2934092
Description
Flashcards by jenny schneider, updated more than 1 year ago
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Created by jenny schneider
over 9 years ago
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| Question | Answer |
| renal drug elimination what are the three processes involved in renal elimination- renal clearance is the net of these three processes | filtration, active secretion reabsorption |
| If fraction of drug excreted unchanged is 0.3 and total CL of drug is 9L/h and drug is only eliminated by renal excretion and hepatic metabolism, what is the renal clearance of the drug? | fe x CL= 0.3 x 9=2.7L/h |
| Which of the following beta blockers is cleared solely by renal elimination? atenolol propranolol metoprolo | atenolol is really excreted, the rest undergo extensive hepatic metabolism |
| True or False: the pharmacokinetics of a drug that is mainly eliminated by renal excretion will not be affected by renal failure | False |
| True or False: morphine is metabolised to glucuronide metabolites (M6G and M3G) which are really excreted. In renal failure, these accumulate in the body and can lead to signs of opioid toxicity | TRUE |
| Blood passes through kidney and is filtered at the glomerulus. What are factors that will govern the ability of drug to be filtered off (diffuse through glomerulus)? | MW cardiac output glomerular integrity renal plasma flow degree of protein binding drug volume of distribution |
| True or False It is only unbound drug that can be filtered off st the glomerulus | True |
| What is active secretion, what is involved and where does it generally occur in kidney? | drug is actively secreted from blood into renal tubule via transporters. There are anionic transporters (acids) and cationic transporters for bases. These are mainly in the proximal tubule |
| What are two important consequences of active secretion being present? | drug-drug interactions saturable kinetics (can saturate the active secretion mechanism) |
| Which type of active secretion transporter does probenecid interact with | anionic (acid) transporter |
| which type of transporter does cimetidine interact with | cation transporter (basic drug transporter) |
| what will happen to the blood levels of penicillin ( weak acid) if it is co-administered with probenecid? | blood levels of penicillin will increase as the probenecid competes for the active secretion transporters and reduces the amount of penicillin that can be secreted into the tubules |
| Drug in the urine in the tubules can undergo passive reabsorption. What are two factors that can influence the extent of reabsorption that occurs | urine pH is drug is ionisable; only unionised drug can cross tubule membrane and get back into systemic blood urine flow rate- if urine flow is large, there will be more dilute solution (and as it is a passive process, crossing membrane is driven by concentration gradient- driving force will therefore be low)- also rate - urine will be excreted faster so less chance for reabsorption to occur |
| A drug has a total CL of 10L/h. The fraction excreted unchanged is 0.4. GFR=7L/h and the fraction unbound of the drug is 0.2. Does this drug undergo significant active secretion or significant reabsorption? | CLR=fe.CL=0.4 x10=4L/h If drug was only filtered off with no secretion or reabsorption then CLR=fu.GFR=0.2 x 7L/h=1.4L/h Since CLR=4L/h and only filtration would be 1.4L/h then drug does undergo active secretion |
| A drug has a Vd of 20L and k=0.4 per h. fe=0.6 and fu=0.5. GFR is 7L/h. Does this drug undergo significant active secretion or reabsorption? | CL=kVd so total CL= 8L/h CLR=fe.CL so CLR=0.6 x 8=4.8L/h If only filtration CLR would be fu.GFR=0.5 x7=3.5L/h since CLR is greater than fu.GFR then significant active secretion is occurring |
| A drug has a total CL of 5L/h. It has a fu=0.2 and fe=0.1. If GFR=7L/h, does this drug undergo significant active secretion or reabsorption? | CLR=fe.CL=0.1 x 5=0.5L/h if only filtration =fu.GFR=0.2 x7=1.4L/h Since CLR <fu.GFR there must be significant reabsorption occurring |
| If we administer a 600mg IV dose to a patient and we collect all urine to ensure we collect all drug that is going to be excreted and amount excreted = 300mg, what is fe? | fe= (amt excreted)/drug reaching systemic circulation fe=300/600=0.5 |
| If we administer 600mg of drug orally and F=0.5 and we collect urine and find that 150mg is excreted in urine, what is fe for this drug? | fe=amt in urine/amt in systemic circulation= 150/(0.5 x 600)=0.5 |
| Creatinine clearance can be estimated using cockcroft gault equation. what are some limitations of this method? | cannot accurately predict CrCL in: patients with unstable renal function cachectic (wasted) patients amputees |
| Which of the following drugs is most likely to be affected to the greatest extent by renal disease? drug A fe=0.5 drug B fe=0.8 drug C fe=0.1 | drug B as fe=0.8 (the renal route is major route of elimination). Drug C will be affected the least as only 10% is excreted unchanged |
| In the Tozer equation which can be used to determine dose in renal dysfunction: dose fail=dose normal (1-fe(1-KF)) what does KF stand for? | KF is the kideny function of the patient compared to normal kidney function eg if CrCl normal is 120mL/min and patient has CrCl of 60mL/min then KF=0.5 |
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