www.accessdata.fda.gov/scripts/cder/ob/docs/tempai.cfm> (of

> particular interest is the RLD column)

>

> Current through October 2008**

>

>

http://www.fda.gov/cder/ob/docs/preface/ecpreface.htm#Reference%20Listed%20Drug

>

<http://www.fda.gov/cder/ob/docs/preface/ecpreface.htm#Reference%20Listed%20Drug\

>

> (Quoted in its entirety below)

>

> Reference Listed Drug (RLD)

>

> A reference listed drug (21 CFR 314.94(a)(3)) means the listed drug

> identified by FDA as the drug product upon which an applicant relies

> in seeking approval of its ANDA.

>

> FDA has identified in the Prescription Drug Product and OTC Drug

> Product Lists those reference listed drugs to which the in vivo

> bioequivalence (reference standard) and, in some instances, the in

> vitro bioequivalence of the applicant's product is compared. By

> designating a single reference listed drug as the standard to which

> all generic versions must be shown to be bioequivalent, FDA hopes to

> avoid possible significant variations among generic drugs and their

> brand name counterpart. Such variations could result if generic drugs

> were compared to different reference listed drugs. However, in some

> instances when listed drugs are approved for a single drug product, a

> product not designated as the reference listed drug and not shown to

> be bioequivalent to the reference listed drug may be shielded from

> generic competition. A firm wishing to market a generic version of a

> listed drug that is not designated as the reference listed drug may

> petition the Agency through the Citizen Petition procedure (see 21 CFR

> 10.25(a) and CFR 10.30). When the Citizen Petition is approved, the

> second listed drug will be designated as an additional reference

> listed drug and the petitioner may submit an Abbreviated New Drug

> Application citing the designated reference listed drug. Therapeutic

> Equivalence Evaluations Codes Products meeting necessary

> bioequivalence requirements explains the AB, AB1, AB2, AB3 coding

> system for multisource drug products listed under the same heading

> with two reference listed drugs.

>

> In addition, there are two situations in which two listed drugs that

> have been shown to be bioequivalent to each other may both be

> designated as reference listed drugs. The first situation occurs when

> the in vivo determination of bioequivalence is self-evident and a

> waiver of the in vitro methodology. The reference listed drug is

> identified by the symbol " + " in the Prescription and Over-the-Counter

> (OTC) Drug Product Lists. These identified reference listed drugs

> represent the best judgment of the Division of Bioequivalence at this

> time. The Prescription and OTC Drug Product Lists identify reference

> drugs for oral dosage forms, injectables, ophthalmics, otics, and

> topical products. It is recommended that a firm planning to conduct

> an in vivo waiver of bioequivalence will be requested, contact the

> Division of Bioequivalence, Office of Generic Drugs, to confirm the

> appropriate reference listed drug.

>

>

>

>

> ------------------------------------------------------------------------

>

>

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8:44 PM

>

[Guest guest]

see below...

>

> ,

>

> Bioequivalence means they adjust the concentration of the T4

molecule so

> that each labeled pill has the exact same potency as the same labeled

> Synthroid dosage. Since the incipients are different, they might

> dissolve or be absorbed a little differently, so the FDA makes them

> standardize the amount based on the biological effect, hence

> bioequivalence.

>

> This has nothing to do with " bioidentical. " In every case, the T4 has

> the exact same molecular structure as that in your thyroid gland.

>

> Incidentally, Forest also has to adjust Armour to get a consistent

ratio

> of T3/T4. That is also a bioequivalence issue.

>

> Chuck

Notice Chuck, I didn't title this bio-'identical'...that isn't the

point of this thread...I am aware Forest adjusts Armour...it's on

their website...specifically, they say they adjust the 'ratio' to

obtain consistent results in their product.

The point of the link I provide, which I was really surprised to

encounter (it came as a result of verifying a reference to an article

I was reading, and from that to another...you know the routine I'm

sure)...but, the Reference Listed Drug (RLD), rating (? would I be

correct to call it this ?) is sporadic at best between manufacturers,

and even then between dosages of those manufacturers...notice that the

RLD is in reference to the 'bio-equivalence' of these various

synthetics, not the 'bio-identity'.

So it would seem to me, that as consumers, we would have to check on

the 'bio-equivalence' status of the medication we were being given,

every time there was a change in our prescription...because, although

the dosage we might currently be on by Manufacturer A might be

'bio-equivalent', we might have to find a Manufacturer B to get a

'bio-equivalent' medication in a newly prescribed dosage...

[Guest guest]

,

You wrote:

> ...So it would seem to me, that as consumers, we would have to check on

> the 'bio-equivalence' status of the medication we were being given,

> every time there was a change in our prescription...

In principle, your concern is well justified, and in the not too distant past,

different formulations of T4 did have different potencies. However, for a drug

to be classed as a " generic " for Synthroid, it must be matched more precisely

for bioequivalence. The term " generic, " incidentally, is a misnomer, since

Synthroid was never patented or patentable.

Chuck