05.12 - Diuretics, Aquaretics (Bahouth) Flashcards
CA Inhibitor
Acetazolamide
___ may be effective in patients w/ impaired renal function when class 1 thiazides are not
Metolazone, Indapamide (class 2 thiazides)
2 main conditions that cause ADH release
Elevation in plasma osmolarity >280; Depletion of ECV
2 Organic Base K-Sparing Diuretics
Triametrene, Amiloride
2 Types of Na Channels in IMCD
(1) CNG: Amiloride-sensitive, cyclic nucleotide gated cation channel; (2) Low-conductance highly-selective Na ENaC channel
3 Clinical uses of Osmotic Diuretics
Intra-cranial pressure, Intra-ocular pressure, Dialysis disequilibrium syndrome
3 Drugs classes associated with SIADH
Psychotropics, Sulfonylureas, Vinca Alkyloids
3 Net Effects of Loop Diuretics
(1) Significant NaCl loss; (2) Increase excretion of K, H; (3) Increase excretion of Ca, Mg
4 Clinical uses of CA inhibitors
Cysteinurea, Intra-ocular pressure, Seizures, Mountain sickness
4 Therapeutic Uses of Loop Diuretics
(1) Edema of cardiac, hepatic, or renal origin; (2) Pulmonary edema; (3) Hypercalcemia; (4) Protect against renal failure
A poor response to Thiazides may reflect
Either an overwhelming load of dietary Na, or impairted renal capacity to excrete Na
Action of ANP
Binds NP receptor-A, activates GC and increases cGMP
Action of BNP
Binds NP receptor-A, activates GC and increases cGMP
Action of CNP
Binds NPR-B in vascular SM cells –> Relaxation
Action of Demeclocycline
Antagonizes ADH at V2R’s
Activation of V1 receptor activates
Gq-PLC-IP3 pathway –> Mobilizes Ca –> Vasoconstriction
Advantages of Torsemide
Also lowers BP; Longer Half Life
Best tolerated drug classes for monotherapy in HTN
Diuretics, ACEi’s
Bindin of ADH to V2 receptor activates
Gs-cAMP, PKA –> Insertion of AP-2, p-lation of urea transporter
Bumetanide vs Furosemide
Bum is 40x more potent
Class 2 Thiazides
Metolazone, Indapamide
Clinical effects of Nesiritide
(1) Increase Na excretion; (2) Useful in CHF
Clinical Uses of Spironolactone
Diuretic in combo with HCTZ; CHF, Cirrhosis
Clinical Uses of Triametrene, Amiloride
Combined with HCTZ to decrease K excretion
Common preventable cause of diuretic resistance
Co-administration of NSAID with Loop
Concentration of urine in Mannitol use
Hypoosmotic (losing free water)
DDAVP is also used in
Bleeding disorders, Nocturnal Enurisis
Desmopressin
Highly selective V2R agonist
Difference between Loop and Osmotic
Loop have high [Na] in urine
Diuretic of choice in Cirrhosis
Spironolactone
Diuretic to use in Chronic Renal Failure
Loop
Diuretic to use in Mild CHF
Thiazide, Loop
Diuretic to use in Moderate or Severe CHF
Loop
Diuretic to use in Nephrotic Syndrome
Loop
Do PG’s increase or decrease with Loop Diuretics?
