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PHA 222 > diuretics > Flashcards

diuretics Flashcards

1
Q

what kind of action do diuretics exhibit?

A

diuretic action

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2
Q

what are the two common examples of purines that have a diuretic effect?

A

Theophylline

2.Caffeine

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3
Q

what kind of a diuretic is caffeine?

A

mild diuretic that shows CNS stimulation

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4
Q

what kind of a diuretic is theophylline?

A

more potent diuretic, but less CNS stimulation. Also operates as a muscle relaxant

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5
Q

how do caffeine and theophylline work?

A

Compounds work by inhibiting phosphodiesterase

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6
Q

what is Aminophylline? and what is it used for?

A

theophylline+ ethylenediamine. Used as a bronchodilator for treatment of asthma and COPD

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7
Q

what is carbonic anhydrase used for?

A

regulation of acid/base balance
production of bicarbonate rich aqueous humor secretion (malfunction leading to glaucoma)
secretion of electrolytes in many tissues, e.g. CSF formation
•Saliva production and bile production

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8
Q

how may different isoforms have been identified of carbonic anhydrase?

A

14 different isoforms have been identified in higher vertebrates

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9
Q

what is carbonic anhydrases function?

A
  • Carbonic anhydrase catalyses a number of chemical reactions.
  • Most important physiological reaction is the reaction of water and CO2to form carbonic acid
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10
Q

what is carbonic anhydrase?

A

Metalloenzyme containing a Zn2+ ion

•The metal sits at the bottom of a 15 Å-cleft and is coordinated by 3 histidine residues

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11
Q

what is the 4th occupied site in carbonic anhydrase?

A

4th coordination site is occupied by a water molecule/hydroxide ion- active

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12
Q

why is the zinc ion critical in the carbonic anhydrase binding?

A

The zinc ion sits at the bottom of a cleft which has two distinct faces –a hydrophobic face and a hydrophilic face
•The hydrophobic face is important for binding the substrate and the hydrophilic face is important for shuttling protons in and out

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13
Q

what is carbonic anhydrases role in the kidney?

A

Bicarbonate is filtered in the glomerulus, but most is reabsorbed
•Bicarbonate reabsorption depends on H+ secretion into the lumen
•H+ are recycled by carbonic anhydrase which is present in the cytoplasm of the cells

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14
Q

what was Acetazolamide used for?

A

in the treatment of glaucoma but not used as a diuretic anymore.

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15
Q

what is the MOA of Acetazolamide?

A

Inhibits CAII which reduces the production of aqueous humour leading to a 25-30% reduction in intraocular pressure

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16
Q

what is Inhibits acetazolamide suppressed by?

A

superseded by other water soluble topical anti-glaucoma agents –dorzolamideand brinzolamide

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17
Q

what affect does acetazolamide inhibiting CA2 have?

A
  • This results in an increase in the secretion of bicarbonate, sodium and potassium ions….
  • …..with the concomitant osmotic equivalent of water
  • this situation produces metabolic acidosis
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18
Q

what functional group does all carbonic anhydrayse inhibitors have?

A

All carbonic anhydrase inhibitors have a sulfonamide group

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19
Q

how do carbonic anhydrases inhibitors, acting on CAII bind ?

A

binding via the ionised sulfonamide moiety

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20
Q

what does a primary sulfonamide mean?- in CAII?

A

primary sulfonamide means that they will have a certain affinity for one or more isoforms of CA
•May not be the main MOA of these drugs

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21
Q

how do loop diuretics work?

A

Loop diuretics work by inhibiting the Na+/K+/2Cl-transporter in the lumenal membrane of the thick ascending limb

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22
Q

what are examples of loop diuretics?

A

Furosemide, bumetamide and torseamide are all examples of loop diuretics•

23
Q

in thiazide like diuretics, what substitution will make it neutral?

A

•3,4-tautomer predominates at pH>8.•Substitution of the sulfonamide H will make that moiety neutral…

24
Q

what does hydrothiazides refer to?

A

Hydrothiaziderefers to 3,4-dihydro-1,2,4-benzothiadiazine-1,1-dioxide
•Still have the acidic sulfonamide

25
Q

what does hydrogenation of the 3,4 double bond in thiazide diuretics do?

A

Hydrogenation of the 3,4-double bond improves diuretic activity but also reduces CA activity

26
Q

true or false thiazides are generally more resistant to hydrolysis in acid and alkali hydrrthiazides?

