Pharmacokinetics and Pharmacodynamics Lecture Review

Flashcards covering key concepts from lecture notes on pharmacokinetics (how drugs move through the body) and pharmacodynamics (how drugs affect the body). Topics include absorption, distribution, metabolism, excretion, routes of administration, drug-receptor interactions, and dosage principles.

What does the 'kinetics' part of pharmacokinetics refer to?

Motion, specifically how drugs move through the body.

What are the four basic principles of pharmacokinetics?

Absorption, Distribution, Metabolism, and Excretion.

Which pharmacokinetic process involves drugs entering the bloodstream from the administration site?

Absorption.

If a patient has elevated BUN and creatinine (kidney labs), which pharmacokinetic process is the nurse most concerned with?

Excretion (and sometimes metabolism).

If medications can only be given through a J-tube, which pharmacokinetic process is primarily affected?

Absorption.

What is the major barrier drugs must cross to start their journey in the body?

The cell membrane (a phospholipid bilayer).

What are the three main ways drugs can cross the cell membrane?

Direct penetration of the membrane, transport systems, and channels/pores.

What is the most common way for drugs to cross the cell membrane?

Direct penetration of the membrane.

Why do very few drugs pass through channels and pores in cell membranes?

Most drugs are too big for these small openings, which are typically reserved for smaller compounds like potassium or sodium.

What characteristic allows a drug to easily pass through the lipid primary cell membrane?

Being lipophilic or lipid-soluble.

What happens to a drug when it undergoes ionization?

It gains a positive or negative charge, making it harder for it to be absorbed if it's an acid in a basic medium or a base in an acidic medium.

If aspirin (an acid) is absorbed in the stomach (an acid), why does it get absorbed easily?

Acids do not need to ionize in acidic media, allowing easy absorption.

How do the rate and amount of absorption affect drug action?

The rate of absorption determines how soon effects begin, and the amount of absorption determines how strong the effects will be.

Name factors that can enhance drug absorption.

Rapid drug dissolution, larger surface area, high blood flow, and high lipid solubility.

What is the difference between enteral and parenteral routes of administration?

Enteral routes go into the GI system (oral, NG, G-tube), while parenteral routes are outside the GI system (IV, IM, SubQ).

Why is the IV route the quickest route to drug absorption?

There are no barriers, and it goes directly into the bloodstream, making absorption instantaneous and complete.

What are some disadvantages of IV drug administration?

High cost, need for specialized training, irreversibility, risk of fluid overload, infection, and embolism.

Why are IM and SubQ routes sometimes preferred for drugs that don't easily cross cell membranes?

They bypass the initial need to cross many cell membranes and can be used for depot preparations that absorb slowly over time.

What is a major advantage of the oral route of drug administration compared to IV?

It is easy, convenient, lower cost, and reversible.

Name one factor that can cause high variability in oral drug absorption between individuals.

Drug dissolution rate, gastric/intestinal pH, stomach emptying speed, food intake, other medications, or special coatings.

What is drug 'distribution' in pharmacokinetics?

The movement of drugs from the blood to tissues and into cells to reach their site of action.

How does the Blood Brain Barrier (BBB) affect drug distribution?

Its tight spaces make it harder for drugs to leave capillary beds in the central nervous system, requiring drugs to pass through cells to reach the brain.

How does the placenta protect a fetus from maternal medications?

It contains P-glycoprotein transporters that pump drugs back into the mother's blood system, although some drugs can still cross.

What happens when a drug binds to albumin in the bloodstream?

The drug may stay in the bloodstream and not leave the capillary beds, potentially increasing drug levels in the body.

What is 'metabolism' (or biotransformation) in pharmacokinetics?

How the body alters the drug structure, primarily in the liver, using enzyme systems like P450.

What is the most important result of drug metabolism?

Accelerated excretion of the drugs from the kidney.

What is a 'prodrug'?

A medication given in an inactive form that is then activated by the liver during metabolism.

What is the 'first-pass effect' in drug metabolism?

When an orally administered drug is completely inactivated by the liver during metabolism before it can reach systemic circulation or its site of action.

How does patient age affect drug metabolism?

Babies have underdeveloped livers, and older adults have slowing livers, requiring dosage adjustments.

What is the primary organ responsible for drug excretion?

The kidneys.

Name three ways drugs are excreted from the body via the kidneys.

Glomerular filtration, passive tubular reabsorption, and active tubular secretion.

What is 'minimum effective concentration'?

The lowest amount of drug in the body required to start feeling therapeutic effects.

What is the 'therapeutic range'?

The range of drug concentration where the most benefit is seen with the least amount of harm.

What is 'half-life' in pharmacology?

The time required for half of the drug concentration to decrease in the body.

What is a 'loading dose' and why is it used?

An initial higher dose of medication given to rapidly reach the therapeutic plateau for drugs that take a long time to achieve steady state.

What is 'pharmacodynamics'?

How drugs produce their effects on the body; how the drugs actually work.

What does a 'graded' dose-response relationship mean?

As the dose of a drug increases, the intensity of the response is also expected to increase.

What is 'maximal efficacy' of a drug?

The largest effect a drug is expected to produce; it's not always desirable or needed to use a drug with the highest efficacy.

Why might Tylenol be preferred over morphine for a headache, despite morphine having higher efficacy?

Tylenol is a lower, safer, effective drug for the patient's condition, avoiding unnecessary risks associated with higher efficacy drugs.

What role do drug receptors play in pharmacodynamics?

Drugs (chemicals) bind to specific receptors (other chemicals) in the body to produce their effects, either mimicking or blocking the body's own actions.

Can drugs create new actions in the body?

No, drugs can only block or mimic the body's existing actions; they cannot create new physiological functions.

What does 'selectivity' mean for a drug and its effects?

A more selective drug binds to fewer types of receptors, generally leading to fewer effects (and often fewer side effects).

According to the modified occupancy theory, what is 'affinity'?

The strength of attraction between a drug and its receptor; drugs with high affinity have high potency and can bind at lower concentrations.

How is 'intrinsic activity' described in the modified occupancy theory?

The ability of a drug to activate the receptor after binding, akin to the dimmer on a light switch (strong bind = strong activation).

What is the difference between an agonist and an antagonist drug?

Agonists activate receptors and mimic the body's normal actions (e.g., opioids), while antagonists prevent receptor activity and block the body's normal actions (e.g., antihistamines).

What is the 'average effective dose' (ED50)?

The dose required to produce a therapeutic effect in 50% of the population, often serving as the standard starting dose.

How is the 'therapeutic index' (TI) determined, and what does a wider TI indicate?

It's the ratio between the average lethal dose (LD50) and the average effective dose (ED50), measuring drug safety; a wider TI indicates a safer drug with more leeway in dosage adjustments.