Question: Viagra was introduced in 1989, which makes it 28 years, and I don’t think it’s generic yet. Why not? Most drugs go off patent in 17 years. Even my doctor and pharmacist don’t know. It can cost from $14 to $30 for one session, if you know what I mean. So, when is Viagra going generic?

Answer: We’ll answer your last question first and then clarify a few statements in your query: Generic versions of the popular prescription for erectile dysfunction are expected in the United States by the end of this year, even though Pfizer Inc.’s patent is good for about three more years, a corporate spokesman said.

“Pfizer’s patent covering the use of Viagra to treat erectile dysfunction (sildenafil citrate 25, 50, and 100 mg tablets) expires in April 2020 (including pediatric exclusivity). As a result of a settlement, Teva Pharmaceuticals will be allowed to launch a generic version of Viagra in the U.S. on December 11, 2017, or earlier under certain circumstances. At that time, Pfizer will continue offering branded Viagra, and Greenstone, a wholly owned subsidiary of Pfizer, will be able to launch an authorized generic sildenafil citrate,” Steven Danehy, a Pfizer spokesman, said in a statement emailed to Kokua Line on Monday.

Generally, the term of a new patent is 20 years from the date on which the application was filed, and allows the holder to “exclude others from making, using, offering for sale, or selling” the invention in the United States or importing it to the country, according to the U.S. Patent and Trademark Office.

Although Pfizer created sildenafil citrate (brand name: Viagra) in about 1989, it did not file for a U.S. patent that year, according to our search of records on the patent office website. (Viagra wasn’t approved for use in the U.S. until nine years later, but that’s a different issue.)

Pfizer did apply for at least two Viagra-related patents in the 1990s, several years apart, for the drug’s formulation and its method of delivery. The earliest original patent expiration year was 2011.

As explained on the patent office’s website, extensions can be sought for several reasons, including if the patent holder cites new ways to use the original invention. Companies protect their research and development investment by extending patents when they can.

Pfizer accomplished that by extending its U.S. patent to April 2020 despite obstacles, according to news reports.

A major challenge occurred in 2010 when Teva Pharmaceutical Industries Ltd., a global manufacturer of generic drugs, announced that it would sell a generic form of Viagra in the United States. Pfizer sued, claiming patent infringement. The companies settled in 2013 with a deal that validated Pfizer’s patent duration and authorized Teva to sell the generic in the U.S. starting in December 2017, as long as it pays Pfizer a royalty until the patent expires. (Teva already sells the generic in countries where Pfizer’s patent has expired.)

In the mid-1990s Pfizer sought U.S. Food and Drug Administration approval for patients’ use of Viagra — a separate process from the patent quest. Viagra hit the American market in March 1998 as the first FDA-approved oral medication to treat erectile dysfunction.

Out-of-pocket costs for each little blue pill vary widely, depending on whether the patient has prescription-drug insurance coverage or participates in a drug-discount program.

Mahalo

Mahalo to the kind man and his son who helped push my car to the road shoulder on the H1 freeway. They saw me having a hard time pushing the car by myself and told me to go inside and steer while they pushed. My engine suddenly stopped just after the Wilder offramp in the Ewa-bound direction. I was in shock and forgot to ask for his name and son’s name. Mahalo, and God bless you and your family! — MLC

Write to Kokua Line at Honolulu Star-Advertiser, 7 Waterfront Plaza, Suite 210, 500 Ala Moana Blvd., Honolulu 96813; call 529-4773; fax 529-4750; or email kokualine@staradvertiser.com.