Drugs That Act On The Kidney Flashcards
What is the Nephron and its role?
It is a filtering structure in your kidneys. It aims to regulate the concentration of water and salts by filtering the blood, re absorbing what is needed and excreting the rest via urine.
What is the job of the kidney?
Balance the ions within the body.
Explain the structure of the Nephron
Glomerulus is a network of capillaries
Proximal convoluted tubule is where the water and solutes pass through and enter the loop of henle
The distal convoluted tubule is where the fluid returns to and passes to the collecting duct to be excreted via urine.
Define diuretics and its 3 main uses
Drugs that increase the amount of fluid and salts excreted by the kidneys
Main uses: - Oedema -Hypertension -Glaucoma
Explain the use of diuretics in oedema
It increases urine production by a) drawing more fluid from swollen areas in tissues and b) reduces the swelling and area returns to normal
Explain the use of diuretics in hypertension
It increases the volume of urine production
Decreases: blood volume, pressure on blood vessels and blood pressure.
How do salts and water move into the body?
Active transport via pumps; energy dependant
NA+/K+ pump, NA+/CI- pump, NA+/K+/CI- Pump.
Passive transport via channels: specific for different ions- no energy required
Osmosis- for water “wherever salts go, water will go” absorbed and excreted
What are the classes of diuretics?
- Thiazides and related drugs
- Loop diuretics
- Potassium sparing diuretics
What is the site of action for thiazides and its related drugs?
Distal convoluted tubule
What are the clinical uses for thiazides?
Oedema
- mild heart failure, liver and kidney disease, steroid/ hormone treatment
Hypertension
- primary treatment for long term illness, affects the blood volume.
Name thiazides drugs
Bendroflumethazide
Cyclopenthazide
Related drugs: metrolazone, chlortalidone, indapamide, xipamide ( end with “ZONE” or “MIDE”.
Where is thiazides drugs metabolised?
Liver
Explain the mechanism of action for thiazides and related drugs
They block the sodium pump, this means absorption is stopped.
Increase secretion of the sodium and chloride pump. Increase excretion of potassium due to the sodium exchanged for potassium in collecting duct via ion channels.
What should the nurse consider when administering thiazides?
- It has moderate potency.- 5-10% filtered NA+ excreted. Urine flow increase spfrom 1ml/min to 3ml/min
- Acts within 1/2 hours
- duration of action up to 24 hours
- take in the morning
- caution with pregnancy/ breast feeding
What are the side effects of thiazides?
- Hypokalemia- confusion, dizziness, arrhythmia
- Hypocalcemia- tiredness, lethargy, muscle fatigue
- Hyperuricmia- high Uric acid: gaut
- Hypergyplycemia- diabetes.
Where is the site of action for loop diuretics?
Ascending loop of henle
What is the clinical uses for loop diuretics?
Oedema
-Very effective if severe heart failure
-Acute ventricular failure
Hypertension
Name the drugs for loop diuretics
End with “MIDE”
Furosemide
Bemetanide
Torasemide
Where is loop diuretics metabolised?
Liver
What is the mechanism of action for loop diuretics?
It blocks the sodium-potassium-chloride pump. This increases the excretion of all three ions. The potassium is exchanged with sodium in the collecting duct
What should the nurse do side before administering loop diuretics?
- very powerful high ceiling effective drug: up to 30%filtered sodium excreted, urine flow from 1ml/min to 8ml/min
- acts within 1hr, lasts for 6 hrs
- twice daily, morning and before 4pm
What are these de effects for loop diuretics?
Hypokalemia Hypocalcemia Hyperuricemia Hyperglycaemia Deafness in very high dose of IM and IV drugs, damage to the 8th cranial nerve
Where is the site of action for potassium soaring drugs?
Late distal tubule and collecting duct
Name the clinical uses for potassium sparing diuretics
Oedema: heart failure and liver disease
Hypertension
Hypokalemia with loop and thiazides
Primary hyperaidosteronism- conns syndrome (spironolactione only)
Example of potassium sparing drugs
Spironolactione
Eplerenone
Both aldosterone antagonist
Amiloride, triamterere
Sodium channel blockers
Where is the potassium sparing drugs metabolised and excreted
Liver
Urine and bile
Explain the potassium sparing diuretics mechanism of action
It increase the sodium and water excretion, as well as chloride and calcium. Decrease excretion of potassium and hydrogen.
Aldosterone is blocked from binding to its receptor (spironolactione)
What should the nurse consider befriend administering potassium sparing diuretics?
- weak diuretic with 5% filtration of sodium excretion
- hyperkalamia look at diet
- close monitoring of electrolyte levels are required especially with ace inhibitors, arbs-Sartans and B- adrenoceptor antagonists
What are anti-diuretics?
It helps to control the bodies water balance by reducing urination, opposite of diuresis.
Where is the site of action for antidiuretics?
The collecting tubule/duct
What are the clinical uses for antidiuretics?
Central diabetes insipdus- lack of ADH
What are the drugs for antidiuretics
Vasopressin
Desmopressin
Explain the mechanism of actions for antidiuretics
ADH Is released from the posterior pituitary gland
The drugs increase the number of water channels by v2 receptors
And increase passive reabsorption of water
Explain the properties of Vasopressin
Is has a short duration of action
Injection/infusion only
Increase blood pressure, v1 receptors in smooth muscle
Explain the properties of Desmopressin
Longer duration of action
Nasal spray or tablets
No effect of blood pressure (v2 receptor selective).
What should the nurse consider before administering antidiuretics
Dosage must be balanced to allow some urine production to prevent water intoxication
