Patho-Pharm: Pharmacokinetics/ Pharmacodynamics

What is the focus of pharmacodynamics?

Pharmacodynamics focuses on what the drug specifically does to the body

What does pharmacokinetics describe?

Pharmacokinetics describes what the body does to the drug

How does understanding pharmacodynamics help medical professionals?

It helps determine therapeutic and adverse effects of the drug

What are the four basic pharmacokinetic processes?

Absorption, distribution, metabolism, and excretion

What is absorption in pharmacokinetics?

Absorption is the movement of a drug from its site of administration into the blood

What factors affect drug absorption?

Rate of dissolution, surface area, blood flow, lipid solubility, and pH partitioning

How does surface area influence drug absorption?

Larger surface area generally leads to faster drug absorption

What is the significance of lipid solubility in drug absorption?

Lipid-soluble drugs can pass directly through cell membranes, leading to faster absorption

What are the common routes of drug administration?

Oral (PO), intravenous (IV), intramuscular (IM), and subcutaneous (subQ)

What is a major advantage of oral medication administration?

It is easily accessible and can be reversible, making it safer than parenteral routes

What is a disadvantage of intravenous (IV) administration?

It is irreversible and must be performed by a professional

What are enteric coated preparations designed to do?

They prevent the drug from dissolving in the stomach and allow it to dissolve in the small intestine

What is the purpose of sustained release preparations?

They dissolve more slowly, allowing for less frequent dosing throughout the day

What is distribution in pharmacokinetics?

Distribution is the movement of a drug from the blood to the interstitial space of tissues and to the site of action

What are the major factors involved in drug distribution?

Blood flow to tissues, ability of the drug to exit the vascular system, and ability to enter cells

How does blood flow affect drug distribution?

The rate at which drugs are delivered to tissues is determined by blood flow to those tissues

What are the four ways a drug may leave the vascular system?

Through the capillary bed, blood-brain barrier (BBB), placental drug transfer, and protein binding

What is a challenge of drug passage through the blood-brain barrier (BBB)?

Tight junctions prevent drugs from passing unless they are lipid soluble or have a transport system

What is the role of the placenta in drug transfer?

The placenta separates the mother's systemic circulation from the fetal circulation and is not an absolute barrier to drug passage

Which types of drugs can pass through the placenta?

Only lipid-soluble and nonionized (no charge) drugs can pass through the placenta

What is the most common protein involved in drug binding?

Plasma albumin is the most common protein for drug binding in the body

What happens to drugs that are bound to albumin?

Drugs bound to albumin cannot leave the blood and must break their bond to reach the site of action

Where does most drug metabolism occur?

Most drug metabolism takes place in the liver

What is the P450 system?

The P450 system is the hepatic microsomal enzyme system that catalyzes a wide variety of drug metabolism reactions

What are the six possible consequences of drug metabolism?

1. Accelerated renal excretion

2. Drug inactivation

3. Increased therapeutic action

4. Activation of prodrugs

5. Increased toxicity

6. Decreased toxicity

What is the most important consequence of drug metabolism?

The promotion of renal drug excretion by converting lipid-soluble drugs into hydrophilic forms

What are substrates in drug metabolism?

Substrates are drugs that are metabolized by P450 hepatic enzymes

What is induction in drug metabolism?

Induction is the process of stimulating enzyme synthesis, increasing the rates of drug metabolism

What is inhibition in drug metabolism?

Inhibition is when drugs decrease the rates of drug metabolism, potentially leading to increased active drug accumulation

What is first-pass metabolism?

First-pass metabolism is the rapid inactivation of some oral drugs as they pass through the liver after absorption

What is enterohepatic recirculation?

It is a cycle where a drug undergoes glucuronidation in the liver, is transported to the duodenum, released by intestinal enzymes, and returned to the liver

What are the three steps of renal drug excretion?

1. Glomerular filtration

2. Passive tubular reabsorption

3. Active tubular secretion

How does lipid solubility affect drug excretion?

Highly lipid-soluble drugs undergo extensive passive reabsorption and cannot be excreted by the kidneys

What is the minimum effective concentration (MEC)?

The MEC is the plasma drug level below which therapeutic effects will not occur

What is the therapeutic range of a drug?

The therapeutic range is the plasma concentration between the MEC and the toxic concentration

What is the half-life of a drug?

The half-life is the time required for the drug concentration in the body to decline by 50%

What is the time needed to reach a plateau in drug levels?

The time needed to reach a plateau is about 4 half-lives

What is pharmacodynamics?

Pharmacodynamics is the study of the biochemical and physiologic effects of drugs on the body and the mechanisms by which these effects are produced

What is the dose-response relationship?

The dose-response relationship is the correlation between the size of an administered dose and the intensity of the response produced

What does maximal efficacy refer to?

Maximal efficacy is the largest effect that a drug can produce

What is the primary effect of Furosemide as a diuretic?

It has high maximal efficacy but can cause dehydration

Why might hydrochlorothiazide be preferred over Furosemide?

It mobilizes a modest amount of water and has lower efficacy

What does relative potency refer to in pharmacodynamics?

The amount of drug needed to elicit an effect, with higher potency allowing for smaller doses

What are drug receptors?

Special chemical sites in the body that drugs interact with to produce effects

What is the definition of a receptor in pharmacodynamics?

Any functional macromolecule in a cell to which a drug binds to produce its effects

What is the primary action of a drug when it binds to its receptor?

It can either mimic or block the actions of endogenous regulatory molecules

What are the four primary receptor families?

1. Cell membrane-embedded enzymes, 2. Ligand-gated ion channels, 3. G protein-coupled receptor systems, 4. Transcription factors

What is the function of cell membrane-embedded enzymes?

They have a ligand-binding domain on the cell surface and an enzyme catalytic site inside

How do ligand-gated ion channels function?

They regulate the flow of ions into and out of the cell when a ligand binds

What are G protein-coupled receptor systems composed of?

A receptor, G protein, and an effector

What is the role of transcription factors in pharmacodynamics?

They regulate protein synthesis and are activated by endogenous ligands or agonist drugs

What is selective drug action?

The ability of drugs to act through specific receptors, each regulating a few processes

What does the simple occupancy theory state?

The intensity of a drug's response is proportional to the number of receptors occupied

What are the two qualities ascribed to drugs in the modified occupancy theory?

Affinity (strength of attraction to the receptor) and intrinsic activity (ability to activate the receptor)

What is the function of agonists in pharmacodynamics?

They activate receptors and mimic the actions of the body's regulatory molecules

How do antagonists work?

They prevent receptor activation by endogenous regulatory molecules and have affinity but no intrinsic activity

What is a partial agonist?

An agonist with moderate intrinsic activity, producing a lower maximal effect than a full agonist

What is interpatient variability in drug responses?

The variation in the dose required to produce a therapeutic response among different patients

Why is understanding pharmacodynamics important for nurses?

It helps ensure patient safety and informs the determination of adverse and therapeutic effects of drugs

What is the relationship between pharmacodynamics and pharmacokinetics?

Both are essential for understanding how drugs act in the body and how the body reacts to drugs