Pharmacology: Diuretics Lectures 5

Flashcards covering the classification, mechanisms, therapeutic uses, and side effects of Loop and Thiazide diuretics based on pharmacology lecture notes.

Diuretic agent

A drug which increases urine volume.

Extra renal diuretics

Agents like albumin used for the mobilization of edema fluid in cases of nephrotic syndrome by correcting plasma oncotic pressure via intravenous administration.

Loop diuretics (high ceiling diuretics)

A class of drugs including Furosemide, Bumetanide, and Torsemide that are rapidly absorbed from the GIT and have a short duration of action up to $4\text{ hours}$.

Renal mechanism of Loop diuretics

Inhibition of the $Na^+/K^+/2Cl^-$ co-transport at the ascending limb of Henle’s loop, preventing reabsorption of about $25\text{\text{\%}}$ of $Na^+$ in the filtrate.

Extra-renal mechanism of Loop diuretics

Venodilator action that may be mediated by increasing prostaglandins ($PGs$).

Pharmacological effects of Loop diuretics

Increased excretion of $Na^+$, $Cl^-$, $K^+$, $H^+$, $Mg^{2+}$, and $Ca^{2+}$, and decreased urinary excretion of uric acid.

Furosemide renal effect

Increases renal blood flow, making it useful in conditions like acute renal failure.

Hypertensive emergencies (Loop diuretics)

Intravenous Furosemide reduces blood volume and decreases vascular smooth muscle sensitivity to catecholamines through hyponatremia and $PGs$ production.

Side effects of Loop diuretics

Includes hypokalaemia metabolic alkalosis, hypovolaemia, hyponatremia, hypomagnesaemia, hypocalcemia, hyperuricaemia, hyperglycemia, hyperlipidemia, and hypersensitivity.

Ototoxicity

A dose-related, reversible side effect of Loop diuretics resulting in hearing loss and tinnitus.

Thiazides

A class of diuretics including Hydrochlorothiazide and Bendroflumethiazide that contain a free sulfonamide radical and have a duration of action between $8\text{ to }24\text{ hours}$.

Thiazide mechanism of action

Acts principally at the proximal part of the distal convoluted tubule ($DCT$) by inhibiting $NaCl$ co-transport, preventing reabsorption of about $10\text{\%}$ of $Na^+$ in the filtrate.

Thiazide effect on Calcium

Decreases urinary excretion of $Ca^{2+}$ due to a relative increase of $Ca^{2+}$ reabsorption in the $DCT$, making them useful for treating hypercalciuria.

Thiazide effect on renal blood flow

Decreases renal blood flow through a direct action on renal vasculature, making them unsuitable for acute renal failure.

Essential hypertension (Thiazides)

Long-term treatment lowers intracellular $Na^+$ and $Ca^{2+}$ in arteriolar smooth muscle, causing relaxation and decreased peripheral vascular resistance.

Loop Loose Calcium

A mnemonic indicating that Loop diuretics increase the loss of calcium in urine.

HyperGLUC

A mnemonic for Thiazide side effects: Hyper- Glycemia, Lipedemia, Urecemia, and Calcemia.

STAy of K+

A mnemonic indicating that $K^+$ sparing diuretics cause the retention of potassium in the body.