Pharmacology: Principles of Pharmacokinetics

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Questions and Answers

What is pharmacokinetics primarily concerned with?

The study of drug absorption, distribution, and elimination (correct)

How organisms metabolize drugs

The chemical properties of drugs

How drugs alter biological structures

Why is knowledge of pharmacokinetics important for drug administration?

It outlines the history of drug discovery

It helps predict the legal status of drugs

It provides insight into the chemical interactions between drugs

It assists in determining appropriate dosage regimens (correct)

What can happen if a drug concentration exceeds a certain level?

The drug will have no observable effects

The drug will become ineffective

The drug’s effects will always improve

Unwanted effects and toxicity may occur (correct)

What defines a drug from a pharmacologist’s perspective?

An agent that alters biological systems chemically Signup and view all the answers

What is one key reason for studying pharmacology?

To comprehend how drugs affect living systems Signup and view all the answers

What is a key disadvantage of oral drug administration?

Limited absorption Signup and view all the answers

Which route of drug administration allows avoidance of the first-pass effect?

Sublingual Signup and view all the answers

What is a characteristic of sustained-release preparations?

Steady drug release that reduces daily doses Signup and view all the answers

What is a common disadvantage associated with enteric-coated preparations?

Dependence on gastric emptying Signup and view all the answers

Which of the following routes of administration is categorized as parenteral?

Subcutaneous Signup and view all the answers

What is a disadvantage of sublingual drug administration?

Limited volume able to be administered Signup and view all the answers

Which of the following is NOT a route of enteral administration?

Intravascular Signup and view all the answers

What is an advantage of oral drug administration?

Can be self-administered Signup and view all the answers

What is one of the main roles of drug metabolism?

To increase drug solubility for urinary excretion Signup and view all the answers

Which phases are involved in drug metabolism?

Phase I and Phase II Signup and view all the answers

What determines drug excretion through glomerular filtration?

GFR and extent of protein binding Signup and view all the answers

How can drugs accumulate in tissues?

By binding to proteins in specific tissues Signup and view all the answers

Which process primarily leads to the termination of drug action?

Drug clearance through metabolism Signup and view all the answers

What happens to drug activity during Phase I metabolic reactions?

Loss of drug activity typically occurs Signup and view all the answers

What is the primary route of drug excretion?

Kidneys Signup and view all the answers

What effect does age have on renal function?

A decline in renal function is expected with age Signup and view all the answers

What is a primary advantage of rectal drug administration?

It bypasses first-pass metabolism. Signup and view all the answers

Which factor does NOT influence drug absorption from extra-vascular sites?

Patient's age and gender Signup and view all the answers

What is a common disadvantage of intravenous drug administration?

May cause venous thrombosis and phlebitis. Signup and view all the answers

Which route of administration is most suitable for drugs that irritate the stomach?

Rectal Signup and view all the answers

What characterizes the first distribution phase of drug distribution in the body?

Quick delivery to well-perfused organs such as the liver and kidneys. Signup and view all the answers

Which of the following statements about protein binding of drugs is true?

Reversible binding can occur through hydrogen bonding. Signup and view all the answers

What is a disadvantage of intramuscular drug administration?

Limited to small volumes of drug. Signup and view all the answers

Subcutaneous drug administration can be characterized by which of the following?

Is suitable for depot injections. Signup and view all the answers

What is a key disadvantage of parenteral routes of drug administration?

They are considered painful and can carry risk. Signup and view all the answers

What is true about the penetration and accumulation of drugs in the body?

Lipid solubility enhances diffusion. Signup and view all the answers

Signup and view all the answers

Study Notes

Pharmacology: General Principles of Pharmacokinetics

Pharmacology is the systematic study of how drugs affect living systems.
Pharmacologists study drug modification within organisms.
A drug, from a pharmacologist's perspective, is any agent that alters biological systems through its chemical properties.
A drug, from a legal perspective, is any FDA-approved (or equivalent) agent for disease treatment or prevention.

Pharmacokinetics and Pharmacodynamics

Pharmacokinetics describes processes affecting drug levels in the body. These include absorption, distribution, and elimination.
Pharmacodynamics describes the relationship between drug concentration at the site of action and the resulting effect. This includes drug-receptor interaction and the target tissue response.

Pharmacokinetics Details

Pharmacokinetics studies how the body affects the drug (absorption, distribution, elimination)
Drug dose is the starting point for pharmacokinetics
Drug dose --> Absorption --> Distribution --> Biotransformation --> Drug effect --> Elimination

Why Study Pharmacokinetics (PK)?

Drugs must reach an effective concentration at the site of action to produce a biological effect
Drug concentrations exceeding a certain level may lead to adverse outcomes (toxicity)
Understanding PK is crucial to controlling drug effects and designing appropriate dosing regimens.

