Drugs Acting on the Renal System PDF

Drugs Acting on the Renal System NCM 106 Pharmacology  Four major functions in the body: a. Maintaining the volume and composition of body fluids within normal ranges, including the following functions: Clearing nitrogenous wastes from protein metabolism Maintaining acid–base balanc...

Drugs Acting on the Renal System NCM 106 Pharmacology  Four major functions in the body: a. Maintaining the volume and composition of body fluids within normal ranges, including the following functions: Clearing nitrogenous wastes from protein metabolism Maintaining acid–base balance and electrolyte levels Excreting various drugs and drug metabolites b. Regulating vitamin D activation, which helps maintain and regulate calcium levels c. Regulating blood pressure through the renin–angiotensin–aldosterone System d. Regulating red blood cell production through the production and secretion of erythropoietin Mo ve me nt Diuretics—drugs that increase the excretion of sodium, and therefore water, from the kidneys—are used in the treatment of edema associated with HF and pulmonary edema, liver failure and cirrhosis, and various types of renal disease and as agents to treat hypertension. Classes of diuretics differ in their sites of action and intensity of effects. Thiazide diuretics work to block the chloride pump in the distal convoluted tubule. This effect leads to a loss of sodium and potassium and a minor loss of water. Thiazides are frequently used alone or in combination with other drugs to treat hypertension. They are considered to be mild diuretics. Thiazide diuretics include chlorothiazide (Diuril), hydrochlorothiazide (generic), and methyclothiazide (generic). Thiazide-like diuretics include chlorthalidone (generic), indapamide (generic), and metolazone (Zaroxolyn). Thiazide and thiazide-like diuretics are among the most frequently used diuretics. Loop diuretics work in the loop of Henle and by blocking the chloride pumps and have a powerful diuretic effect, leading to the loss of water, sodium, and potassium. These drugs are the most potent diuretics and are used in acute situations, as well as in chronic conditions not responsive to milder diuretics Loop diuretics are also referred to as high- ceiling diuretics because they cause a greater degree of diuresis than other diuretics. Four loop diuretics are available: Ethacrynic acid (Edecrin), the first loop diuretic introduced, Bumetanide (generic), Furosemide (Lasix), and Torsemide (Demadex) Carbonic anhydrase inhibitors work to block the formation of carbonic acid and bicarbonate in the renal tubule. These drugs can cause an alkaline urine and loss of the bicarbonate buffer. Carbonic anhydrase inhibitors are used in combination with other diuretics when a stronger diuresis is needed, and they are frequently used to treat glaucoma because they decrease the amount of aqueous humor produced in the eye. The carbonic anhydrase inhibitors are relatively mild diuretics. Available agents include acetazolamide (Diamox), dichlorphenamide (Keveyis), and methazolamide (generic) Potassium-sparing diuretics are mild diuretics that act to spare potassium in exchange for the loss of sodium and water in the urine. These diuretics are preferable if potassium loss could be detrimental to a patient’s cardiac or neuromuscular condition. Patients must be careful not to become hyperkalemic while taking these drugs The potassium-sparing diuretics are not as powerful as the loop diuretics, but they retain potassium instead of wasting it. Drugs include amiloride (Midamor), eplerenone (Inspra), spironolactone (Aldactone), and triamterene(Dyrenium). These diuretics are used for patients who are at high risk for hypokalemia associated with diuretic use (e.g., patients receiving digitalis or patients with cardiac arrhythmias) The osmotic diuretic mannitol uses hypertonic pull to remove fluid from the intravascular spaces and to deliver large amounts of water into the renal tubule. There is a danger of sudden change of fluid volume and massive fluid loss with this drug. This drug is used to decrease intracranial pressure, to treat glaucoma, and to help push toxic substances through the kidneys. Osmotic diuretics pull water into the renal tubule without sodium loss. Currently, only one osmotic diuretic is available, mannitol (Osmitrol). Urinary tract antiinfectives destroy bacteria in the urinary tract that could be causing infections. Urinary tract–specific antibiotics prevent bacterial reproduction and cause bacterial cell death. Some urinary tract antiinfectives kill urinary tract bacteria by acidifying the urine, making the tract a poor host for bacterial growth, or by killing the bacteria outright. Hygiene measures, proper diet, and extra hydration are activities that help decrease harmful bacteria in the urinary tract, which promotes the effect of urinary tract antiinfective agents. Urinary tract antispasmodics (Table 52.3) block the spasms of urinary tract muscles caused by various conditions. The antispasmodics that are available include the anticholinergics flavoxate (generic), oxybutynin (Ditropan XL), tolterodine (Detrol), fesoterodine (Toviaz), darifenacin (Enablex), solifenacin (VESIcare), and trospium (Sanctura) and the beta-agonist mirabegron (Myrbetriq) Smooth muscle spasms affecting the urinary tract may be caused by inflammation and irritation; effects of the spasms include dysuria, urinary urgency, incontinence, nocturia, and suprapubic pain. Antispasmodics block parasympathetic activity, thereby relaxing detrusor and other urinary tract muscles. The newest drug for this disorder, mirabegron, is a beta-agonist and causes the detrusor muscle to relax, allowing increased urine storage and improved muscle pressure and urine outflow.  Urinary Tract Analgesics The agent Bladder phenazopyridine Protectant (AzoStandard, Baridium, and others) is a dye The bladder protectant pentosan polysulfate that is used to relieve sodium (Elmiron) is urinary tract used to coat or adhere pain to the bladder mucosal wall and protect it from irritation related to solutes in urine.  Urinary Tract Analgesics Phenazopyridine is a urinary tract analgesic that is used to decrease Bladder bladder pain that could Protectant result in changes in bladder function and Pentosan is a bladder protectant. It is a heparin- emptying. This drug is a like drug that protects dye, and patients need to the inner lining of the be warned about bladder from irritation by changes in the color of solutes in the urine. urine and potential for Because it is a heparin-like staining skin and clothing drug, the risk of bleeding must be considered. Drugs for Treating Benign Prostatic Hyperplasia Basic Drug Action alpha-adrenergic relax the sympathetic Benign prostatic blockers doxazosin effects on the bladder hyperplasia (BPH), (Cardura), tamsulosin and sphincters. also called benign (Flomax), alfuzosin prostatic (Uroxatral), silodosin hypertrophy or (Rapaflo), and enlarged prostate, terazosin (generic) is a common and drugs that block problem in men, testosterone and it increases in production, finasteride (Proscar) incidence with and age.. block the body’s dutasteride (Avodart) production of a powerful androgen