Changes in drug pharmacokinetics and pharmacodynamics in patients with renal faliure

Question 1

how does renal failure affect phK

Answer 1

affects drug distribution

affects drug clearance

Question 2

how does renal failure affect drug distribution

Answer 2

severe azotemia causes an increase in free fraction drugs unbound to plasma proteins increasing distribution
(phenytoin)

oedema increases the volume of distribution of water sol drugs
(methotrexate)

Question 3

drugs predominantly affected by impaired clearance in RF

Answer 3

WATER sol drugs
methotrexate
water sol bb

drugs with narrow therapeutic ratio

aminoglycosides

Question 4

drugs causing hyperkalemia in renal failure

Answer 4

potassium containing drugs
potassium sparing diuretics
ace inhibitors

Question 5

why is methotrexate contraindicated in renal failure

Answer 5

adr of methotrexate has causal relationship with duration of action instead of peak conc

thus impaired clearance increases risk of ADR

Question 6

drugs causing renal toxicity

Answer 6

aminoglycosides
-tubular necrosis

methicillin- interstitial nephritis

Question 7

effect of NSAIDS on kidney

Answer 7

retention of water by sodium resorption by inhibi prostaglandin

Question 8

effect of lithium salt on kidneys

Answer 8

nephrogenic db insipidus

Question 9

therapeutic approaches to drug admin in renal failure

Answer 9

prolong dose interval in type 1 antibiotics

reduce dose in drugs w/ narrow therapeutic window

• digoxin
• antiarrythmics

use drugs w/ hepatic excretion

avoid drugs w/ dual routes of elim

avoid poly therapy