Exam 3 Flashcards
Clearance in the liver is sensitive to
high extraction ratio drugs
Changes in blood flow
Normal value for glomerular filtration rate
120-125 mL/min
Clearances of drugs and extraction ratios depend upon:
Organ perfusion
Plasma protein binding
Inherent characteristics within the cells
Normal renal arterial blood pressure
~100 mm Hg
Cells of the tubular epithelium remove certain molecules and ions (Such as______) from blood and secrete them into the filtrate within the tubules
(H+ and K+)
Elimination in the liver becomes __
Low extraction rate drugs
Rate-limited at a step other than perfusion-
Usually metabolism
Carries blood from general circulation to liver
Hepatic artery
Most common and most important phase II reaction
Glucuronidation and sulfate conjugation
afferent arterioles
blood into the glomerular part of the nephron, Bowman’s capsule
Heme-containing oxidative enzymes
Cytochromes P450
Ideal body weight calculation
Males=50kg+(2.3* inches more than 5ft)
Females= 45.5 kg + (2.3*inches more than 5ft)
Insensitivity or decreased sensitivity of cells to drugs that ordinarily cause growth inhibition or cell death
Drug resistance
Because tubules are very long
a lot of water reabsorbed
Carries nutrients to the liver, accounts for 75% of blood flow to the liver
Portal vein
pH of urine
variable, 4.5 – 8
Drugs that may require carrier-mediated transport and specific transporters for liver drug transport
Polar or ionized drugs
_____ transporters → broad substrate specificity; will bind many ionized drugs
Tubular
Main mechanism of reabsorption
passive transcellular diffusion through the epithelial membrane of tubules
Adjusted body weight calculation
IBW+[(actual body weight-IBW)x0.4]
The region between the sinusoids and hepatocytes
Space of Disse
By-products of P450 reactions
Reactive oxygen species (ROS)
The cycle in which the drug is absorbed, excreted into the bile, and reabsorbed
Enterohepatic circulation
Number of P450s encoded in human genome
57
Renal clearance corrected for plasma protein binding
Extraction ratio
~ 175nm in diameter, 6-8% sinusoidal surface area, no basal lamina→ free passage of large molecules, explains the metabolism of tightly protein-bound xenobiotics
Sinusoidal junctions
Are protein bounds drugs filtered?
No, Protein-bound drugs are not filtered
Drugs excreted mainly m bile have MW
> 500
Renal blood pressure fall to _______ in glomerulus
~45-60 mm Hg
Secretion involves _______, since these solutes more concentrated in the filtrate than in plasma
active transport
Glomerular filtration rate (GFR)
the volume of blood filtered by the kidneys per minute is ~125 ml/min, or ~20% of the RPF
Total ability of the liver to metabolize a drug in the absence of flow limitation
Intrinsic clearance
Kidneys receive ~ ____ L of blood per minute
1.2
Schwartz equation
Children
CrCl (mL/min) = (height in cm) x (0.413) / SCr
Phagocytes tissue macrophages- engulf old red blood cells and foreign material
Kupffer cells
As filtrate moves to the collecting tubule, it is progressively _________ in solutes as a results of reabsorption of water
Concentrated
Renal blood flow (RBF)
volume of blood flowing through the renal vasculature per unit time:
~1.2 L/min or 1700 L/day
Because filtration is driven by hydrostatic pressure, the concentration of a drug (or metabolite) in the filtrate is the _____ as in plasma
same
Class of P450s that metabolize endogenous compounds: cholesterol and bile acids, steroids, prostaglandins, vitamins AandD, eicosanoids
Class 1
Liver lobes secrete
Bile acids
Drugs excreted in expelled air
Sulfanilamide, sulfapyridine
Clearance ratio =1
Drug is filtered only
During __________, drug is progressively removed from the bloodstream and tissues, and thus from the site of action
Elimination
Drug that may stimulate biliary excretion
Phenobarbital
Cells become resistant to drugs with different structures and mechanisms
Multiple drug resistance
4 phase II reactions
Glucuronide conjugation
Peptide conjunction
Methylation
Acetylation
Vegetable and fruit diets, including citrus fruits (high amounts of alkaline minerals: K, Ca, Mg) →
Higher pH
- Removes waste products from blood
- Returns water and other essential substances back to blood
- Removes normal components of blood present at greater than normal concentrations – excess water, Na+, Ca2+, etc.
- When concentration of normal components lower than normal – reclamation increases
Role of Urine
Diets rich in protein: meat, fish, poultry and dairy products (rich in choline, P and S), also grains and cereals →
Lower pH
GFR controlled is by
Hydrostatic pressure
Consequence of the interaction of the drug, the individual, and the environment
Drug dependence
Cenobitic metabolizing P450 class
Class 2
Formed by P450 oxidation of various compounds, such as PAHs
Epoxides