WEEK 5- Diuretics Flashcards
Diuretic Agents
Drugs that increase the rate of urine formation
Result: removal of sodium and water (where water goes, sodium follows)
hypokalemic
Mechanism of Action
Cause dilation of the arteries
Therefore decrease peripheral vascular resistance
They decrease extracellular fluid through increased urination
Decrease fluid volume and plasma
Therefore decreasing cardiac workload (therefore the heart doesn’t have to work so hard)
Diuretic Agents-CATEGORIES.
Carbonic anhydrase inhibitors Loop diuretics Osmotic diuretics Potassium-sparing diuretics Thiazide and thiazide-like diuretics
These agents are classified according to their site of action in the nephron –don’t need to know 1
Their potency is determined by its function in the nephron to inhibit Na+ and water from being reabsorbed
The greater the blockage of absorbing Na+ and water the greater the amount of diuresis therefore the greater the potency
Carbonic Anhydrase Inhibitors CAIs: Indications
Not v popular, a lot of side effects
Use as adjunct agents in the long-term management of open-angle glaucoma (they use beta-blockers to treat glaucoma)
To lower intraocular pressure before ocular surgery
Also useful in the treatment of:
Glaucoma
Edema
Eg: acetazolamide (Diamox)
CAIs: mechanism
glomerulus in THE proximal tubules where 2/3 of water and sodium is reabsorbed here
CAIs do not allow sodium and water to be reabsorbed into the blood and therefore is eliminated in the urine (blocking action)
Not commonly used due to the potential for severe metabolic acidosis with prolonged use
Loop Diuretics
Furosemide (Lasix)
Primarily used for pulmonary edema, heart failure, liver disease, nephrotic syndrome and ascites
**FIRST LINE FOR WHEN - fast diuresis is necessary
Half life 1-2hr, onset 1hr, peak 1-2hr duration 4 to 8hr
If there is a shift of fluid this quick, this effects BP and become hypotensive
The pnt needs to be catherized (IV)
Ascites—
accumulation of fluid into the peritoneal area
Loop Diuretics: Mechanism of Action
Act directly on the ascending limb of the loop of Henle to inhibit sodium and chloride reabsorption
Increase renal prostaglandins, resulting in the dilation of blood vessels and reduced peripheral vascular resistance
Loop Diuretics: Drug Effects
**Potent diuresis and subsequent loss of fluid Decreased fluid volume causes: Reduced BP Reduced pulmonary vascular resistance Reduced systemic vascular resistance Reduced central venous pressure Reduced left ventricular end-diastolic pressure Potassium depletion
Loop Diuretics:Indications
Edema associated with heart failure, hepatic or renal disease
Control of hypertension
Useful when rapid diuresis is needed - effect lasts 2hr
They can still work when the kidney function is diminished
Does not damage the kidney
Single daily dose is usually given in the morning- so they don’t get up all night using the bathroom
Major side effect of loops is
electrolyte imbalance—prolonged high doses may cause hearing loss–ototoxicity
Loop Diuretics: Side Effects
Dizziness, headache, tinnitus (ringing in the ear) (prolonged high doses may cause hearing loss—ototoxicity), blurred vision, neutropenia, thrombocytopenia, hyperglycemia, hyperuricemia
Osmotic Diuretics
Mannitol (Osmitrol)
Used to reduce intracranial pressure and cerebral edema –like brain tumors, infection, head injury, CVA, or if they are on VIT.A (if overdosed can cause intracranial pressure. The pnt would be vomiting if they overdosed)
Elevated intra-ocular pressure
Administer through filter—may crystallize when exposed to low temperatures
Osmotic Diuretics: Mechanism of Action
Work in the proximal tubule
Pull water into the blood vessels and nephrons from the surrounding tissues
Inhibits tubular reabsorption of water and solutes increasing urine production
Slight loss of electrolytes especially sodium
Osmotic Diuretics: Drug Effects
Reduced cerebral edema
Increased urine production, causing diuresis
Reduced excessive intraocular pressure
Osmotic Diuretics: Indications
Used in the treatment of patients in the early, oliguric phase of acute renal failure (ARF)
To promote the excretion of toxic substances
Reduction of intracranial pressure
Treatment of cerebral edema
Treatment of increased intra-ocular pressure
Potassium-Sparing Diuretics
Spironolactone (Aldactone)
Amiloride (Midamor)
Loop directs, take away potassium and K-sparing diur. leave it AND can cause it to become hyperkalimic
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Potassium-Sparing Diuretics: Indications
Spironolactone
Hypertension
Reversing the potassium loss caused by potassium- losing drugs ie. Loop diuretics
So if they can handle lasix and the K deletion, they got to take this.
Drug drug interaction would not be safe on the fact that it would retain too much fluid
Potassium-Sparing Diuretics: Side Effects
Dizziness, headache,Cramps, nausea, vomiting, diarrhea, Urinary frequency, weakness hyperkalemia
Thiazide and Thiazide-like Diuretics
** Hydrochlorothiazide (HydroDIURIL)**
Inhibit tubular reabsorption of sodium and chloride ions
Action primarily in the ascending loop of Henle and early distal tubule
Result: water, sodium, and chloride are excreted
Potassium is also excreted to a lesser extent
Dilate the arterioles by direct relaxation
Thiazide and Thiazide-like Diuretics: Indications
Hypertension (one of the most prescribed group of agents for this – generally first line drug WITH NO OTHER UNDERLING PROBS because it’s a v safe drug and can change doses easily. They can use this drug for a long time)
Edematous states
Idiopathic hypercalciuria
Diabetes insipidus (lacking hormone ADH and you have to pee all of the time
Adjunct agents in treatment of heart failure (HF), hepatic cirrhosis
Thiazide and Thiazide-Like Diuretics: Side Effects
Dizziness, headache, blurred vision, paresthesias, decreased libido
Anorexia, nausea, vomiting, diarrhea
Potassium
Potassium is critical for the normal functioning of the muscles, heart, and nerves
It plays an important role in controlling activity of smooth muscles (such as the muscle found in the digestive tract) and skeletal muscles (muscles of the extremities and torso), as well as the muscles of the heart
It is also important for normal transmission of electrical signals throughout the nervous system within the body
Hyperkalemia
Hyperkalemia can be asymptomatic, sometimes, patients with hyperkalemia report vague symptoms including:
Nasuea, fatigue, muscle weakness and tingling
Severe hyperkalemia can cause suppression of electrical activity of the heart which includes a slow heartbeat and weak pulse and can cause the heart to stop beating resulting in fatal cardiac standstill
Hypokalemia
Potassium affects the way neuromuscular cells discharge energy (depolarize) and then regenerate (repolarize) that energy to be able to fire again. When potassium levels are low, the cells cannot repolarize and are unable to fire repeatedly, so the muscles and nerves can function normally
The effects of low potassium include can cause the following symptoms:
Muscle weakness, muscle aches, muscle cramps, cardiac palpitations
Instruct patients to take their medication in the morning to avoid interference with sleep patterns
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normal K range
3.5-5mmol/L
Patients taking diuretics along with a digitalis preparation
should be taught to monitor for digitalis toxicity (low potassium levels increase its toxicity) aka digoxin
