ABSTRACT
Despite the low bioavailability of drugs compared to the intravascular injection through veins (intravenously) or arteries (intra-arterially), the extravascular administration through oral, nasal, intramuscular, subcutaneous, dermal, pulmonary, and rectal routes offers clear advantages in terms of patient compliance and safety. The unique anatomical, biochemical, and cellular features of each of the extravascular routes account for its distinctive barriers to drug delivery en route to the bloodstream.