Increase
Drug interactions of Furosemide
Li, Indomethacin, Probenecid, Warfarin
Effect of ADH on urea transport
V2 –> PKA p-lates urea transporter –> inc. permeability of CD to urea
Effect of Furosemide on K, H, Ca, Mg
Increases secretion of all
Effect of Furosemide on Renal PG’s and Venous capacitance
Increases both
Effect of Osmotic Diuretics on PCT
Osmotically inhibit Na/H2O reabsorption
Effect of Thiazides on Ca, Mg
Decrease excretion of Ca, Increase secretion of Mg
Effect of Thiazides on Na, K, Cl
Loss of all three –> Hypokalemia
Effect of Triametrene, Amiloride on Na, K, H
Weak excretion of Na; Inhibit secretion of K, H
Eplerenone vs Spironolactone
Lower affinity for AR’s so less side effects
Found in urine, paracrine regulator of Na transport
Urodilantin
Furosemide vs Indomethacin
NSAIDs inhibit PG effect of Furosemide
Furosemide vs Probenecid
Compete for secretion by Organic Acid Transporter
Furosemide vs Warfarin
Compete for protein binding
General MOA Acetazolamide
CA Inhibitor
General MOA Mannitol
Osmotic Diuretic
General MOA of AVP, DDVAP
V2R Agonism, Collecting Duct
General MOA of Conivaptan, Tolvaptan
V2R Antagonism, Collecting Duct
Given in large doses, Osmotic Diuretics
increase osmolarity of plasma
Highly selective V2R agonist
Desmopressin
How are Loop diuretics administered
IV in hypertensive crisis or in Acute Pulmonary Edema
How are Thiazides unlike Loops
Thiazides decrease secretion of Ca
How do Load-Dependent Principal cells work
The more Na is delivered, the more is absorbed in exchange for K secretion
How do Loop Diuretics affect Macula Densa
MD thinks very little Na, so it secretes PG’s –> Increase RBF and FF
How do PG’s affect actions of Loops
Reduce Na re-absorption in distal nephron, antagonize ADH, distribute renal blood from cortex to JG
How does Furosemide reach the luminal symporter
Secreted by Organic Acid Transporter
How does Furosemide travel in blood
Extensively protein bound
How does Hypovolemia lead to Hyponatremia
Hypovolemia stimulates ADH-mediate retention of H20
How does Nesiritide increase Na excretion
Inhibits CNG_nonspecific cation channel in IMCD; Inhibits RAAS
How will V2R agonist affect Central vs Nephrogenic DI
Increase urine osmolarity in central by not nephrogenic
In CHF, Cirrhosis, or Nephrotic Syndrome, hypovolemia is exacerbated by
Diuretics
In what condition is Mannitol contraindicated
CHF
Indications for Vaptans
Significant Hypervolemic and Euvolemic Hyponatremia (including patients with HF, Cirrhosis, SIADH)
Inhibiting CA results in loss of what in urine
Bicarbonate
K-Sparing Diuretics are useful in what patients
At risk of K depletion; Hyperuricemia
Late DCT, CD Principal cells are involved in __ re-absorption and __ secretion
Na reabsorption, K secretion
Like Loops, Thiazides require
secretion into tubular fluid to exert effect
Loop Diuretics
Furosemide, Bumetanide, Torsemide
Loop that also lowers BP
Torsemide
MOA of Loop Diuretics
Inhibit Na-K-2Cl symporter in TALH
MOA of Thiazide Diuretics
Inhibit NaCl reabsorption in the Na-K Aldosterone-independent sement of distal tubule
MOA of Triametrene, Amiloride
Inhibit Na re-absorption in late distal tubule (sodium load segment)
MOA of Vaptans
Selective V2R antagonists
Most popular drug for HTN
HCTZ
Most potent class of diuretics in mobilizing NaCl
Loop
Most Thiazides are ineffective when
GFR < 30-40 mL/minute
Net Effect of Aldosterone Antagonists
Increase excretion of Na; Inhibit secretion of K, H
Net effect of Osmotic Diuretics
Significantly increase urine
On which part of nephron do Triametrene, Amiloride act
Late Distal Tubule, Sodium Load segment
On which part of nephron does Furosemide act
TALH
Osmolarity of urine with ADH present
1200
Osmolarity of urine without ADH
50
Osmotic Diuretic
Mannitol
Patients with what type of HTN show better responses to Thiazides
Volume-dependent HTN (low renin)
Pharmacokinetics of Furosemide
