Viagra, The Strange Duck

Sildenafil, the active ingredient of Pfizer’s blockbuster erectile dysfunction drug Viagra, lost exclusivity in the U.S. on Nov. 6 – but don’t expect to see generic Viagra here anytime soon. 

The LOE affects only the drug’s use in pulmonary arterial hypertension (PAH), for which Pfizer sells it under the brand name Revatio.Viagra, on the other hand, continues to be protected by a use patent through April 2020, as "The Pink Sheet"’s Brenda Sandburg noted in an article on Nov. 12. It is available in 25 mg, 50 mg and 100 mg tablets; Revatio on the other hand only comes in a 20 mg strength, which is recommended to be taken three times daily. The recommended dosing for Viagra is 50 mg as needed, but not more than once daily, although depending on effectiveness and tolerance, a higher or lower dose can be taken. 

The AWP for both brands, likewise, is somewhat similar. A 90-tablet bottle (one month supply if used according to the label) of Revatio lists for  $2,107.04, with a 25% mark up on the wholesale acquisition cost, or direct price. Viagra’s AWP is calculated at 100 50 mg tablets for $2,783.49, with a 25% mark up, according to Elsevier’s The Gold Standard (roughly a three months or longer supply).

Four generic competitors have FDA-approved ANDAs for sildenafil, including Pfizer’s Greenstone subsidiary, which is selling the authorized generic. Despite the competition, the list price (AWP) for the generic appears to be only slightly discounted—but of course, the launch is only in its earliest days and AWPs don’t capture the true value of a drug, especially a generic, after rebating. 

So what’s to stop cost-conscious consumers from asking docs for generic Revatio and taking multiple tablets instead of one Viagra?

Plenty, say experts. Companies aren’t likely to promote the generic’s off label use in ED because of the threat of huge government fines for off-label promotion. Moreover, the drugs are prescribed by different kinds of doctors, who aren’t likely to try to game the system when they have nothing at stake. Pulmonary or cardiology specialists prescribe Revatio, while general practitioners primarily write scripts for Viagra, so a massive educational effort would seem to be in order, but generic companies generally do not engage in such activities on a grand scale.

Payers would be another obstacle:  private insurers aren’t likely to cover off label use of a generic when an on-label brand is available; furthermore, many require prior authorization before covering Revatio. Medicare doesn’t cover Viagra anyway, so many patients will just keep doing what they’re already doing: paying out of pocket.

That said, there’s little precedent for a drug going off patent in one indication while remaining exclusive in another; most dual brands lose exclusivity at the same time. The few examples that come to mind are old and harken back to days when the competitive landscape was quite different (Prozac and Sarafem, suggested one consultant).   

Sildenafil is an outlier because Pfizer has a use patent protecting exclusivity for ED, at least in the U.S. -- a protection that a U.S. district court reinforced last year in a ruling against Teva (Teva is appealing). However, Pfizer lost a court case over the patent in Canada on Nov. 8, so Viagra will face generic competition there shortly. 

Given the similarities, and the availability of a generic active ingredient, the question comes to mind as to whether this means much of anything for the Viagra blockbuster franchise. The question’s important to Pfizer in particular because Viagra is by far the bigger seller; its sales for the nine months ended Sept 30 were $1.5B, while Revatio sales were $414M.  

The bet is that Viagra won’t get hit too hard. In any event, Pfizer will surely be watching closely for competitors’ missteps, particularly regarding off label promotion. In the words of one consultant: “This really is a strange duck.”

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