Diuretics

Question 1

Furosemide (Lasix)

Answer 1

Loop Diuretic

Uses;

• Tx HTN
• Tx increased ICP
• Tx hypercalcemia
• Acute relief of edema r/t heart failure
• Mobilize edema from renal/hepatic failure

MOA:
blocks Na/K/2Cl channel in the loop of Henle blocking reabsorption of Cl, Na and H20; excretion of Cl, Na, H20, calcium, magnesium and K+

Dose; 0.1 - 1 mg/kg IV
(IV injection should be given slowly)

Pharmacokinetics;

• onset; 5 min (IV)
• DOA; 2 hrs (IV)
• Pb; 90%

Side Effects;

• orthostatic hypotension
• N/V
• dizziness, headache, vertigo
• thrombophlebitis
• electrolyte abnormalities (hypo;K, Cl, Mg, Ca, hyper;Na)
• metabolic alkalosis
• urinary frequency

Contraindicated;
-Abnormalities in fluid/ electrolyte balance

Caution;

• Succinylcholine action may be increased
• potentiated effects of NMBD (hypoK)
• increased risk of Lithium toxicity
• aminoglycosides increased risk of oto/nephrotoxicity
• cephalosporin increased nephrotoxic risk

Question 2

Mannitol

Answer 2

Osmotic Diuretic
6-carbon sugar
02 free radical scavenger

Uses;

• Tx increased ICP r/t cerebral edema
• decreases IOP
• promotes urinary excretion of toxic substance (radioactive dye)
• Irrigant used in TURP procedure
• Scavenges 02 free radicals

MOA;

• promotes movement of intracellular/ extracellular fluid into the plasma out of other tissues (like the brain)
• temporary increase in plasma volume occurs followed by diuresis bc mannitol is filtered but NOT reabsorbed; during filtration mantel pulls fluid and electrolytes (Na, Cl, HC03) into the urine; increasing urine output

Dose; 0.25 - 1 g/kg over 30 - 60 min

Pharmacokinetics;
onset; 15 min
DOA; 3 -6 hours

NO metabolism; eliminated unchanged in the urine

Side Effects;

• headache
• seizure
• N/V
• dramatic increase in intravascular volume
• hypovolemia/ electrolyte imbalance in prolonged use
• Pulmonary edema n pt with poor myocardial function

Contraindicated;

• severe renal dysfunction
• active brain bleed
• severe myocardial dysfunction (unable to handle rapid volume expansion)
• severe pulmonary edema

Question 3

Hydrochlorothiazide

Answer 3

Thiazide Diuretic

Uses;

• maintenance and tx of essential HTN
• Mobilization of edema from renal/hepatic failure
• Treatment of edema r/t CHF
• Less powerful and better tolerated than loop diuretics

MOA:

• inhibits the reabsorption of Na, Cl and water by blocking the Na/Cl co-transport in the Distal tubule causing diuresis and increase in Na, Cl, K, H+ and HC03 ion excretion
• poorly understood vasodilatory effect

Dose; 25 -100 mg/day PO
max daly dose 200mg

Pharmacokinetics;

• onset; 2 hrs
• DOA; 6 -24 hrs
• Vd; 3.5 - 8 L/kg
• Pb; 68%

Not metabolized
Excreted unchanged in the urine

Side Effects;

• metabolic alkalosis
• decreased K and Cl
• increased risk of arrhythmias and muscle weakness with decreased K
• increased risk of digoxin toxicity
• potentiates effects of NMBD
• hyperglycemia/ aggregate DM
• orthostatic hypotension

Contraindications

• hypersensitivity
• pregnancy
• renal decompensation