Short half-life; Extensively protein-bound
Pharmacokinetics of Vaptans
CYP3
Physiological effects of Aldosterone
NaCl transport enhanced; Increased secretion of K, H+
Retention phenomena of Thiazides
Hyperuricemia, Hypercalcemia
Role of Renin in Loop Diuretic use
Potently increased
Route of Acetazolamide
Oral
Route of HCTZ
Oral
Route of Mannitol
Injection
Selective V2R antagonists
MOA of Vaptans
SIADH Tx:
Water restriction, Loops, Demeclocycline, Vaptans
Side effects of Acetazolamide
Metabolic Acidosis, K loss (hypokalemia)
Side effects of Furosemide
Hypokalemia, Ototoxicity; Elevated BUN, Hyperglycemia, Hyperuricemia
Side effects of Mannitol
Volume overload (don’t use in CHF)
Side effects of Nesiritide are related to
its narrow therapeutic index
Side effects of Spironolactone
Hyperkalemia; AR: Gynecomastia, Hirsutism, Uterine Bleeding
Side effects of Triametrene, Amiloride
Hyperkalemia, Megaloblastic Anemia in cirrhosis
Side effects of Vaptans
Hyperglycemia, GI disturbances, Clotting probs
Sodium loss in Thiazides results in chronic
Reduced GFR
Spironolactone vs Canrenone
Sp is a pro-drug that is extensively metabolized; Can is active metabolite with longer half-life
T/F: Diuretics only reduce mortality from HTN when used with BB’s
False, effective alone or in combo
T/F: Nesiritide reduces mortality in CHF
FALSE
Therapeutic Uses of Thiazides
Edema, Hypercalciurea, Essential HTN, Osteoporosis, Nephrogenic Diabetes Insipidus
Thiazides are widely used to treat
Mild or Moderate HTN
Tx of Central DI
Selective V2R agonists
Tx of Nephrogenic DI
Thiazide Diuretics
Type A Principal cells are regulated by
Hormone: Aldosterone
Type B Principal cells are regulated by
Load dependent
Type of channel in Aldosterone Sensitive Channel
Aldosterone-Sensitive ENaC Channel: Na-K/H
Type of channel in Na-K Aldosterone-independent segment
Na-Cl symporter
Type of Channel in Sodium Load Segment
ENaC Channel: Na-K/H
Type of channels affected by Aldosterone in DCT
Epithelial Sodium Channels (ENaC) are increased
Urine with Acetazolamide use
Alkaline, bicarbonate loss into it
Urodilatin arises from same precursor as
ANP
Use of Loop Diuretics for Non-Pulmonary edema
Oral use in Cardiac, Hepatic, or renal origin edema (GFR<30)
Uses of V1R agonists
Post-op Ileus; Esophageal varices; Acute Hem Gastritis
V2R agonism
Arginine Vasopressin, Desmopressin (DDAVP)
V2R Ant-agonism
Conivaptan, Tolvaptan
What causes acidosis with CA inhibitors
Enhanced chloride reabsorption
What is substituted for Furosemide in patients receiving Warfarin
Bumetanide
When are class 1 Thiazides perferably used
When GFR >50
When are class 2 Thiazides used
More potent, so when GFR<50 but greater than 30
When are K-Sparing Diuretics contraindicated
Significant Renal Insufficiency (GFR<75); Other K-retaining conditions
When are Loop used over Thiazides
Severe Htn unresponsive to Thiazides, especially w/ renal insufficiency, cardiac failure, cirrhosis
Where do CA inhibitors mostly act
Proximal Tubule (90%), Distal (10%)
Where do CNP’s originate
Endothelium and Kidneys
Where do Loop Diuretics act
Inhibit Na-K-2Cl symporter in TALH
Where do Vasopressin and Desmopressin act
Collecting duct, V2R agoism
Where is V1 receptor found
Vascular SM
Where is V2 receptor found
Principal Cells in Renal CD
Which are more potent anti-hypertensives: Thiazides or K-Sparing
Equipotent
Which class of drugs creates largest volume of urine
Osmotic Diuretics
Which is preferred: Terlipressin or 8-arg vasopressin
Terlipressin has less side effects
Which parts of nephron have Aquaporin-1
Proximal Convoluted Tubule, Descending Limb
Which parts of nephron have Aquaporin-2
Collecting Duct
Why are Thiazides only mild diuretics
Act on distal tubule, which only absorbs 5% of Na
Why is Nesiritide useful in CHF
Decreases SVR, Decreases LVP, Increases CO
Wide margin of safety; Dose-response curve influence by renal disease
Furosemide