Introduction to Pharmacokinetics Flashcards
Name the four stages a drug may go through after introducing it into a patient.
- Absorption
- Distribution
- Metabolism
- Elimination
A process of absorption that does not require energy and cannot proceed against gradients.
Passive (Diffusion) Absorption
Filtration and Diffusion are under which of the 4 stages?
Absorption (Passive)
When combining the ionized and the unionized form of drugs together, what should the total percentage add up to?
ALWAYS 100%
Differentiate between Ionized and Unionized Compounds.
Ionized: DO NOT easily cross the lipid bilayer and are not readily reabsorbed; Therefore they are typically ELIMINATED
Unionized: EASILY cross the lipid bilayer and can be reabsorbed readily; Therefore, they are typically NOT ELIMINATED
The ionization status depends on which 2 factors?
- pka
2. pH
What are two important areas in the body where the pH changes drastically?
- GI Tract
2. Kidneys
What is the ratio of “ionized:unionized” when the pka=pH?
50%:50% Ratio
Energy Requiring, Saturable and Movement against gradients are all characteristics of which of the 4 stages?
Absorption (Active)
True or False. Facilitated Transport is considered active transport.
TRUE
What’s the big difference between Absorption and Distribution?
PROTEIN BINDING (within distribution)
What does alpha represent when talking about protein binding?
Unbound Fraction (% of free drug in the body)
Can also be used as the availability of the drug to give pharmacological action
Biotransformation/the ways the body uses to increase the likelihood of drug elimination from the body is the main goal of which process?
Metabolism (adMe)
Which drug is extensively metabolized into 2 metabolites with 100% and 25% Potency?
Lidocaine
Which phase of Biotransformation is responsible for formation of new or modified functional group or cleavage of chemical groups (i.e. Oxidation, Reduction, Hydrolysis Rxns)?
Which enzyme is mainly used?
PHASE 1
CYP450 is mainly used
A compound that requires an isoenzyme (i.e. CYP450) to be metabolized is a __________ .
Substrate
- _________ prevent the enzyme from processing substrates.
2. _________ aid the enzyme in processing substrates.
- Inhibitors
2. Inducers
- Use ________ to stop an active drug from getting metabolized into an inactive compound.
- Use _________ to help an inactive prodrug metabolize into an active compound.
- Inhibitors
2. Inducers
What are reactions that involve conjugation (covalent linkages; Glucuronidation, Sulfation, Acetylation) with an endogenous substance?
Phase 2
Drugs that are ingested orally need to first go through the portal circulation to the liver. This is an example of which phenomenon?
First Pass Effect
- ** Atenolol is NOT metabolized at all by the liver
- ** Propranolol is almost ENTIRELY metabolized by the liver
List the primary routes of elimination of drugs (3).
- Lungs
- Skin (sweat)
- Bile/Feces
What are the three main processes of elimination in the kidneys (in relation to active vs. passive)? What do you need to do if these processes are disturbed?
- Passive Glomerular Filtration
- Passive Tubular Diffusion
- Active Tubular Secretion
*** Might need to change the dose if the renal function has decreased!
The fraction of the total amount of change in the Cp remains constant over time is an example of which pharmacokinetic property of drugs?
First-Order
The fraction of the total amount of change in the Cp is not constant over time is an example of which pharmacokinetic property of drugs?
Zero-Order
