Chapter 3
Pharmacokinetics: Drug Absorption
Fases de administração e terapia de medicamentos: visão geral
Drugs are chemicals used for diagnosing, treating, or preventing diseases. The four phases of drug product preparation are pharmaceutic, pharmacokinetic, ...
Absorção de medicamentos: visão geral
The process of drug absorption involves the passage of a drug from its administration site into the plasma. It is influenced by factors like ...
Drug Delivery: Visão geral
The choice of a drug's delivery route depends on its physicochemical features, such as lipid or water solubility and ionization, as well as ...
Drug Delivery: Via Enteral
Enteral administration of drugs can occur via oral, sublingual, and buccal routes. Oral administration involves swallowing a pill; in sublingual delivery, ...
Drug Delivery: Via Parenteral
The parenteral route delivers drugs directly into the systemic circulation. It facilitates rapid onset of action and is the preferred route for poorly ...
Drug Delivery: Rotas Diversas
Drug delivery methods, such as oral inhalation, nasal sprays, transdermal patches, eye drops, intravitreal, and intrathecal injections, mostly offer ...
Membranas Celulares e Transporte de Medicamentos
Drugs encounter multiple barriers to reach their target site within the body, including the multiple-cell layered skin, single-layered intestinal ...
Mecanismos de Absorção de Medicamentos: Transporte Paracelular, Transcelular e Vesicular
After administration, drugs must cross cell membranes to reach their target site in the body. For example, oral drugs must navigate intestinal epithelial ...
Difusão Passiva: Visão Geral e Cinética
Passive diffusion allows small lipophilic drugs to cross the cell membranes along a concentration gradient. During this process, the drug absorption rate ...
Transporte de poros e transporte de pares iônicos
Most drugs cross the membrane barriers through passive transport mechanisms, moving along the concentration gradient.
Many low molecular weight drugs move ...
Transporte mediado por transportadora
Carrier-mediated transport facilitates the movement of lipid-insoluble drugs via membrane-spanning transporters.
As drug concentration increases during ...
Difusão facilitada
The plasma membrane consists of several transporters or carrier proteins interspersed between the lipid bilayer that facilitate solute transport.
...
Transporte Ativo
Active transport is the process of moving lipid-insoluble molecules against their concentration gradient using energy and specialized transporters.
There ...
Transporte vesicular: endocitose, transcitose e exocitose
Endocytosis is a process where the cell membrane folds inward as vesicles to engulf large-sized drugs.
This process includes pinocytosis and
...
Fatores que influenciam a absorção de drogas: parâmetros anatômicos
Drug absorption entails transporting drugs from the administration site to the bloodstream.
GI motility moves drugs through the digestive tract, entering ...
Fatores que influenciam a absorção de medicamentos: estados de doença e farmacologia
Various disease conditions can influence the body's blood flow and the functioning of the gastrointestinal system, influencing the drug absorption ...
Fatores que influenciam a absorção de medicamentos: parâmetros físico-químicos
The physicochemical properties of drugs are essential parameters for designing stable and bioavailable drug products.
A drug's solubility depends on ...
Fatores que influenciam a absorção de medicamentos: parâmetros farmacêuticos
For drug products like tablets and capsules, dissolution and absorption are greatly influenced by the manufacturing methods and inactive components or ...
Fatores que influenciam a absorção de medicamentos: dissolução de medicamentos
The drug absorption process from solid oral dosage forms, like tablets or capsules, into the systemic circulation involves sequential events.
Firstly, ...
Fatores que influenciam a absorção de drogas: eliminação pré-sistêmica
Most oral drugs are absorbed from the intestines into the hepatic portal vein, passing through the liver before entering the systemic circulation. This ...
Teorias da Dissolução: Modelo de Camada de Difusão
Dissolution, the process of drug particles dissolving in a solvent, is explained by the diffusion layer model.
According to this model, initially, a thin ...
Teorias da Dissolução: O Modelo de Danckwerts e o Modelo de Barreira Interfacial
Various dissolution theories elucidate factors impacting the dissolution rate.
Danckwert's model postulates that the dissolution medium shows ...
Fatores que afetam a dissolução: tamanho da partícula e área de superfície efetiva
Recall the Noyes-Whitney equation, which suggests a direct correlation between dissolution rate and a drug's surface area.
A solid drug's surface ...
Fatores que afetam a dissolução: polimorfismo, amorfismo e pseudopolimorfismo
Drug dissolution is influenced by polymorphism, which refers to the existence of a drug substance in multiple crystalline forms like polymorphs, solvates, ...
Fatores que afetam a dissolução: pKa do medicamento, lipofilicidade e pH gastrointestinal
Drug absorption in the gastrointestinal tract depends mainly on the absorption site's pH, the drug's dissociation constant, and lipophilicity.
The ...
Fatores que afetam a dissolução: permeabilidade, estabilidade e estereoquímica de medicamentos
Most orally administered drugs travel through the GI tract and diffuse passively through intestinal membranes to enter the systemic circulation.
The ...
Métodos para estudar a absorção de medicamentos: in vitro
Various in vitro methods utilize different biological barriers to study drug absorption.
In the diffusion cell technique, a donor compartment with the ...
Métodos para estudar a absorção de medicamentos: In situ
In situ drug absorption methods mimic in vivo conditions by perfusing a drug solution through an anesthetized rat's intestinal segment.
It includes ...
Vias de Absorção de Drogas Extravasculares Não Orais
Non-oral extravascular routes mainly diffuse drugs passively to reach the systemic circulation. Factors influencing extravascular drug absorption include ...
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