Suggest Safe Dosage Of Deriphyllin For Asthma

I am taking Deriphyllin 150 retard twice a day, one in the morning and one at night. After suffering Asthma for the last 40 years, a young doctor in India asked me to try this medicine. After two week s use, I felt like a different person. My C.O.P.D is completely negotiated. I have no wheezaing or coughs now. Some say this medicine has an effect on the heart. Do you think the doze I am taking is safe?