Pharmacology Chapter on Drug Excretion

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Questions and Answers

What is the primary method by which protein-bound drugs are secreted from the blood into tubular fluid?

Passive diffusion

Filtration through cell membranes

Glomerular filtration

Tubular secretion (correct)

How does urine pH specifically influence drug excretion via passive diffusion?

It enhances the filtration rate at the glomerulus.

It increases the blood flow to the kidneys.

It impacts the ionization state of the drugs. (correct)

It alters the molecular structure of the drugs.

Which method is NOT an example of excretion mentioned in the content?

Respiratory excretion

Hormonal excretion (correct)

Biliary excretion

Urinary excretion

What is defined as the biological half-life (t½) of a drug?

The time needed for the drug concentration to reduce by 50%. Signup and view all the answers

Which of the following compounds is known for potential excretion through sweat and saliva?

Lithium Signup and view all the answers

Which metabolic process is primarily involved in the addition of an acetyl group to a drug molecule?

Acetylation Signup and view all the answers

Which factor is not typically considered to influence drug metabolism?

Time of ingestion Signup and view all the answers

What is the primary route for excretion of most drugs in the body?

Kidneys Signup and view all the answers

What mechanism allows for drug excretion through the renal system?

Glomerular filtration Signup and view all the answers

Which of the following drugs is likely to be excreted more slowly due to high protein binding?

Phenylbutazone Signup and view all the answers

Which conjugation reaction is responsible for drug detoxification involving sulfate?

Sulfate Conjugation Signup and view all the answers

What role does intestinal microflora play in drug metabolism?

May affect drug bioavailability Signup and view all the answers

Which condition is least likely to directly impact drug metabolism?

Physical activity levels Signup and view all the answers

What primary aspect does the bioavailability of a drug encompass?

The rate and extent of absorption from a preparation Signup and view all the answers

Which of the following is categorized under biological factors affecting drug absorption?

Site of Absorption Signup and view all the answers

Which example illustrates a physico-chemical factor linked to drug absorption?

Dissociation constant and pH Signup and view all the answers

Among the factors affecting drug absorption, which one is primarily related to dosage forms?

Physical nature of the drug formulation Signup and view all the answers

What is an example of a factor that can enhance drug absorption due to its chemical interactions?

Presence of EDTA Signup and view all the answers

Why is the viscosity of a drug formulation significant in drug absorption?

It influences the rate of movement through membranes Signup and view all the answers

Which factor does not influence the route of drug administration?

Cost of production Signup and view all the answers

What role do food and other salts play in drug absorption?

They can affect the rate and extent of absorption Signup and view all the answers

Which of the following accurately describes a mechanism of drug action?

Replacement Signup and view all the answers

What is the primary distinction between local and systemic drug actions?

Systemic actions act after absorption and affect central systems. Signup and view all the answers

Which factor is not considered when modifying drug action?

Drug withdrawal symptoms Signup and view all the answers

What type of drug actions do local anesthetics like lignocaine represent?

Topical action Signup and view all the answers

Which of these statements about tolerance is incorrect?

All patients will develop tolerance to any drug. Signup and view all the answers

Which of the following best defines pharmacodynamics?

The investigation of drug effects and mechanisms of action. Signup and view all the answers

Which of the following statements regarding drug resistance is false?

All drugs lead to the same level of resistance. Signup and view all the answers

What does the term 'bactericidal' refer to in the context of drug action?

Drugs that kill bacteria. Signup and view all the answers

What term describes the drug's ability to bind to a receptor?

Affinity Signup and view all the answers

What type of drug has no intrinsic activity at the receptor site?

Antagonist Signup and view all the answers

Which drug type is described as having lower intrinsic activity compared to a full agonist?

Partial agonist Signup and view all the answers

What action does an agonist perform at the receptor level?

Mimics endogenous substances Signup and view all the answers

What is the expected behavior of an inverse agonist at the receptor?

Reduces the activity below baseline level Signup and view all the answers

How is intrinsic activity defined in the context of drug interaction with receptors?

The potential to produce a pharmacological response Signup and view all the answers

Which of the following statements about drug receptors is false?

Drugs can only bind to surface receptors. Signup and view all the answers

What distinguishes a full agonist from other drug types?

High intrinsic activity at the receptor Signup and view all the answers

What is the primary effect of pentazocine at cholinergic muscarinic receptors?

It produces a partial agonist effect. Signup and view all the answers

Which statement best describes the concept of synergism in drug interactions?

The combined action of two drugs increases the effect of one. Signup and view all the answers

How can drug antagonism be characterized?

