Excretion Flashcards
What is the definition of renal clearance?
the volume of plasma that is freed of the substance (drug) per unit of time
How do you calculate the renal clearance?
Clr = excretion rate of drug/ [Drug]plasma
= [Drug]urine x F/ [Drug]plasma
What is GFR determined by?
- PAH- the worst way to determine GFR- not accurate
- Creatinine - endogenous product is secreted so it will over estimate the GFR
- Inulin is a naturally occurring polysaccharide. MW of 5000 so it is filtered by the glomerulus and is not secreted and not reabsorbed. This gives a good idea of the GFR and is the most accurate
In the glomerulus, there is _____ of water being filtered, and there is a lot of water being reabsorbed
130 ml/min (this is the GFR)
How can you increase the plasma concentration of the drug?
you can do this by blocking the transporter - probenecid is what blocks the transporter
What occurs when the renal clearance is the same as the GFR?
there is filtration occurring, but nothing is being secreted or absorbed
What occurs when the renal clearance is much higher than the GFR?
The compound will be both filtered and secreted
What occurs when the renal clearance is much lower than the GFR?
it fill be filtered, and will probably be reabsorbed
What generally happens when the clearance rate of the dug is much larger than the bile flow rate itself?
the drug is being secreted- it also uses an ABC transporter that uses energy
- you know that the bile is being actively pumped into the bile cannicula
When the MW of the drug is under 300, it is being excreted in the _____
urine
When the MW of the drug is over 300, it is being excreted in the ____
bile
What is the general rate of bile flow?
05-0.8 ml/min
What can the biliary clearance rate reach up to?
500 ml/min
Why are the microbes in the small intestine important to metabolism?
In the small intestine, there are microbes that are very important to metabolism - allows the drug to get into enterohepatic circulation and eventually be glucuronidated by the liver
What is an example of medication that goes through enterohepatic recirculation and what are the implications of this?
- it is important in BC pills - it allows the concentration of the drug to be low (decreases the risk of SE) because we rely on enterohepatic circulation to deglucuronate medications
Why are there potential problems when on antibiotics and killing off the intestinal bacteria?
- the antibiotics are killing off the intestinal bacteria
- this is an issue because we rely on the intestinal bacteria to deglucuronate the BC pills - this causes the person to excrete the medication unmetabolized in the feces
What is the whole process of enterohepatic circulation?
tablet -> small intestine -> superior mesenteric vein -> portal vein -> liver -> (this is where glucuronidation occurs) -> excreted into the common bile duct and out as feces
What are some other examples of drugs excreted in the bile?
morphine
digoxin
bile acids
steroids
What is the definition of equivalence?
compares one drug product to another
What is the definition of pharmaceutical equivalents?
drug products that contain the same active drug ingredients and are identical in strength or concentration, dosage form and route of administration
What is considered a pharmaceutical alternatives?
drug products that contain the same therapeutic moiety but as different salts, esters or complexes
What is considered a bioequivalent drug product?
are pharmaceutical equivalents that have similar bioavailability when given in the same molar dose and studied using similar experimental conditions
