Urinary/Renal Drugs

Question 1

bethanechol (Duvoid, Urecholine) drug class, mechanism of action, therapeutic uses, pharmacokinetics adverse/side effects, drug interactions, preparations, patient teaching and administration

Answer 1

class: cholinergic agonist
moa: binds to and activates cholinergic muscarinic receptors resulting in voiding d/t contraction and relaxation of bladder muscles. Also affects a variety of smooth muscles and increases glandular secretions
Therapeutic use: Treat urinary retention s/t surgery or post-partum.
Administration: Oral. Can cause nausea if taken w food–take 1 h before/2 h after meals.
AE: Dizziness, bradycardia, hypotension, excessive salivation, incr. gastric acid, abd cramps, diarrhea, bronchoconstriction. Contraindicated in pts w low BP/HR, GI ulcers, bowel surgery, intestinal obstruction, weak bladder wall, asthma.

Question 2

oxybutynin (Ditropan)

Answer 2

Class: anticholinergic
MoA: blocks M3 muscarinic receptors resulting in relaxation of bladder muscle & decreased desire to void
Uses: overactive bladder
Administration: PO syrup, tablets short/long acting. Transdermal long acting patch.
AE: Dry mouth, blurred vision, dry eyes, constipation, urinary retention, decreased perspiration, drowsiness.
Considerations: Avoid alcohol and other CNS depressants, avoid overheating, interacts with antihistamines, tricyclic antidepressants & some antipsychotics.

Question 3

furosemide (Lasix)

Answer 3

Class: loop diuretic
MoA: blocks Na+ and Cl- reabsorption in ascending loop of henle, results in Na+ Cl- & H2O excretion
Uses: Situations that require mobilization of large amounts of fluid: pulmonary edema, HTN, edema. Works well even in pts with renal impairment.
Administration: Oral, IV or IM.
AE: Hypokalemia, hyponatremia, hypochloremia, dehydration, hypotension, incr blood glucose.
Considerations: low K+ + incr risk for digoxin toxicity, incr risk for hypotension if taken with anti-HTN meds, risk of hearing loss if used with ototoxic drug, lithium toxicity if hyponatremia present. Hold if K+ < 3.5.

Question 4

hydrochlorothiazide (HCTZ, Hydrodiuril)

Answer 4

Class: Thiazide diuretic
MoA: Blocks Na+ and Cl- reabsorption (and thus H2O) in the early segment of the distal convoluted tubule. Needs adequate kidney function to work. Less intense diuresis than loop diuretics.
Uses: 1st choice for HTN. Mobilize fluid in mild-moderate HF, treat edema in hepatic and renal disease.
Administration: Oral.
AE: Hypokalemia, hyponatremia, hypochloremia, dehydration, hypotension, incr. blood glucose, hypomagnesemia, incr. cholesterol.
Considerations: low K+ + incr risk for digoxin toxicity, incr risk for hypotension if taken with anti-HTN meds, lithium toxicity if hyponatremia present. Hold if K+ < 3.5.

Question 5

Spironolactone (Aldactone)

Answer 5

Class: Potassium sparing diuretic
MoA: Blocks action of aldosterone in nephron, results in retention of K+ and excretion of Na+ and H2O. Also has some endocrine effects.
Uses: Treat HTN, edema, HF. Often used together with loop/thiazide diuretic to counteract K+ wasting.
Administration: Oral. Slow onset: 24-48h. Lasts 48-72h.
AE: Hyperkalemia. ACE inhibitors and angiotensin II receptor blockers can increase risk for hyperkalemia.
Considerations: Potential for fetal harm when handling, don gown and 2 gloves if crushing. Pts should limit dietary potassium and salt substitutes containing K+. Hold if K+ >5.

Question 6

mannitol (Osmitrol)

Answer 6

Class: Osmotic diuretic
MoA: Creates passive osmotic force which keeps water in the nephron and prevents it from being reabsorbed back into circulation, resulting in more water being excreted.
Uses: Prevent renal failure in situations w low renal blood flow d/t dehydration, severe hypotension, hypovolemic shock. Used to decrease ICP.
Administration: IV only–does not get absorbed in intestine.
AE: HF w pulmonary edema, HA, N/V, electrolyte imbalances.
Considerations: Hold if HD, PE, &/or renal failure. Crystallizes in cold temps, may need to warm prior to admin. Use filter needle to draw up and in-line filter.