It inhibits the action of one drug by another. Signup and view all the answers

What type of antagonism describes when two drugs chemically react to form a biologically inactive product?

Chemical antagonism Signup and view all the answers

When aspirin is combined with paracetamol, what type of drug interaction occurs?

Additive interaction Signup and view all the answers

In what scenario would you typically use drug antagonism in clinical practice?

To treat drug poisoning. Signup and view all the answers

Which of the following describes a mechanism by which antagonists can act?

Blocking receptor sites from being activated. Signup and view all the answers

Which statement accurately differentiates between additive and supra-additive drug interactions?

Additive interactions result in a total effect equal to the sum, while supra-additive interactions exceed that sum. Signup and view all the answers

Study Notes

Pharmacokinetics and Pharmacodynamics

Pharmacokinetics studies the rate and concentration of a drug in the body, including onset, peak action time, and duration of action. This also determines the route and frequency of drug administration.
Absorption is the drug's entry into the bloodstream via the biological membrane from the site of administration.
Biopharmaceutics studies factors that influence the extent and rate of drug absorption and release from dosage forms.
Factors affecting drug absorption include biological factors (passage through body membranes, site of absorption, presence of food and salts, and routes of administration) and physicochemical factors (lipid solubility, dissociation constant, pH, dissolution rate, viscosity, crystal form, and drug complexes/ionization).
Pharmaceutical factors involve the various dosage forms and their physical nature (like aqueous solutions, suspensions, powders, tablets, and capsules).
Bioavailability describes the rate and extent of a drug's absorption, calculated through amounts in various bodily fluids (blood, urine, etc.).
Calculations like loading dose (Vd x TC / F) help determine drug dosage, where Vd is volume of distribution, TC is target plasma concentration, and F is bioavailability.
Distribution involves the movement of the drug into various body fluids (intestinal fluid, transcellular fluids, fluids in the gastrointestinal tract, CSF, etc.)
Distribution factors include plasma protein binding, redistribution, blood-brain barrier, and placental barrier.
Metabolism, mainly in the liver, chemically alters the drug within the body. Other metabolic sites include the intestine, kidney, lung, and plasma.
Drug metabolism involves phases 1 (like oxidation, reduction, and hydrolysis) and 2 (conjugation to form more excretable products). The pathways often include enzymes like CYP3A4/5, CYP2C19,2CYP2D6, CYP2C8/9, CYP2E1, and CYP1A1/2
Factors affecting drug metabolism include age, sex, nutrition, disease conditions, and pregnancies. They are affected by the intestine and liver microflora.
Excretion mainly occurs via the kidneys, skin, lungs, and the alimentary tract. Volatile drugs like chloroform are excreted through the lungs. Renal excretion involves glomerular filtration, tubular secretion (the process removing bound drugs), and passive diffusion. Factors like pH can impact these processes.
Clearance is the rate of urinary excretion divided by the average plasma concentration. Biological half-life (t½) is the time taken for drug concentration to decrease by 50%.

Pharmacodynamics

Pharmacodynamics studies the effects of drugs (biochemical and physiological) and their mechanisms of action.
Drug action types include stimulation, irritation, depression, replacement, and bactericidal/cytotoxic effects.
Sites of drug action can involve localized regions (e.g., topical anesthetics like lignocaine and procaine) or systemic effects after absorption (e.g., general anesthetics).
Drug action modifications due to factors like age, sex, body size, species/racial differences, genetics, routes and time of administration, pathological conditions (renal, hepatic, gastrointestinal, head injury, congestive heart failure, hyperthyroidism), tolerance, drug resistance, and medications.
Tolerance is when dosages need to be increased to get a response. Drug resistance is similar but applied to microorganisms. Tachyphylaxis is rapid tolerance development
Types of drug combination effects include additive (when effects are in the same direction), synergistic (one drug enhances the action of another), and supraadditive (overall effect is greater than the sum of individual effects).
Antagonism occurs when one drug diminishes another's effect, either through physical or chemical interactions. Used to treat drug poisoning in some situations
Important concepts include relating drug structure (SAR) to its activity, dose-response relationships, mechanisms of drug action, receptors, receptor classifications (like ligand-gated ion channels and G-protein coupled receptors), affinity (drug binding to receptors), and intrinsic activity (pharmacological response from receptor interaction).

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Description

Test your knowledge on drug excretion mechanisms, including the influence of urine pH and the biological half-life of drugs. This quiz covers key concepts in pharmacokinetics related to protein-bound drugs and various excretion pathways.