Which route of administration generally does not use solutions?

The sublingual route of administration typically does not utilize solutions because it involves placing a solid dosage form, such as a tablet or film, under the tongue. This method allows for the quick absorption of the medication directly into the bloodstream through the mucous membranes in the mouth. The design of sublingual formulations focuses on rapid disintegration and absorption rather than relying on a liquid form of the drug.

In contrast, the vaginal, rectal, and intranasal routes are often associated with solutions. For example, vaginal creams and suppositories deliver medication in a liquid or semi-liquid state, while rectal administration can involve solutions or suppositories for local effects. Intranasal delivery frequently utilizes liquid formulations or sprays to effectively administer the medication through the nasal mucosa. This distinction highlights the unique characteristics of the sublingual route and its preference for solid forms of medication for effective delivery.