Update of Besin's reply, actually Propharma's (a pharmacovigilance company) reply.
A somewhat blunt and quite absurd reply saying 'there is no data regarding irregular bleeding when Utrogestan (progesterone) is used with Diazepam in the Patient Information Leaflet (PIL) or Summary of Product Characteristics (SPC)'.
There must be a misunderstanding or they haven't actually read the PIL. I agree there is no 'data', but it's obvious that the interaction is mentioned and I have asked for references that confirm this alleged interaction, and I have been clear that if this is a post marketing anecdotal interaction, I would understand the lack of scientific data. They simply don't engage in conversation, they choose to ignore the questions and reply in a way that is supposed to let me think I'm not up to the task of understanding anything and that only a medical doctor or pharmacist will be able to understand. Patronising customer service.
I have replied again and am waiting for the next chapter of this cheap sitcom.
On a brighter note, this book chapter is a clear comprehensible doc on the interaction of progesterone, estradiol and benzos in relation to GABA-A receptors.
http://www.scicompdf.se/pms_scientific/backstrom_13.pdf