Pharmacology Basics Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What role do endogenous opioids play in the body?

They primarily reduce body temperature.

They block all pain signals completely.

They influence pain perception, mood, and other physiological functions. (correct)

They only cause euphoria.

What is the primary therapeutic use of morphine?

Mood elevation.

Constipation treatment.

Relief of pain. (correct)

Cough suppression.

Which of the following is NOT a direct effect of opioids?

Respiratory depression.

Constipation.

Sedation.

Increased gut motility. (correct)

Which statement about opioid receptors is true?

They are involved in various physiological responses. Signup and view all the answers

What often occurs with repeated doses of opioids?

Tolerance and potential dependence. Signup and view all the answers

What is the primary purpose of drug therapy?

To achieve desired beneficial effects with minimal adverse effects Signup and view all the answers

Which of the following best describes pharmacodynamics?

Mechanisms of action—what the drug does to the body Signup and view all the answers

What does the term 'medicine' refer to?

A form of drug administered for therapeutic purposes Signup and view all the answers

Which concept relates to the study of what the drug does to the body?

Pharmacodynamics Signup and view all the answers

What factors influence the choice of a drug for therapy?

Mechanism of action, dose, route, and formulation Signup and view all the answers

What is the main function of agonists in pharmacology?

To stimulate receptors Signup and view all the answers

What effect may result from the blockade of beta-receptors in the lungs for asthmatics?

Bronchoconstriction Signup and view all the answers

Which of the following describes the process of absorption in pharmacokinetics?

The transport of a drug to the bloodstream from the site of administration Signup and view all the answers

Which route of drug administration bypasses gastrointestinal absorption entirely?

Intravenous Signup and view all the answers

Which of the following processes is NOT part of the ADME pharmacokinetics framework?

Transmission Signup and view all the answers

What defines absolute bioavailability?

AUC non-intravenous divided by AUC intravenous Signup and view all the answers

Which of the following is not a formulation factor affecting bioavailability?

Gastric emptying Signup and view all the answers

How is the volume of distribution (Vd) calculated?

Amount of drug in the body divided by plasma drug concentration Signup and view all the answers

What primarily determines the distribution of a drug in the body?

Physical and chemical properties of the drug Signup and view all the answers

Which compartment contains the largest volume of body water?

Intracellular Signup and view all the answers

What does pharmacodynamics primarily focus on?

How drugs affect the body Signup and view all the answers

What is the significance of drug-receptor interactions in pharmacodynamics?

They allow drugs to exert their specific biological effects Signup and view all the answers

Which of the following statements about the temporary effects of drugs is true?

Drug effects are temporary due to body detoxification systems. Signup and view all the answers

What analogy is often used to explain drug-receptor interactions?

Lock and key Signup and view all the answers

In pharmacodynamics, which term refers to the specific organs or tissues affected by a drug?

Site of action Signup and view all the answers

What type of drug is morphine classified as?

Opioid Signup and view all the answers

Which of the following is NOT a component of pharmacokinetics?

Receptor Binding Signup and view all the answers

What is the primary site of drug metabolism after absorption through the portal circulation?

Liver Signup and view all the answers

Which mechanism of drug absorption does not require energy and involves diffusion through transport proteins?

Facilitated diffusion Signup and view all the answers

What determines the ratio of ionized to unionized forms of a drug in a solution?

pKa and pH Signup and view all the answers

Which type of drugs is best absorbed in the stomach due to their properties?

Weak acids Signup and view all the answers

What is the effect of first-pass metabolism on a drug's bioavailability?

It reduces bioavailability to less than 100% Signup and view all the answers

Which statement best describes active transport in drug absorption?

It moves substances against a concentration gradient and requires energy. Signup and view all the answers

Which type of drug is expected to penetrate cell membranes most rapidly?

Lipid-soluble drugs Signup and view all the answers

What is a characteristic feature of simple diffusion in drug absorption?

It moves drugs down a concentration gradient. Signup and view all the answers

Why do small molecules generally penetrate cell membranes more rapidly than larger ones?

They have a higher lipid solubility. Signup and view all the answers

What role does pH play in the absorption of drugs?

It influences the ratio of unionized and ionized forms. Signup and view all the answers

Study Notes

Course Information

Course Name: PHM 10303 Pharmacokinetics
Course Description: Principles of ADME
Instructor: Dr. Azyyati Mohd Suhaimi, Faculty of Pharmacy UniSZA
Adapted from: Dr. Shazia Jamshed, Uni of Alberta, MIT Open Course

Course Structure

Test 1: 10%
Test 2: 10%
Practical Report 1: 10%
Practical Report 2: 10%

Definitions

Drug: A chemical or substance that causes changes in the structure or function of living organisms.
Medicine: The vehicle for administering a drug (active ingredient) to a human or animal (e.g., tablet, capsule, injection, ointment, inhaler, suppository).
Pharmacokinetics: The study of the kinetics of absorption, distribution, metabolism, and excretion (ADME) of drugs and their corresponding pharmacological, therapeutic, or toxic responses in humans and animals.
Pharmacology: The science of drug actions and uses.
Pharmacodynamics: The mechanisms of action (what the drug does to the body).
Toxicity: The manifestation of harmful effects of a drug after exposure to high levels (intoxication or poisoning).
Therapeutics: The use of drugs for intended clinical benefits (e.g., curing a disease or relieving symptoms).

