Absorption Of Drugs Flashcards
Between the stomach and the intestines, which one has a greater blood flow to it?
Intestines
Would severe diarrhea increase or reduce absorption of a drug?
Reduce b/c it doesn’t have as long in the body
If transport of a drug is delayed out of the stomach, such as sympathetic input (exercise or stress) or the presence of food in the stomach, will absorption be increased or decreased?
It will be decreased
What is the bioavailabilty of a drug?
The fraction (F) of the administered dose that reaches the systemic circulation
The fraction of the administered dose of a drug that reaches the systemic circulation
Bioavailability of a drug
Drugs that are give by IV have an F (bioavailabilty) of what?
100% = 1.0
If F=0.8, what is the percent bioavailability, and can you rule out a route of administration?
80%
-not IV (this would have been 100% = 1.0)
What are some factors that influence bioavailability?
- first-pass hepatic metabolism (dec F)
- solubility of drug (hydrophilic drugs have lower F)
- chemical instability (penicillin G, insulin)
Equation for finding bioavailability
Bioavailability (F) = ((AUC oral)/(AUC injected)) x 100
*AUC = area under curve
What is the standard route of administration when you are measuring bioavailability?
IV
When looking at the plasma level curves, what is the lag time?
Time from administration to appearance in blood
Swallow pill; sit in stomach before 1st molecule makes it into the blood
When looking at the plasma level curves, what is the onset of activity?
Time for administration to reach MEC (minimum effective concentration)
(Time 0 to MEC = when drug starts working)
When looking at the plasma level curves, what is the duration of action?
Time plasma concentration remains above MEC (minimum effective concentration)
(How long the drug works)
If a patient has renal dysfunction, what will happen to the duration of action of a drug in the plasma?
It will increase the duration of action because less is getting eliminated from the body
-give pt lower dose so they don’t reach toxicity
Taking tums can affect how drugs work that you take after eating the tums. Explain why.
Tums increases the pH of the stomach (makes it more basic); some drugs need more of an acidic environment to absorb into, and if this environment is too basic, they will be eliminated instead.
