The two fastest routes of administration are intravenous infusion and topical application. Intravenous infusion is the method of entering the blood circulation of the body through intravenous drip or intravenous injection, and reaching the site of action with blood circulation. Because intravenous infusion works with the blood circulation of the body, it does not have the first pass elimination effect of oral drugs, thus it works fast and maintains its efficacy better. Topical medications act directly on certain parts of the body, such as infections or swelling caused by trauma. Since the medication is applied directly to the affected area, the medication works faster. Different medications are administered by different routes, some can only be used intravenously, while others can only be used externally. It is necessary to choose the best route of administration, taking into account the specific disease and the chemical principles of the medication itself.