drugs that act on the kidney Flashcards
what is the role of the kidney?
to balance salts and fluid in body
describe the path of water through the kidney
- glomerulus
- proximal tubule
- loop of henle
- distal tubule
- collecting duct
what are diuretics?
drugs taht increase the amount of fluid and salts excreted by the kidneys
what are the main uses of diuretics?
- oedema - fluid collection in tissue
- hypertension - high BP
- glaucoma - decreases fluid pressure in the eye (intraocular pressure)
how do diuretics help to treat oedema?
by increasing urine production → this draws fluid from swollwn areas of tissue thus reducing swelling
how do diuretics help to treat hypertension?
- increase urine production
- decrease blood volume
- decrease blood pressure
- decrease pressure on blood vessels
name three ways in which salts and water move
- active transport - via pumps
- passive transport - via channels
- osmosis
name three ‘pumps’ within the body which move salts - what is required for this to occur?
- sodium/potassium (Na+/K+pump)
- sodium/chloride (Cl- pump)
- sodium/ potassium / chloride (Na+/K+/ Cl- pump)
* all use energy to move salts
what are channels? and do they require energy?
channels are ion selective openings in the cell membrane - no energy required
what is the osmotic effect?
where salts go water follows
name the three classes of diuretic
- thiazide and related diuretics
- potassium sparing diuretics
- loop diuretics
what is the site of action for thiazide and related duiretics?
distal convoluted tubule
what are the clinical uses of thiazide and related diuretics?
- oedema
- hypertension - long term
- mild heart failure
- liver and kidney disease
- steriod/hormone treatment
name two thiazide diuretics
- bendroflumethazide
- cyclopenthiazide (navidrex®)
name four thiazide related diuretics
- metolazone (metenix®)
- chlortalidone (hygroton®)
- indapamide (natrilix®)
- xipamide (duirexan®)
where are thiazide and related diuretics metabolised and excreted?
metabolised - liver
excreted - kidneys
describe the mechanism of action of thiazide and related diuretics
- blocks chloride pump
- increases excretion of sodium and chloride
- increases excretion of potassium (due to sodium exchangeof potassium in collecting ducts via ion channels)
what is the potency of thiazide and related diuretics?
moderate
what % of filtered sodium is excreted due to thiazide diuretics?
5-10%
when taking thiazide diuretics how much is the urine flow increased by?
from 1ml/per/min to 3ml/per/min
how long do thiazide diuretics take to act and what is the duration of action?
acts within 1-2hrs
duration of action 24hrs
what are the side effects associated with taking thiazide diuretics?
- hypokalemia
- hypocalcemia
- hyperuricemia - high uric acid
- hyperglycemia
what is the site of action of loop diuretics?
ascending loop of henle
what are the clinical uses of loop diuretics?
- oedema
- hypertension
- severe heart failure
- acute ventricular failure (pulmonary oedema)
give three examples of loop diuretics
- furosemide (lasix®)
- bumetanide (burinex®)
- torasemide (torem®)
where are loop diuretics metabolised and excreted?
metabolised - liver
excreted - urine
describe the mechanism of action of loop diuretics
- blocks sodium /potassium /chloride pump
- increases excretion of:
- sodium
- chloride
- potassium - exchange with sodium in collecting ducts
what are the side effects of loop diuretics?
- hypokalemia
- hpocalcemia
- hpyeruricema
- hyperglycemia
- deafness - very high dose IM, IV dosing (8th cranial nerve damage)
what % of filtered sodium is excreted when using loop diuretics?
very powerful - 30% filtered sodium excreted
what is the increase in urine flow when taking loop diuretics?
from 1ml/per/min to 8ml/per/min
how long do loop diuretics take to act and how long do they work?
act within 1hr
work for 6hrs
when should loop diuretics be given?
upto twice daily (morning and before 4pm)
what is the site of action of potassium sparing diuretics?
late distal tuble and collecting duct
what are the clincal uses of potassium sparing diuretics?
- oedema - heart failure/live disease
- hypertension
- hypokalemia - caused by loop or thiazide diuretics
- primary hyperaldosteronism (Conn’s syndrome)- use spironolactione only
name four potassium sparing diuretics
- spironolactone (aldactone®)
- eplerenone (inspra®)
aldosterone antagonists
- amiloride
- trimterene (dytac®)
sodium channel blockers
where are potassium sparing diuretics metabolised and excreted?
metabolised - liver
excreted - urine and bile
what is the mechanism of action of potassium sparing diuretics?
- increased sodium and water excretion
- chloride and calcium also excreted
- decreased excretion of potassium and H+
how much filtered sodium is excreted when using potassium sparing diuretics?
fairly weak diuretic - 5% of filtered sodium excreted
what are the side effects of using potassium sparing diuretics?
hyperkalaemia - low potassium diet required
close monitoring of electrolyte levels - especially with ACE inhibitors, angiotensin receptor antagonists and beta adrenoceptor anatagonists
what is the site of action for antidiuretic drugs?
collecting tubules
what are the clinical uses of antidiuretics?
central diabetes insipidus (lack of ant-diuretic hormone
what is the mechanism of action of antidiuretics?
- released from posterior pituitary gland
- increases no. of water channels in V2 receptors
- increases passive reabsorption of water
name two antidiuretic drugs
- vasopressin
- desmopressin
describe the action, administeration and use of vasopressin
- very short acting
- injection/infusion only
- increases blood pressure (V1 receptors in smooth muscle)
describe the action, administeration and use of desmopressin
- longer duration of action
- nasal spray or tablets
- no effect on blood pressure (V2 receptors - selective)
*dose needs to be balanced to avoid H2O intoxication
what information must be gathered before and during administeration of diuretics?
- patient history - allergies, meds, organ impairment
- administer in morning
- check urine output
- monitor weight
- monitor serum electrolytes
- check oedema/congestion is reducing
- check BP - hypotension
- diet - rich/low in potassium and low in sodium
