Qualitative Pharmacokinetics Flashcards Preview

Pharmacology Basic Principles > Qualitative Pharmacokinetics > Flashcards

Flashcards in Qualitative Pharmacokinetics Deck (17):
1

Weak acids and weak bases

Acids can be trapped in basic compartments, bases trapped in acidic. Relates to excretion in urine, breast milk, gut, ect.

2

Bioavailability

The percenta of oral dose that reaches systemic circulation. Decreased bioavailability is compensated for by increasing the oral dose

3

First pass metabolism

Portal circulation brings drugs from intestine first to liver, where it can be altered before it reaches therapeutic targets

4

Volume of distribution - how to calculate

Administer known drug concentration IV, take blood samples at timed intervals, plot concentration on a log graph, extrapolate straight line to time 0.

5

Vd equation

= (amount administered)/(concentration at t=0)

6

Lipid solubility and Vd

High lipid solubility = low plasma concetration = large Vd

7

Binding to plasma protein and Vd

High binding affinity to plasma proteins = trapping of the drug in blood = small Vd

8

Significance of Vd

Apparent volume of plasma that would have yielded the extrapolated concentration. Relates the amount of drug in the body to the concentration in the blood/plasma

9

Vd = 5-10L

highly charged species or bound to plasma protein

10

Vd = 20-40L

Moderately lipid soluble

11

Vd = 40L

Lipid soluble enough to distribute to total body water

12

Vd > 40L

Highly lipid soluble, sequestered in fat, nervous tissue and muscle

13

Hepatic metabolism

Highly lipid soluble drugs will accumulate in hepatocytes and be acted on by CYP450 system. CNS drugs that can cross BBB will be hepatically eliminated

14

Urinary excretion

Hydrophilic xenobiotics eliminated renally, highly polar molecules remain in filtrate unless specifically reabsorbed by carriers and transporters

15

Probenecid

Gout medication. Kidney can normal transport some drugs against the concentration gradient into the urine. Probenecid inhibit tubular secretion of penicillins increasing and prolonging plasma concentrations

16

Passive Renal Tubular Re-absorption

Non-ionized, lipid soluble drugs are take back up into plasma. Higher urine pH favors weak acid excretion to urine

17

Biliary Excretion

Not well understood, can be reabsorbed in intestine leading to enterohepatic cycling. Cholestyramine used to interrupt cycling. Ezetimibe harnesses enterohepatic cycling to decrease LDL blood levels by competing with the reabsorption of cholesterol