Pharmacokinetics Flashcards
What is pharmacodynamics?
What the drug does to the body
What is pharmacokinetics
What the body does to the drug
What are the four domains of pharmacokinetics?
- Absorption of a drug
- Distribution of the drug to the site of action in the body
- Metabolism of the drug to an active or non-active metabolite
- Elimination of the drug from the body
What is the function of the cell membrane?
- The cell membranes structure makes it relatively impermeable to large, highly polar molecules
What is passive diffusion
It is how most drug move
What will affect the state of ionization in a drug?
- Differences in pH
What is facilitated diffusion?
- Carrier mediated process
What is active transport?
- Requirement of energy to move a solute against an electrochemical gradient
What is absorption
Movement of drug from its site of administration into circulation
What is bioavailability
- Fractional extent to which an administered dose of a drug reaches systemic circulation
Where are most drug absorbed?
- The small intestine
What does majority of drug absorption from the GI tract happen by?
Passive diffusion
Where are weak acids (pH 1-2) better absorbed?
From the stomach
Where are weak bases (3-6) better absorbed?
Intestine
What do the villi of the upper intestine provide?
- A larger surface area than the stomach
*The rate of absorption from the intestine will be greater than from the stomach
Where does sublingual administration absorb to?
- To the SVC
*will by-pass the first effect
What effects distribution of a drug to a specific site?
- Rate of blood flow to individual organs or compartments
- Capacity of organ/ region to interact with drug
What are factors that affects distribution into the tissues?
- Cardiac output
- Regional blood flow
- Capillary permeability
- Tissue volume
What type of drugs does albumin bind?
- Acidic drugs
What type of drug does alpha 1- acid glycoprotein bind?
- Basic drugs
What does lipophilic and BBB relate to each other?
- The more lipophilic a drug, the more likely it is to cross the BBB
What are other things that can affect drug distribution?
- Tissue binding
*Drugs can accumulate in certain tissue increase in either duration of action or potential for toxicity - Redistribution
*drug goes for site of action to other tissues
*usually happens with very lipophilic drug administered as a rapid bolus
Are lipophilic drugs easily passed for elimination?
- No
*there needs to be metabolism of lipophilic drugs to more hydrophilic metabolites
What is zero order kinetics?
- A constant amount of drug is metabolizes per unit of time
What is first order kinetics?
- Amount of drug metabolized per unit of time is proportional to the plasma concentration of the drug
*the rate of drug metabolism depends on drug concentration in the body
Where does bio transformation of drugs into more polar hydrophilic metabolites happen?
In the liver
What is the rate at which some CYP metabolize drugs based no?
Genetics
*pharmacogenomics
where is the most common place for elimination of drugs?
Renal (kidneys)
What is steady state?
- When the rate of drug elimination equals the rate of drug administration
*dosing rate=clearance rate X [steady state]
What is volume of distribution?
- Relates to the amount fo drug in a body compartment to the concentration in the blood or plasma
What does a high V4 mean?
Lots of tissue binding or high distribution into fat
What does low v4 mean?
Generally water soluble and distributes mostly into plasma
What does loading dose mean>
- A larger than normal dose to achieve a desired concentration in the blood at a much quicker rate
