The modern pharmacist is responsible for the quality of the chemicals compounded for and dispensed to a patient. The pharmacist is also responsible for helping to ensure that a proper program is appropriate for a patient, based partly on how much detailed and timely knowledge of the patient's condition is at hand. Further, he or she should inform the person administering or taking the chemical about its proper use, side effects, and dangers. Federally funded health-care programs require pharmacists to monitor the effectiveness of chemical therapy in certain patients and to make recommendations about continuance or change. Their preparation, and their proper use to treat illness by cure, control, and prevention.
Modern pharmacy is so complex and rapidly changing that no one can know or practice all of it.
In only one part of the health-care system do pharmacists alone dominate in the dispensing of items prescribed by physicians. The concerns of pharmacy and pharmacists begin with chemical discovery and end with evaluating and improving drug effectiveness in a single patient at a given time. These are created either through synthesis by pharmaceutical chemists or through collection and purification from natural sources by experts in pharmacognosy. The scientific study of the effects is called pharmacology.