Final answer:
External infections are best treated with topical medications applied directly to the infection site. Oral medications are preferred for home administration of systemic infections, but parenteral methods like intramuscular injections are used if oral intake is not possible.
Step-by-step explanation:
External infections are typically treated with medications that are applied directly to the site of infection. The different routes of administration include intramuscular, surface, and topical application. For infections like superficial skin infections or vaginal yeast infections, topical treatment is the most common and effective form. Topical medications are applied to the skin or mucous membranes to treat infections caused by bacteria, fungi, or viruses. For instance, topical antifungal medications are used to treat yeast infections of the vagina, and antibiotics can be either applied topically or taken orally to treat bacterial infections.
When selecting an antimicrobial for a systemic infection that requires home administration, the oral route is often preferred due to convenience. However, for infections where a high plasma level of antibiotic is necessary or when the patient cannot take oral medications, parenteral administration, such as intramuscular or intravenous injections, might be adopted, often in a health-care setting. It's critical to choose the correct route of administration based on factors such as the site of infection, the drug's absorption and metabolism, and the patient's health status.
The final answer for the administration route of drugs applied directly to the site of infection is: 3) Topical
For the treatment of external infections, the topical route of administration is the most appropriate as it involves applying medication directly to the site of the infection. This local application allows for the drug to act at the site of infection effectively, providing targeted therapy which is convenient for home administration.