Sublabial, literally 'under the lip', from Latin, refers to the pharmacological route of administration by which the active substance is placed between the lip and the gingiva. The Frenulums may be irritated when in contact with corrosive materials but can be avoided.
It is usually used for drugs such as Glyceryl trinitrate, for example, in angina pectoris.1
Upper lip administration
Some drugs are inactive in the digestive tract that can be avoided by held it between the upper lip and gum to avoid getting the substances swallowed with salivation as normally occur between the lower lip and gum. This permits slow release of drug to prolong the duration of action.