Renal Pharmacology Flashcards
(31 cards)
Loop diuretics: Site of action and effectiveness
Ascending loop of Henle
Most effective diuretics
Loop diuretics: Drugs
Furosemide, Torsemide, Bumetanide
Loop diuretics: Mechanism
Inhibits NaCl reabsorption at the thick ascending loop of Henle
- Block Na reabsorption, furosemide prevents passive reabsorption of water
- More than 20% of NaCl reabsorbed in TAL so block here -> profound diuresis
Loop Diuretics: Pharmacokinetics
Both oral and parenteral
- Oral onset: 1-2 hour; IV onset: 5 min
- Duration: 2-3 h
Extensively bound to plasma protein
Elimination
- GF and tubular secretion (organic acid secretory system)
- Includes uric acid
Loop Diuretic: Action
High diuresis
- Rapid onset
- Wide use in emergency information
- Treatment of edematous conditions refractory to thiazide diuretics (Chronic renal failure)
- Also may produce a greater K loss than thiazides if continuous action
- K loss from increased Na in tubules reaching late DCT/ Collecting Duct
- Shorter duration than thiazides
- Allows for wash out
Loss of K, Cl, and H can result in hypokalemic or hypochloremic alkalosis
Increase in renal blood flow and increase in GFR
Can increase loss of Ca and Mg
Loop diuretics: Use
Pulmonary edema associated with CHF
Acute renal failure
- Promotes diuresis even when renal blood flow and GFR are low; flushes intratubular casts
Hypercalcemic states
- Hyperparathyroidism, malignancies
Hyperkalemia
- Caused by potassium sparing diuretic
Loop Diuretics: Adverse effects
Hyponatremia, hypochloremia, and dehydration
- Dry mouth, thirst, oliguria, dehydration
- May promote thrombosis and embolism
Hypotension
- Loss of volume, relaxation of smooth muscle
- Monitor
Hypokalemic metabolic alkalosis
Ototoxicity
Hyperuricemia (gout)
Hyperglycemia
Lipid abnormalities
- Increase in LDL and total cholesterol,even triglycerides
- Often times not bad enough to be concerned
Hypomagnesemia
- pretty rare
Loop diuretics: Drug interactions
Aminoglycosides
- Ototoxic
- Can cause irreversible deafness
Digoxin
- Arrhythmia
- Activity and toxicity of digoxin increases when K is decreased
- Increased digoxin binding on Na-K-ATPase
Lithium
- Lower Na, suppresses lithium excretion; reduce lithium dosage
Potassium-sparing diuretics
- Nullifies the potassium wasting effects of loop diuretics
Thiazide diuretics: mechanism
Inhibits reabsorption of Na, Cl, K and water
- Less effective than loop diuretics
Elevates plasma uric acid and glucose
Increase cholesterol
Thiazide diuretics: Differences from Loop Diuretics
Ineffective when GFR low
Enhances calcium reabsorption
Thiazide: clinical uses
Essential hypertension
Edema
Nephrogenic diabetes insipidus (ADH deficiency, or lithium toxicity)
- Reduces urine production
- Decrease in effective plasma volume resulting in decreased GFR causing a decrease in urine production
Nephrolithiasis
- Reduces hypercalcuria
Thiazide: Adverse effects
Hyponatremia, hypochloremia, and dehydration
Hypokalemia
- Biggest concern especially if digoxin is present
- Correction
- High K diet
- Could lower the dose
- Possibly use potassium supplements
- Add spironolactone
Hyperglycemia
- Concerns with people with diabetes
Hyperuricemia
- Gout
Hyper-lipidemia
- Hypercholesterolism
Allergic reactions
- Structure has a sulf group in it so sulfa allergy is a concern
Avoid during pregnancyPotassium-sparing diuretics: Effects
Modest increase in urine production
Substantial decrease in K excretion
Potassium-sparing diuretics: Subclasses
Aldosterone antagonists - Spironolactone - Eplerenone Non-aldosterone antagonists - Triamterene
Spironolactone: Mechanism
Blocks the action of aldosterone in the distal nephron
- Inhibits Na excretion
- Decreases K excretion
- Scanty diuresis, delayed action
Spironolactone: Clinical use
Liver cirrhosis, hypertension, edema, hyperaldosteronism
Nullify potassium wasting
Spironolactone: Adverse effects
Hyperkalemic metabolic acidosis
- Serum K > mEq/L causes arrhythmia
- Insulin injection can help lower K levels
- Caution: K supplements, ACE-inhibitors
Inhibition of androgen receptors
- Gynecomastia, BPH, menstrual irregularities
GI disturbances
Eplerenone: Benefit over spironolactone
Greater receptor selectivity, fewer steroid-like effects
Triamterene: Action
Inhibits Na channels in the collecting tubule causing Na excretion
K sparing effect
- Doesn’t matter how much aldosterone is present
Triamterene: Metabolism
Extensively metabolized
Amiloride
- Excreted unchanged
Triamterene: Clinical uses
Adjunct with thiazide or loop diuretic in CHF or hypertension
Triamterene has low t1/2
Triamterene: Toxicities
Hyperkalemia, metabolic acidosis
Acute renal failure
- Triamterene in combination with indomethacin
- Decrease the amount of prostaglandin
Potassium-sparing Diuretics: C/I
K supplements, K rich food
Renin-angiotensin-aldosterone system blunting agents
- ACE inhibitors, beta-blockers
Kidney stones (Triamterene)
Osmotic Diuretics: Effect
No effect on salt
Water diuresis
