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.
Serious adverse events Case reports have described acute inferior-wall myocardial infarctions characterized by low atrial rhythms (Kounis syndrome) secondary to propyphenazone use.
Excerpt from WHO comments
Banned Propyphenazone is banned in some countries including Sri Lanka, Malaysia, and Thailand.
Synthesis
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.
See also Propyphenazone/paracetamol/caffeine Metamizole
References