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Medicine Phase 2a > Endocrine Pharmacology > Flashcards

Endocrine Pharmacology Flashcards

1
Q

Give example of a Biguanide

A

Metformin

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2
Q

Indications of Biguanide (Metformin)

A

Treat DMT2
first choice medication for control of blood glucose, alone or in combination with other hypoglycaemics such as sulphonyl ureas or insulin

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3
Q

Mechanisms of Biguanide (Metformin)

A
  • Lowers blood glucose by increasing response to insulin
  • suppresses hepatic glycogenolysis and gluconeogenesis
  • increases glucose uptake and utilisation by skeletal muscle and suppresses intestinal glucose absorption
  • DOES NOT cause hypoglycaemia as does not stimulate pancreas
  • Reduces weight gain and can induce weight loss, which can prevent worsening of insulin resistance
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4
Q

Does Biguanide (Metformin) cause hypoglycaemia?

A

No as does not stimulate pancreas

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5
Q

Adverse effects/contraindications of Biguanide (Metformin)

A
  • GI disturbance (weight loss)
  • Lactic acidosis can occur in intercurrent lines such as renal or hepatic impairment or cardiac failure
  • Contraindicated in severe renal impairment
    • should be withheld in acute kidney injury and severe tissue hypoxia
    • used with care in hepatic impairment and alcohol intoxication
  • Can interact with IV contrast media for scan so must be withheld before these investigations
  • Use with caution with other drugs that may impact renal function i.e. ACE inhibitors, diuretics or NSAIDs
  • Prednisolone, thiazide and loop diuretics elevate blood glucose and may reduce efficacy of metformin
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6
Q

What drugs are contraindicated for Biguanides (Metformin)

A

ACE inhibitors
Diuretics
NSAIDs
(others that may impair renal function)

Prednisolone
Thiazide
Loop diuretics
(elevate blood glucose)

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7
Q

Give example of a sulphonylurea

A

Gliclazide

Glipizide

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8
Q

Indications of sulphonylurea (gliclazide)

A

DMT2
single agent to control blood glucose and reduce complications where metformin is contraindicated/not tolerated
- Can be used in combination with metformin and other hypoglycaemics in uncontrolled glucose levels

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9
Q

Mechanisms of sulphonylureas (gliclazide)

A
  • Lower blood glucose by stimulating pancreatic insulin secretion
  • They block ATP dependent K+ channels in pancreatic beta cell membranes, causing depolarisation of the cell membrane and opening of voltage gated Ca2+ channels thereby stimulating insulin secretion

(Only effective in patients with residual pancreatic function i.e. not effective in DMT1)

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10
Q

Why can’t sulphonylureas be used for DMT1?

A

Only effective in patients with residual pancreatic function

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11
Q

Adverse effects/contraindications of sulphonylureas (gliclazide)

A

*Hypoglycaemia
*GI disturbances - WEIGHT GAIN
(more seriously hypoglycaemia can occur, especially when used with other hypoglycaemic medications)

  • Hypersensitivity reactions causing hepatic toxicity, rash and fever and haematological abnormalities (rare)
  • Use with care in hepatic impairment and renal impairment, and in people at increased risk of hypoglycaemia
  • Risk of hypoglycaemia is increased by drugs such as metformin, glitazone and insulin
  • Efficacy is reduced by prednisolone, thiazide and loop diuretics which increase glucose
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12
Q

What drugs run risk of hypoglycaemia if used alongside sulphonylureas?

A

Metformin
Glitazone
Insulin

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13
Q

Give an example of a glitazone

A

Pioglitazone

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14
Q

Indications of (pio)glitazone

A

DMT2
alone if metformin is contraindicated or in combination with metformin or a sulphonylurea when glucose levels are uncontrolled

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15
Q

Mechanisms of (pio)glitazone

A

-Activates peroxisome proliferator-activated receptors (PPARs)
bind free fatty acids and induce genes that enhance insulin action in skeletal muscle, adipose tissue and the liver
- Increases peripheral glucose uptake and utilisation and reduces hepatic gluconeogenesis
- Increase in the storage of fatty acids in adipocytes, decreasing the amount present in circulation

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16
Q

Why does (pio)glitazone have low hypoglycaemia risk?

