Foundations of Pharmacology Flashcards
Which main transport protein helps with preventing passage to the blood-brain barrier
P-glycoprotein (Pgp) - efflux pump facilitating removal of drugs and toxins out of the cell.
What does a low partition coefficient signify about a drug’s properties?
The drug is hydrophilic and primarily resides in water.
What is the partition coefficient of a drug?
Concentration of unionized drug in n-octanol phase (organic phase)
DIVIDED BY
Concentration of unionized drug in water phase.
What term describes drugs that are soluble in water?
hydrophilic
What is the difference between pharmacokinetics and pharmacodynamics?
Pharmacokinetics = what the body does to the drug
Pharmacodynamics = what the drug does to the body
What does MTC stand for? (plasma concentration)
Maximum tolerated concentration
What does MEC stand for? (plasma concentration)
Minimum effective concentration
How is a drug’s onset of action determined?
measuring the time it takes for plasma drug concentrations to reach the minimum effective concentration (MEC).
What does the therapeutic range or window refer to?
The therapeutic window is the range of drug plasma concentrations that provide a therapeutic effect while limiting adverse effects and toxicity.
Which of the following is the formula for calculating the therapeutic index (TI)?
TI = TD50/ED50.
The therapeutic index (TI) is calculated by dividing the dose that produced toxicity in 50% of patients (TD50) by the dose that produced a favorable or effective response in 50% of patients (ED50).
How is oral systemic bioavailability calculated?
F = Fa X Fg X Fh
Fa stands for?
Intestinal absorption (a=absorption)
Fg stands for?
Intestinal metabolism (g=gut metabolism)
Fh stands for?
Hepatic metabolism
What does first-pass effect mean?
Hepatic enzymes metabolize a fraction of the drug before it enters systemic circulation.
Why do drugs absorb better in the small intestine than the stomach?
Drugs absorb better in the small intestine than the stomach due to its higher surface area, blood flow, and permeability.
Why are acidic drugs more likely to be absorbed in the stomach than basic drugs?
The low pH of the stomach means acids mostly exist in their unionized form. This allows them to permeate cell membranes and be absorbed.
What role does gastric emptying play in drug absorption?
Gastric emptying influences how quickly a drug is moved from the stomach to the small intestine. Slow gastric emptying, caused by factors such as high-fat food or certain medications, can delay drug absorption.
How do efflux transporters like P-glycoprotein (Pgp) impact systemic drug absorption?
Efflux transporters like Pgp can limit systemic absorption by pumping drug molecules back into the intestinal lumen, reducing the amount of drug available for absorption into the systemic circulation.
Which kinds of agonists bind to and activate receptors but do not elicit the same magnitude of response as endogenous agonists?
Partial agonists
Which group of enzymes is the most common for polarizing a drug for renal excretion?
CYP450
How can genetic polymorphism affect CYP450 enzyme function?
Polymorphism, attributed to genetic variations between individuals, can increase or decrease the efficiency of CYP450 enzymes.
What are the top three CYP450 enzymes responsible for most drug metabolism?
- CYP3A4 = 36%
- CYP2D6 = 19%
- CYP2C9 = 16%
Which type of CYP450 enzyme activity can lead to increased serum concentration of a drug?
A. Inhibitors
B. Reducers
C. Enhancers
D. Inducers
A. Inhibitors.
Inhibitors of CYP450 enzymes may decrease their metabolic activity. This can lead to increased serum drug concentrations.