Short answer:
The original U.S. patent that covers the chemical compound ivermectin (US 4,520,748) expired on 2 March 2002. Since then the drug has been on the generic market in the United States and in most other countries.
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How that date is calculated
| Item | Detail |
|------|--------|
| Patent number | US 4,520,748 – “Ivermectin” |
| Applicant | Novartis (originally owned by Ciba-Geigy) |
| Filed | 30 June 1982 |
| Issued | 2 March 1985 |
| Patent term | 17 years from the issue date (the rule in force before the 1995 patent law change) |
| Expiration | 2 March 2002 |
Because the patent law in the U.S. at that time granted a 17‑year term from the issue date (rather than 20 years from filing), the term ran exactly from March 1985 to March 2002.
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What happened after the expiration
| Year | Milestone |
|------|-----------|
| 2002 | Core ivermectin patent expires. Generic versions become eligible. |
| 2003 | The first U.S. generic ivermectin formulation receives FDA approval for veterinary use (for treating heartworm in dogs). |
| 2017 | FDA approves the first generic oral ivermectin for human use (for onchocerciasis and strongyloidiasis). |
| 2018–2023 | Various other patents covering improved formulations, dosing regimens, or new indications (e.g., for COVID‑19, viral infections, or antiparasitic combinations) expire at different times, but none cover the core chemical itself. |
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Key points to keep in mind
1. Core chemical patent expired in 2002. That means the active ingredient—ivermectin itself—can be produced by any manufacturer without infringing that original patent.
2. Secondary patents remain. Novartis and other companies still hold patents on specific formulations, delivery devices, or new therapeutic indications. Those patents can extend market exclusivity for those particular products, but they do not prevent the generic production of plain ivermectin.
3. Global variation. While the U.S. patent expired in 2002, other jurisdictions may have had different filing dates or patent terms. In many countries, the drug entered the generic market around the same time, but some still have active secondary patents until the 2020s.
4. Regulatory status. In the U.S., ivermectin is now available as a generic drug for human and veterinary use (under brand names like Mectizan, Stromectol, and Ivermectin). It is also sold over the counter in some countries for parasitic infections, though its use for other indications (e.g., COVID‑19) is not FDA‑approved.
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Bottom line
- Core ivermectin patent expiration: 2 March 2002.
- Generic entry: Shortly thereafter, with generics now widely available.
- Remaining patents: Cover specific formulations or new indications, but none extend to the base compound itself.
If you’re looking at a particular product or formulation, let me know the brand or indication, and I can check if there are any remaining patent barriers in that specific jurisdiction.