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Renal > 3.7: Drugs Acting on the Kidney 2 > Flashcards

3.7: Drugs Acting on the Kidney 2 Flashcards

1
Q

Major class of drugs that work on the kidneys?

A

Diuretics

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2
Q

Give an example of Osmotic Diuretics?

How are they adminstered?

A

Mannitol

Given IV

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3
Q

Osmotic Diuretics:

How do they work pharmacologically?

How do they work physiologically?

What part of the nephron do they work at?

A

Pharmacologically inert

Physiologically, they produce an osmotic effect to cause inhibit water reabsorption

Work at proximal tubule

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4
Q

Osmotic Diuretics:

  • Describe filtration at glomerulus?
  • Describe their reabsorption?
A

Freely filtered at glomerulus

Cannot be reabsorbed

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5
Q

What is the action of osmotic diuretics in the proximal tubule?

A

Inhibit reabsorption of water

This dilutes the filtrate

Causes inhibition of sodium reabsorption (Secondary)

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6
Q

Give some examples where osmotic diuretics would be used?

A
  • Given IV in acute kidney failure (Eg: After Hypovolaemia where kidneys stop producing urine and the distal tubule is at risk of drying up)
  • Raised intracranial and intraocular pressure

-

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7
Q

Can mannitol (osmotic diuretic) enter organs that have tight junctions?

Describe the effect on these organs?

Give two example organs?

A

No, unable to enter

Instead increases plasma osmolarity to remove water from these organs

Reduces pressure

Eg: Eyes and Brain

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8
Q

Give two examples where osmotic diuresis can occur (accidentally) without the use of diuretics?

A
  • Type 2 Diabetes (Glucose transporters are saturated, causes hyperosmotic filtrate –> Osmotic Diuresis)
  • Contrast Dyes
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9
Q

Name a carbonic annhydrase inhibitior?

A

Acetazolamine

(A-SEAT-O-ZOLAMINE)

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10
Q

How do carbonic annhydrase inhibitors work?

A

Inhibit the action of carbonic annhydrase in the proximal tubule

This increases excretion of bicarbonate, sodium and water

Produces alkaline urine

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11
Q

Use of carbonic annhydrase inhibitors?

A

No longer used a diuretics

  • Glaucoma and after eye surgery
  • Prophylaxis of altitude sickness
  • Infantile Epilepsy
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12
Q

What causes alkaline urine?

Why would you want alkaline urine?

A

Carbonic Annhydrase Inhibitor

Oral Bicarbonate

Citrate Salts

Relief of dysuria

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13
Q

Where is adolsterone secreted from?

Describe its affect on the collecting tubule?

A

Adolsterone secreted from adrenal cortex

Causes enhanced tubular sodium reabsorption and salt retention

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14
Q

Where is ADH secreted from?

What is its affect on the collecting duct?

A

Secreted from posterior pituitary

Causes enhanced H20 reabsorption

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15
Q

What is diabetes insipidus?

What are the symptoms?

A

Rare form of diabetes caused by ADH deficiency

Symptoms:

  • Thirst
  • Polydipsia
  • Polyuria
  • Large volume of dilute urine
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16
Q

What are the two types of Diabetes Insipidus?

Treatments?

A

Neurogenic = A failure of ADH secretion from posterior pituitary

Treatment: Desmopressin

Nephrogenic = Lack of responsivess of the V2 receptor to ADH.

No treatment

17
Q

Describe the affect of ethanol on ADH?

Describe the affect of nicotine on ADH?

A

Ethanol = Inhibits ADH secretion

Nicotine = Stimulates ADH secretion

18
Q

Give another use for Desmopressin?

A

Noctural Enuresis in children over 10

  • Not used in children under 10
  • Not used in adults over 65
19
Q

Describe the mutation in Nephrogenic Diabetes Insipidus?

A

Defect of V2 receptor

X-Linked (Seen in males)

Recessive

AVPR2 recessive x linked mutations

20
Q

What is the function of Vaptans?

Another name?

A

Competitive antagonists of vasopressin (ADH) receptors

Cause excretion of water (NOT SODIUM) and therefore increase sodium concentration

Another name is Aquaretics

21
Q

When are Vaptans/Aquaretics used?

Give an example?

A

In syndrome of inappropriate anti diuretic hormone secretion (SIADH) - Eg: TolVaptan

22
Q

Describe how inhibitors of sodium/glucose co-transporter 2 (SGLT2) work?

A

This inhibit reabsorption of glucose

Cause glucose excretion in the urine

(Basically you pee out the glucose)

23
Q

Glucose reabsorption is mediated by SGLT1 and SLGT2

Where does each one act?

How much does each absorb?

A

SGLT1 = Entire Kidney (Areas S2 and S3)

SGLT2 = Proximal Kidney only (Area S1 only)

SGLT1 = 10%

SGLT2 = 90%

24
Q

How do SGLT2 inhibitors cause decreased blood glucose?

A

Secondary active transport coupled to Na+ influx

(Sodium Glucose Co-transporter 2)

This moves glucose into filtrate

Excreted in urine

25
Q

Describe the effect on the urine by SGLT2 inhibitors?

What condition does this mimic?

A

Glucosuria

Familal Renal Glucosuria

26
Q

Name some SGLT2 inhibitors?

A

Dapaglifozin

Canaglifozin

27
Q

Describe effect of SGLT2 inhibitors on:

  • Glucose reabsorption?
  • HbA1c?
  • Weight?
A

Decreased glucose reabsorption
Decreased HbA1c

Weight Loss

28
Q

Side effects of SGLT2 inhibitors?

Why?

A

Increase in genital and urinary bacterial/fungal infections

Probably due to excess glucose in the urine

29
Q

Where are prostaglandins produced?

A

Prostaglandins are produced by the kidney

PGE2 is produced by medulla

PG12 is produced by glomeruli

30
Q

Action of prostaglandin?

When are they synthesised?

A

They have a vasodilator affect

Released in response to trauma of the kidneys

31
Q

Describe the effect of prostaglandins on renal blood flow and glomerular filtration rate under normal conditions?

During vasoconstriction?

A

No effect/very little effect

Become more important during vasoconstriction - they help the kidney to adapt to the hypoperfusion and maintain urine output by causing compensatory vasodilation.

32
Q

How exactly do prostaglandins cause vasodilation?

A
  1. Vasodilator affect directly on afferent arteriole
  2. Cause release of renin (this increases level of angiotensin 2 and causes efferent arteriole vasoconstriction)
33
Q

Name some conditions where renal blood flow is dependent on prostaglandins?

What happens if NSAIDs are given to these patients?

A
  • Cirrhosis of liver
  • Heart failure
  • Nephrotic Syndrome

Acute Renal Failure

34
Q

A combination of a XXX, an XXX and a XXXX can be particularty detrimental and can cause a ‘triple whammy’.

Fill in the blanks?

Explain why?

A

ACE Inhibtor (Blocks angiotensin 2)

Diuretic (Decrease plasma volume)

NSAIDs (Blocks renal prostaglandins)

Renal (34 decks)

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