| Original Discoverer / Developer |
Pfizer, Inc. (through a joint venture with Warner–Lambert) |
| Key Patent Numbers (US) |
• US 5,779,154 – “Sildenafil Citrate” (composition & use)
• US 5,910,012 – “Sildenafil Citrate for use in erectile dysfunction”
• US 6,030,500 – “Sildenafil‑based combination therapies” |
| Key Patent Numbers (International) |
• WO 90/23344 – International application (covers the core composition and uses).
• EP 1 928 507 – European Patent covering sildenafil citrate. |
| Filing / Grant Dates |
• 5,779,154: filed 15 Sep 1994, granted 5 Dec 1998.
• 5,910,012: filed 28 Feb 1994, granted 2 Apr 1999. |
| Typical Patent Life |
20 years from filing date (subject to extensions). |
| Expiration (US) |
5,779,154: 15 Sep 2014 (original term).
Because of Patent Term Extension (PTE) for regulatory delays, the effective expiration date was moved to 2018 (Jan 1 2018).
Other patents (5,910,012, 6,030,500) also expired around 2018‑2020, depending on PTE and territorial claims. |
| Effect of Expiration |
- Generics: The first FDA‑approved generic sildenafil (generic “sildenafil citrate”) entered the U.S. market in June 2017 under the brand Caveril (generic trade name).
- Brand Protection: The trademark “Viagra” remains protected, so generic manufacturers cannot use that name. |
| Current Status |
- Pfizer still holds patents on specific formulations and delivery methods (e.g., delayed‑release tablets, combination products with other active ingredients).
- Other companies hold patents on novel formulations or uses (e.g., sildenafil‑based treatments for pulmonary arterial hypertension).
- The core composition (sildenafil citrate) is now in the public domain in most jurisdictions, allowing a wide range of generic manufacturers worldwide. |
| Typical Patent Claims |
1. Composition claims – sildenafil citrate crystals, tablets, capsules, and liquid preparations.
2. Method claims – use of sildenafil for treating erectile dysfunction (ED) and pulmonary arterial hypertension (PAH).
3. Formulation claims – specific excipients, release rates, and dosage strengths.
4. Combination claims – sildenafil combined with other drugs (e.g., antihypertensives) for synergistic effects. |