Pharmacology 2 Flashcards
Name an osmoic diuretic?
mannitol IV
What is special about osmotic diuretics?
they are membrane impearmeable polyhydric alcohols so can only be given via IV
What is the mode of action of osmotic diuretics?
enter the nephron by glomerular filtration, but are not reabsorbed
act in the proximal tubule as it is freely permeable to water, and oppose the absorption of water
they secondarily reduce Na reabsorption
When are osmotic diuretics used?
presentation of acute hypervolaemic renal failure
urgent treatment of acutely raised intraocular/intracranial pressure - solute does not enter the brain or eye due to BBB but it creates an osmotic gradient
What are the adverse effects of osmotic diuretics?
transient expression of blood volume and hyponatreamia
What are the two other situations where an osmotic diuresis can occur?
hyperglycaemia - reabsorptive capacity of proximal tubule for glucose is exceeded
iodine radiocontrast dyes - glucose in the fluid retains fluid leading to an osmotic load
Name a carbonic anhydrase inhibitor?
acetazolamide
What is the role of carbonic anhydrases?
increase excretion of HCO3, Na, K and H20 resulting in an alkaline diuresis which results in a metabolic acidosis
When is it useful to have an alkaline diuresis (urine)? - can cause by giving citrate salts
relief of dysuria
prevents crystilisation of weak acids with limited aqueous solubility - i.e. prevents uric acid stones
enhance secretion of weak acids
When are carbonic anhydrase inhibitors given?
glaucoma and following eye surgery - reduces aqueous humour production
prophylaxis of altitude sickness
some forms of infantile epilepsy
What are the two types of diabetes insipidus?
nephrogenic - inability of nephron to respond to vasopressin
neurogenic - lack of vasopressin secretion
What are the two vasopressin receptors, what is their role?
V1 - regulation of smooth muscle tone
V2 - regulates water permeability in the collecting duct, increased AQP2 expression on membrane
How is neurogenic DI treated?
desmopressin - a vasopressin analogue with V2 receptor selectivity
What inhibits vasopressin release?
alcohol
What stimulates vasopressin release?
nicotine
What can cause nephrogenic DI?
X linked recessive mutations in V2 receptor gene - AVPR2
What is the treatment for nephrogenic DI?
NONE
How can the kidneys action to sense vasopressin be inhibited?
lithium
demeclocyline
vaptans
What are Vaptans?
AQUA DIURETICS - cause water to be lost but not solute
Give an example of Vaptans?
tolvaptan (V2)
convivaptan (V1A and V2)
What is the mode of action of Vaptans?
competitive antagonists of vasopressin receptors
- blockage of V2 receptors cause H20 excretion (WITHOUT NA) and so therefore increase Na concentration
Where are Vaptans used in?
still trialing - hypervolaemic hyponatreamia
tolevaptan is used in SIADH
Name 3 SGLT-2 inhibitors?
cangliflozin
dapagliflozin
empagliflozin
How is glucose reabsorbed in the nephron?
proximal tubule by SGLT-1 and SGLT-2
What SGLT absorbs the most glucose?
SGLT-1 - 10%
SGLT-2 - 90%
Where in the body is SGLT-1 expressed?
intestines and kidney
Where in the body is SGLT-2 expressed?
purely kidney - want to selectively block this
How does glucose reabsorption occur on the apical membrane?
active transport
How does glucose reabsorption occur on the basolateral membrane?
facilitated diffusion
Which SGLT comes first in the proximal tubule?
SGLT-2 before SGLT-1
What are the characteristics of SGLT-1 in terms of affinity and capacity?
high affinity but low capacity
2 Na for every 1 glucose
What are the characteristics of SGLT-2 in terms of affinity and capacity?
low affinity but high capacity
1 Na for every 1 glucose
What does the inhibition of SGLT-2 result in?
glycosuria
What is familial renal glycosuria?
mutation of the SGLT-2, so glycosuria - doesnt cause any problems in life
What do SGLT-2 inhibtiors cause?
excretion of glucose
decreased HbA1c
weight loss
What is a common side effect of SGLT-2 inhibitors?
UTIs
What are prostaglandins formed from?
fatty acid arachidemic acid by cycle-oxygenase enzymes (COX 1 and 2)
What are the major prostaglandins synthesised in the kidney?
PGE 2- medulla
PGI2 - glomeruli
What is the role of prostaglandins?
act as vasodilators and are natiuretic (secrete Na)
When are prostaglandins synthesised?
in response to: ischeamia mechanical trauma angiotensin 2 ADH bradykinin
What is the role of prostaglandins in response to vasoconstriction or decreased arterial blood volume?
cause compensatory vasodilation
direct vasodilator affect on afferent arteriole
increased angiotensin 2 vasoconstricts the efferent arteriole causing an increased filtration rate
What do NSAIDs inhibit?
COX
What may NSAIDs cause in cirrhosis, heart failure and nephrotic syndrome?
renal failure because the renal arteriole flow is due to prostaglandin vasodilator affects
What is uric acid formed by?
catabolism of purines
Name three uricosuric agents?
probenecid
sulfinpyrazole
allopurinol
What is the role of allopurinol?
inhibits urate synthesis
What is the role of probenecid and sulfinpyrazole?
block reabsorption of urate in the proximal tubule
