VIDEO
HIGHLIGHT
Log InSign up
SummaryTranscriptChat

Introduction

The instructor introduces the topic of pharmacokinetics and specifically focuses on the process of bio transformation or drug metabolism.

Bio Transformation and Drug Metabolism

  • Bio transformation is a necessary process that drugs undergo to be eliminated from the body.
  • It can involve biochemical transformations that activate the drug or convert it into its active form.
  • Some drugs, known as prodrugs, require bio activation in order to become pharmacologically active.
  • The liver is the primary organ responsible for drug metabolism, followed by the kidneys and other tissues.
  • Liposoluble drugs are preferred in pharmaceutical production as they enhance absorption but can be difficult to eliminate from the body.

Process of Drug Bio Transformation

The instructor explains that drug bio transformation is a biochemical process that occurs primarily in specific organs, with the liver being the main site of metabolic activity.

Organs Involved in Drug Bio Transformation

  • The liver is the primary organ responsible for drug bio transformation.
  • Other organs involved include the kidneys, intestinal mucosa, blood-brain barrier, and various tissues.
  • While these organs can also perform bio transformation, their contribution is relatively minor compared to the liver.

Drug Metabolism in the Liver

The instructor discusses how drug metabolism occurs when liposoluble drugs reach the liver and describes where specific enzymes involved in bio transformation are located within cellular organelles.

Enzymes Involved in Drug Metabolism

  • Enzymes responsible for drug metabolism are primarily located in certain cellular organelles such as smooth endoplasmic reticulum, mitochondria, peroxisomes, and lysosomes.
  • These enzymes are embedded within membranes and play a crucial role in drug bio transformation.

Enzymes in Cellular Organelles

The instructor further explains the presence of enzymes involved in drug metabolism within cellular organelles and their structural similarities to the cell membrane.

Enzymes in Cellular Organelles

  • Cellular organelles involved in drug metabolism, such as smooth endoplasmic reticulum, have membranes composed of phospholipids.
  • These membranes contain various types of proteins, including structural and enzymatic proteins.
  • Enzymatic proteins located within these organelle membranes are responsible for drug bio transformation.

The transcript does not provide further information beyond this point.

Enzymes and Microsomes

This section discusses the role of bio-transforming enzymes located in membranous organs called microsomes. It explains how microsomes are obtained through maceration and centrifugation, resulting in different layers of substances. The microsome fraction contains enzymes responsible for phase 1 reactions, which convert liposoluble drugs into polar metabolites.

  • Microsomes are small bodies derived from the process of maceration and ultra-centrifugation.
  • They contain enzymes that perform phase 1 reactions, such as hydroxylation, oxidation, and reduction.
  • These reactions transform liposoluble drugs into less liposoluble and more hydrophilic forms.
  • The resulting metabolites are generally inactive and easier to eliminate from the body.

Phase 2 Enzymes

This section focuses on phase 2 enzymes, which perform conjugation reactions to further transform the drug metabolites produced in phase 1. Conjugation involves joining the drug molecule with another compound, often glucuronic acid. This process increases the water solubility of the drug, making it easily eliminable by the kidneys.

  • Phase 2 enzymes are responsible for conjugating drug metabolites with compounds like glucuronic acid.
  • Glucuronidation is an example of a conjugation reaction performed by these enzymes.
  • Conjugation makes the drug more hydrophilic and polar, facilitating its elimination through urine.
  • The transformation of drugs into polar forms prevents their reabsorption in renal tubules.

The transcript continues beyond this point but does not provide any additional relevant information for note-taking purposes.

Enzymatic Conjugation and Microsomal Fraction

This section discusses the process of enzymatic conjugation and its role in making molecules easily eliminable and water-soluble. It also mentions the presence of conjugating enzymes in the microsomal fraction.

Enzymatic Conjugation

  • Enzymes can conjugate molecules with sulfhydryl radicals, making them polar and hydro-soluble.
  • This process, known as enzymatic conjugation, allows for easy elimination of substances from the body.
  • Different substances can be conjugated by these enzymes during the bio-transformation process.

Microsomal Fraction

  • The microsomal fraction contains enzymes involved in enzymatic conjugation.
  • Apart from the microsomal fraction, there are other fractions that also contain conjugating enzymes.
  • The microsomal fraction represents the intracellular fluid without organelles that have been centrifuged.

Cyto-Soluble Fraction

This section explains the cyto-soluble fraction, which represents both extracellular and intracellular fluids without membrane-bound organelles. It highlights how this fraction contains enzymes capable of conjugating drugs.

Cyto-Soluble Fraction

  • The cyto-soluble fraction is a representative sample of both extracellular and intracellular fluids without membrane-bound organelles.
  • Enzymes present in this fraction can perform drug conjugations, converting them into polar and easily eliminable substances.
  • Also known as non-microsomal fraction or soluble cytosolic fraction.

Factors Influencing Drug Bio-transformation

This section discusses various factors that influence drug bio-transformation. It emphasizes physiological factors such as age and liver function as important determinants of drug metabolism.

Factors Influencing Drug Bio-transformation

  • Age is a significant factor in drug bio-transformation. Newborns and young children have immature liver function, affecting their ability to metabolize drugs efficiently.
  • In contrast, elderly individuals experience a decline in the functional capacity of various organs, including the liver. This can lead to slower drug metabolism and increased risk of toxicity.
  • Hepatic diseases, such as acute or chronic hepatitis or cirrhosis, can also impact drug bio-transformation.

Age as a Factor in Drug Bio-transformation

This section focuses on age as a crucial factor in drug bio-transformation. It explains how the immaturity of organ systems in newborns and young children affects their ability to metabolize drugs effectively.

