''I read somewhere, they interfere with each others actions.''
You have different kind of interactions. You have major interactions which means that a drug should never be taken with the interfering drug and you have interaction which is usually said to be ''caution advised''.
For example if i take diazepam and codeine i will have an interaction but only a caution advisory because both drug are acting in an additive way on your nervous system. For example the combo may result result in vasodilation, hyporetension, CNS and respiratory depression, psychomotor impairment ( additive effects ). But the 2 drugs can be taken safely together even tho they are interacting together when taken as resonable dose.
But i would go with what Paxiled suggested and consult a different practitioner and try to have the opinion of a specialist too, in your brother's case it would be a neurologist and even a psychotherapist and maybe bring the list of medication to a different pharmacist to get a different opinion.
Best regards,
M4
Any of the drugs could be the problem if he's taking so many. He may be too drugged up. He might want to consult a different practitioner to get another opinion.