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Pharm II Unit II > Diuretics > Flashcards

Diuretics Flashcards

1
Q

Conditions that promote the development of edema

A

Altered blood circulation (inc arterial or venous pressure)

Altered blood composition (dec osmotic gradient, salt and water retention)

Inadequate lymphatic drainage

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2
Q

Diseases often associated with edema

A

HF

Hepatic cirrhosis

Nephritis, nephrosis, renal damage due to HTN

Diseases involving increased steroid hormone secretion

Pre-eclampsia, toxemia

Hypersensitivity reactions (anaphylaxis)

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3
Q

_____% of all fluid filtered by the glomerulus is reabsorbed

A

> 99%

Anything <43kD is filtered

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4
Q

_____% of Na+ is reabsorbed in the proximal tubule

A

65%

H+ and Na+ via active transport - NaK ATPase

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5
Q

What diuretics work in the proximal tubule?

A

Acetazolamide (diamox)

Osmotic diuretics

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6
Q

What occurs in the loop of Henle?

A

Passive H2O reabsorption —> concentration of urine

NOTE - the loop of Henle is thinner b/c this portions need lots of mitochondria to produce energy for ACTIVE transport

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7
Q

What diuretics work on the loop of Henle?

A

Osmotic diuretics

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8
Q

What exchanges occur in the thick ascending limb of LOH?

A

Active reabsorption of K+, 2Cl-, Na+

Passive reabsorption of K+, Ca2+, Mg2+, Na+

25% of Na+ is reabsorbed here, but no H2O

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9
Q

What diuretics work on the thick ascending limb of LOH?

A

LOOP diuretics

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10
Q

What occurs in the early distal tubule?

A

Reabsorption of NaCl (not H2O) by active transport

4-8% of total Na+ reabsorption occurs here

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11
Q

What diuretics work in the early distal tubule?

A

Thiazides

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12
Q

What occurs in the late distal tubule?

A

Ca2+ reabsorption

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13
Q

What occurs in the collecting duct?

A

K+ and H+ excretion (via Na+/K+ and Na+/H+ exchange)

NaCl reabsorption by aldosterone

H2O reabsorption by ADH

Some K+ and H+ independent of aldosterone

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14
Q

What diuretics work on the collecting duct?

A

Aldosterone antagonists (by inhibiting NaCl reabsorption)

ADH antagonists (by inhibiting H2O reabsorption)

Osmotic diuretics

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15
Q

Where does potassium reabsorption and secretion occur?

A

Reabsorption in proximal tubule (CANNOT be influenced by drugs)

Secretion in late distal tubule and collecting duct
• Exchange of Na+ with K+, with or w/o aldosterone
• Can be modified by aldosterone antagonists and K+ sparing diuretics

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16
Q

What affects reabsorption of Calcium and Magnesium occur?

A

Thiazides diuretics —> increase Ca2+ reabsorption

Loop diuretics —> increased Ca2+ and Mg2+ excretion

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17
Q

The rate of diffusion of organic compounds depends upon…

A

Lipid solubility, pKa, and pH

Weak acids at low pH will remain mostly unionized (lipid soluble) and are easily diffusible across the epithelium and vice-versa

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18
Q

What do we need to know about uric acid?

A

It’s secreted and reabsorbed by carrier dependent mechanisms

ACID DRUGS will compete for uric acid excretion —> gouty attack

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19
Q

What drugs are carbonic anhydrase inhibitors?

A

Acetazolamide (Diamox)
Dorzolamide (Truspot)
Brinzolamide (Azopt)

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20
Q

MOA for carbonic anhydrase inhibitors

A

Inhibits carbonic anhydrase enzyme

Blocks H2CO3 production

Decreases H+ for exchange with Na+, resulting in increased Na+ and H2O loss

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21
Q

What are the indications for carbonic anhydrase inhibitors?

A

GLAUCOMA (that’s why two of the drugs are eye drops) —> inhibition of bicarbonate transport in the eye and the chorionic plexus —> decreased aqueous humor and CSF

Alkalinization of the urine

Metabolic ALKALOSIS due to acute mountain sickness

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22
Q

Why are CA inhibitors not used as a regular diuretic?

A

Their effectiveness decreases after several days b/c metabolism —> build up of H+

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23
Q

Adverse effects of CA inhibitors

A

HYPERCHLOREMIC METABOLIC ACIDOSIS b/c the Na+ is in the form of NaHCO3 and not NaCl

Hypokalemia (b/c inc Na+ in lumen —> inc Na+/K+ exchange in DCT)

Renal stones (b/c inc PO4 and Ca2+ in urine)

HYPERURICEMIA b/c they are acids and compete for uric acid excretion

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24
Q

Contraindications for CA inhibitors

A

Hepatic cirrhosis (from dec ammonia excretion)

Sulfa hypersensitivity

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25
Q

What drugs are Loop Diuretics?

