it's a prescription only medicine, you can only get from government clinic, it has many side effect like drowsiness, tremor, hallucination and withdrawal syndrome if you stop it abruptly. Overdose is dangerous cause of death, because a benzodiazepine basically suppress your central nervous system. If his anxiety problem has been more than few months, I suggest that you bring your brother to seek help from psychiatrist rather than taking it yourself. Generalized Anxiety Disorder(GAD) is a common yet treatable illness by both psychotropics and psychotherapy