Module 7 - Drugs Acting on the Renal System PDF

Module 7 Drugs Acting on the Renal System MONECELLE JOY D. PESINABLE,RN Instructor Lesson 1 Diuretics MONECELLE JOY D. PESINABLE,RN Instructor Diuretics promote the excretion of water and electrolytes by the kidneys 2 main purposes: to lower blood pressure and to decrease edema* in hear...

Module 7 Drugs Acting on the Renal System MONECELLE JOY D. PESINABLE,RN Instructor Lesson 1 Diuretics MONECELLE JOY D. PESINABLE,RN Instructor Diuretics promote the excretion of water and electrolytes by the kidneys 2 main purposes: to lower blood pressure and to decrease edema* in heart failure and renal or liver disorder major diuretics thiazide and thiazide-like loop potassium-sparing osmotic carbonic-anhydrase inhibitors Thiazide & Thiazide-like sulfonamide derivatives include thiazide: bendroflumethiazide, benzthiazide, chlorothiazide*, hydrochlorothiazide**, hydroflumethiazide, methyclothiazide, polythiazide, trichlormethiazide thiazide-like: chlorthalidone, indapamide Thiazide & Thiazide-like Pharmacokinetics thiazide absorbed rapidly but incompletely from the GIT after oral administration cross placenta and secreted in the breastmilk differ in how well they are metabolized thiazide-like absorbed from GIT excreted primarily in the urine Pharmacodynamics work by preventing sodium from being reabsorbed in the kidney increase the excretion of chloride, potassium and bicarbonate which can result in electrolyte imbalance Thiazide & Thiazide-like Pharmacotherapeutics long term treatment of hypertension and also used to treat edema caused by mild to moderate heart failure, liver disease, kidney disease and corticosteroid and estrogen therapy diabetes insipidus*: paradoxically decrease urine volume, possibly through sodium depletion and plasma volume reduction Side Effects and Adverse Reactions cause loss of Na, K and Mg but promote Ca reabsorption affect glucose tolerance and hyperglycemia can occur** block Ca and uric acid secretion leading to hyperuricemia and hypercalcemia increase serum cholesterol, LDL and triglyceride levels leading to hyperlipidemia Thiazide & Thiazide-like Drug Interactions altered fluid volume, blood pressure and serum electrolyte levels may increase blood glucose levels requiring higher doses of insulin and oral antidiabetic drugs taking corticosteroids, corticotropin and amphotericin may cause hypokalemia risk of digoxin toxicity increases due to potential changes in potassium levels risk of lithium toxicity may increase if these drugs are combined Loop Diuretics high ceiling diuretics* act on the thick ascending loop of Henle to inhibit chloride transport of Na into the circulation include bumetanide, ethacrynate sodium, ethacrynic acid, torsemide and furosemide Pharmacokinetics absorbed well and distributed rapidly highly protein bound undergo partial or complete metabolism in the liver except for furosemide, which is excreted primarily unchanged excreted by the kidneys Loop Diuretics Pharmacodynamics most potent drugs available high potential for causing severe adverse reactions act primarily on the thick ascending loop of Henle to increase the secretion of sodium, chloride and water; may also inhibit the reabsorption of these substances Pharmacotherapeutics edema associated with heart failure hypertension: usually with a potassium-sparing diuretic or a potassium supplement to prevent hypokalemia edema associated with liver disease of nephrotic syndrome* Loop Diuretics Adverse Reactions reduced blood volume, orthostatic hypotension, hyponatremia, hypokalemia, hypocalcemia, hypomagnesemia, hypochloremia Drug Interactions increased risk of ototoxicity when taken together with aminoglycosides and cisplatin reduce the hypoglycemic effect of oral antidiabetic drugs, possibly resulting in hyperglycemia may increase risk of lithium toxicity increased risk of electrolyte imbalances that can trigger arrhythmias when taken together with digitalis glycosides Potassium-Sparing Diuretics have weaker diuretic and antihypertensive effects than other diuretics but have the advantage of conserving potassium* include amiloride, spironolactone and triamterene Pharmacokinetics available orally and absorbed in the GIT metabolized in the liver except for amiloride** excreted primarily in the urine and bile Potassium-Sparing Diuretics Pharmacodynamics urinary excretion of sodium and water increases as does the excretion of chloride and calcium ions excretion of potassium and hydrogen ion decreases spironolactone* is structurally similar to aldosterone and acts as aldosterone antagonist Potassium-Sparing Diuretics Pharmacotherapeutics edema diuretic-induced hypokalemia in patients with heart failure cirrhosis nephrotic syndrome hypertension hyperaldosteronism and hirsutism including hirsutism associated with Stein-Leventhal Syndrome commonly used with other diuretics to potentiate their action or counteract