Pharmacology Review: Pharmacokinetics, Pharmacodynamics, and Therapeutic Index (Ch 1-9)

A comprehensive set of question-and-answer flashcards covering pharmacokinetics, pharmacodynamics, dosing concepts, aging effects, and common drug interactions from Chapters 1-9.

What are the four phases of pharmacokinetics?

Absorption, Distribution, Metabolism, and Excretion.

Define absorption in pharmacokinetics.

Movement of a drug from the site of administration into the bloodstream.

List major factors that influence absorption.

Route of administration, drug formulation, dose, surface area of absorption site, digestive motility, blood flow, lipid solubility, and presence of food or pH.

Which route provides the fastest drug absorption?

Intravenous (IV) administration.

Which route is typically the slowest for absorption?

Oral (PO), especially with solid tablets; liquids absorb faster than pills.

How does food in the stomach affect absorption?

Food can delay absorption; some medications require empty stomach; exceptions exist for GI irritation.

What is the purpose of enteric coating on some tablets?

To delay absorption in the stomach and promote absorption in the small intestine, protecting the stomach from acidity.

What is the first-pass effect?

Oral drugs are inactivated by the liver on their first pass through hepatic circulation, reducing bioavailability.

How can the first-pass effect be bypassed?

Use alternate routes (IV, buccal, sublingual) or adjust the dose to compensate.

Define distribution in pharmacokinetics.

The movement of a drug throughout the body from the bloodstream to tissues and sites of action.

What is the biggest barrier to distribution?

Blood flow to tissues; conditions like atherosclerosis or poor circulation can impede distribution.

What is displacement in pharmacokinetics context?

When a drug is displaced from a receptor or binding site by another drug, increasing free drug levels and toxicity risk.

What is synergism in drug interactions?

Two drugs produce an effect greater than the sum of their individual effects (e.g., two drugs producing enhanced relief).

What is an antagonist?

A drug that binds to a receptor and blocks activation by agonists or endogenous substances.

What is a partial agonist?

A drug that binds to a receptor and produces a weaker effect than a full agonist.

What is pharmacodynamics?

The study of how drugs produce effects in the body, including receptor interactions and efficacy.

Which organ is the primary site of drug metabolism?

The liver (hepatic metabolism) via hepatic enzymes.

What are enzyme inhibitors and enzyme inducers?

Inhibitors decrease metabolism of drugs by inhibiting enzymes; inducers increase enzyme activity, speeding metabolism.

Why are infants and older adults at risk for altered metabolism?

Infants have immature liver/kidney function; older adults have reduced metabolic capacity and organ function, increasing toxicity risk.

Which labs indicate liver function?

AST and ALT (liver enzymes).

Which labs indicate kidney function?

BUN, creatinine, and estimated GFR.

What is excretion?

Elimination of drugs from the body, primarily via the kidneys (urine); other routes include biliary/feces, respiration, and sweat.

What is the primary route of drug excretion?

Urine (kidneys).

What is the therapeutic index?

The range between therapeutic and toxic concentrations; higher TI means a wider safety margin; narrow TI requires close monitoring.

What are ED50 and LD50?

Median Effective Dose (ED50) and Median Lethal Dose (LD50); used in research to describe potency and toxicity (not commonly in humans).

What is a loading dose?

An initial higher dose given to rapidly achieve therapeutic drug concentrations.

What is a maintenance dose?

A dose given to maintain drug levels within the therapeutic range.

What are onset, peak, duration, half-life, and trough?

Onset: time to initial effect; Peak: time of maximum effect; Duration: how long the effect lasts; Half-life: time for concentration to fall by half; Trough: lowest concentration before next dose.

Why is knowing onset and peak important in nursing care?

To anticipate when the patient will feel relief and when to reassess or redose; helps timing of reassessment and monitoring.

What is a loading dose used for in practice?

To reach therapeutic range quickly, often followed by maintenance dosing (e.g., antibiotics like Zpak).

What is pharmacogenetics?

Study of how genetic differences affect drug metabolism and response, guiding personalized medicine.

What is the difference between potency and efficacy?

Potency is the amount of drug needed to achieve a given effect (drug strength); efficacy is the maximum effect a drug can produce.

What is the role of the blood-brain barrier in pharmacokinetics?

A barrier that protects the brain by limiting drug entry; some drugs must cross it to treat CNS conditions.

What is placental (fetal) barrier and its relevance?

Barrier between mother and fetus; some drugs cross and can affect the fetus; important for pregnancy safety.

What is the effect of grapefruit juice on drug absorption?

Can alter gastric pH and absorption for certain medications, and interact with drug metabolism (noted in class as affecting absorption).

What is the general guidance for drug dosing in the elderly?

Older adults require lower doses and careful monitoring due to decreased hepatic metabolism, decreased renal clearance, increased fat, and slower GI motility.

What labs are important before administering drugs with potential hepatic impact in older adults?

AST/ALT for liver function; BUN/creatinine for kidney function.

Why is knowledge of peak and trough levels important for drugs with narrow therapeutic index (e.g., vancomycin)?

To avoid toxicity while maintaining therapeutic effect by adjusting dose based on blood levels.