Pharmacology: Routes of Drug Administration and ADME Process

Drug Metabolism and Administration

• First-pass metabolism refers to the initial metabolism of a drug by the liver after oral administration before it reaches systemic circulation.
• Sublingual administration bypasses both gastric and hepatic metabolism, enabling rapid drug absorption directly into the bloodstream.

Administration Routes and Patient Conditions

• Rectal administration is useful for patients who may be vomiting or unconscious, as it doesn’t require swallowing and provides an alternate route for medication absorption.
• Intravenous (IV) drug delivery offers an instantaneous response, allowing for immediate drug effects.

Drug Solubility and Absorption

• Oral administration may require surfactants to enhance drug dissolution, improving absorption in the gastrointestinal tract.
• Drugs administered via the buccal route are characterized by their ability to dissolve directly in the mouth's mucous membranes, providing rapid absorption into systemic circulation.

Drug Delivery Preferences

• Intramuscular (IM) administration is often preferred for anticancer drugs due to its ability to deliver larger volumes of medication and sustain absorption over time.

Transport Mechanisms

• The primary energy source for symporters in secondary active transport is the sodium gradient, often established by primary active transport mechanisms.
• Endocytosis is the process of drug absorption that involves the engulfment of macromolecules to form vesicles.

Pharmacokinetics Factors

• In pharmacokinetics, the rate of reversible interaction between a drug and its carrier is influenced by factors such as the drug's affinity for the carrier and concentration gradients.
• The gastric region of the gastrointestinal tract is known for its acidic environment, which can significantly impact the solubility and absorption of various drugs.

Physicochemical Properties

• The lipophilicity of drugs plays a crucial role in determining their absorption and excretion rates, impacting how well drugs penetrate cell membranes.
• Enteric-coating in oral drugs is primarily designed to protect the drug from degradation in the acidic stomach and to allow for release in more neutral intestinal pH.

Membrane Permeability

• Polar (toxic) materials struggle to enter cell membranes easily due to their hydrophilic nature, which inhibits membrane permeability.
• Non-polar molecules, due to their size and solubility characteristics, can easily permeate lipid membranes.

Diffusion and Transport Mechanisms

• The partition coefficient refers to the quantitative measure of a substance's ability to dissolve in lipids, influencing its absorption.
• The ability of a substance to mix with oily phases is primarily determined by its lipophilicity, impacting lipid diffusion.
• Cell membranes act as a barrier that permits lipid-soluble and unionized drugs to pass while restricting water-soluble substances.
• Passive diffusion mechanisms facilitate easier passage for non-ionized drugs across biological membranes, allowing for effective drug absorption.

Learn about the process drugs go through in the body - from liberation to excretion, and the different routes of drug administration including local (topical, nasal, oral) and systemic (enteral, parenteral). Explore examples like bronchial dilators and clotrimazole troches.