Alternative to a drug. Advantages!

A friend Of mine is using a drug named mephentermine sulphate 30mg/ml since 6 month By injecting it IV or IM mostly IV He says it calms him and helps him in concentrating. And also in exercises I thought that he is addicted to it but i checked by stopping it for a week and he never demanded it He started with 2ml once a day But now he is becoming immune to it. He sometimes takes 2 doses a day of 4ml each. When i asked him to stop as it may be harmful he said find a safer alternative to it which acts in the same way. Atleast the mental part so that he can prepare for the competition exams and stay energetic. It has also controlled his random one sided headache problem. He lives alone and has family issues. So please suggest an alternative.also tell me about the safe dosage and results. Pros Concentration Activeness Anti depressant Energetic Cons hard stool pain in excrement aftr 3days without going to toilet.no other problems recorded. mostly advantages