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PHARM3 > Nephrology and dosing-final > Flashcards

Nephrology and dosing-final Flashcards

1
Q

What are the excretory fxns of the kidney?

A
  • making urine
  • regulating electrolytes
  • regulating osmolarity and water balance
  • acid-base balance
  • metabolite and waste elimination
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2
Q

What are the endocrine actions of the kidney?

A
  • Secretion of renin
  • Production and secretion of eythropoietin
  • Production and metabolism of prostaglandins and kinins
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3
Q

What does RAAS do?

A
  • Maintains intraglomerular pressure
  • Maintains systemic blood pressure
  • Regulates sodium excretion
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4
Q

What are the metabolic fxns of the kidney?

A
  • Activation of Vitamin D
  • Gluconeogensis
  • Metabolism
    * Insulin
    * Steroids
    * Xenobiotics
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5
Q

True or false; the kidneys have an effect on blood pressure, RBC production, and bone health?

A

True

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6
Q

What is the best overall index of kidney fxn?

A

GFR

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7
Q

What is GRF?

A

The volume of plasma filtered across the glomerulus per unit time
Represents sum total filtration rates of all functional nephrons in both kidneys

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8
Q

What is normal GFR in an adult?

A

> 90ml/min

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9
Q

What is the criteria for an ideal marker for GFR estimation?

A

•Stable plasma concentration
•Freely filtered = freely diffuses across the glomerulus and into Bowman’s capsule
•Not reabsorbed, secreted, synthesized, or metabolized by the kidney
Does not alter renal function

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10
Q

What is clearance?

A

volume of plasma “cleared” of a marker per unit time (mL/min)

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11
Q

What is the GOLD STANDARD for measuring GFR?

A

Inulin clearance ….inulin is a substance that is a small, inert polysaccharide molecule that readily passes through the glomeruli into the urine without being reabsorbed by the renal tubules.

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12
Q

Why is inulin gold standard?

A

•Distributed only in extracellular fluid
•Not bound to plasma proteins or tissues
•Easily passes through glomerular pores (freely filtered)
•Not secreted, reabsorbed, or metabolized in renal tubules
•No nonrenal elimination
HIGHLY ACCURATE

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13
Q

Why is inulin clearance not used often?

A

•Procedure highly complicated
Requires continuous IV infusion
Collection of series of blood and urine samples
Need reliable assay to measure inulin in samples
•$$$$
•→ NOT convenient for clinical practice

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14
Q

What is an accepted alternative to inulin clearance?

A

CrCl

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15
Q

What is normal CrCL?

A

100-120 ml/min

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16
Q

What is creatinine?

A

Product of creatine metabolism from muscle and dietary meat intake (endogenous molecule)

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17
Q

What is production and release of creatinine related to?

A
  • Production and release related to age, sex, & muscle mass

* Released at relatively constant rate

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18
Q

Where is creatinine filtered?

A

Freely filtered at the glomerulus and not reabsorbed or metabolized by the kidneys

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19
Q

What is the relationship of creatning to GFR?

A

Creatinine concentration increases proportionally to GFR decrease

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20
Q

What are some limitations of using SrCr as GFR marker?

A
  • Delayed SCr increase in early renal disease and acute renal failure
  • Compounds can interfere with SCr secretion (cimetidine (OTC), trimethoprim)
  • Compounds can interfere with SCr plasma assay (cephalosporins
  • variability with fluid status, age, gender, muscle mass, and diet
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21
Q

What is the Cockcroft gault equation used for?

A
  • Estimate renal function in adults… used to dose adjust drugs
  • Uses SCr to estimate CrCl (approximates GFR)
  • Accounts for ↑SCr with ↑weight, and ↓SCr with ↑age
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22
Q

What is the Cockcroft gault equation?

A

CrCl = (140-age)ABW / 72xSrCr X 0.85 if female

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23
Q

What body weight should be used for obese pts?

A

Ideal body weight if actual is >30% above ideal

24
Q

What wt should be used in underwt patients?

A

If actual body wt is

25
Q

What are limitations of 24hr CrCl?

A

•Inconvenient
•↓ accuracy with incorrect sample collection and storage
Shorter collection times tend to be less accurate

26
Q

What is the normal range for BUN?

A

10-20 mg/dl

27
Q

Why is BUN less useful than SCR?

A

BUN changes independently of GFR

28
Q

What factors affect BUN but NOT renal fxn?

