Pharmacology 3: Other Renal Drugs Flashcards
how do osmotic diuretics enter the nephron
given IV - by glomerular filtration and are not reabsorbed
how do osmotic diuretics work (2)
1) increase osmolarity of filtrate which attracts water and sodium across 2) opposes water reabsorption in some parts of the nephron
where do osmotic diuretics act in the nephron
proximal tubule
what are clinical indications for osmotic diuretics (2)
1) prevents acute hypovolaemic renal failure by maintaining flow 2) urgent treatment of raised ICP or raised intraoccular pressure (increases plasma osmolarity)
what are adverse effects of osmotic diuretics (2)
transient expansion of blood volume, hyponatramia
how can hyperglycaemia cause osmotic diuresis
reabsorptive capacity in proximal tubule by SGLT1/2 is exceeded - glucose stays in filtrate and causes water to be excreted with it
how can iodine radiocontrast dyes cause osmotic diuresis
dye is filtered but not reabsorbed which increases osmolarity of the filtrate and causes fluid to be excreted
name an osmotic diuretic
IV mannitol
how do carbonic anhydrase inhibitors work
carbonic anhydrase supplies H for Na/H exchange so this is inhibited - also excreted HCO3 with some Na, K and H20
what can carbonic anhydrase inhibitors cause
metabolic acidosis and alkaline diuresis
when are carbonic anhydrase inhibitors used
glaucoma after surgery, prophylaxis of altitude sickness, infant epilepsy
what other agents can alkalise urine and why is this useful
citrate salts - relieves dysuria, prevents weak acid crystals, enhances excretion of weak acids
where is aldosterone released from and what does it eventually cause
adrenal cortex –> enhanced tubular Na reabsorption and retention
how does aldosterone effect Na/KATPase and ENaC to increase Na reabsorption
increases synthesis of Na/KATPase pump (K excretion) /// increases activity of ENaC which is a Na channel
where is vasopressin released from and what does it eventually cause
enhanced H2O reabsorption by increases number of aquaporin channels in apical membrane
what is neurogenic diabetes insipidus
lack of ADH (vasopressin) released from post pit which causes increases water excretion
how is neurogenic diabetes insipidus treated
desmopressin
what effects do nicotine and ethanol have on ADH
ethanol inhibits ADH secretion and nicotine enhances ADH secretion (raised BP)
what is nephrogenic diabetes insipidus and what usually causes it.
nephron does not respond to vasopressin - usually caused by X-linked recessive gene on V2 receptor
how do you treat nephrogenic diabetes insipidus
no current treatment
what drugs can cause vasopressin inhibition in the kidneys (3)
lithium, demeclyocyline (AB), vaptans
when is vasopressin used in children
bedwetting (nocturnal enuresis) >10
how do vaptans/ aquaretics work
competitive antagonist of vasopressin receptor (v1 and 2) - stops aquaporins being activated and causes water excretion with no Na loss
what can vaptans cause
hypernaetraemia
