Pharmacology is the scientific study of how drugs interact in the human body. It is an important field of study for individuals because it teaches pharmacologists how certain medications will affect its users. Pharmacologists can use this information to decide whether there is a level of toxicity for patients who are coming into the pharmacy to fill a prescription. If it is possible that a medication can cause problems in users, based on other prescriptions that they are taking or their health, they will make suggestions on safe alternatives. Pharmacologists use the field of pharmacology to make decisions on the usefulness and effectiveness of drugs.