their K-wasting effects Potassium-Sparing Diuretics Adverse Reactions few with these drugs can lead to hyperkalemia especially when taken together with potassium supplement or a high potassium diet Osmotic Diuretics pull water into the renal tubule without sodium loss example is mannitol* effects are not limited to kidneys because the injected substance pulls fluid into the vascular system from extravascular spaces, including the aqueous humor used in acute situations when it is necessary to decrease IOP before eye surgery or during acute attacks of glaucoma diuretic of choice in cases of increased ICP or acute renal failure due to shock, drug overdose or trauma Osmotic Diuretics Pharmacokinetics mannitol is only available for IV use freely filtered at the renal glomerulus, poorly reabsorbed by the renal tubule and resistant to metabolism * action depends on the concentration of osmotic activity in the solution Contraindications and cautions mannitol is contraindicated in patients with renal disease and anuria from severe renal disease, pulmonary congestion, intracranial bleeding, dehydration and heart failure** Osmotic Diuretics Adverse Effects the most common and potentially dangerous adverse effect is the sudden drop in fluid levels nausea, vomiting, hypotension, light headedness, confusion, and headache can be accompanied by cardiac decompensation and even shock patients receiving this drug should be closely monitored for fluid and electrolyte imbalance Carbonic Anhydrase Inhibitors mild diuretics include acetazolamide and methazolamide Pharmacokinetics rapidly absorbed and widely distributed can be orally or IV drugs peak in 2-4 hours, 15 minutes if given IV; duration is 6-12 hours excreted in the urine have been associated with fetal abnormalities, and should not be used during pregnancy Carbonic Anhydrase Inhibitors Pharmacodynamics block the effects of carbonic anhydrase thereby slowing down the movement of hydrogen ions; as a result, more sodium and bicarbonate are lost in the urine* used as adjuncts to other diuretics when a more intense diuresis is needed used to treat glaucoma** Carbonic Anhydrase Inhibitors Adverse Effects related to disturbances in acid-base and electrolyte balances such as metabolic acidosis and hypokalemia others include paresthesia*, confusion, and drowsiness** Drug Interactions there may be an increased excretion of salicylates and lithium if they are combined with these drugs Lesson 2 Drugs for Fluid & Electrolyte Balance MONECELLE JOY D. PESINABLE, RN Instructor Introduction illness can easily disturb the homeostatic mechanisms that help maintain fluid and electrolyte balance loss of appetite, medication administration, vomiting, surgery and diagnostic tests can also alter the balance electrolyte is a compound or element that carries an electrical charge when dissolved in water electrolyte replacement drugs are mineral salts that increase depleted or deficient electrolyte levels Potassium major cation in ICF adequate amounts must be ingested daily* potassium supplement can be accomplished orally or IV with potassium salts, such as potassium bicarbonate, potassium chloride, potassium gluconate, potassium sulfate normal amount: 3.5-5.5 mEq/L dietary requirement: 40-60 mEq Potassium Pharmacokinetics absorbed readily from GIT after absorption into the ECF, almost all potassium passes into the ICF normal serum levels of potassium are maintained by the kidneys, which excrete most of the excessive potassium intake; the rest is excreted in the feces and sweat Potassium Pharmacodynamics moves quickly into the ICF to restore depleted potassium levels and re-establish balance essential element in determining cell membrane potential and excitability necessary for proper functioning of all nerve and muscle cells for nerve impulse transmission essential for tissue growth and repair and for maintenance of acid-base balance needed for enzyme action used to change carbohydrates to energy and amino acids to proteins Potassium Pharmacotherapeutics vomiting or diarrhea; excessive urination; some kidney diseases; cystic fibrosis; burns; excess of antidiuretic hormone (ADH) or therapy with a potassium-depleting diuretic; alkalosis; insufficient potassium intake from starvation; administration of a glucocorticoid, IV amphotericin or IV solutions that contain insufficient potassium; used to decrease the toxic effects of digoxin* Potassium Adverse Reactions oral potassium sometimes causes nausea, vomiting, abdominal pain, and diarrhea enteric coated tablets may cause small bowel ulceration, stenosis, hemorrhage and obstruction IV infusion of potassium preparations can cause pain at the injection site and phlebitis if given rapidly, IV administration may cause cardiac arrest infusion of potassium in patients with decreased urine production increases the risk of hyperkalemia Drug Interactions Should be used cautiously in patients