3.3
薬物送達：概要
薬物の投与経路の選択は、脂質または水への溶解性やイオン化などの物理化学的特性、および即時効果や持続効果などの治療要件によって決まります。これらの経路は、経腸投与、非経口投与、局所投与の 3 つの主要なカテゴリに分類できます。
経腸投与では、薬の飲み込み、舌下投与、または内頬への塗布によって薬剤を直接…
薬物の送達経路の選択は、脂質や水の溶解性、イオン化などの物理化学的特性と、即時作用や長期作用などの治療ニーズによって異なります。
薬物は、経腸、非経口、および局所経路で送達できます。
経腸経路は一般的に使用される薬物送達経路であり、薬物を直接飲み込んだり、舌の下、または歯茎と頬の間に保持したりできます。経口薬は主に消化管を通過して全身吸収されます。
経腸分娩には、吸収不良、胃の刺激、胃の低pHの不安定性、腸内フローラによる代謝などの欠点があります。
非経口投与では、血流、筋肉、または皮膚の下に直接薬物を注入し、さまざまなバイオアベイラビリティを確保します。
その中でも、静脈内投与は高いバイオアベイラビリティと迅速な作用開始をもたらします。
局所経路では、皮膚または粘膜に直接薬を塗布して、毒性を最小限に抑えて局所的な効果を得ることができます。
View the full transcript and gain access to JoVE Core videos
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.