A

as does not stimulate pancreas

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17
Q

Adverse effects/contraindications of (pio)glitazone

A
  • Fluid retention (increases Na+ reabsorption) - may worsen HF
  • Weight gain (fluid retention + fat gain)
  • Increased fracture risk, peripheral oedema, anaemia and mild weight gain
  • Increases risk of bladder cancer
  • Lower risk of hypoglycaemia than other agents - but risk is increased in combination
  • Contraindicated in those with heart failure, DMT1 and diabetic ketoacidosis
    and must be used with care in hepatic impairment
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18
Q

Examples of insulins

A 
Insulin aspart
Insulin glargine
Biphasic insulin
Soluble insulin
Isophane insulin
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19
Q

Indications of insulins

A
  • Insulin replacement in people with DMT1 and for the control of blood glucose in those with DMT2 where oral hypoglycaemic treatment is inadequate or poorly tolerated
  • Given IV in diabetic emergencies such as diabetic ketoacidosis and hyperglycaemic hyperosmolar state
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20
Q

Mechanisms of insulins

A
  • Stimulates glucose uptake from the circulation into tissue and increases the use of glucose as an energy source
  • Stimulates glycogen, lipid and protein synthesis and inhibits gluconeogenesis and ketogenesis
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21
Q

Different insulin preparations

A

rapid acting (insulin aspart), short acting (soluble insulin), intermediate acting (isophane insulin) and long acting (insulin glargine)

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22
Q

What is biphasic insulin

A

contains a mixture of rapid and intermediate acting insulin

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23
Q

Adverse effects/contraindictions of insulins

A

HYPOGLYCAEMIA
which can cause lipohypertrophy (fatty lumps) if administered by injection in the same site
- Use with care in renal impairment as there is an increased risk of hypoglycaemia
- Combinations with other hypoglycaemic agents increases risk of hypoglycaemia and use with corticosteroids increases the dose required to have same effect

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24
Q

Example of thyroid replacement drug hormone

A

Levothyroxine (synthetic T4)

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25
Q

Indications of Levothyroxine

A

Used in primary hypothyroidism and hypothyroidism secondary to hypopituitarism

26
Q

Mechanisms of Levothyroxine

A

Thyroid hormones regulate metabolism and growth so hypothyroidism produces lethargy, weight gain and slowing of mental processes which are treated by replacement hormones
- Thyroxine (T4) is converted to the active triiodothyronine T3 in target tissues

27
Q

Adverse effects/contraindications

A
  • Usually due to excessive doses are symptoms of hyperthyroidism - GI disturbance, cardiac arrhythmias and neurological tremors
  • Thyroid can increase heart rate and metabolism and can precipitate cardiac ischaemia, so used with care in coronary artery disease (CAD)
  • Corticosteroid therapy must be initiated alongside levothyroxine if patient has hypopituitarism to avoid Addisonian crisis!
  • GI absorption is reduced by antacid, Ca2+ and iron
  • An increase in dose may be required with cytochrome 450 inducers such as
    carbamazepine
  • Levothyroxine may increase insulin or other hypoglycaemic requirements in diabetes and enhance the effects of warfarin
28
Q

What must be initiated alongside levothyroxine if patient has hypopituitarism to avoid Addisonian crisis

A

Coritcosteroid therapy

29
Q

Example of a cytochrome p450 inducer

A

Carbamazepine

30
Q

Example of an antithyroid drug

A

Carbimazole

31
Q

Indications fo carbimazole (antithyroid drug)

A

Graves’ disease (hyperthyroidism) as long term treatment

May be taken before thyroid surgery to lower hormone levels

32
Q

Mechanisms of carbimazole (antithyroid drug)

A
  • Prevents thyroid peroxidase enzyme from coupling and iodinating the tyrosine residues on thyroglobulin, so reduces the production of the thyroid hormones T3 & T4
33
Q

Why is relief of clinical hyperthyroid symptoms slow, by carbimazole (antithyroid drug)?

A

large store of preformed T3 and T4 must be depleted before an effect can be seen - can be months

34
Q

Adverse effects/contraindications of carbimazole (antithyroid drug)

A
  • Rashes and pruritus are common and can be treated with antihistamines, more rarely and severely there can be bone marrow suppression
    resulting neutropenia and agranulocytosis can occur!!
  • Use with care in patients with past or current blood disease (aplastic anaemia, leucopenia or thrombocytopenia) or liver impairment
  • Is a CYP450 enzyme inhibitor so drugs metabolised by this e.g. warfarin may become toxic if dose is not lowered!!
35
Q

Example of a Growth Hormone Receptor Antagonist

A

Pegvisomant

36
Q

Indications of Pegvisomant (GH receptor antagonist)

A

Treatment of acromegaly if the pituitary tumour cannot be controlled with surgery or irradiation

37
Q

How is Pegvisomant (GH receptor antagonist) administered?

