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Diuretic Agents
Weiwei HUhuww@zju.edu.cnDept. Pharmacology, Medical School, Zhejiang University
2525 %% NaNa++
65-7065-70 %% NaNa++
1010 %% NaNa++
酮
Proximal Tubule
HCO3- reabsorption: carbonic
anhydrase (CA)
Organic acid secretory systems
are located in the middle third of
the proximal tubule: uric acid,
NSAIDs, diuretics, antibiotics.
Organic base secretory systems:
H2R antagonists, choline,
morphine, etc.
acetazolamideӨ
Proximal Tubule
Organic acid secretory systems
are located in the middle third of
the proximal tubule: uric acid,
NSAIDs, diuretics, antibiotics.
Organic base secretory systems:
H2R antagonists, choline,
morphine, etc.
Loop of Henle
25% of the filtered sodium
Water impermeable
Loop diuretics
Ө
Distal Convoluted Tubule
10% of the filtered NaCl
Water impermeable
thiazide diuretics
parathyroid hormone
K+
Ө
⊕
Collecting Tubule
2–5% of NaCl reabsorbed Principal cells are the major
sites of Na+, K+, and H2O
transportation Intercalated cells are the
primary sites of proton
secretion.^
Classification of diureticsLoop diuretics: high-ceiling diuretics (high efficacy), acting at
thick ascending limb of Henle loop, inhibiting Na+-K+-2Cl- symport : furosemide (呋塞米 )
Thiazide diuretics: moderate efficacy, acting at distal convoluted tubule, inhibiting Na+-Cl- symport: hydrochlorothiazide (氢氯噻嗪 )
K+-sparing diuretics: low efficacy, late distal tubule and collecting duct, inhibiting ADH and renal epithelial Na+ channels: spironolactone (螺内酯 )
Carbonic anhydrase inhibitors: acetazolamide (乙酰唑胺 )
Osmotic diuretics: mannitol (甘露醇 )
常用利尿药对电解质排泄及排钠力的比较
药物
尿电解质排泄滤过
Na+ 量%
主要作用部位 机制Na+ K+ Cl- HCO3
-
高效利尿药
+++ + ++++ 0 23髓袢升支粗段髓质和皮质部
抑制 Na+ -K+-2Cl-
共同转运系统中效
利尿药++ + ++ + 8 远曲小管近段 抑制 Na+ -Cl- 共同
转运系统低效
利尿药+ - + 0 2
远曲小管远段和集合管
对抗醛固酮,阻滞 Na+ 通道
乙酰唑胺
+ ++ 0 +++ 4 近曲小管 抑制胞内 H+ 形成,抑制 H+ -Na+ 交换
Carbonic Anhydrase Inhibitorsacetazolamide (乙酰唑胺)
• Inhibit bicarbonate reabsorption;
• HCO3- depletion leads to enhanced
NaCl reabsorption by the remainder of the nephron;
• Causes significant bicarbonate losses and hyperchloremic metabolic acidosis;
• Clinical use: glaucoma, metabolic alkalosis, acute mountain sickness (cerebral edema), urinary alkalinization
Basic Pharmacology of Diuretic AgentsBasic Pharmacology of Diuretic Agents
Carbonic Anhydrase Inhibitors
Toxicity:
• Hyperchloremic metabolic acidosis
• Renal stones
• Renal potassium wasting
• Drowsiness and paresthesias
• Allergy
Basic Pharmacology of Diuretic AgentsBasic Pharmacology of Diuretic Agents
sulfonamide derivative phenoxyacetic acid derivative
the diuretic activity correlates with their secretion by the proximal tubule
Loop diureticsLoop diuretics
呋塞米呋塞米
布美他尼布美他尼
依他尼酸依他尼酸
Pharmacodynamics
(1) Diuretic effects
Inhibiting the Na+-K+-2Cl- symport of the luminal membrane in
the thick portion of the ascending limb of the loop of Henle, and
reducing the reabsorption of Na+, K+ and Cl-.
Most efficacious among the diuretic drugs, because the
ascending limb accounts for the reabsorption of 25-30% of filtered
NaCl and downstream sites are not able to compensate for this
increased Na+ load.
Foresemide
Impairing kidney’s ability to excrete a dilute
urine.
Blocking kidney’s ability to concentrate urine
during hydropenia, by decreasing the hypertonic
medullary interstitium.
Increasing excretion of Ca2+, Mg2+ by abolition of
transepithelial potential difference.