receiving potassium-sparing diuretics or ACE inhibitors to avoid hyperkalemia Calcium almost all calcium in the body is stored in the bone, where it can be mobilized if necessary* chronic insufficient calcium intake can result in bone demineralization promotes normal nerve and muscle activity and increases the contraction of the heart’s muscle replaced orally or IV with calcium salts, such as calcium carbonate, calcium chloride, calcium citrate, calcium gluconate, calcium glubionate, calcium lactate normal amount: 4.5 to 5.5 mEq/L or 8.5 to 10.5 mg/dl daily requirement: 1,300 mg (14-18); 1,000 mg (19-50 yo); 1,200 mg (above 50 yo) Calcium Pharmacokinetics absorbed readily from the duodenum and proximal jejunum pH of 5 to 7, parathyroid hormone and vitamin D all aid calcium absorption distributed primarily I the bone calcium salts are eliminated primarily in the feces; the rest is excreted in the urine Calcium Pharmacodynamics extracellular ionized calcium plays an essential role in normal nerve and muscle excitability calcium is integral to normal functioning of the heart, kidneys and lungs and it affects the blood coagulation* rate as well as cell membrane and capillary permeability calcium is a factor in neurotransmitter and hormone activity, amino acid metabolism, vitamin B12 absorption and gastrin secretion plays a major role in normal bone and tooth formation Calcium Pharmacotherapeutics helpful in treating magnesium intoxication strengthen myocardial tissue after defibrillation* pregnancy and breast-feeding major indication for IV calcium is acute hypocalcemia**: tetany, cardiac arrest, vitamin D deficiency, parathyroid surgery, and alkalosis oral calcium is used to supplement a calcium- deficient diet and prevent osteoporosis, chronic hypocalcemia, osteomalacia, rickets and vitamin D deficiency Calcium Adverse Reactions hypercalcemia: early signs include drowsiness, lethargy, muscle weakness, headache, constipation, metallic taste in the mouth ECG: elevated serum calcium levels may lead to a shortened QT interval and heart block severe hypercalcemia can cause cardiac arrhythmias, cardiac arrest, and eventually coma Calcium Drug Interactions preparations administered with digoxin may cause arrhythmias calcium replacement drugs may reduce the response to calcium channel blockers calcium replacements may inactivate tetracyclines calcium supplements may decrease the amount of atenolol available to the tissues resulting in decreased effectiveness of the drug Magnesium most abundant cation in ICF after potassium essential in transmitting nerve impulses to muscle and activating enzymes necessary for carbohydrate and protein metabolism stimulates parathyroid hormone secretion thus regulating ICF calcium levels aids in cell metabolism and the movement of sodium and potassium across cell membranes typically replaced in the form of magnesium sulfate normal value: 1.5-2.5 mEq/L daily requirement: 19-30 years, 400 mg (men) and 310 mg (women); 31 years and older, 420 mg (men) and 320 mg (women) Magnesium Pharmacokinetics distributed widely throughout the body; IV magnesium sulfate acts immediately, whereas after IM administration, it acts within 30 minutes not metabolized and is excreted unchanged in the urine; some are excreted in the breast milk Pharmacodynamics replenishes and prevents magnesium deficiencies; also prevents seizures by blocking neuromuscular transmission Magnesium Pharmacotherapeutics DOC for replacement therapy in magnesium deficiency seizure, severe toxemia and acute nephritis* in children Drug Interactions may lead to heart block if given together with digoxin may increase CNS depressants if given with alcohol, narcotics, antianxiety drugs, barbiturates, antidepressants, hypnotics, antipsychotics or general anesthetics Adverse Reactions life threatening ARs include hypotension, circulatory collapse, flushing, depressed reflexes, respiratory paralysis Sodium major cation in ECF maintains the osmotic pressure and concentration of ECF, acid-base balance and water balance* contributes to nerve conduction and neuromuscular function** replacement is necessary for conditions that deplete it such as excessive GI fluid loss and excessive perspiration*** normal value: 135-145 mEq/L daily dietary requirement: 2 g Sodium Pharmacokinetics oral and parenteral preparations are quickly absorbed and distributed widely throughout the body not significantly metabolized, primarily eliminated in the urine Pharmacodynamics replaces deficiencies of the sodium and chloride ions in the blood plasma Pharmacotherapeutics water and electrolyte replacement in patients with hyponatremia from electrolyte loss of severe sodium chloride depletion Sodium Drug Interactions and Adverse Reactions no significant drug interactions except for some reports when taken with lithium and tolvaptan adverse reactions include pulmonary edema, hypernatremia and potassium loss