Pharmacokenetics and Pharmacodynamics Flashcards
What aspects of drug usage and mechanism does pharmacokinetics look at?
Pharmacokinetics of the drug looks at the dose administration (oral or IV), pathway it takes to reach blood stream/systematic circulation, drug distribution, drug absorption throughout its pathway, and clearance. Basically looking at:
- ABSORPTION, DISTRIBUTION, METABOLISM, ELIMINATION/EXCRETION
What aspect of drug usage/mechanism does the pharmacodynamic look at?
Pharmacodynamic looks at the receptors the drug will bind to and the effect of the drug.
What is the difference between oral and IV dose in terms of bioavailability? define bioavailability as well
- Bioavailability is the fraction/percentage of the drug that reaches the blood circulation and is bio-available to be distributed to the rest of the body
- Oral dose has less than 100% bioavailability due to drug being absorbed at different stages of travel (GI or liver) to the blood circulation.
- IV dose has 100% bioavailability due to it going straight to systematic circulation without having to go through other organs
What is directly related to the effect of the drug? The dose of drug or the concentration of drug in the blood circulation?
Concentration of drug in the blood circulation is directly related to the effect of the drug because some concentration of drug can be absorbed by the GI tract or liver if the drug passes through those organs.
What are different routes of drug administration?
- oral
- sublingual (under tongue) (100% of drug is bioavailable as it travels directly to the blood stream)
- inhalation (less used as it is unpredictable)
- Rectal
- topical
- transdermal
- intraosseous (directly into bone marrow)
Parenteral routes (travels straight to blood circulation, avoids GI or liver or any other organs) include: - IV
- IM
- Subcutaneous
What does it mean if the drug lacks acid stability and what is the solution to it?
The pH of the stomach is between 1-2. So if the drug lacks acid stability, it means that the drug can’t survive the pH of the stomach and gets dissolved. This is a problem as the drug won’t be bioavailable to provide any effect. The solution to this problem is coating of the drug. This coating protects the drug from stomach acid and won’t be released until it reaches the intestines.
What does it mean when a drug has a high first pass effect?
- first pass effect is when the concentration of the drug is greatly reduced before it reaches the systematic circulation due to liver metabolism of the drug. So if the drug has a high first pass effect, it means that the drug was metabolized in great quantity in the liver, and by the time it first reaches the blood circulation there is very little drug left to make any effect. So consider alternative route such as IV if drug has high first pass effect for oral drug.
What is CYP450?
CYP450 is an enzyme in liver that metabolizes drugs
What are the AST and ALT test?
AST and ALT are liver function test. Higher levels of either means liver damage
Where does most of the drug metabolism and absorption occur?
Metabolism = liver Absorption = GI (small intestines)
Two examples of drugs that are absorbed in small intestine but not metabolized in liver?
lithium and metformin are two drugs that get absorbed in the small intestine but are not metabolized in the liver. It gets filtered out by the kidneys.
What is the equation to calculate bio-availability?
- F = (area under the curve of oral dose)/(area under the curve of IV dose) has to be same dose
What is the lag time on the pharmacokinetic graph of plasma drug concentration over time?
- Lag time can be due to time it takes to orally swallow the drug, or drug being absorbed in the GI or metabolized in the liver, before it reached the blood circulation.
- No lag time in IV drug dose as it reaches blood circulation very quickly
What is Cmax?
Cmax is the maximum amount of drug concentration in the blood plasma
What is Tmax?
Tmax is the time point when the concentration of drug in plasma is the highest.