Inhibit Carbonic Anhydrase at large dose, increase
excretion of HCO3-
Foresemide
loop diuretics loop diuretics urine concentrationurine concentration
urine diluteurine dilute
(2) Vasodilatation (induced renal prostaglandin synthesis)
Renal vasodilatation: renal blood flow Dilating veins: cardiac preload ,
pulmonary edema
Foresemide
Clinical Indications:(1) Severe edema: not first choice for chronic
edema, used for those are ineffective by thiazides
(2) Acute pulmonary edema: heart failure
(3) Hypercalcemia
(4) Detoxication of toxins or drug overdose
Foresemide
Clinical Indications:
(5) Others:
In mild hyperkalemia;
Acute renal failure: increase the rate of urine flow and
renal blood flow, ameliorate cell edema and jam in
the kidney tubules. Normally combined with
dopamine.
Anion overdose: bromide, fluoride, and iodide
Foresemide
Toxicity(1) Hypokalemia, hypomagnesemia, hyponatremia,
hypochloremic metabolic alkalosis
(2) Ototoxicity: hearing damage, contraindicated to
combine with aminoglycoside antibiotics or the patients
who have diminished renal function.
(3) Hyperuricemia: decreased excretion and enhancement
of uric acid reabsorption in the proximal tubule, .
Foresemide
Toxicity(4) Allergic reactions: Skin rash, interstitial nephritis.
(5) Other effects: nausea, vomit, GI bleeding.
Foresemide
Other loop diuretic drugs
Bumetanide 布美他尼: stronger than furosemide, but less adverse effects
Torasemide 托拉塞米: stronger and longer actions
Etacrynic acid 依他尼酸: weaker actions and more severe adverse effects
Thiazides
• This kind of drugs are come from the effort to
synthesize more potent carbonic anhydrase
inhibitors.• Some of the thiazides retain significant carbonic
anhydrase inhibitory activity.
苄氟噻嗪苄氟噻嗪
氯噻嗪氯噻嗪
氢氯噻嗪氢氯噻嗪
氢氟噻嗪氢氟噻嗪
甲氯噻嗪甲氯噻嗪
泊利噻嗪泊利噻嗪
三氯噻嗪三氯噻嗪
Thiazides
短效
短效
中效
中效
长效
长效
长效
1. PharmacokineticsAll of the thiazides can be administered orally,
chlorothiazide is the only thiazide available for parenteral administration.
All of the thiazides are secreted by the organic acid secretory system in the proximal tubule, and compete with the secretion of uric acid.
Thiazides
2. Pharmacodynamics
(1) Diuretic effects
Acting on distal convoluted tubule, inhibiting Na+-Cl-
symport, decreasing kidney’s ability to dilute urine
Increasing the excretion of Na+, Cl-, K+, Mg2+, HCO3-, but
increasing the reabsorption of Ca2+ in distal convoluted tubule
(2) The action of thiazides depends in part on renal prostaglandin production like loop diuretics.
Thiazides
thiazides thiazides
urine diluteurine dilute
3. Clinical Indications:
(1) Antihypertensive effects
Blood volume , spasm responsiveness of arterial smooth
muscles
(2) Edema:
Used in treatment of mild and moderate edema in cardiac
and renal diseases, and hepatic diseases with cautions;
(3) Nephrolithiasis due to idiopathic hypercalciuria ( 先天性
高尿钙症 )
Increase Ca2+ reabsorption.
Thiazides
(4) Diabetes insipidus ( 尿崩症)Thiazides have the unique ability to produce a
hyperosmolar urine, and can substitute for the
antidiuretic hormone (ADH) in the treatment of
nephrogenic diabetes insipidus.
The urine volume of such individuals may drop
from 11 L/day to 3 L/day when treated with the
drug.
Thiazides
4. Adverse effects(1) Imbalance of electrolytes hypokalemia hypomagnesemia
hyponatremia
cautions: dose individualization, K+ supplement
(2) Dysfunction of metabolism hyperglycemia hyperlipidemia
hyperuricemia
contraindicated in diabetes and gout (痛风 ) patients
Thiazides
4. Adverse effects
(3) Hypersensitivity Bone marrow suppression, dermatitis, necrotizing vasculitis,
interstitial nephritis, etc.
(4) Others Weakness, fatigability, and paresthesias
Thiazides
Chlortalidone ( 氯噻酮 )
Indapamide ( 吲达帕胺 )
Metolazone ( 美托拉宗 )
Quinethazone ( 喹乙宗 )
Xipamide ( 希帕胺 )
(1) Antagonize aldosterone at the late distal tubule and cortical collecting tubule
Spironolactone 螺内酯 Eplerenone 依普利酮 (2) Inhibit Na+ influx in the luminal membrane
Triamterene 氨苯喋啶 Amiloride 阿米洛利
Potassium-sparing diuretics
Spironolactone (antisterone)Spironolactone (antisterone)A synthetic steroidBlocking aldosterone receptorDecreasing Na+ reabsorption and K+ excretion
Weaker, slow acting, and lasting duration
EplerenoneEplerenone, a new spironolactone analog with greater selectivity for the aldosterone receptor.
