Pharmacokinetics Flashcards
What does enteral administration mean?
Using the GI tract (oral, sublingual, buccal, rectal)
What does parenteral mean?
Non-GI delivery
IV, IM, SQ, intrathecal, epidural
What route of administration get the greatest level of compliance?
Enteral
What is the problem with using the GI tract for administering drugs?
Digests the drugs
What is buccal administration? What is the advantage of using this route, as compared to other enteral routes?
Placing drug between tongue and cheek
Bypasses the liver
What are the two major disadvantage of parenteral administration of a drug?
Pierce the skin, lowers compliance
No way to reclaim drug
Which route of administration gives the highest bioavailability?
Parenteral (IV)
What is the general type of chemical that is absorbed across the buccal mucosa?
Lipid soluble
What percent of a drug that is given rectally bypasses the liver?
~50%
What can significantly impact the absorption of a drug administered IM?
Exercise/fat distribution
What is the specific advantage of SQ administration of a drug?
Constant rate of absorption over a long period of time
What is intrathecal administration of a drug?
Injection into the subarachnoid space
What is transdermal administration?
Think patches
Lipophilic, or hydrophilic drugs are more likely to be successful with paradermal route of administration
Lipophilic
What type of drug side effects should cause concern for giving them via inhalation?
Anything that upsets the heart
What is the charged form of a weak base: protonated or unprotonated?
protonated
What is the charged form of a weak acid: protonated or unprotonated?
Unprotonated
Which can pass through a lipid bilayer more easily: charged or uncharged substances?
Uncharged
How can the henderson-hasselbach equation be used in pharmacokinetics?
check protonated form in relation to the pH of a given solution
What is the pKa?
pH at which [protonated form] = [unprotonated form]
Weak acids are more likely to be absorbed where?
stomach d/t low pH
Weak bases are more likely to be absorbed where?
Intestines
What are the four major factors of drug distribution?
- Cardiovascular factors
- Tissue binding
- Drug molecule size
- Lipid solubility
What is the technical definition of drug distribution?
The process by which a drug leaves the circulation and enters the tissues perfused by the blood
What is the role of proteins in the blood and drug distribution?
Drugs can bind to proteins, leaving less available to distribute
What is phase I of biotransformation?
Generate a more polar molecule by exposing a functional group on the parent compound.
What is phase II of biotransformation?
Reactions yielding a more water soluble conjugated product to be excreted
What is the rate limiting step in biotransformation?
p450 enzymes in the ER
Where are the products of phase II of biotransformation excreted?
Bile canaliculi
Do all drugs go through phase I and II biotransformation?
no
What are the three most common reactions done in phase II?
Glucuronidation
Sulfation
Acetylation
What is the role of UDP?
Conjugates metabolites to be excreted
What is the “first pass” effect?
Drug absorbed by the stomach or intestines will initially be carried to the liver by the portal vein
What are the three major factors that determine the renal excretion?
GFR
Plasma protein binding
pH of urine
How are most drug metabolites excreted into feces? (2)
Bile
Hepatocytes secrete directly into GI tract
What is the volume distribution?
The measure of space in the body available to contain a drug
What is clearance?
Measure of the ability of the body to eliminate a drug
What are the two major factors that determine the amount of drug within the body?
Distribution and elimination
