| 1982‑84 |
Pfizer’s cardiovascular research team at the University of Dundee begins screening compounds for angina treatment. |
The team is looking for a potent, short‑acting vasodilator. |
| 1988 |
Sildenafil (later sildenafil citrate) is first synthesized by researchers at Pfizer. |
The molecule shows strong inhibition of phosphodiesterase‑5 (PDE‑5) – a promising target for blood‑flow disorders. |
| 1990‑1993 |
Phase I/II clinical trials for angina and hypertension. |
Side‑effects (e.g., headaches, flushing) and limited anti‑anginal efficacy lead Pfizer to pause the program. |
| 1993 |
Redirection: The drug is repurposed for erectile dysfunction (ED). |
A small Phase II study shows dramatic improvement in erections—sudden “clinical gold‑mine.” |
| 1994 |
FDA reviews the new indication; Pfizer files an NDA for “Viagra.” |
The name is a trademark; the marketing team decides on a sleek, memorable brand. |
| May 25, 1998 |
FDA approves Viagra for ED. |
1st blockbuster drug for a “discreet” disorder; sales quickly reach $200 m in the first year. |
| 1999 |
Viagra becomes the face of the ED market. |
Massive advertising campaigns, celebrity endorsements, and a cultural shift in discussing sexual health. |
| 2002 |
Pfizer receives “Drug of the Year” award (American Medical Association). |
Recognition of Viagra’s impact on men’s health and on pharmaceutical marketing. |
| 2003‑2004 |
FDA expands indications: pulmonary arterial hypertension (PAH) – drug renamed Revatio (2008). |
Highlights the versatility of PDE‑5 inhibition beyond ED. |
| 2006–2008 |
First generics hit the market after patent expiry. |
Price drops from ~$2000/month to ~$20–$60, widening access. |
| 2010s |
Continued research: use in heart failure, erectile dysfunction post‑prostatectomy, and sexual dysfunction in women (mixed results). |
Demonstrates the drug’s broad therapeutic potential. |
| 2020‑2024 |
Ongoing global patent litigation, biosimilar development, and new indications (e.g., for Raynaud’s phenomenon). |
Viagra remains a major revenue source for Pfizer and a staple in sexual medicine. |