3.29 : 非口服血管外药物吸收途径

Non-oral extravascular routes mainly diffuse drugs passively to reach the systemic circulation. Factors influencing extravascular drug absorption include the drug's physicochemical properties and the anatomy and pathophysiology of the patient.

Lipophilic drugs, stable at salivary pH 6 and poorly binding to the oral mucosa, are absorbed better through sublingual and buccal delivery. Sublingual nitroglycerin drains from the mouth's venous system into the superior vena cava, bypasses first-pass hepatic metabolism, and improves blood flow to the heart.

Drugs applied topically on the foot and palm are absorbed slowly because of the thick stratum corneum. However, medications for burned or injured skin exhibit rapid absorption, aided by occlusive dressing to maintain skin moisture.

Intramuscular injections yield rapid absorption from arms, rich in blood supply, compared to thighs, and slowest from the buttocks.

Gaseous and aerosol drugs given by inhalation are absorbed rapidly because of the lung's large surface area and high vascularity.