Term
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Definition
| Agents that increase the rate of urine formation |
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Term
| List four characteristics of osmotic diuretics |
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Definition
1. Free glomerular filtration
2. Limited tubular reabsorption
3. Inert/nontoxic
4. Resistant to metabolic alteration |
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Term
| What is a true physiologic diuretic? |
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Definition
| Water- body load of H2O or electrolyte can function as a diuretic to increase fluid excretion. |
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Term
| Describe the basic mechanism of action of diuretics |
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Definition
| Increases urine volume and rate of formation by decreasing osmolarity of blood and decreasing ADH secretion |
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Term
| What are the general therapeutic uses of diuretics? |
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Definition
1. Increases the rate of excretion of irritating or toxic drugs
2. Dilute drugs which may precipitate in kidney |
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Term
| What is the mechanism of action of an osmotic diuretic? |
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Definition
Increases the osmotic activity in the renal tubule, especially the loop of Henle.
Osmotic agent is not reabsorbed and carries with it an equivalent amount of fluid and increases excretion of all electrolytes. |
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Term
| Give some side effects of osmotic diuretics |
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Definition
- acute rapid expansion of extracellular fluid volume (initial effect) may cause cardiac decompensation/failure in C.V. disease
- headache, nausea are common |
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Term
| List four general uses of osmotic diuretics |
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Definition
1. acute renal failure
2. regulation of intraocular press. (glaucoma)
3. mobilize edema fluid
4. reduce spinal fluid vol./press before neurosurgery |
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Term
| Define mannitol (Osmitrol) |
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Definition
An osmotic diuretic
- most common
- poor GI absorption, generally given IV |
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Term
| Define Isosorbide (Ismotic) |
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Definition
An osmotic diuretic
- can be used orally
- poor diuresis |
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Term
| Describe the overall action of carbonic anhydrase inhibitors |
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Definition
1) Alkaline urine- HCO3 excretion increased
2) Metabolic acidosis- H+ excretion reduced
3) Excretion of Na+, K+, HCO3 and H20
- Diuretic effect of CAI is self-limiting since metabolic acidosis reduces the filtered load of H CO3-
4. Diuresis |
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Term
| Describe the absorption and distribution of carbonic anhydrase inhibitors |
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Definition
- Absorption rapid and complete
- Half-life 6-9 hrs |
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Term
| Give an example of a carbonic anhydrase inhibitor |
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Definition
Acetazolamide (Diamox)
The prototype carbonic anhydrase inhibitor |
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Term
| List five therapeutic uses of carbonic anhydrase inhibitors |
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Definition
1. not used as a primary diuretic
2. open-angle glaucoma
3. reduces epileptic seizure (petit mal/grad mal)
4. used to alkalinize urine
5. treat acute symptoms of mountain sickness |
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Term
| List four side effects of carbonic anhydrase inhibitors |
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Definition
1. Parasthesia (numbness in extremeties)
2. drowsiness - common
3. alkaline urine --> precip. Ca PO4 --> kidney stones
4. hypersensitivity/allergic reactions (rare) |
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Term
| Describe the mechanism of action of thiazide diuretics |
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Definition
| Inhibit Na and Cl symport reabsorption in the distal tubule, which causes these ions to act as an osmotic agent for water to be taken into the collecting duct to urine |
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Term
| Give an example of a thiazide diuretic |
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Definition
Chlorothiazide (Diuril)
The prototype |
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Term
| How do thiazides inhibit Na-Cl symport through the distal tubule? |
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Definition
- competes at the Cl- binding sites on the Na-Cl symport protein
- cause a significant K+ loss due to excess Na remaining in the distal tubule |
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Term
| Other than Na and Cl retention, what are effects of thiazides? |
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Definition
- chronic use decreases uric acid excretion
- decrease Ca excretion and increase Mg excretion
- will increase excretion of other halogens (eg. Iodine, bromine) |
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Term
| Describe the absorption and distribution of thiazides |
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Definition
- orally active (relatively incomplete GI absorption) - 10-20%
- relatively long action due to protein binding
- protein binding and duration varies greatly among thiazides |
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Term
| List five side effects of thiazide |
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Definition
1. Mild GI symptoms
2. Hyponatremia and dehydration
3. K+ depletion – important in CV disease
- use K sparing diuretic in combination with thiazide
- use K supplement
4. Hyperglycemia
- in diabetic/prediabetic - may unmask latent diabetes
5. Uric acid retention- gout |
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Term
| List general uses of thiazide diuretics |
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Definition
- hypertension – most common use
- edema of congestive heart failure or with chronic liver and renal disease |
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Term
| List three common qualities between high ceiling (loop) diuretics |
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Definition
1. Prompt onset and short duration
2. Inhibit Na and Cl transport in the ascending loop
3. Little or no acid/base change |
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Term
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Definition
1. Furosemide (Lasix)
2. Ethacrynic acid (Edecrin) |
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Term
| Describe the mechanism of action of loop diuretics |
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Definition
The loop diuretics inhibit the symport of Na and Cl, decreasing the concentration gradient countercurrent multiplier
This causes less fluid to be reabsorbed, a lot more fluid is excreted.