A
  • Dehydration/hypovolemia (↑)
  • Hypervolemia (↓)
  • High protein diet (↑)
  • Catabolism (↓)
    * Febrile illness
    * Steroids
  • Liver disease (↓)
  • Decreased cardiac output (↑)
29
Q

What are causes of red-brown urine?

A
  • Hematuria, myoglobinuria, hemoglobinuria
  • Drugs: nitrofurantoin, metronidazole
  • Food: beets, rhubarb
30
Q

What are causes of orange urine?

A
  • Drugs: phenazopyridine, rifampin

* Food: Carrots

31
Q

What are causes of blue green urine?

A

Drugs: methylene blue, propofol, amitriptyline

32
Q

If RBC are found in microscopic UA, what could it indicate?

A

Glomerular damage, kidney trauma, UTI

33
Q

If WBC are found in microscopic UA, what could it indicate?

A
  • UTI, pyelonephritis

* Acute interstitial nephritis (eosinophiluria)

34
Q

If renal tubular or epithelial cells are found in microscopic UA, what could they indicate?

A

Tubular damage

35
Q

If squamous cells are found in microscopic UA, what could they indicate?

A

Lower genital tract

skin contamination

36
Q

If casts are found in microscopic UA, what could they indicate?

A

•cylindrical bodies composed of proteins and/or cells
•Indicates various types renal injury
Types: hyaline, RBC, WBC, granular, waxy

37
Q

If crystals are found in microscopic UA, what could they indicate?

A
  • Oxalate, phosphate

* Drugs: indinavir, acyclovir

38
Q

What are some reasons the pH of urine would be >8?

A

Aged urine, systemic alkalosis, UTI

39
Q

What are some reasons the pH of urine would be

A

Metabolic acidosis

Large amount of dietary meat intake

40
Q

What does specific gravity measure?

A

Urine concentrating ability of the kidneys

41
Q

What is protein in the urine?

A

Marker of kidney damage

42
Q

Why might there be glucose in the kidneys?

A

Uncontrolled DM

43
Q

What do ketones in the urine indicate?

A

Diabetic ketoacidosis

Fasting or starvation

44
Q

What are the pharmacokinetic changes in CKD?

A

Absorption
Distribution
Metabolism
Elimination

45
Q

What are changes in distribution related too?

A

Protein and tissue binding alterations

Vd changes

46
Q

What is elimination dependent on?

A

Amount of drug normally excreted unchanged in urine

Degree of renal impairment

47
Q

What drugs have accumulation d/t there renally excreted metabolites? What are there toxic or therapeutic effects?

A 
Morphine → morphine-6-glucuronide
            Prolonged analgesia, sedation, respiratory depression
Meperidine → normeperidine
          Seizures
Propoxyphene → norpropoxyphene
           Cardiotoxicity
Sulfadiazine → acetylsulfadiazine
        Crystaluria, nephrolithiasis
48
Q

What is likely to develop in a pt with renal impairment if they receive lorazepam IV?

A

Propylene glycol toxicity

lactic acidosis, hyperosmolality, hypotension during administration of higher than recommended doses

49
Q

What is Cockcroft-Gault equation used for?

A

To estimate CrCl

50
Q

When is the MDRD equation used?

A

To estimate GFR- used to ID and stage chronic kidney dz

51
Q

What are advantages of reducing each dose while maintaining normal dosing intervals?

A

Provides sustained serum concentrations

Desirable for antibiotics with time dependent bactericidal activity

52
Q

What are disadvantages of reducing each dose while maintaining normal dosing intervals?

A

Lower peaks
Higher troughs
May require unusual dosages
Associated with a higher risk of toxicities if the dosing interval is inadequate to allow for drug elimination

53
Q

What is an extended interval?

A

Normal doses are maintained, but the dosing interval is lengthened to allow time for drug elimination before re- dosing.

54
Q

What are advantages to extended interval dosing?

A

Similar peak and trough concentrations to those achieved in normal renal function
Ideal for antibiotics with concentration dependent bactericidal activity
Less pharmacy/nursing time

55
Q

What are disadvantages to extended interval dosing?

A

Interval may be “impractical” (every 90 hours)
Associated with a lower risk of toxicities but a higher risk of subtherapeutic drug concentrations, especially toward the end of the dosing interval.

56
Q

What are exceptions to the general hemodialysis dosing rule? Why are they exceptions?

A

Erythropoetin
Darbepoetin
These drugs too large to fit through dialyzer

PHARM3 (16 decks)

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