Potassium-sparing diuretics
Action of spironolactone:
Blocking the effects of aldosterone
AIP: aldosterone induced protein
1. Activation of Na+ membrane-bound channels
2. Redistribute (3)3. De novo synthesis of (3)4. Activation of membrane-
bound Na+/K+ ATPase5. Redistribution of (4)6. De novo synthesis of (4)7. Changes in permeability
of tight junctions8. Increased mitochondrial
production of ATP
TriamtereneTriamterene 氨苯喋啶氨苯喋啶AmilorideAmiloride 阿米洛利阿米洛利Amiloride is excreted unchanged in the urine.
Triamterene is metabolized in the liver and renal excretion, has a shorter half-life and must be given more frequently than amiloride.
Blocking renal epithelial NaBlocking renal epithelial Na++ channels: channels: decreasing Nadecreasing Na++-K-K++ exchange exchange
Potassium-sparing diuretics
spironolactone
Clinical Indications: In states of mineralocorticoid excess:
Primary hypersecretion (Conn's syndrome, ectopic ACTH production)
Secondary aldosteronism (from heart failure, hepatic cirrhosis, nephrotic syndrome, and other conditions associated with diminished effective intravascular volume)
Combined with other diuretic drugs
Potassium-sparing diuretics
ToxicityToxicity(1) Hyperkalemia
(2) Hyperchloremic Metabolic Acidosis: By inhibiting H+ secretion in parallel with K+ secretion,
(3) Sex hormone-like effects: Gynecomastia( 男性乳腺发育 )
(4) Acute renal failure: only found in the combination of triamterene with indomethacin
(5) Kidney Stones: triamterene (poorly soluble)
(6) GI reactions
(7) CNS reactions: headache, fatigue
Potassium-sparing diuretics
Dehydrant Agents (Osmotic Diuretics)
• Increase plasma osmotic pressure, induce tissue dehydration.
• Excreted usually by glomerular filtration and not reabsorbed, to induce osmotic diuretic effects.
• To reduce increased intracranial pressure and to promote prompt removal of renal toxins.
Pharmacodynamics(1) Dehydrant effects
(2) Diuretic effects (osmotic diuretic effects)
MannitolMannitol 甘露醇甘露醇
OH OH OH OHOH OH OH OH
OH OHOH OH
Clinical IndicationsClinical Indications
(1) Increase in urine volume
(2) Reduction of intracranial and intraocular pressure: used in brain edema and glaucoma
(3) Acute renal failure: prevention and early treatment
Mannitol
Toxicity
(1) Extracellular volume expansion: pulmonary edema, etc.
(2) Hypernatremia and dehydration: headache, nausea, vomiting, etc.
Contraindicated in anuric due to severe renal diseases, active cranial bleeding, heart failure
Mannitol
Other dehydrant drugs
Sorbitol 山梨醇Hypertonic glucose (50%) 高渗葡萄糖
Diuretic Combinations
1.1. Loop Agents & ThiazidesLoop Agents & Thiazides
• Salt and water reabsorption in either the thick ascending limb or the distal convoluted tubule can increase when the other is blocked.
• Thiazide diuretics may produce a mild natriuresis in the proximal tubule that is usually masked by increased reabsorption in the thick ascending limb.
• Mobilize large amounts of fluid and K+-wasting is extremely common.
2. Potassium-Sparing Diuretics & Loop Agents or Thiazides
• When hypokalemia cannot be managed with dietary NaCl restriction or KCl supplements in patients using loop diuretics or thiazides, the addition of a potassium-sparing diuretic can significantly lower potassium excretion.
• it should be avoided in patients with renal insufficiency
Diuretic Combinations
A 65-year-old man comes to the emergency department with severe shortness of breath. His wife reports that he has long known that he is hypertensive but never had symptoms, so he refused to take antihypertensive medications. During the last month, he has noted increasing ankle edema, reduced exercise tolerance, and difficulty sleeping lying down, but he reports no episodes of chest pain or discomfort. He now has pitting edema to the knees and is acutely uncomfortable lying down. Vital signs include blood pressure of 190/140 mm Hg, pulse 120/ min, and respirations 20/min. Chest auscultation reveals loud rhonchi, but an electrocardiogram is negative except for evidence of left ventricular hypertrophy. He is given a diuretic intravenously and admitted to intensive care. What diuretic would be most appropriate for this man’s case of acute pulmonary edema associated with heart failure? What are the possible toxicities of this therapy?
CASE
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