Pharmacokinetics Flashcards
How do you calculate the required loading dose of a medication?
What is the bioavailability of an IV medication?
It’s always equal to 1, because it’s being injected directly into the bloodstream. There is no first pass effect
Steady state is achieved after:
About five half lives
What is steady state?
When the rate of administration is equal to the rate of elimination
When the amount of drug entering the blood stream is equal to the amount of drug being excreted
What is the elimination half life?
The time required for the amount of drug in the plasma to decrease by 50%
After three half lives, what percentage of a drug is removed?
Which is more likely to undergo renal elimination: an ionized or non-ionized drug?
An ionized drug, because it is hydrophilic
Which is more likely to undergo hepatic metabolism: an ionized drug or a non-ionized drug?
A non-ionize drug, because it is lipophilic
Fetal pH is typically _________ than maternal pH
lower
Ion trapping is of highest concern in a ______ mother and ______ fetus
alkalotic mother and acidotic fetus
What local anesthetic is the most likely to undergo fetal ion trapping?
Lidocaine
Chloroprocaine is the least
Albumin typically binds acidic or basic drugs?
Acidic
Alpha-1 Glycoprotein typically binds acidic or basic drugs?
Basic
Plasma concentrations of albumin are decreased by:
Liver Failure
Renal Disease
Old Age
Malnutrition
Pregnancy
Plasma concentrations of Alpha 1 Glycoprotein is increased by:
Surgical stress
MI
Chronic Pain
Rheumatoid Arthritis
Advanced Age
Plasma concentrations of alpha 1 glycoprotein are decreased by:
Neonates
Pregnancy
Zero order kinetics occur when:
there is more drug than enzyme, so the enzyme metabolized at a set rate
What are some drugs that follow zero order kinetics?
Alcohol
Aspirin
Phenytoin
Warfarin
Theophylline
Heparin
What’s the difference between zero order and first order kinetics?
Zero order: constant AMOUNT per time unit
First order: constant FRACTION per time unit
Drug metabolism is divided into three phases:
- Modification
- Conjugation
- Excretion
What is biotransformation?
The process of altering a molecule’s chemical structure
It’s just another word metabolism
What is the purpose of metabolism?
To change a lipid-soluble, pharmacologically active compound INTO
a water-soluble, inactive compound
What are some common examples of phase 1 reactions?
Oxidation
Reduction
Hyrolysis
What happens in phase 2 reactions?
conjugation of a highly polar, water-soluble substrate to the molecule, inactivating the drug and making it easier to eliminate
What happens in phase 3 reactions?
ATP-dependent transport across a cell membrane
What happens when lipophilic drugs that do not undergo biotransformation reach the kidney?
Most phase 1 biotransformations are carried out by:
the liver P450 system
For drugs with a low hepatic extraction ratio, clearance is dependent on:
the ability of the liver to extract the drug
(extraction dependent)
The amount of blood flow through the liver has very little effect
For drugs with a high hepatic extraction ratio, clearance is dependent on:
liver blood flow (perfusion dependent)
Hepatic blood flow exceeds enzymatic activity, so changes in perfusion have very little effect
What is the hepatic extraction ratio?
the ratio of drug delivered vs. drug extracted
Co-adminstration of which drug decreases the efficacy of codeine?
Fluoxetine
Which P450 enzyme is responsible for 50% of drug metabolism?
CYP 3A4
The P450 system is the most important mechanism of drug _________
biotransformation (metabolism)
Where are P450 enzymes located?
the smooth endoplasmic reticulum of hepatocytes
Which drugs are CYP inducers?
Which drugs are CYP inhibitors?
Which drugs are CYP substrates?
Acidic urine favors:
- Reabsorption of acidic drugs
- Excretion of basic drugs
Basic urine favors:
- Reabsorption of basic drugs
- Excretion of acidic drugs
Which drugs are metabolized by pseudocholinesterase?
Which drugs are metabolized by nonspecific esterases?
Pharmacokinetics explains:
what the body does to the drug
Pharmacodynamics explains:
what the drug does to the body
