Propyphenazone (known as isopropylantipyrine in Japan) is a derivative of phenazone with similar analgesic and antipyretic effects. Originally patented in 1931, propyphenazone is marketed as a combination formulation with paracetamol and caffeine for treatment of primary headache disorder.
Case reports have described acute inferior-wall myocardial infarctions characterized by low atrial rhythms (Kounis syndrome) secondary to propyphenazone use.
Propyphenazone is banned in some countries including Sri Lanka, Malaysia, and Thailand.
Ethyl 2-isopropylacetoacetate (1) and phenylhydrazine (2) are combined to form the pyrazolone ring in the intermediate (3), which is alkylated with methyl iodide to yield propyphenazone.