Therapeutic Prescribing

The primary goal of drug therapy is to achieve the desired beneficial effects with minimal adverse effects.
Drug choice depends on the mechanism of action (pharmacodynamics).
Drug dose, route, and formulation are determined by pharmacokinetics (how the body handles the drug).

Pharmacology

Pharmacology deals with the actions of drugs on the body (pharmacodynamics) and the fate of drugs in the body (pharmacokinetics).
For a drug to work, it must enter the body and be distributed to its site of action, often a macromolecular receptor in target tissue.
Drug effects are typically temporary due to the body's detoxification and elimination systems.

Relationship between Pharmacokinetics and Pharmacodynamics

Pharmacokinetics describes how the body acts on the drug (absorption, distribution, metabolism, excretion).
Pharmacodynamics describes how the drug acts on the body (receptor binding, biological effects).

Pharmacodynamics Basic Principles

Mechanism of action: Specific molecular processes by which drugs work (e.g., enzyme inhibition, receptor stimulation).
Mode of action: General description of the type of drug action (e.g., analgesics, supplements).
Site of action: Specific organs, tissues, or cells affected by the drug (e.g., sensory neurons, myocardium, bronchi).

Mechanism of Action

The fundamental principle of pharmacodynamics is drug-receptor interactions.
Specific receptors in the body allow for drug interactions.
Drugs must have the correct molecular shape to interact with a particular receptor; the analogy often used is "lock and key."

Example: Morphine

A naturally occurring substance found in opium poppies.
Part of a family of natural substances known as opiates or opioids (also includes codeine).
Some synthetic derivatives are available (e.g., heroin, methadone, pethidine).
Used therapeutically and recreationally throughout history.

Opioid Receptors

In the 1970s, pharmacologists identified endogenous opioids (e.g., enkephalins, endorphins).
These have a role in pain perception, mood, and other physiological functions.
Opioid receptors are found in key areas of the body (e.g., brain, spinal cord, gut, eye).
Only substances with a similar chemical structure to morphine can attach to opioid receptors (key-lock analogy).
These substances are called opioid agonists; when they attach, they trigger responses.

Effects of Opioids (Morphine)

Relief of pain (analgesia).
Mood elevation (euphoria).
Sedation.
Pupil constriction (miosis).
Reduced gut motility (constipation).
Cough suppression (anti-tussive).
Tolerance and dependence with repeated doses.
Respiratory depression leading to death in overdose.

Mixed Effects of Opioids

Because of the variety of opioid receptors, separating desirable and undesirable effects of opioids (e.g., morphine, codeine) is challenging.
For example, patients receiving opioids for chronic pain often experience constipation.

Agonists and Antagonists

Agonists: Drugs that stimulate receptors (e.g., salbutamol).
Antagonists: Drugs that block receptors (e.g., metoprolol).

Pharmacokinetics - ADME

Absorption: The process by which a drug proceeds from the site of administration to the measurement site (bloodstream) in the body.
Distribution: The process by which a drug is transported within the body to its site of action.
Metabolism: The process by which the body chemically alters a drug to facilitate excretion.
Excretion: The process by which the body removes a drug or its metabolites.

ADME - Simplified

Absorption- Where do and how many MDNS get in?
Distribution- Where do and how many MDNS go?
Metabolism- How many MDNS turn into?
Excretion- How many MDNS are excreted?

Routes of Drug Administration

Parenteral (injection, intravenous, intramuscular, topical)
Enteral (oral, rectal, respiratory)

Absorption

The process by which a drug moves from the administration site to its measurement site (bloodstream) within the body.
Necessary for a therapeutic effect.
Most drugs are absorbed through the gastrointestinal tract, with bloodstream absorption occurring following intravenous administration.
Factors influencing absorption include membrane transport.

Mechanisms of Drug Absorption

Simple diffusion (passive diffusion)
Active transport
Facilitated diffusion
Pinocytosis (endocytosis)

Absorption (Simple Diffusion)

Drugs diffuse across a cell membrane from high to low concentration.
Rate depends on factors such as lipid solubility, size, ionization state, and surface area of absorption. -Lipid-soluble drugs usually absorb more rapidly.
Smaller molecules diffuse more readily.
Involves passive passage, no energy required.
Water-soluble drugs may need channels or pores in the cell membrane.