A

as a powder solution injection

38
Q

Mechanisms of Pegvisomant (GH receptor antagonist)

A

Blocks the action of growth hormone at the growth hormone receptor to reduce production of insulin like growth factor-1 (IGF-1)
IGF-1 is responsible for most of the symptoms of acromegaly

39
Q

Adverse effects/contraindications of Pegvisomant (GH receptor antagonist)

A
  • Reactions at the injection site and GI disturbance can occur
  • More rarely hypoglycaemia, chest pain and hepatitis
  • Blocking the growth hormone receptor reduces feedback control of GH regulation, leading to *Increased GH levels
  • Use with care in diabetics and patient with malignant tumours or liver impairment
40
Q

Example of Vasopressin antagonist

A

Tolvaptan

41
Q

Indications of vasopressin antagonist (tolvaptan)

A

Treatment for euvolaemic (i.e. syndrome of inappropriate ADH secretion) and hypervolaemic hyponatraemia

42
Q

Mechanisms of vasopressin antagonist (tolvaptan)

A
  • Inhibits vasopressin-2 receptor (V2) so increases fluid excretion
  • Causes aquaresis (excretion of H2O with NO electrolyte loss) leading to increased Na+ in hyponatraemia
43
Q

Adverse effects/contraindications of vasopressin antagonist (tolvaptan)

A

More common side effects are GI disturbance, headache, increased thirst and insomnia
Hypersensitivity reactions occur rarely
Contraindicated in hypovolaemic hyponatraemia and in severe renal
impairment
Can interact with statins (HMG-CoA reductase inhibitors) and cause serious muscle problems
Side effects may be increased with macrolides
Can causes enhanced effects of benzodiazepines and digoxin when used together

44
Q

What enzyme is inhibited by statins

A

HMG-CoA reductase

45
Q

Example of a vasopressin analogue

A

Desmopressin

46
Q

Indications of vasopressin analogue (desmopressin)

A

Treatment of diabetes insipidus

Also used to distinguish cranial from nephrogenic diabetes insipidus

47
Q

Mechanisms of vasopressin analogue (desmopressin)

A

Replaces endogenous vasopressin that is missing in cranial diabetes insipidus.
Works on the renal collecting duct by binding to V2 receptors, which signal aquaporin 2 to be inserted into the collecting duct apical membrane and thus increase water reabsorption from the urine

48
Q

Adverse effects/contraindications of vasopressin analogue (desmopressin)

A
  • Side effects include headaches, facial flushing, nausea and seizures
  • Hyponatraemia can occur
  • Contraindicated in moderate to severe renal impairment and patients with hyponatraemia
  • Use with tricyclic antidepressants, SSRIs, NSAIDs, opioid analgesics should be monitored carefully as may increase risk of water intoxication with hyponatraemia
49
Q

Example of an adrenal corticosteroid inhibitor

A

Metyrapone

50
Q

Indications of adrenal corticosteroid inhibitor (metyrapone)

A
  • Used in the diagnosis of adrenal insufficiency

- To control cortisol hypersecretion in Cushing’s disease

51
Q

Mechanisms of adrenal corticosteroid inhibitor (metyrapone)

A

Blocks cortisol synthesis by reversibly inhibiting steroid 11 beta-hydroxide enzyme.
This enzyme, normally stimulates adrenocorticotropic hormone secretion and this increases plasma 11-deoxycortisol levels which is metabolised to cortisol - so inhibiting the enzyme leads to a reduction in cortisol

52
Q

Adverse effects/contraindications of adrenal corticosteroid inhibitor (metyrapone)

A

Common side effects are GI disturbance, headache, dizziness and drowsiness
Possible hirsutism (excessive hair growth) can occur because of the excess androgen precursors created
Contraindicated in adrenal cortical insufficiency and in patients taking corticosteroids
Use with care in patients on paracetamol as liver damage can be increased, and insulin or other hypoglycaemics as side effects may be increased
Corticosteroid, oestrogen and phenytoin can reduce effectiveness

53
Q

Why can metformin cause lactic acidosis?

A

These patients have reduced drug elimination or reduced tissue oxygenation. Lactate uptake by liver is reduced with metformin because lactate is a substrate for hepatic gluconeogenesis (metformin inhibits gluconeogenesis), usually this slight increase in lactate can be cleared by kidney but severely impaired kidney may lead to problems.

54
Q

Example of a DPP4 inhibitor

A

Sitagliptin

55
Q

Mechanism of action of Sitagliptin (DPP4 inhibitor)

A 
Inhibit DPP4 (so increase effect of incretins (GLP-1 and GIP) which stimulates insulin secretion)
Eat -> Increases incretin -> more insulin secretion (inhibited by DPP4)
56
Q

What are incretins

A

A group of hormones released after eating & augment secretion on insulin (inhibited by DPP4)

57
Q

Weight change from Biguanide (Metformin)

A

Weight lost

58
Q

Weight change from Sulfonylurea (Gliclazide)

A

Weight gain

59
Q

Weight change from DPP4 inhibitors (Sitagliptin)

A

No change

60
Q

Weight change from Glitazones (Plioglitazone)

A

Weight gain

Medicine Phase 2a (22 decks)

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