Hi, "new". Do you have a diagnosis of lupus? Or suspect something's gone off since starting a new med?
There was a discussion here about DILE (drug-induced lupus) very recently, also about meds that can cause or exacerbate SLE (systemic lupus). Being curious, I'd looked up a long list of meds. Metoprolol (Lopressor) wasn't cited, but other BP meds were: Atenolol, Captopril, Dilitazem, Hydralazine, Methyldopa, and Reserpine. (Note the list may not be complete or totally current.)
But I don't know if Metoprolol is chemically similar to the BP meds listed. Thus I don't know... (Plus, anyway, I'm just a dumb patient!) But the fact that so many BP meds can be culprits is interesting. Maybe you could ask the rheumatologist to comment further, and maybe your pharmacist could shed some light. Good luck. Sincerely, Vee