Which method involves administering a liquid medication drop by drop?

Instillation is the method that involves administering a liquid medication drop by drop. This technique typically targets specific areas in the body, such as the eyes, ears, or nasal passages, where precise dosing is essential for effective treatment. By delivering the medication in this controlled manner, instillation allows for maximum absorption and minimizes waste, ensuring that the intended therapeutic effect is achieved. This is particularly important in cases where the medication needs to act locally at the site of administration, making it a preferred method for applications such as eye drops or ear drops.