3.3
Administración de medicamentos: descripción general
La selección de la vía de administración de un fármaco depende de sus propiedades fisicoquímicas, como la solubilidad en lípidos o agua y la ionizació…
La elección de la vía de administración de un fármaco depende de sus características fisicoquímicas, como la solubilidad en lípidos o agua y de la ionización, así como de la necesidad terapéutica, como la acción inmediata o prolongada.
Los medicamentos se pueden administrar por vía enteral, parenteral y tópica.
La vía enteral es una vía de administración de fármacos de uso común, en la que un fármaco puede tragarse directamente, mantenerse debajo de la lengua o entre las encías y las mejillas. Los fármacos orales atraviesan principalmente el tracto gastrointestinal para su absorción sistémica.
El parto enteral tiene inconvenientes, como mala absorción, irritación gástrica, inestabilidad en el pH gástrico bajo y metabolismo de la flora intestinal.
La vía parenteral consiste en inyectar fármacos directamente en el torrente sanguíneo, los músculos o debajo de la piel, lo que garantiza una biodisponibilidad variable.
Entre ellos, la administración intravenosa produce una alta biodisponibilidad y un rápido inicio de acción.
La vía tópica consiste en aplicar la medicación directamente sobre la piel o las membranas mucosas para obtener un efecto localizado con una toxicidad mínima.
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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.