A

Furosemide (Lasix)
Bumetanide
Torsemide
Ethacrynic acid

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26
Q

MOA for Loops

A

Block the NaK2Cl co-transporter** —> inc Na+ in lumen =—> diuresis

Induce kidney prostaglandins —> reduced salt transport in kidney and VASODILATION

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27
Q

Loops still work for diuresis in patients with _______ when other diuretics will not

A

Low GFR

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28
Q

Indications for Loops

A

HF (b/c they move large amounts of water)

PULMONARY EDEMA - relieves pulmonary congestion by increasing systemic venous capacitance

Severe refractory peripheral edema

HYPERCALCEMIA (b/c dec reabsorption of Mg2+ and Ca2+ by reducing K+ gradient)

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29
Q

Pharmacokinetics of loops

A

Oral or parenteral (for faster action)

Renal excretion

30
Q

Adverse effects of Loops

A

High potency —> electrolyte imbalance

HYPOKALEMIC METABOLIC ALKALOSIS (b/c induces K+ and H+ loss at the DCT)

Hypochloremia

HYPOCALCEMIA

HYPOMAGNESESMIA

HYPERURICEMIA

GI upset

IRREVERSIBLE OTOTOXICITY

31
Q

All looks are ototoxic but ______ is the worst

A

Ethacrynic acid

32
Q

Ototoxic effects of loops are worse when given concurrently with…

A

Aminoglycosides

33
Q

Contraindications for Loops

A

SULFA hypersensitivity (EXCEPT ETHACRYNIC ACID)

Drug interactions
• COX inhibitors interfere with its action
• Aminoglycosides (ototoxicity)
• Lithium (loss of Na+ increases Li+ retention —> toxicity)
• Digoxin (loss of K+ —> toxicity)

Overzealous use is dangerous in 
• Hepatic cirrhosis 
• Borderline renal failure
• HF
(We use them still but very carefully)
34
Q

What makes Ethacrynic acid special?

A

MOA the same and adverse effects are similar to Lasix BUT

It’s not a sulfonamide so it can be used in pt with sulfa allergy

It has the highest risk of ototoxicity

35
Q

What drugs are thiazides diuretics?

A

Hydrochlorothiazide***
Chlorothiazide

Related compounds:
Chlorthalidone
Metolazone
Quinethazone
Indapamide
36
Q

Which diuretics are the most widely used?

A

Thiazides

37
Q

MOA for thiazides

A

Inhibition of sodium resorption at the early distal tubule via inhibition of the Na-Cl cotransporter

Effect is dependent on PG synthesis

38
Q

Main clinical indications for thiazides

A

HYPERTENSION

HF (not as effective at reducing edema as loops but can start them on a loop and then switch to HCTZ for maintenance)

Nephrolithiasis

Nephrogenic diabetes insipidus

39
Q

What are the beneficial and adverse effects of the ATP-dependent K+ channels opened by thiazides —> hyperpolarization of cell membranes

A

Beneficial: relaxation of smooth muscle cells —> VASODILATION

Adverse: REDUCED INSULIN SECRETION

40
Q

What are the indications for Thiazides?

A

Lower systemic BP and enhance the anti-HTN action of other drugs (ACE-I, ARBs, ß-blockers)

Decrease Ca2+ excretion by increasing activity of PTH-dependent Ca2+ channels (not b/c of PTH but b/c inc luminal Na+)

NOT effective in osteoporosis

May be beneficial in renal calculosis

41
Q

What’s special about thiazide pharmacokinetics?

A

Oral, well-absorbed

Secreted by the organic acid secreting system —> COMPETES WITH URIC ACID

42
Q

How is Chlorthalidone different from other thiazides?

A

Slowly absorbed, therefore appears to have longer duration

Therefore PREFERRED b/c it has the best pharmacokinetics of the class

43
Q

How is Indapamide different from other thiazides?

A

Excreted by the biliary system, therefore is useful in patients with RENAL INSUFFICIENCY

44
Q

Adverse effects of thiazides

A

Dizziness, weakness, fatigue, leg cramps common

HYPOKALEMIC METABOLIC ALKALOSIS*** b/c of K+ and H+ loss at the DCT

HYPERURICEMIA***

MAGNESIUM LOSS

Iodide and Bromide loss

HYPERGLYCEMIA*** May dec release of insulin and inc glucose intolerance

ELEVATED SERUM LIPID LEVELS

45
Q

Which thiazide is the exception to the rule of thiazides increasing serum lipid levels?

A

Indapamide

46
Q

Contraindications of thiazides

A

SULFA HYPERSENSITIVY (may be inhibited by NSAIDs)

HYPOKALEMIA can precipitate digitalis toxicity (arrhythmias) and hepatic coma in CIRRHOTIC patients

HYPERGLYCEMIA and carb intolerance may occur in DIABETICS

HYPERURICEMIA so don’t give to someone with GOUT

HYPONATREMIA if too hydrated

HYPERCALCEMIA with latent primary HYPERPARATHYROIDISM

LITHIUM TOXICITY b/c Li clearance reduced

47
Q

What is unique about Metolazone

A

Able to produce diuresis in patients with a reduced GFR

Loop diuretics can work at low GFR but most thiazides don’t, except METOLAZONE

48
Q

What is unique about Indapamide?

