General Pharmacology -pharmacokinetics - I

The term "biotransformation" refers to the process of physicochemical and biochemical alteration of a drug in the body. This process involves the metabolism of drugs, where they are broken down into different compounds or transformed into more water-soluble forms that can be easily eliminated from the body. Biotransformation plays a crucial role in drug metabolism and clearance, as it helps in the elimination of drugs from the body and prevents their accumulation. Accumulation of substances in a fat tissue, binding of substances with plasma proteins, and accumulation of substances in a tissue are not specific to the term "biotransformation" and do not encompass the entire process.

Pharmacokinetics refers to the study of how drugs are absorbed, distributed, metabolized, and eliminated by the body. It specifically focuses on the processes of drug distribution within the organism. This includes understanding how drugs are transported through the bloodstream to their target sites, how they are distributed among different tissues and organs, and how their concentrations change over time. By studying pharmacokinetics, researchers and healthcare professionals can gain insights into how drugs are processed by the body, which can help optimize drug dosing and improve therapeutic outcomes.

Active transport refers to the movement of substances across a cell membrane against their concentration gradient, meaning from an area of lower concentration to an area of higher concentration. This process requires energy expenditure by the cell, usually in the form of ATP. Therefore, the correct answer implies that active transport involves the movement of drugs or other substances against their concentration gradient, requiring energy consumption by the cell.

A hydrophilic medicinal agent has a low ability to penetrate through the cell membrane lipid because hydrophilic substances are water-loving and are not easily able to pass through the hydrophobic lipid bilayer of cell membranes.

Lipophilic substances have a high affinity for lipids and can easily pass through barriers such as cell membranes. This allows them to be widely distributed in various fluids, including plasma, interstitial fluids, and cell fluids. Therefore, it is true that a small amount of the volume of distribution is common for lipophilic substances.

Microsomal oxidation is a metabolic process that occurs in the liver, where drugs and other foreign compounds are oxidized by enzymes in the microsomes. This oxidation reaction can result in the formation of more polar and water-soluble metabolites. Therefore, microsomal oxidation can increase the ionization and water solubility of a drug, which can facilitate its excretion from the body.

Conjugation metabolism refers to the process of coupling a drug with an endogenous substrate. In this process, the drug molecule is chemically combined with a naturally occurring substance in the body, such as glucuronic acid, sulfate, or amino acids. This conjugation reaction helps in the elimination of the drug from the body by making it more water-soluble and facilitating its excretion through urine or bile. Conjugation metabolism is an important phase II metabolic pathway that enhances the elimination of drugs and their metabolites from the body.

In liver disorders accompanied by a decline in microsomal enzyme activity, the duration of action of some drugs is enlarged. This means that the drugs will stay in the body for a longer period of time and take longer to be metabolized and eliminated. The decline in microsomal enzyme activity in the liver affects the drug metabolism process, leading to a slower breakdown of drugs. As a result, the drugs remain in the body for an extended duration, potentially causing an increased risk of side effects or toxicity.

Hydrophilic substances cannot permeate membranes by passive diffusion because they are water-loving and cannot easily pass through the hydrophobic interior of the lipid bilayer that makes up the cell membrane. Unlike lipid-soluble and non-ionized substances, which can dissolve in the lipid bilayer and diffuse across the membrane, hydrophilic substances are repelled by the hydrophobic environment and require specific transport proteins or channels to facilitate their movement across the membrane.

Biotransformation of drugs involves chemical reactions that modify their structure, usually to make them more water-soluble and easier to eliminate from the body. Therefore, the correct answer is "Less lipid soluble," as biotransformation typically decreases the lipid solubility of drugs.