sublingual administration

Sublingual administration means placing a tablet or spray under the tongue and letting it dissolve there, rather than swallowing it. The floor of the mouth has a thin lining and a rich blood supply just beneath, so a suitable drug can pass quickly into the bloodstream — almost like a shortcut into the circulation through the mouth.

The big advantage is that drug absorbed under the tongue drains into veins that empty into the general circulation directly, bypassing the gut and the liver's first-pass metabolism. A drug that would be largely destroyed by the liver if swallowed can therefore reach the blood intact and act within minutes. This combination of speed and first-pass avoidance is the route's defining feature.

Sublingual delivery only works for drugs that are potent (small doses), highly fat-soluble, and non-irritating, since the absorbing area is small. The patient must not swallow, eat, or drink while the tablet dissolves, and the route is not practical for large or slow-dissolving doses.

A closely related route, buccal administration, places the drug between the cheek and gum and works on similar principles. Both belong to the broader oromucosal routes that exploit the mouth's lining for rapid, first-pass-sparing absorption.