Diuretics Flashcards
What are diuretics, and how do they work?
Diuretics, also called “water pills,” increase diuresis (the production of urine), decrease blood volume (stroke volume), and help get rid of excess fluid in the body.
Where do loop diuretics act in the body, and what is their mechanism of action?
Loop diuretics act at the Na/K/2Cl transporter (NKCC) in the loop of Henle. They inhibit the transporter, which prevents sodium from leaving the tubule, causing water to remain in the tubule due to osmosis. Examples include furosemide and bumetanide.
What are some clinical uses of loop diuretics?
Loop diuretics are used for the relief of breathlessness in acute pulmonary oedema, fluid overload in chronic heart failure, and fluid overload in other oedematous states.
What are some side effects or contraindications of loop diuretics?
Some side effects of loop diuretics include hypovolemia (low blood volume), hypotension (low blood pressure), and hypokalemia, which can increase the risk of digoxin toxicity.
Where do thiazide diuretics act, and what is their mechanism of action?
Thiazide diuretics act at the NaCl transporter (NCC) in the distal convoluted tubule, inhibiting the transporter so sodium ions cannot leave, trapping water in the tubule due to osmosis. Examples include indapamide and Bendroflumethiazide.
What are some clinical uses of thiazide and thiazide-like diuretics?
Thiazides are used as an alternative first-line treatment for hypertension where calcium channel blockers are unsuitable, and as an add-on treatment with calcium channel blockers, ACE inhibitors, or angiotensin receptor blockers.
What are some adverse effects of thiazide diuretics?
Adverse effects include hypokalaemia, hyponatremia, and impotence.
What is the mechanism of action for aldosterone antagonists, a type of potassium-sparing diuretic?
Aldosterone antagonists prevent the action of aldosterone, leading to a decrease in epithelial sodium channels (ENaC) in the collecting duct, which prevents sodium reabsorption and allows water to stay in the tubule. This also causes potassium retention. An example is spironolactone.
What is the mechanism of action for ENaC inhibitors, another type of potassium-sparing diuretic?
ENaC inhibitors block the epithelial sodium channels (ENaC) in the collecting duct, which causes potassium retention. Like aldosterone antagonists, they have little diuretic effect on their own and are used in combination with loop or thiazide diuretics. An example is amiloride.
What are the clinical uses of potassium-sparing diuretics?
Potassium-sparing diuretics are used in combination therapy to treat hypokalaemia, usually alongside loop or thiazide diuretics.
What are some adverse effects of potassium-sparing diuretics?
Adverse effects are uncommon but may include gastrointestinal upset, hypotension, and electrolyte disturbances.
How do loop diuretics affect the body’s sodium and water balance?
Loop diuretics prevent sodium from leaving the tubule by blocking the Na/K/2Cl transporter, leading to water remaining in the tubule due to osmosis. This decreases blood volume and helps remove excess fluid from the body.
What are thiazide diuretics commonly used for in treating hypertension?
Thiazide diuretics are commonly used as an alternative first-line treatment for hypertension when calcium channel blockers are unsuitable, or as an add-on treatment with other antihypertensive medications like ACE inhibitors or angiotensin receptor blockers.
How do potassium-sparing diuretics help with hypokalaemia?
Potassium-sparing diuretics, such as aldosterone antagonists and ENaC inhibitors, help counteract hypokalaemia (low potassium) by preventing the excessive loss of potassium, which can occur with loop and thiazide diuretics.
Why do potassium-sparing diuretics have little diuretic effect when used alone?
Potassium-sparing diuretics have little diuretic effect alone because they primarily act by reducing sodium reabsorption, but their diuretic action is weaker compared to loop and thiazide diuretics. They are typically used in combination with other diuretics to enhance their effect.
What is a major difference between loop diuretics and thiazide diuretics in terms of where they act in the kidney?
Loop diuretics act at the Na/K/2Cl transporter in the loop of Henle, while thiazide diuretics act at the NaCl transporter in the distal convoluted tubule of the kidney.