A

3 major differences from other thiazides:

  1. Causes pronounced vasodilation (Ca2+ channel blocker)
  2. DOES NOT increase plasma lipids**
  3. Metabolized in the liver and kidney 50/50**
49
Q

What are the two classes of potassium sparing diuretics?

A

Aldosterone antagonists

Direct inhibitors of Na+ flux

50
Q

How do potassium sparing diuretics work in general?

A

Interfere with Na+ reabsorption at the distal exchange site —> permits loss of Na+ and H2O and cause conservation of K+

WEAK diuretics compared to thiazides/loops

Reduce K+ loss and alkalosis by other diuretics

Used IN COMBO with other K+ losing drugs

51
Q

MOA for Aldosterone Antagonists

A

Competitive inhibition of aldosterone

High doses —> inhibits glucocorticoid and sex hormone receptors

Aldosterone inhibition promotes the excretion of Na+ and retention of K+ at the DCT
• Less Na+ channels, blocked Na+ conductance, reduced K+ excretion

52
Q

What is the prototype aldosterone antagonist?

A

Spironolactone

53
Q

What are the indication for Spironolactone?

A

Edema associated with HF, cirrhosis, and nephrotic syndrome (in combo)

Most effective drug for treating HYPERALDOSTERONISM

HIRSUTISM (androgen receptor antagonist)

54
Q

Adverse effects of spironolactone

A

GYNECOMASTIA (b/c androgen receptor antagonist)

Occasional HYPERKALEMIA (usually only when in combo)
• Use with caution with ACE/ARBs
55
Q

Contraindications for Spironolactone

A

Hyperkalemia (burn patients)

Chronic renal insufficiency

Liver damage, hyperchloremic acidosis may occur in these patients

56
Q

How is Eplerenone (Inspra) different from Spironolactone?

A

Selective aldosterone receptor antagonist

Has the same effects as Spironolactone except…

Decreased endocrine related side effects (NO MAN BOOBS)

Metabolized by CYP3A4 —> drug interactions

57
Q

What is the MOA for Amiloride and Triamterene?

A

Inhibit the Na+/K+ ion exchange mechanism INDEPENDENT OF ALDOSTERONE by directly inhibiting the aldosterone-sensitive Na+ channel

Leads to a decreased K+ excretion

58
Q

Indications for Amiloride/Triamterene

A

Combo with K+ losing diuretics (weak diuretic effect on their own)

NO HYPERURICEMIA b/c they are not acids*** The only diuretic class that are not

59
Q

DOC for Li+ induced diabetes insipidus

A

Amiloride

60
Q

Adverse effects of potassium sparing diuretics

A

HYPERKALEMIA in chronic use or combo with other potassium sparing agents

61
Q

In whom are potassium sparing diuretics contraindicated

A

Burn patients (b/c prone to hyperkalemia)

62
Q

Examples of Osmotic diuretics

A

Mannitol

Isosorbide

Glycerin

Urea

***All are IV only (give diarrhea if given orally)

63
Q

MOA for osmotic diuretics

A

Keeps water in the tubules

Produce water diuresis (not dependent upon sodium)

64
Q

Indications for Osmotic Diuretics

A

IV ONLY - very specialized use

Prophylaxis for ACUTE RENAL FAILURE

Reduce intraocular pressure prior to eye surgery

Reduce intracranial pressure in pt with brain edema

Protect kidney against nephrotoxic substances

65
Q

Adverse effects of osmotic diuretics

A

HA, N/V***, chills, dizziness, polydipsia, lethargy, confusion, chest pain (basically dehydration symptoms)

Excessive administration —> extracellular volume expansion**

PULMONARY EDEMA IN HF (CONTRAINDICATION)

EXCESSIVE CELLULAR DEHYDRATION

66
Q

Tell me all there is to know about Desmopressin

A

Synthetic ADH

Activates V2»V1 receptors

Used to treat CENTRAL DIABETES INSIPIDUS

Acts to decrease H2O excretion

Can be given Oral, IV, SC, or intranasal

Side fx:
• GI, HA, Allergy, HYPOnatremia

67
Q

What drugs are ADH antagonists?

A

Conivaptan***

Tolvaptan

Demeclocycline (FYI - for SIADH)

Lithium (FY)

68
Q

What’s special about Conivaptan?

A

IV ONLY

Adverse effects:
• HYPOKALEMIA
• Injection site rxn
• Orthostatic hypotension, a fib, hypotension

Contraindications:
Hyponatremia associated with HYPOVOLEMIA

69
Q

How is Tolvaptan different from Conivaptan?

A

Non-peptide V2 vasopressin receptor antagonist

Administered orally

Initiated and re-initiated in a hospital and then continued on an outpatient basis

70
Q

What happens when you combine loops and thiazides?

A

May produce diuresis when none of them is effective alone

71
Q

What happens when you combine potassium sparing diuretics and loops or thiazides?

A

May balance out potassium losses

72
Q

Put the diuretics in order of maximum diuretic effect

A

Loop&raquo_space; thiazides&raquo_space; [CA inhibitors] > K+ sparing

**CA inhibitors only work for a few days

Pharm II Unit II (8 decks)

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