Age and Drug Bio-transformation

  • Newborns and young children have immature organ systems, including the liver and kidneys.
  • The immaturity of these organs can result in reduced enzymatic activity, leading to slower drug metabolism.
  • For example, insufficient production of bilirubin glucuronosyltransferase enzyme in newborns can cause jaundice due to inadequate conjugation of bilirubin.

Senescence and Drug Metabolism

This section explores how aging affects drug metabolism. It highlights that elderly individuals may experience decreased efficiency in drug bio-transformation due to age-related changes in organ function.

Senescence and Drug Metabolism

  • Aging leads to a decline in the functional capacity of various organs, including those involved in drug metabolism.
  • Elderly individuals may have reduced enzymatic activity, resulting in slower drug metabolism compared to younger individuals.
  • This decreased efficiency can increase the risk of drug accumulation and potential toxicity.

Hepatic Diseases and Drug Metabolism

This section discusses how hepatic diseases can impact drug metabolism. It emphasizes that individuals with liver diseases may have impaired drug bio-transformation, leading to potential toxicity.

Hepatic Diseases and Drug Metabolism

  • Liver diseases such as acute or chronic hepatitis and cirrhosis can affect drug metabolism.
  • Impaired liver function can result in reduced enzymatic activity, leading to slower drug metabolism.
  • This decreased efficiency can cause drugs to accumulate in the body for longer periods, increasing the risk of toxicity.

The transcript is not in English.

Role of Liver and Kidney in Drug Metabolism

This section discusses the role of the liver and kidney in drug metabolism and how certain diseases can affect this process.

Hepatopathies and Impaired Bio Transformation

  • Hepatopathies, or liver diseases, can lead to impaired bio transformation of drugs, causing toxic reactions.

Nephropathy and Renal Function

  • Nephropathy, or kidney disease, is another factor that can affect proper bio transformation. The kidneys play a significant role in drug metabolism as they are responsible for eliminating drugs from the body.
  • If the kidneys are not functioning properly, drugs that require renal bio transformation may not be activated. For example, vitamin D undergoes hydroxylation in the kidneys to become active. If there is renal insufficiency, this activation process may be affected.

Impaired Drug Elimination

  • In some cases, even if the liver metabolizes a drug correctly, impaired kidney function can result in reduced drug elimination from the body. This can lead to drug accumulation and potential toxicity.

Factors Affecting Drug Transformation and Elimination

  • Other factors such as drug interactions and associations between medications can also impact drug transformation and elimination. It is important to be aware of problematic medication combinations to avoid potential adverse effects.

Drug Interactions - Enzyme Induction

This section explains enzyme induction as a type of drug interaction that can affect drug metabolism.

Enzyme Induction

  • Enzyme induction is a molecular interaction that occurs at the nucleus of hepatocytes. It involves certain drugs stimulating genes responsible for producing drug-metabolizing enzymes, leading to increased enzyme levels.
  • This increase in enzyme activity results in faster drug metabolism and elimination from the body. As a result, the drug may have a shorter duration of action than expected.

Drug Interactions - Enzyme Inhibition

This section discusses enzyme inhibition as another type of drug interaction that can impact drug metabolism.

Enzyme Inhibition

  • Enzyme inhibition occurs when one drug inhibits the activity of enzymes responsible for metabolizing another drug. This can lead to decreased metabolism and slower elimination of the affected drug from the body.

The transcript continues with further explanations on enzyme inhibition, but it exceeds the recommended length for this section.

Drug Competition and Enzymatic Transformation

This section discusses the competition between drugs for enzymatic transformation and how it can affect their elimination from the body.

Drug Competition and Enzymatic Transformation

  • Drugs can compete with each other for enzymatic transformation.
  • Some drugs may be transformed by the same enzyme, resulting in competition.
  • One drug may have a higher affinity for binding to the enzyme, leading to faster transformation and elimination.
  • The drug with lower affinity will be eliminated more slowly, potentially causing accumulation and toxicity.
  • Genetic variations can also influence enzymatic production, affecting drug metabolism and potential toxicity.

Cytochrome P450 Enzymes

This section explains the role of cytochrome P450 enzymes in metabolizing various substances, including medications.

Cytochrome P450 Enzymes

  • Cytochrome P450 is a large family of enzymes responsible for metabolizing numerous substances, including medications.
  • There are over 50 families of cytochrome P450 enzymes with slight differences in their structure and function.
  • These enzymes play a crucial role in oxidizing and reducing substances within the body.
  • Other enzyme systems besides cytochrome P450 are also involved in drug metabolism.

Phase 2 Enzymes

This section focuses on phase 2 enzymes involved in conjugation reactions during drug metabolism.

Phase 2 Enzymes

  • Phase 2 enzymes, including glucuronosyltransferase and sulfotransferase, are involved in conjugation reactions during drug metabolism.
  • These enzymes are present not only in microsomes but also in non-microsomal fractions of cells.
  • They play a role in reducing the toxicity of certain substances through conjugation with molecules like glucuronic acid and sulfhydryl groups.
  • Some phase 2 enzymes are also found in the membranes of organelles like the endoplasmic reticulum.

Conclusion and Additional Resources

This section concludes the discussion on drug metabolism and suggests additional resources for further study.

Conclusion and Additional Resources

  • Drug metabolism is a crucial aspect of pharmacokinetics, involving various enzymatic processes.
  • The recommended textbook for studying pharmacology is "Pharmacology" by Harvey (6th edition).
  • Other extensive books on pharmacology, such as Guzmán and Hillman's, provide more in-depth explanations.
  • It is important to review both the text and video lectures to gain a comprehensive understanding of the topic.