Simple Diffusion-Ionization

Most drugs exist in both ionized and unionized forms.
Unionized form = lipid soluble.
Ionized form = water soluble.
The proportion of each form depends on pH and pKa (dissociation constant) of the drug.

Simple Diffusion pKa Factors

pKa = pH at which the concentrations of ionized and unionized forms are equal.
pH of the medium affects ionization of drugs.
Weak acids = best absorbed in stomach.
Weak bases = best absorbed in intestine.

Facilitated Diffusion

A type of passive transport.
No energy required.
Uses transport proteins for diffusion of solutes across the plasma membrane.
The solute moves down the concentration gradient.

Active Transport

Selective energy expenditure
Transport against a concentration gradient.
For substances structurally similar to endogenous substances (e.g., ions, vitamins, sugars, amino acids).
Usually occurs across small intestine through specific sites.

Passive vs. Active Transport

Passive transport moves along a concentration gradient (from high to low).
Active transport moves against a concentration gradient (from low to high), requiring energy.
Facilitated diffusion is a type of passive transport using carrier proteins.

Pinocytosis (Endocytosis)

Fluid or particles are engulfed by a cell membrane.
Membrane invaginates, encloses fluid/particles, forming a vesicle.
Vesicle detaches and moves to the cell's interior.
Energy expenditure is required.
In drug transport, it is important for protein drugs and other large molecules.

Bioavailability

The fraction of an administered dose reaching the systemic circulation.
Drugs given intravenously have 100% bioavailability.
Drugs administered in other ways have bioavailability values less than 1.
Bioavailability is influenced by factors like the drug formulation and physiological variables in the body.
Bioavailability is determined by comparing the area under the plasma drug concentration-time curve (AUC) following non-intravenous and intravenous administration.

Factors Affecting Bioavailability

Formulation factors: Excipients, particle size, crystalline or amorphous form of the drug.
Physiological factors: Gastric emptying, intestinal motility, changes in GIT pH, nature of intestinal wall.

Distribution

Process of drug movement to body tissues after entering systemic circulation.
Affected by factors like partitioning across membranes, binding to tissue components, binding to blood components (RBC, plasma proteins), and physiological volumes.
Total body water (intra, interstitial, and intracellular fluid compartments) influences distribution.

Apparent Volume of Distribution(Vd)

The theoretical volume in which the total drug amount in the body would distribute to give the measured plasma concentration.
Influenced by factors like blood flow rate, capillary structure, and protein binding.

Protein Binding

Many drugs bind to plasma proteins in the bloodstream.
This limits drug distribution.
Key binding proteins include albumin, alpha-1-acid glycoprotein, and lipoproteins.

Blood-Brain Barrier (BBB)

Brain capillaries have tight junctions that limit the passage of water-soluble substances.
Lipophilic, positively-charged molecules with low molecular weight can cross the BBB.

Elimination

The irreversible removal of parent drugs from the body.
Two main processes:
- Drug metabolism (biotransformation).
- Excretion.

Drug Metabolism

The liver is the primary site of drug metabolism.
Drugs are chemically modified to facilitate excretion.
Enzymes (e.g., CYPs) catalyze oxidation, reduction, hydrolysis, hydration, conjugation, or isomerization metabolic reactions.

Drug Metabolism: Phases

Phase I: Converts parent compounds into more polar metabolites. This can be achieved by adding or unmasking functional groups.
Phase II: The main detoxification step; involves conjugation reactions with endogenous substances.

Cytochrome P450 (CYP)

The most important enzyme system for phase I metabolism.
A microsomal superfamily of isoenzymes.
Involved in the oxidation of many drugs.
Activity is influenced by drugs and other substances, causing drug interactions.

Renal Excretion

Kidneys are the primary organs for drug excretion.
Filtered substance, nearly all water, and most electrolytes are passively and actively reabsorbed in the renal tubes.
However, most polar substances and drug metabolites are excreted via the kidneys.
Tubular secretion can enhance elimination.

Summary

ADME and the factors influencing each process are crucial for understanding drug action.

Drug R&D

The process of developing new drugs can take 10-15 years and only about 10% are successful for commercialization.
R&D costs typically range from $800 million to $1 billion.

Why Drugs Fail

Pharmacokinetic issues.
Animal toxicity.
Miscellaneous factors.
Adverse effects in humans.
Commercial reasons.
Lack of efficacy are some major reasons why drugs fail.

Importance of Pharmacokinetic Studies

Toxic drugs may accumulate.
Useful drugs may lack therapeutic benefit due to the dose not being sufficient.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge of pharmacology concepts with this quiz. It covers essential topics such as endogenous opioids, drug therapy, and pharmacokinetics. Perfect for students or anyone interested in the field of medicine.