Fibromyalgia. Its be serious alarming?

The usual dose range to treat fibromyalgia is milnacipran 30-200 mg in divided doses and duloxetine 60 mg. Maximum for both the drug is as mentioned while the dose that works in most of the patients is 100 mg for milnacipran and 60 mg for duloxetine. As in your case both has been prescribed together but in low doses, this may have been done due to side effects profile in the patient as that is the main reason for selecting medicines in psychiatry because most drugs have similar efficacy in treatment. Hence the molecules will achieve the treatment levels in the brain together while the side effects may be minimal for each of the medicine. I guess this is the reason. Otherwise I see no point in combining two drugs of similar mechanism together at subtherapeutic doses. Hope this helps.