Chapter 6 - Renal and urinary tract disorder drugs

What the renal system consists of

• 2 kidneys

• 2 ureters

• urinary bladder

• urethra

Renal system responsibilities

• Filter waste from the bloodstream

• Recirculate needed elements (like electrolytes)

Nephron

• basic functional unit of the kidney

• regulates water and electrolyte balance in the body

• filters blood under pressure

Renal system waste products

• urea

• uric acid

• water

How kidneys promote homeostasis

• acid base balance

• regulation of electrolyte concentrations

• blood volume control

• regulating BP

• Communicate with other organs through the release of hormones (such as erythropoietin)

what can renal failure cause

• infectious disease (lepto)

• diabetes mellitus

• toxins (onions, garlic, grapes, antifreeze, etc.)

• immunologic disorders (like lyme which is infectious and immunologic)

Renal disease classifications

• prerenal

• renal

• post renal

what can renal disease be termed as (different from classifications)

• acute

• chronic

• end-stage

Prerenal renal disease

• decreased renal perfusion

• dehydration

kidneys not getting enough blood caused by dehydration

Postrenal renal disease

• inadequate drainage or urine distal to kidneys such as blockage

Diuretics

• remove extracellular fluid by increasing urine flow and Na (sodium) excretion

• reduce hypertension

Loop diruetics

• inhibit tubular reabsorption of Na

• rapid onset of action

• patients may need K+ supplement

• Furosemide (Lasix)

osmotic diuretics

• exert high osmotic pressure in the tubules therefore limit tubular reabsorption

• mannitol 20%

Thiazide diuretics

• reduce edema by inhibiting reabsorption of Na, Cl, H2O

• Longer duration than loop diuretics

• Chlorothiazide

Potassium sparing diuretics

• Not as strong as diuretics so they are able to conserve K+

• Also called aldosterone antagonists

• Spironolactone

• Is the drug to use if patient is hypokalemic

Carbonic anhydrase inhibitors

• decrease the rate of carbonic acid and H+ production in kidney which increases urinary output

• useful in the treatment of glaucoma

Cholinergic agents

• mimic natural acetylcholine causing smooth muscle contraction > increase contractility of the urinary bladder

Anticholinergic agents

• block acetylcholine

• can be used to treat urge incontinence by promoting urine retention

Renin angiotensin aldosterone system (RAAS)

• Renin > converts angiotensinogen to angiotensin 1 > angiotensin converting enzyme converts angiotensin 1 to angiotensin 2

system purpose is to increase blood pressure

Antidiuretic hormone (ADH)

• Secreted by the posterior pituitary gland

• regulates fluid balance in the body

if inadequate amounts made PU/PD may occur > diabetes insipidus

Urinary acidifiers

• produce acid urine which helps decrease the formation of struvite uroliths

• not routinely used due to acidifying diets

• Methionine

Urinary alkalizers

• used in management of ammonium acid urate, Ca Oxalate, cystine urolithiasis

• K citrate

• not routinely used due to prescription diets

urinary incontinence

• classified as a neurogenic or non-neurogenic disorder

• Baclofen (treat urinary retention), don’t use in cats

Diethylstilbestrol (DES)

• not commonly used anymore

• Synthetic estrogen

• can cause bone marrow suppression and blood dyscrasias

Phenylpropanolamine (Proin)

• used to treat urethral sphincter hypotonus

• estriol (incurin) - estrogen hormone (hormones responsive urethral incompetence)

• Amitryptyline (Tricyclic antidepressants)

  • used to treat FLUTD

Other agents

• Epakitin

  • nutritional supplement that binds P in the intestine

  • helps lower elevated P noted in renal failure

• Azodyl

  • Helps slow down uremic toxin buildup and helps reduce further kidney damage

Both have questionable efficacy

Phenoxybenzamine

• adrenergic antagonist

• can cause increase IOP, tachycardia, nasal congestion, inhibition of ejaculation, GI effects and constipation in horses

Diethylstilbestrol (DES)

• Synthetic estrogen, only available through compounding pharmacies

• can cause bone marrow suppression and cause blood dyscrasias (cancers, etc)

• not commonly used anymore

Phenylpropanolamine (Proin)

• used to treat urethral sphincter hypotonus