Darvon and Darvocet (and their generics) have been used as Migraine rescue medications and for treating some other headache disorders.
Now, all medications containing propoxyphene have been pulled from the market following FDA studies of safety risks. Given that these medications have been on the market for more than 50 years, and that the study upon which this decision was made had only 18 participants, this is a very controversial decision.
Karen Lee Richards has written about this...

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