Renal drugs Flashcards
What is nephrotic syndrome?
A disorder of glomerular filtration, allowing large protein (mainly albumin) to appear in the urine (proteinuria).
Why is fluid retained in congestive heart failure?
Cardiac output goes down therefore get activation of RAAS.
How does Hepatic Cirrhosis With Ascites occur?
Increased pressure in the hepatic portal vein, combined with decreased production of albumin, causes loss of fluid into the peritoneal cavity and oedema (ascites)
At what 4 points in the nephron can Na be reabsorbed?
Proximal tubule
Ascending limb of loop of Henle
Distal tubule
Collecting duct
What five mechanisms exist for Na reabsorption?
Na diffusion Na/H exchange NaKCl triple transporter NaCl cotransporter NaK exchanger
Where do most diuretics work?
Apical/luminal membrane
How do diuretics get into the filtrate?
Filtration
Secretion into proximal tubule
What two transport processes exist for secretion of diuretics into the proximal tubule?
Organic anion transporters (OATs)
Organic cation transporters (OCTs)
What type of drugs to OATs secrete?
Acidic (loop and thiazide)
What type of drugs to OCTs secrete?
Basic (triamterene and amiloride)
How do loop and thiazide diuretics cause hypokalemia?
Less K reab as less Na reab in proximal tubule and LoH
Increased Na reab in distal tubule loses K via NaK exchanger.
What are the two forms of DI?
Neurogenic diabetes insipidus
Nephrogenic diabetes insipidus
What is the etiology of Neurogenic diabetes insipidus?
Don’t produce ADH from post pit
What is the etiology of Nephrogenic diabetes insipidus?
Nephrons can’t respond to ADH
How do you treat Neurogenic diabetes insipidus?
Give desmopressin
What treatment id there for Nephrogenic diabetes insipidus?
None
What are the 4 categories of diuretic?
Loop
Thiazide
Potassium sparing
Osmotic
How do loop diuretics work?
Inhibit NaKCl triple transporter in the ascending LoH
Where do loop diuretics work?
Ascending LoH
How are loop diuretics transported in the blood?
Plasma bound
In addition to Na, K and Cl loss what other effects can loop diuretics have?
Vasodilation
Ca and Mg loss
Give two examples of loop diuretics
Furosemide
Bumetanide
What are some indications for starting a loop diuretic?
Acute pulmonary oedema Chronic heart failure Chronic kidney failure Nephrotic syndrome Increase urine volume in acute kidney failure Reduce acute hypercalcaemia Hypertension
What are some contraindications of loop diuretics?
Severe hypovolaemia/dehydration Severe hypokalaemia Severe hyponatraemia Hepatic encephalopathy Gout
What are some side effects of loop diuretics?
Hypokalaemia Metabolic alkalosis Hypocalcaemia Hypomagnesaemia Hypotension Hyperuricaemia Dose-related loss of hearing
How do thiazide diuretics work?
Inhibit the NaCl cotransporter in the distal tubule
Where do thiazide diuretics work?
Distal tubule
In addition to Na and K loss what other effects do thiazide diuretics have?
Vasodilation
Ca retention
Give some examples of thiazide diuretics
Bendroflumethiazide
Chlortalidone
Indapamide
Metolazone
What are the indications for starting a thiazide diuretic?
Mild heart failure Hypertension Severe resistant oedema Renal stone disease Nephrogenic diabetes insipidus
What are some contraindications for starting thiazide diuretics?
Hypokalaemia
Hyponatraemia
Gout
What are some side effects of thiazide diuretics?
Hypokalaemia Metabolic alkalosis Hypotension Hypomagnaesmia Hyperuricaemia Erectile dysfunction Impaired glucose tolerance in diabetics
Where do all K sparing diuretics work?
Late distal and collecting tubule
Through which two mechanism can K sparing diuretics work?
Block the apical sodium channel and decrease Na+ reab therefore reduce K excretion.
Compete with aldosterone for binding to intracellular receptors preventing its translocation of Na channels.
Which two K sparing diuretics work by blocking the apical Na channel?
Amiloride and Triamterene
Which two K sparing diuretics work by blocking aldosterone?
Spironolactone and Eplerenone
What are the indications for starting a K sparing diuretic?
Use in combo with diuretics causing hypokalemia
Use in combo with loop and thiazide as it blocks RAAS they activate
Heart failure
Primary hyperaldosteronism (Conn’s syndrome)
Resistant essential hypertension
Secondary hyperaldosteronism (due to hepatic cirrhosis with ascites)
What are the contraindications for starting a K sparing diuretic?
Severe renal impairment
Hyperkalemia
Addison’s disease
Give an example of an osmotic diuretic?
Mannitol
How is mannitol given?
IV
How do osmotic diuretics work?
Freely filtered but not reabsorbed so increase osmolarity of filtrate drawing water back and stopping Na reab.
What are the indications for starting an osmotic diuretic?
Prevention of acute hypovolaemic renal failure to maintain urine flow
Urgent treatment of acutely raised intracranial and intraocular pressure
Why are osmotic diuretics used for intracranial/ocular pressure?
Does not enter the eye, or brain, but increased plasma osmolality extracts water from these compartments.
What are some side effects of osmotic diuretics?
Transient expansion of blood volume
Hyponatraemia
Hyperglycaemia
What drugs can inhibit ADH receptors?
Li
Demeclocycline
‘Aquaretics’ or ‘Vaptans’
How do ‘Aquaretics’ or ‘Vaptans’ work?
Inhibit ADHR
What do ‘Aquaretics’ or ‘Vaptans’ do?
Excretion of water without accompanying Na+ and thus raises plasma Na+ concentration.
What are some indications for ‘Aquaretics’ or ‘Vaptans’?
Hypervolaemic hyponatraemia
SIADH
Which two SLGTs are found in the kidney?
SLGT1 and 2
Where is SLGT1 found in the kidney?
DIstal tubule
Where is SLGT2 found in the kidney?
Proximal tubule
How much of the glucose in the urine does SLGT2 absorb?
90%
How does SLGT2 work?
Facilitative transporter requiring Na
Compare SLGT1 and 2
SLGT1: 2Na:1Glucose, High affinity/low capacity
SLGT2: 1Na:1Glucose, Low affinity/high capacity
What do uricosuric drugs do?
Inhibit urate absorption
Give some examples of uricosuric drugs.
Probenecid
Sulfinpyrazole
What kind of drugs modify urine pH?
Carbonic Anhydrase Inhibitors
Give an example of a CA inhibitor
Acetazolamide
What effects do CA inhibitors have?
Excretion of HCO3- with Na+, K+ and H2O
Alkalize urine
What are some indications for starting CA inhibitors?
Glaucoma and following eye surgery Prophylaxis of altitude sickness Relief of dysuria Prevention of the crystallization of weak acids Enhancing the excretion of weak acids
Which prostaglandins are synthesized by the kidneys?
PGE2- Medulla
PGI2 (prostacyclin)- Glomeruli
What physiological effects do prostaglandins have on the kidney?
Vasodilators
Na excretion
Under normal conditions how much of an effect do have on renal blood flow (RBF), or glomerular filtration rate (GFR)?
Very little
When are prostaglandins important to the kidneys?
conditions of vasoconstriction, or decreased effective arterial blood volume, where they cause compensatory vasodilation.
What are prostaglandins synthesized in response to?
Ischaemia Mechanical trauma Angiotensin II ADH Bradykinin
What can inhibit prostaglandins synthesis?
NSAIDs