Sublingual (abbreviated SL), from the Latin for "under the tongue", refers to the pharmacological route of administration by which substances diffuse into the blood through tissues under the tongue. The sublingual glands receive their primary blood supply from the sublingual and submental arteries, which are branches of the lingual artery and facial artery, respectively. These arteries are both branches of the external carotid artery. The sublingual vein drains into the lingual vein, which then flows into the internal jugular system. The sublingual glands receive their parasympathetic input via the chorda tympani nerve, which is a branch of the facial nerve via the submandibular ganglion. The nerve functions in a secretomotor capacity. The chorda tympani branches from the motor branch of the facial nerve in the middle ear cavity, which then exits the middle ear through the petrotympanic fissure. The chorda tympani then travels with the lingual nerve to synapse at the submandibular ganglion. The postganglionic fibers reach the sublingual gland, and release acetylcholine and substance P. Acetylcholine, the primary neurotransmitter and the muscarinic receptors work to increase salivation. Many drugs are absorbed through sublingual administration, including cardiovascular drugs, steroids, barbiturates, benzodiazepines, opioid analgesics, THC, CBD, some proteins and increasingly, vitamins and minerals. Principle When a chemical comes in contact with the mucous membrane beneath the tongue, it is absorbed. Because the connective tissue beneath the epithelium contains a profusion of capillaries, the substance then diffuses into them and enters the venous circulation. In contrast, substances absorbed in the intestines are subject to first-pass metabolism in the liver before entering the general circulation. Sublingual administration has certain advantages over oral administration. Being more direct, it is often faster, and it ensures that the substance will risk degradation only by salivary enzymes before entering the bloodstream, whereas orally administered drugs must survive passage through the hostile environment of the gastrointestinal tract, which risks degrading them, by either stomach acid or bile, or by enzymes such as monoamine oxidase (MAO). Furthermore, after absorption from the gastrointestinal tract, such drugs must pass to the liver, where they may be extensively altered; this is known as the first pass effect of drug metabolism. Due to the digestive activity of the stomach and intestines, the oral route is unsuitable for certain substances, such as salvinorin A. Forms Pharmaceutical preparations for sublingual administration are manufactured in the form of: Sublingual tablets—tablets which easily melt in the mouth,