Metronidazole patent expired 1982?

Short answer: the main patent covering the metronidazole molecule generally expired in the early 1980s (US often cited around 1982), but patent term dates vary by country and by which patent claim you’re talking about (composition of matter vs. salts, processes, or specific formulations).

Important nuances:
- Country matters. Expiry can be 1982 in the US, but different jurisdictions may have a different expiry date.
- There are multiple patents around metronidazole (the core molecule, various salts, manufacturing processes, and delivery formulations). Some of these could have extended protection into later years in certain markets.
- By now, metronidazole and many of its formulations are widely off-patent and available as generics in most places.

If you want a precise date for a specific country or for a specific patent (e.g., the original composition patent vs. a salt or a gel/cream formulation), tell me the country and which patent type, and I can help narrow it down. If you’d like, I can also guide you on how to look this up in patent databases (USPTO/Espacenet/Patentscope).