You have not given the details. However there are some options.
1...if patients has insight and disease is relatively mild like depression or anxiety. Then motivate him
2 ..if psychotic and has no insight then you may give him drops of antipsychotics drugs for some time till insight returns.
3....in any case go to psychiatrist discuss whole case. He will decide what to give and how to give
Last resort is to bring the patient against the will. Different psychiatric facilities have this facility.
Better to visit a psychiatrist yourself to give detailed which will guide the patients condition and advise can be given thanks
Sir i am patient of depression.. Mera 4 saal sy treatmnt bhi horaha hy magr theek naii hota.. Mera roony ko, kisi b happy event p naa jany ko dil krta h..