NORMAL REGULATION OF FLUID AND ELECTROLYTES BY THE KIDNEYS
Approximately about 16 to 20 percent of the blood plasma entering the kidneys is filtered from the glomerular capillaries into the Bowman capsule.
The filtrate, although normally free of proteins and blood cells, does contain most LMW plasma components in approximately the same concentrations as are found in the plasma. These include glucose, sodium bicarbonate, amino acids, and other organic solutes as well as electrolytes, such as Na+, K+, and Cl–.
The kidney regulates the ionic composition and volume of urine by the active reabsorption or secretion of ions & the passive reabsorption of water at five functional zones along the nephron:
1) the proximal convoluted tubule
2) the descending loop of Henle
3) the ascending loop of Henle
4) the distal convoluted tubule
5) the collecting tubule and duct
Thiazide Diuretics
Hydrochlorothiazide (HCTZ), Chlortalidone or Chlorthalidone
thiazide diuretics is lower blood pressure initially by increasing sodium and water excretion.
Mechanism of Action:
Decrease blood pressure by Increasing sodium and water excretion by reducing reabsorption of sodium and chloride at the early part of the distal convoluted tubule in the nephrons. Resulting in decrease extracellular volume, decrease cardiac output thus decrease blood pressure.
Therapeutic Uses
1) Mild and moderate hypertension.
2) Congestive heart failure (CHF).
3) Nephrolithiasis (Idiopathic hypercalciuria).
4) Nephrogenic diabetes insipidus.
Side Effects:
1) hypokalemia, Hyponatremia & Hypomagnesaemia.
2) Hypercalcemia and Hyperuricemia.
3) Hyperlipidemia and Hyperglycemia.
4) Hypersensitivity.
5) Metabolic alkalosis.
Contraindications:
1) Digitalis; hypokalemia & hypercalcemia increase toxicity.
2) Hepatic cirrhosis and renal failure.
3) Patients with a history of sulfonamide allergy.
4) Gout and Diabetes mellitus.
Drug Interactions:
1) Lithium; due to decrease renal lithium excretion.
2) Digitalis; due to increase digitalis toxicity.
3) NSAIDS; due to decrease diuretic effect of thiazide.
Indapamide
It is the first of a new class of (antihypertensive/diuretics). It have a unique mechanism of action; act by combining diuretic effects with a direct vasodilatation effect.
Loop Diuretics (high Ceiling)
Furosemide, Torsemide, Bumetanide & Ethacrynic acid
Furosemide, Torsemide, Bumetanide sulfonamide loop diuretics.
Ethacrynic acid is not a sulfonamide diuretics.
Mechanism of Action:
Decrease blood pressure by increasing sodium and water excretion by reducing reabsorption of Na+, K+& Cl- at the thick ascending limb of Henle's loop (TAL) in the nephrons. Decrease renal vascular resistance and increase renal blood flow via increase the production of vasodilator prostaglandins, so NSAIDS can reduce the efficacy of loop diuretics.
Therapeutic Uses:
1) Edema; caused by congestive heart failure, hepatic cirrhosis, renal impairment, nephrotic syndrome, cerebral or pulmonary edema.
2) Hypertension; Oral; in hypertension alone or in combination. IV in emergency.
3) Oliguria (< 400 ml urine/day); Use only high dose tablet (500 mg) or injection (250 mg).
4) Other non-specific uses; Hyperkalemia.
Side Effects:
1) Hypokalemia, Hyponatremia & Hypomagnesaemia.
2) Ototoxicity. May mild hypocalcemia and Hyperuricemia.
3) Hyperlipidemia and Hyperglycemia.
4) Hypersensitivity.
5) Metabolic alkalosis.
Contraindications:
1) Digitalis; hypokalemia & hypercalcemia increase toxicity.
2) Hepatic cirrhosis and renal failure.
3) Patients with a history of sulfonamide allergy.
4) Gout and Diabetes mellitus.
Drug Interactions:
1) Lithium; due to decrease renal lithium excretion.
2) Digitalis; due to increase digitalis toxicity.
3) NSAIDS; due to decrease diuretic effect of thiazide.
4) Aminoglycoside
5) Warfarin
6) Probenecid.
Potassium (K+) Sparing Diuretics (Low Ceiling)
Spironolactone & Eplerenone
Inhibits the effects of aldosterone, by competitive antagonist at mineralocorticoid receptors in the distal convoluted renal tubule thus increase Na+ and water excretion, K+ is retained, decrease H+.
Spironolactone has other effects e.g.; antiglucocorticoidic, antiandrogenic, progestogenic & estrogenic effects.
Spironolactone uses:
1) Primary hyperaldosteronism
2) Edema (CHF, Cirrhosis or Nephrotic syndrome)
3) Essential hypertension
4) Hypokalemia
5) Antiandrogen (Hirsutism, acne fin women] & androgenic alopecia).
Eplerenone uses:
1) Congestive heart failure
2) post-myocardial infarction
3) Hypertension.
Side Effects:
1) Hyperkalemia (risk of this complication is greatly increased by, Renal disease, K+ supplements or diet rich in K+,B-blockers, NSAIDS, ACEIS, ARBS and Aliskiren)
2) Metabolic acidosis.
3) Endocrine abnormalities
4) Gynecomastia
5) Impotence
6) benign prostatic hyperplasia (BPH is very rare) all have been reported only with spironolactone.
Amiloride & triamterene
are direct inhibitors of Na influx in the CCT (cortical collecting tubule) thus increase loss of Na+ and water with decrease K+ and H+ secretion.
Used as adjunctive treatment with thiazide diuretics or loop diuretics in congestive heart failure or hypertension.
Acetazolamide
is a sulfonamide derivatives, is a prototypical of Carbonic Anhydrase inhibitor diuretics
used in glaucoma and acute mountain sickness (Altitude sickness).
Comments
Post a Comment