Which of the following routes involves inhaling small particles of medication?

Inhalation is the route that involves inhaling small particles of medication directly into the respiratory system. This method is particularly effective for delivering medications intended to act locally on the lungs or for systemic effects, as the absorbed medication enters the bloodstream rapidly through the lungs' extensive surface area.

When medication is inhaled, it can come in various forms such as aerosols, powders, or vapors, allowing for swift absorption and onset of action. This route is commonly used for respiratory conditions like asthma and chronic obstructive pulmonary disease (COPD), where medications must reach the lungs directly for maximal therapeutic effect.

Other routes have distinct modes of administration that do not involve inhalation. Transdermal involves the application of medication through the skin for systemic effect, oral is about swallowing medication for gastrointestinal absorption, and topical refers to the application of medication on the skin surface for localized treatment. Each of these methods differs significantly from inhalation in terms of delivery and absorption mechanisms.