Schizophrenia patient. Should we do now?

My father has been suffering from Schizophrenia for a long time and it has been only 6 years since we have found out about it. During 2010 we consulted a doctor since things were getting worse and he adviced to take sirilept 50. After 3 months my father discontinued the medicine and never consulted the doctor after that. Bt my mother always gave him the medicine by mixing it in his food and after two three days he was back to normal again. Whenever there were synptoms that there was something wrong we used to give him that medicine. 6 months ago we took him to the doctor again and the doctor adviced him to take Oleanz rt 10 and Tremlin 2mg. But the situation got worse after that. So the doctor again switched back to sirilept 50. But now the problem is that the medicine is not available anywhere. I tried to buy it online with valid prescription but cannot find it anywhere. I have also asked our doctor but he said that this was the only medicine that can cure him. What should we do now ?