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77 Cards in this Set

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The amount of drug excreted by any process per unit time depends on these 2 things
1. Rate of elimination for that process

2. concentration of drug in plasma
A drug with a large Vd (volume of distribution) will be eliminated more slowly or more quickly than a drug with a lower volume of distribution?
More slowly
Drugs with a MW < _____ are COMPLETELY filtered when passing through the glomerulus
5000
What are the only forms of drugs that are filtered in the Kidney?
Free, unbound
Drugs with a MW of ______-_____ are PARTIALLY FILTERED when passing through the glomerulus
5000-100,000
Drugs not protein bound or not reabsorbed after being filtered are eliminated at a rate approximately equal to?
Creatinine clearance = 125 ml/min
T or F: Both IONIZED and NONIONIZED forms of a drug are filtered in the Kidney
TRUE
What are the 3 processes in the kidney in clearance?
1. Filtration
2. Tubular secretion
3. Reabsorption
Creatinine clearance changes depending on what?
Body mass
Which form of drugs can undergo ACTIVE SECRETION and ACTIVE or PASSIVE REABSORPTION?
Non-ionized
Mechanism by which tubular secretion in the Kidney occurs and where its located
TRANSPORT mechanism located in the MIDDLE SEGMENT of the PROXIMAL CONVULOTED TUBULE
What are the two transport systems in Tubular Secretion?
1. Anionic = weak organic acids

2. Cationic = weak organic bases and quaternary ammoniums
Rapid process: drugs eliminated by Tubular Secretion and NOT reabsorbed (penicillin) are cleared at a rate approaching ______ flow = _____ ml/min
Renal Plasma flow

660
An organic acid that is actively secreted and is used to measure renal plasma flow
p-aminohippurate (PAH)
What drug inhibits penicillin secretion in the kidney?
Probenicid
T or F: Tubular secretion is not a saturable process
False -> transporters are the site of interactions
Molecule used to measure anion secretion
PAH = p-aminohippurate
Molecule used to measure cationic secretion rate
N-methylnicotinamide
7 Acids (anionic) that are tubular secreted
1. PAH
2. Penicillins
3. Cephalosporins
4. Salicylates
5. Thiazide diuretics
6. Glucuronide conjugates
7. Uric Acid

PPG-CUTS
8 bases (cations) that are tubular secreted
1. N-methylnicotinamide
2. Procaine
3. Quinine
4. TetramethylammonIUM
5. TetraethylammonIUM
6. HexamethonIUM
7. Neostigmine
8. Pyridostigmine

QUIN, the NEW SMOKING PRO PYRAMID has 3 AMMONIUMs
Compound that is actively secreted and actively reabsorbed
Uric Acid
Type of drugs that can be reabsorbed in the Kidney
Lipid soluble drugs (nonionized) = have relatively longer 1/2 lives
What could be added to urine to increase the renal excretion of Weak Acids by "ion-trapping"?
1. Sodium bicarbonate (NaHCO3)= base

2. Acetazolamide
3 Weak acidic drugs whose excretion can be increased by "ion-trapping"
Phenobarbital
Methotrexate
Aspirin
What could be added to urine to increase the renal excretion of Weak Bases by "ion-trapping"?
Ammonium Chloride (NH4Cl) = acid
2 weak basic drugs whose excretion can be increased by "ion-trapping"
Amphetamine

Phencyclidine
Drugs secreted into bile are not always excreted but often go through this cycle
Enterohepatic
T or F: Drugs that enter the Enterohepatic cycle often have long half-lives
True
T or F: Smaller compounds are secreted into bile
False -> larger compounds MW > 325 are secreted into bile
Some glucuronides that are secreted into the bile are cleaved by glucuronidases in the Small Intestine. What does this allow for?
It releases the parent compound for re-absorption
What are 2 agents that bind drugs in the intestine that enhance excretion?
1. Charcoal

2. Cholestyramine

*they are Glucuronidase binding agents = inhibits the cleavage of Gluronides from the Parent Compound and enhances excretion
Does Enterohepatic Circulation of drugs increase or decrease the Apparent Volume of Distribution?
Increase
What do these 5 drugs have in common?

