Mental Capacity: Is it important in our daily practice?

A middle aged man complaining of chest pain walks into the emergency department of a teaching hospital in Karachi. After examination and investigatigations, he is informed that he has suffered a myocardial infarction and would benefit from a thrombolytic agent. The patient refuses the treatment on the grounds that he will be subjected to the risk of internal bleeding as a side effect and would prefer herbal (hikmat) medication at home. What should be done now? Should he be allowed to go home, knowing the risks associated with his illness? In another real anecdotal experience at Karachi, an elderly lady lies on the bed of a hospital. She is diagnosed with moderate to severe dementia and chronic renal failure. She has now stopped eating. The physician walks in and declares to the family members that he is planning a percutaneous endoscopic gastrostomy (PEG). When the relatives show some reluctance, he further declares, I am not asking your permission but simply informing you! and walks out. Is this ethically justified?