Nexium and me-too drugs

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Alex Tabarror writes about "me-too" drugs and specifically cites Nexium:
AstraZeneca introduced Nexium just as their drug Prilosec was going off patent. Nexium is very similar to Prilosec and for almost all patients it offers few additional benefits - it is widely cited as a me-too drug. The Nexium problem, however, is quite different from the gold-mine problem. The Nexium problem is, Why do people buy the expensive brand when the cheap generic would be just as good? The Nexium problem is that customers think, or act is if they think, that Nexium is not a me-too drug.

The situation with Nexium is actually quite interesting. The basic chemical in both Nexium and Prilosec, omeprazole, comes in two stereoisomers. Prilosec came first and is an equal (racemic) mixture of the R- and S- isomers. Both isomers are metabolized to the same non-chiral drug. However, it turns out that the S-form is metabolized 70-90% more effectively than the R-form. Nexium (esomeprazole) consists solely of the S-form. As far as I know, there's no evidence that exomeprazole is any more effective than omeprazole in equivalent serum concentrations.

While it's certainly fair to call Nexium a me-too drug, that doesn't mean that people are buying it because they don't know that. It's true that there are generic versions of Prilosec (prescription-only), but the more important factor is that Prilosec is now available over the counter, which means that your insurance may not cover it. Nexium is only available by prescription, so it's still covered. I'm not sure if this is so much of an issue of customer ignorance as of customer rational choice.

UPDATE: A similar situation obtains with Claritin and Clarinex. Claritin (loratadine) turns into Clariniex (desloratadine) in the body. Generic OTC loratadine is readily available. Clarinex is still under patent and prescription only.

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It's worth noting an important difference between the Claritin/Clarinex pairing and the Prilosec/Nexium pairing.

Clarinex is farther down the metabolic pathway than Claritin, thus potentially producing fewer side effects. I assume, though did not look up, that the two stereoisomers have essentially the same pathway or at least the number of steps.

This was a big issue for the Seldane/Allegra pairing. Seldane (terfenadine) is metabolized into Allegra (fexofenadine), which is the active antihistamine. However, some other drugs can inhibit this metabolization, as can grapefruit juice for some reason. Evidently, this can cause ventricular arrhythmias (prolonged QT interval).

So I personally wouldn't refer to drugs farther down the metabolic pathway as "me too".

Fair enough, though in the particular case of Clarinex/Claritin, there seems to be no significant clinical difference.

Sure, but you don't necessarily know that going in.

'It's true that there are generic versions of Prilosec (prescription-only), but the more important factor is that Prilosec is now available over the counter, which means that your insurance may not cover it. Nexium is only available by prescription, so it's still covered. I'm not sure if this is so much of an issue of customer ignorance as of customer rational choice.'

It seems absurd that insurance would not cover OTCs. Why is this?

Also, regarding whether it's a rational choice -- what is the relative price difference to the consumer between an OTC medication and a prescription one, once health insurance is taken into account? If it works out as cheaper to the consumer because the insurance covers enough of the prescription cost -- ie. the copay is less than the OTC med's price -- then that seems pretty rational. (at least, if you're the consumer.)

"Sure, but you don't necessarily know that going in."
Define "going in". That's exactly the kind of thing I would expect the clinical trials to show.

I don't know why insurance doesn't cover OTCs but it's quite common. That's why there was so much pressure from insurance companies for Claritin to go OTC. WRT to price difference, it depends on your copay. Prilosec OTC is abt 20/month, so if your copay is less than $20...

"Going in"="when the second drug comes out". The Seldane link to prolonged QT intervals was not uncovered in the clinical trials. I can't remember whether it was uncovered prior to Allegra's release.

Actually, this is precisely the type of thing I would expect clinical trials not to show. There are too many potential metabolic interactions to uncover reliably in a relatively small sample.

The problems with Seldane were known for 5 years before the approval of Allegra. Indeed, I suspect that that was a driving force behind the development of Allegra.

Well there you go. In this case, you knew going in. All I'm saying is that you may not necessarily know. So choosing the new drug farther down the metabolic pathway may be rational because of your preference probability for this case and the value you put on your life. Especially if your gradparents were Congolese, Aborigine, Inuit, and Icelandic and you're a vegan that's allergic to wheat. You've gotta think that your metabolism is a wee bit different ;-)

Kevin, did you say grapefruit? Grapefruit inhibits P450-3A4, so naturally it interacts with Seldane. See my Recondite post Eat barbeque, sleep better.

I actually did know the mechanism. I read before positing originally to refresh my memory on Seldane.

But why grapefruit should happen to have this ability is rather strange to my mind.

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