U.S. Pharmacopeia has relegated some of the pharmaceutical industry's biggest blockbuster drug "classes" to the status of "recommended subdivisions" in its draft model Medicare formulary.

Among the groups of drugs typically referred to as being in their own class but not defined as such in the USP model are COX-2 inhibitors and statins, which are among the most frequently prescribed drugs for arthritis/pain and high cholesterol, respectively.

USP's draft model formulary ¹ guidelines for the Medicare drug benefit contain 146 unique therapeutic categories and pharmacologic classes (see ² Also see "USP Draft Medicare Formulary Sets 146 Drug Categories And Classes" - Pink Sheet, 23 August, 2004. ).

Under the implementing regulations proposed by the Centers for Medicare & Medicaid Services, prescription drug plans would be required to have at least two products on formulary in each USP-designated category and class (³ Also see "Formulary Balancing Act: Medicare Rules Weigh Access Versus Cost Control" - Pink Sheet, 2 August, 2004., p. 17).

The USP model also contains a list of "recommended subdivisions" of the pharmacologic classes that "would serve to assure beneficiary access to medications, but, unlike the categories and classes, may not necessarily require multiple drugs," USP said.

USP chose to base its pharmacologic classes on mechanism of action, but grouped all non-steroidal anti-inflammatory drugs in the same class, regardless of whether the drug acts specifically on the COX-2 enzyme or not.

Instead, COX-2 inhibitors are listed among the "recommended subdivisions" within the therapeutic category "anti-inflammatories" and the pharmacologic class "nonsteroidals."

Other subdivisions of the nonsteroidal class are salicylates, which includes aspirin, and "nonsteroidals, other." The other anti-inflammatory class is corticosteroids (see chart: " ⁴ USP Model Formulary', following pag e).

From a business perspective, it is unlikely that a prescription drug plan competing to enroll Medicare beneficiaries would choose to leave COX-2 inhibitors or statins off its formulary entirely.

However, by grouping COX-2s like Merck's Vioxx and Pfizer's Celebrex and Bextra with other NSAIDs like Boehringer Ingelheim's Mobic , as well as older NSAIDs, plans would have much greater price negotiating power than if the COX-2s were given their own class with the two-product requirement.

The situation is similar for other therapeutic categories, such as cholesterol-lowering agents, in which HMG CoA reductase inhibitors - including the statins - are one of five recommended subdivisions.

Other subdivisions of the guidelines' "antilipemic agents" class are absorption inhibitors, bile acid sequestrants, fibrates and nicotinic acid derivatives.

As a result, Pfizer's Lipitor , Merck's Zocor , AstraZeneca's Crestor , Bristol-Myers Squibb's Pravachol and lovastatin (Merck's Mevacor and generics and Andrx' Altoprev ) will compete for formulary placement against products such as Merck/Schering-Plough's Zetia , Bristol's Questran , Sankyo's Welchol and gemfibrozil (Pfizer's Lopid and generics).

The Merck/Schering product Vytorin (Zocor plus Zetia) would also be in the class.

The Pharmaceutical Research & Manufacturers of America, which is pushing for a large number of narrowly defined drug classes, criticized the model guidelines for clustering "commonly prescribed types of medicines" with "outmoded forms of treatment." The association claims the model would allow plans to exclude many of the drugs physicians prescribe most.

PhRMA specifically points to heart disease as one condition for which USP's guidelines would help "set back treatment."

In comments submitted to the USP Medicare Model Guidelines Expert Committee as it was developing the draft, PhRMA used antihypertensives as an example of how it believes drug classes should be divided.

The association suggested five classes of antihypertensives (beta blockers, calcium channel blockers, ACE inhibitors, angiotensin II receptor blockers and antihypertensive combinations), as well as several subclasses based on the pharmacological characteristics of beta blockers and CCBs.

However, the model guidelines split the "cardiovascular medications" into a total of 11 classes: renin-angiotensin-aldosterone system inhibitors; direct cardiac inotropic agents; alpha agonists; alpha blockers; beta blockers; CCBs; diuretics; direct-acting arterial vasodilators; direct-acting venous vasodilators; antilipemic agents; and antiarrhythmics.

ACE inhibitors and ARBs are lumped together as subdivisions of the renin-angiotensin-aldosterone system inhibitor class.

The various types of beta blockers and calcium channel blockers are not recognized as distinct classes, but are recommended subdivisions.

PhRMA also mentions depression as a troublesome category in the model.

The antidepressants category groups all "reuptake inhibitors" into the same class, leaving the subdivisions to distinguish the newer and commonly prescribed selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors from the older tricyclic drugs. Monoamine oxidase inhibitors and "other" antidepressants have their own classes.

Despite drug manufacturers' concerns, it appears that formulary standards under development at CMS will prevent attempts by Medicare drug plans to avoid covering commonly prescribed drugs.

CMS will use its standards to "review formularies to rule out discriminatory exclusions, cost-sharing and/or administrative requirements," a ⁵ CMS discussion paper on the draft guidelines says.

A Medicare drug plan's "available drug choices must represent a full range of drug therapies necessary to adequately support current medical practice," CMS said. "This requirement could be satisfied with two drugs in some categories and classes, but the majority will need to include more drugs."

CMS added that it will review formularies "on a more granular level" than described in the model guidelines "to make sure they include sufficient choices of clinically significant drugs...This will likely include evaluating available formulary choices and conditions at the sub-class level."

COX-2s, Statins Have No Class In USP Medicare Draft Formulary

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