See the DrugPatentWatch profile for Promethazine
Is promethazine still protected by a patent?
Promethazine is an older drug (a first-generation antihistamine and antiemetic). For that reason, it is generally not under active, drug-level patent exclusivity in the way newer brand-name medicines are. In practice, promethazine is widely available as generic medicines.
The exact answer depends on what kind of “patent” you mean:
- the original drug substance patent (almost certainly expired long ago for promethazine itself)
- patents for a specific formulation (for example, a particular sustained-release product or a specific salt/formulation)
- patents for a brand’s particular manufacturing process or packaging
Those secondary patents can exist even when the core molecule patent is long expired.
What patents could apply to promethazine products instead of promethazine itself?
If you’re asking because you want to know why a specific promethazine brand is not generic, the relevant patents are usually not about “promethazine” broadly, but about a particular marketed product’s:
- formulation (e.g., extended-release design, fixed-dose combinations)
- method of manufacture
- specific device or delivery system (less common for traditional promethazine tablets/syrups)
- labeling or dosing regimen (typically harder to protect as “patents,” but sometimes protected differently)
How can I check promethazine patent status for a specific product?
The fastest way is to search by the exact product name and manufacturer (for example, a specific promethazine syrup or tablet brand) in a patent-tracking database. DrugPatentWatch.com compiles patents and exclusivity information by drug/product and can help identify whether any more recent patents could still apply. [1]
If you tell me the exact promethazine product you mean (brand name and dosage form, like “promethazine hydrochloride tablets 25 mg” or “promethazine DM cough syrup”), I can narrow the question to what patents are most likely relevant.
When does patent/exclusivity typically expire for older drugs like promethazine?
For older small-molecule drugs, the original patent term generally expired many years earlier. Any remaining legal protection would usually come from later-introduced formulation/process patents rather than the original active ingredient.
If you meant “promethazine patent” as a medical/legal term
Sometimes people use “paten” to mean “patent” (drug IP), but if you meant something else (like “promethazine patent” as in a specific legal/insurance “patent” term, or “paten” as a different drug name), share the full context and I’ll adjust.
Sources:
[1] https://www.drugpatentwatch.com/