3.3
药物递送：概述
药物递送途径的选择取决于其物理化学性质，包括脂质或水溶性和离子化，以及治疗要求，例如即时或持续效果。这些途径可分为三大类：肠内、肠外和局部递送。
肠内给药包括直接通过吞咽、舌下放置或口腔应用直接给药。口服药物主要通过胃肠道进行全身吸收。然而，这种方法有局限性，例如吸收不足、胃部刺激、低胃 pH 值不…
药物给药途径的选择取决于其理化特性，例如脂溶性或水溶性以及解离程度，同时也取决于治疗需求，例如需要立即起效或长效作用。
药物可以通过肠内、肠外和局部途径给药。
肠内给药是一种常用的药物递送途径，药物可直接吞服，或含于舌下，或置于牙龈与脸颊之间。口服药物主要通过胃肠道进行全身吸收。
肠内给药存在一些缺点，包括吸收不良、胃部刺激、在低胃pH环境下不稳定以及被肠道菌群代谢。
注射给药途径包括将药物直接注入血液、肌肉或皮下，从而确保不同的生物利用度。
其中，静脉注射具有较高的生物利用度和快速的起效速度。
局部给药途径是指将药物直接应用于皮肤或黏膜，以实现局部作用并尽量减少毒性。
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Q1: What factors determine which drug delivery route to use?
Drug delivery route selection depends on the drug's physicochemical features, including lipid or water solubility and ionization, as well as therapeutic needs such as immediate or prolonged action. These factors determine whether enteral, parenteral, or topical administration is most appropriate for achieving desired therapeutic outcomes.
Q2: What are the main limitations of enteral drug delivery?
Enteral delivery has several drawbacks: poor absorption, gastric irritation, drug instability in low gastric pH, and metabolism by intestinal flora. However, most enteral drugs are designed with protective coatings and formulations to overcome these limitations and ultimately achieve good absorption in the gastrointestinal tract.
Q3: Why does intravenous administration provide faster drug effects than other routes?
Intravenous administration yields the highest bioavailability and fastest onset of action because drugs are injected directly into the bloodstream, bypassing absorption barriers. This parenteral route ensures rapid systemic distribution and therapeutic response compared to enteral routes that require gastrointestinal absorption and processing.
Q4: How do topical drugs achieve systemic effects?
While topical administration typically targets local effects on skin or mucous membranes with minimal toxicity, some drugs applied topically can achieve systemic effects. For example, transdermal fentanyl patches deliver drugs systemically over time through skin absorption into the bloodstream for widespread therapeutic distribution.
Q5: What are the different types of parenteral drug administration?
Parenteral delivery involves injecting drugs directly into the bloodstream, muscles, dermis, or subcutaneous tissue, providing varying degrees of bioavailability. Intravenous injection offers the highest bioavailability and fastest onset, while intramuscular and subcutaneous routes provide different absorption rates and therapeutic profiles for various clinical needs.
Q6: How do enteral drugs enter systemic circulation?
Orally administered drugs primarily traverse the gastrointestinal tract for systemic absorption. The drug must dissolve, be absorbed through the intestinal epithelium via mechanisms like paracellular transcellular and vesicular transport, and enter the bloodstream for distribution throughout the body and therapeutic action.
Q7: Why is drug formulation design important for enteral delivery?
Drug formulations are specifically designed to address enteral delivery challenges such as gastric degradation and poor absorption. Protective coatings limit drug degradation in the stomach's low pH environment, allowing drugs to reach the intestines intact for better systemic absorption and improved therapeutic efficacy.