A

false- opposite

27
Q

what position is the preferred sulfonamide group on the benzene ring of thiazides and hydro thiazides preferred at?

A

must have a 10 sulfonamide group (preferably in position 7)

28
Q

does saturation in positions 3 and 4 makethe thazide more or less active?

A

more active

29
Q

what position is a halogen important on in thiazides/ hydro?

A

position 6

30
Q

what happens when there is substitution at position 3?

A

Substitution at the 3 position gives rise to a set of compounds with diverse activity –the cyclopentyl methyl moiety is optimum

31
Q

what is tolerated in position 2?

A

small alkyl group

32
Q

what can the sulphone in position one be replaced by?

A

can be replaced with a carbonyl group and activity maintained

33
Q

what are thiazides MOA?

A
  • Thiazides operate in the distal convoluted tubule where they inhibit the Na+/Cl-cotransporter
  • they bind to the Cl-binding site of the protein
  • The result is the loss of Na+and Cl-, which leads to a contraction in blood volume
  • Also increased renin secretion, angiotensin formation, and ultimately aldosterone secretion
34
Q

what are the 2 aldosterone antagonists?

A

spironolactone and eplerenone- competitive antagonists - both have a weak diuretic effect

35
Q

what does aldosterone do?

A

•Aldersteroneis a hormone produced by the adrenal cortex that promotes Na+reabsorptionin the collecting ducts

36
Q

what are the 4 structure relation activity for aldosterone antagonists?

A
  1. Ketone at C-3 is important for activity
  2. A relatively planar A/B ring juncture –better if C=C double bond at C4,C5
  3. Substitution in the B ring is important for oral absorption
  4. A 5-membered spirolactoneof specific configuration at C17 (R)
37
Q

what would a clinical investigation of AKI entail?

A

full family history/ physical examination/ urine and blood examination and radiological studies

38
Q

what are the 3 pathologies of AKI and what are their clinical findings?

A

Hypovolaemia-Hypotension /Low cardiac output/Shock
Oliguria-Fluid overload
Hyperkaelmia- Arrhythmias

39
Q

what is the management for Hypovolaemia?

A

Plasma, dextran, saline( Inotropes)

40
Q

what is the management for Oliguria?

A

Osmotic or loop diuretic (highdose)Fluid / Na restriction Bladder catheter

41
Q

what is the management Hyperkaelmia?

A

Mild: Binding in gut with cationic ion exchange resin –polystyrene sulphonate

42
Q

what is the intracellular and extracellular concentration of potassium?

A

intracellular concentration of 140 to 150 mEq/L

•The extracellular concentration of 3.5 to 5.0mEq/L

43
Q

what are the two mechanisms which plasma potassium is regulated by?

A

–Renal mechanisms that conserve or eliminate potassium

–A transcellular shift between the ICF and ICFcompartments

44
Q

define hypokalemia

A

Hypokalemia refers to a decrease in plasmapotassium levels below 3.5 mEq/L

45
Q

define hyperkalemia

A

Hyperkalemia refers to an increase in plasma levels of potassium in excess of 5.0 mEq/L

46
Q

what changes in an ECG in hyperkalemia and hypokalemia?

A

hyper-low p wave, prolonged PR/ widening of QRS/ peaked T

hypo- PR prolongation/ depressed ST segment/ low T/ prominant U wave.

47
Q

what are the 3 ways to treat hyperkalemia?

A

Stabilise cellmembrane potential
shift K+ into cells
remove k+ from body

48
Q

how do you stablise membrane potential?

A

I.V calcium gluconate (10ml of 10%solution )

49
Q

how do you shift k+ into cells?

A

Inhaled Beta 2 agonists eg. SalbutamolIV
glucose (50ml of 50%solution )
Insulin (5U Actrapid)
Intravenous sodium bicarbonate(100mlof 8.4%)

50
Q

how do you remove k+ from the body?

A

IV furosemide and normal saline Ion exchange resin (eg. Resonium)Dialysis

51
Q

how would you identify and manage acidosis?

A

Low plasma bicarbonate-Bicarbonate infusion

52
Q

how would you identify and manage Uraemia?

A

Nausea, vomiting Diarrhoea Pruritus-Osmotic or loop diuretic (high dose)Fluid / Na restriction Bladder catheter

53
Q

how would you identify and manage Non-specfic azotaemia?

A

Tiredness ,lethargy -Adequate non-nitrogenous caloric intake

PHA 222 (41 decks)

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