3.3 : 药物递送：概述

The choice of a drug's delivery route depends on its physicochemical features, such as lipid or water solubility and ionization, as well as therapeutic need, such as immediate or prolonged action.

Drugs can be delivered through enteral, parenteral, and topical routes.

The enteral route is a commonly used drug delivery route, where a drug can be swallowed directly, kept under the tongue, or between gums and cheeks. Oral drugs primarily traverse the GI tract for systemic absorption. 

Enteral delivery has drawbacks, including poor absorption, gastric irritation, instability in low gastric pH, and metabolism by intestinal flora.

The parenteral route involves injecting drugs directly into the bloodstream, muscles, or beneath the skin, ensuring varying bioavailability.

Amongst them, intravenous administration yields high bioavailability and a rapid onset of action.

The topical route entails applying medication directly to the skin or mucous membranes for a localized effect with minimal toxicity.