3. Viagra

PfizerViagraTablet

Company: Pfizer
Disease: Erectile dysfunction
2016 U.S. sales: $1.148 billion
U.S. generic competition: December 11

Pfizer’s legendary blue pill is set for year-end generic competition after long ago winning its FDA green light.

It’s had quite a run since its 1998 approval. Viagra has been a reliable sales engine, partly because of Pfizer's ability to push the brand—and new, locally appropriate formulations—into international markets. In the U.S., which is what matters for this ranking, the med and its TV spots quickly became cultural touchstones, even if its evening advertising made for some embarrassing family-viewing moments.

The top pharma even had some success prolonging Viagra's U.S. exclusivity, by successfully defending a 2019 method patent. But now, under agreements with the New York pharma giant, Teva Pharmaceutical and Mylan are set to take a first stab at the Viagra brand starting December 11.

Back in 2013, after years of legal wrangling, Pfizer settled with Teva, allowing the Israeli generics giant to launch its copycat this December, years before Viagra’s last key patent expiration. Under the deal, Teva will owe royalties. Mylan and Pfizer entered a similar agreement in 2015.

With two generics giants fighting for a piece of Viagra’s annual haul, Pfizer might face a tough time hanging onto its sales from the get-go. Often, just one generics maker wins the first-to-file prize that gives it six months of copycat exclusivity, which gives the brand a bit of a breather before the real pricing war begins. Though not part of the deals with Pfizer, other generics firms including Apotex, Torrent, Amneal and Aurobindo also have tentatively approved copycats at the FDA.

EvaluatePharma’s sales forecast bears that out. The analysts predict Viagra will fall to $359 million in sales next year and sink to $188 million by 2022. That's a big drop from the $1.1 billion predicted for 2017.

In the nearly two decades since Viagra’s approval, Pfizer has done a great deal to make the most out of its product. It’s been a regular on television screens for years, and Pfizer in 2015 launched a single-pack that can be taken on the go. Along with chief rival Cialis, the drug has been a mainstay atop pharma marketing spending tallies. Just last month, the company kicked off a text-for-coupon TV campaign to keep its advertising support behind the brand.

3. Viagra