The oral mucosa has a thin epithelium and a rich vascularity that favors absorption, but contact is usually too brief, even for drugs in solution, for appreciable absorption to occur.

• 口腔粘膜上皮很薄，血管丰富，有利于药物吸收。但是，接触的时间太短暂，即使是溶液剂也来不及等到明显的吸收发生。