Routes of Drug Administration

Enteral: Oral, sublingual, rectal
Parenteral: Intravascular (IV), intramuscular (IM), subcutaneous (SC), intradermal (ID)
Other: Intranasal, topical (including mucous membranes and eye)
Different routes of administration affect drug absorption, bioavailability, and onset of action

Advantages and Disadvantages of Oral Administration

Advantages:*
Safest
Convenient
Economical
Self-administered
Painless
Disadvantages:*
Limited absorption
Slow action
Irritable or unpalatable
Stomach acid degradation
First-pass effect (drug metabolism in the liver before reaching systemic circulation)
Variability in patient cooperation

Oral Drug Preparations

Tablets: drug + binders/fillers; vary in dissolution/disintegration rates
Enteric-coated: dissolves in the intestine, protects from stomach acid
Sustained-release: drug in a capsule that dissolves slowly, controls release rate

Sublingual Administration

Advantages:*
Economical
Quick absorption
Avoids first-pass effect
Quick termination
Self-administered
Disadvantages:*
Unpalatable/bitter drugs
Oral mucosa irritation
Limited dosage form

Rectal Administration

Advantages:*
Bypasses first-pass metabolism (50% of rectal drainage)
Useful for vomiting or unconscious patients
High concentration can be achieved
Suitable for drugs irritating the stomach
Disadvantages:*
Embarrassing
Inconvenient
Absorption can be slow
Possible irritation of rectal mucosa

Parenteral Administration

Advantages:*
Useful for poorly absorbed drugs
Useful for unconscious patients, emergencies
Rapid onset of action
High control over dose delivered
Disadvantages:*
Risk of infection, pain
Risk of embolism, necrosis
Potential for venous thrombosis and phlebitis

Intravenous (IV) Administration

Advantages:*
Rapid drug delivery and absorption (avoids first-pass)
Ideal for emergencies and rapid onset of action
Precise control over the dose
Disadvantages:*
Risk of serious complications (embolism, infection), cannot be recalled
Requires sterility and trained personnel

Intramuscular (IM) Administration

Advantages:*
Relatively uniform absorption
Rapid onset of action
Suitable for drug irritants
Avoids gastric absorption factors
Disadvantages:*
Limited volume
Potential for pain, abscess, nerve damage
Less control over the rate of absorption

Subcutaneous (SC) Administration

Advantages:*
Smooth but slow absorption
Depot injections/implants
Disadvantages:*
Small volume capacity for administration
Irritant drugs can cause necrosis
Not suitable for emergencies

Topical Administration

Delivery of drugs to mucous membranes (eye, ear, nose).
Can also be creams and ointments on the skin.

Factors Affecting Drug Absorption

Physiochemical properties of the drug.
Properties of the environment (degradation).
Dosage form used
Anatomy & physiology of the absorption site (surface area, motility, blood flow)

Modes of Drug Transport

Passive (diffusion)
Active (transport mechanisms)

pH and pKa

The pH difference between blood and interstitial fluid does affect drug ionization and penetration.
However, these differences are typically not significant for most organs.

Drug Distribution

Drug distribution is influenced by physicochemical characteristics, tissue perfusion, regional blood flow, and capillary permeability.
First-pass distribution includes highly perfused organs. Second is muscle, viscera and skin.

Drug Accumulation

Drugs can accumulate in tissues passively or by binding to macromolecules.
High partition coefficients contribute to fat accumulation.

Drug Elimination (Clearance)

Elimination of drugs from the body via metabolism and excretion.
Metabolism transforms drugs into more water-soluble forms, helping with excretion.
The main excretion route is through the kidneys (urine).

Drug Metabolism

Phase I reactions involve functionalization, often creating active metabolites or converting inactive drugs into active ones
Phase II reactions involve conjugation (combining a Phase I product with a highly polar residue), making drugs more hydrophilic and promoting renal excretion

Drug Excretion

Renal elimination: glomerular filtration, passive reabsorption, active secretion
Other routes: bile, sweat, saliva, tears

Glomerular Filtration

Small molecules (Mwt <500) are filtered.
Ionization status of the drug influences filtration rates.

Active Tubular Secretion

Active (energy-requiring) process
Affected by carrier proteins
Protein binding does not hinder secretion

Passive Reabsorption

Depends on ionization status, concentration gradient (water/sodium)
Alkalization and acidification can affect the absorption of acidic/basic drugs.

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Description

Explore the fundamental concepts of pharmacokinetics in this quiz. Understand how drugs are absorbed, distributed, metabolized, and eliminated in the body. Delve into the relationship between drug concentration and its effects on biological systems.