Furosemide also inhibits carbonic anhydrase (minor diuretic effect) |
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Term
| List other effects of loop diuretics besides reducing the concentration gradient of the countercurrent multiplier |
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Definition
- Increase potassium excretion
- Increase Mg and Ca excretion
- decrease uric acid excretion --> retention |
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Term
| List the therapeutic uses of loop diuretics |
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Definition
1. edema of pulmonary, cardiac, hepatic and renal origin
2. refractory edema – i.e. little or no response to thiazides
3. drug overdose to enhance the rate of drug elimination. |
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Term
| List side effects of the loop diuretics |
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Definition
1. Dehydration
2. Hyponatremia, hypokalcemia, hypomangesia (arrhythmias)
3. Uric acid retention- gout
4. ototoxicity, tinnitus - ethacrynic acid most common |
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Term
| Describe the mechanism of action of K+ sparing diuretics |
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Definition
| Aldosterone receptor antagonist in the distal tubule and collecting ducts to enhance Na and water excretion and enhance K retention |
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Term
| Give an example of a type-1 K+ sparing diuretic |
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Definition
| Spironalactone (Aldactone) |
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Term
| Why is spironalactone only effective for a short time as a diuretic by itself? |
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Definition
| The body will make more aldactone to compensate for its antagonism |
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Term
| Describe the pharmacokinetics of spironalactone |
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Definition
- Oral - well absorbed
- Half-life - 1.5 hours
- Half-life 17h for active metabolite |
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Term
| List three side effects of spironalactone |
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Definition
- hyperkalemia
- GI symptoms
- androgen-like effects |
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Term
| List two therapeutic uses for spironalactone |
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Definition
1. Edema of hypertension – with thiazides
2. Combination with thiazides to prevent K+ loss (ex. Aldactazide) |
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Term
| Give two examples of a type-2 K+ sparing diuretic |
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Definition
| Amiloride (Midamor) and Triamterene (Dyrenium) |
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Term
| What is the mechanism of action of a type-2 K+ sparing diuretic? |
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Definition
- acts on late distal tubules and collecting ducts
- causes Na, Cl and H2O loss but K+ retention
- the Na loss osmotically increases water excretion |
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Term
| Describe the pharmacokinetics of a type-2 K+ sparing diuretic |
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Definition
- oral well absorbed (30-70%)
- peak action 1-2 hrs
- half-life 6-12 hrs |
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Term
| List three side effects of the type-2 K+ sparing diuretics |
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Definition
1. Hyperkalemia
2. Dizziness
3. Nausea |
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Term
| List two therapeutic uses of of type-2 K+ sparing diuretics |
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Definition
- edema of hypertension – used with thiazides
- used with other diuretics (e.g. thiazides) to augment Na excretion
to reduce K loss (ex. Dyazide) |
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