1. bile acids
2. Bilirubin glucuronide
3. Sulphobromphthalein
4. Penicillins
5. Glucuronide conjugates
ANIONIC drugs that are present in BILIARY secretions
List 2 Neutral molecules/drugs that are involved in Biliary secretion
Steroids

Ouabain
List 2 Cationic molecules/drugs involved in Biliary Secretion
N-methynicotinamide

Tubocurarine
In general, small glucuronide conjugates = _______ secretion
urinary
In general, large glucuronide conjugates = _______ secretion
Biliary
The lungs are most important for the excretion of this group of drugs
Gaseous Anesthetics
T or F: The walls of the stomach and intestine constitute a large lipid membrane across which lipid drugs can be transferred from blood to lumen
True
In zero-order kinetics using the log scale, is the slope straight or curved?
Curved

*Arithmetic scale = straight
In first-order kinetics using the log scale, is the slope straight or curved?
Straight

Arithmetic = curved
What is rate limiting in Zero-order kinetics
The biological system = enzymes or transporters are saturable
In Zero-order kinetics, the rate is independent of _________
drug concentration
Explain the rate in Zero-order kinetics
A constant amount of drug is eliminated per unit time

Example: 10 mg eliminated every hour
-40->30->20->10->0
-4 hours to be eliminated
What drug/chemical always follows Zero-order kinetics?
Ethanol
In zero-order kinetics, the pseudo half-life is proportional to what?
the dose
Name 2 drugs that, as you increase the dose there is a switch from 1st order to zero-order kinetics = Dose-dependent pharmacokinetics
Phenytoin
Salicylates

*due to saturation of elimination mechanisms
First-order kinetics is proportional to what?
Concentration of the drug

*the higher the amount, the more rapid the elimination
What is rate-limiting in First-Order kinetics?
Drug concentration
In First-order Kinetics, drug concentration changes by some _______ per unit of time
constant fraction eliminated (i.e. 0.1/h)
What is constant in First-order kinetics?
Half-life
Is First-order kinetics Dose-dependent or Dose-independent?
Independent
Rate constant equation equals = ?
-
Half-life equation
-
Equation for the Amount of Drug in the body
-
Properties of the Log Scale in the One Compartment Kinetic Model (3)
1. Straight Lines
2. Parallel lines
3. Rapid equilibrium between plasma and tissues
Properties of the Log Scale in the Multicompartment Kinetic Model
1. Multiphasic Curves
2. Un-parallel lines
3. Slow equilibrium between plasma and tissues
What is the alpha phase in Multicompartment kinetics
Distribution
What is the beta phase in the Multicompartment kinetic model?
Elimination
When is the Multicompartment Kinetic model common?
Drugs with high avidity for tissues
Definition of Clearance
Apparent volume from which a drug is COMPLETELY CLEARED per unit time (mL/min)
Clearance = ?
Rate of elimination from the body / plasma concentration
What is Clearance independent of?
Concentration and Dose
How is Clearance calculated?
-
Clearance approaches _____blood flow for very rapidly metabolized drugs = ____ mL/min
Liver

1500
Clearance approaches ______ blood flow for drugs SECRETED by the renal tubule = _____ mL/min
Renal

660
Clearance approaches ________ rate for drugs eliminated by filtration = _____ mL/min
Glomerular

123-130
The Elimination Rate Constant (K-el) depends on these 2 UNRELATED physiological variables
1. Plasma clearance (Cl-b)

2. Apparent Volumes of Distribution (Vd)
Plasma Clearance equation
Kel = Elimination Constant
The extent to which the drug reversibly leaves the circulation and enters the tissues of the body
Apparent Volumes of Distribution
The ability of the organs of elimination to extract the drug from the general circulation and remove it from the body
Plasma Clearance
Renal Clearance equation for SECRETION
Clearance = (urine flow) X (Concentration of drug in urine/Concentration of drug in plasma)
Renal Clearance equation for Glomerular Filtration
Clearance = Urine flow X (conc. of drug in urine / conc. of free drug in plasma)

***only FREE drug is filtered***
Relative amount of administered drug that reaches the general circulation
Bioavailability

*IV doses have 100% bioavailability
What scale is used for AUC?
Arithmetic
What does AUC represent?
total amount of drug available over time
Bioavailability equation
-