Vasodilators Flashcards

1
Q

What effect does cGMP have in the process of myocyte contraction?

A

It has a negative inotropic effect.

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2
Q

What protein activates myosin light chain kinase?

What is the function of myosin light chain kinase?

A
  • Calmodulin activates myosin light chain kinase.
  • Myosin light chain kinase phosphorylates myosin so that it is able to bind to actin (once troponin has moved from the actin binding site by way of Ca2+).
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3
Q

What are the two types of vasodilators?

A

1 - Direct vasodilators.

2 - Indirect vasodilators.

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4
Q

How do indirect vasodilators cause vasodilation?

A

By blocking other substances that cause vasoconstriction.

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5
Q

How do direct vasodilators cause vasodilation?

A

1 - By interfering with the pathways that raise intracellular Ca2+.

2 - By interfering with cGMP.

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6
Q

What is the cause of angina pectoris?

Which drugs are used to treat it?

A
  • Inadequate coronary blood flow for higher levels of activity, usually due to atheromatous obstruction.
  • Both direct and indirect vasodilators are used to treat angina.
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7
Q

List 2 nonvasodilator drugs that can decrease cardiac work.

A

1 - Beta blockers.

2 - Ivabradine.

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8
Q

Briefly describe the mechanism of action for ivabradine.

A

It inhibits the mechanisms that underpin the pacemaker potential.

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9
Q

List 3 direct vasodilators.

A

Organic nitrates:

1 - Glyceryl trinitrate (GTN).

2 - Isosorbide mono/dinitrate.

Calcium channel blockers:

3 - Dihydropyridines (DHPs) such as amlodipine.

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10
Q

Describe the mechanism of organic nitrates.

A

Organic nitrates spontaneously break down to release nitric oxide, which increases cGMP.

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11
Q

What type of vessel is most strongly affected by glyceryl trinitrate (GTN)?

Why is this advantageous?

A
  • Veins (more effect than on arteries).

- This decreases venous return (primary effect of GTN), so decreases cardiac work.

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12
Q

What is the secondary effect of glyceryl trinitrate (GTN)?

A

To cause vasodilation at coronary arteries, which increases coronary flow.

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13
Q

List 2 unwanted effects of glyceryl trinitrate (GTN).

A

1 - Excess vasodilation, causing hypotension and headaches.

2 - Decreases activity of other smooth muscle, such as the GIT and bronchi.

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14
Q

List 2 symptoms of hypotension in a patient that is being treated for heart failure.

A

1 - Syncope.

2 - Reflex tachycardia.

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15
Q

How is glyceryl trinitrate (GTN) administered?

Why?

A
  • Sublingually or via transdermal patches (for patients that need GTN all the time).
  • To avoid 1st pass metabolism that the drug would otherwise be subjected to if it was taken orally.
  • To increase speed of action (faster than orally).
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16
Q

How do dihydropyridines differ from other calcium channel blockers such as verapamil?

A

Verapamil primarily targets cardiac myocytes whereas dihydropyridines primarily target the vasculature.

17
Q

Give an example of a calcium channel blocker that affects both cardiac myocytes and the vasculature to an equal degree.

A

Diltiazem.

18
Q

What type of vessel is most strongly affected by calcium channel blockers?

Why is this advantageous?

A
  • Arteries.

- This decreases total peripheral resistance, so decreases cardiac work.

19
Q

What is the secondary effect of calcium channel blockers?

A

To cause vasodilation at coronary arteries, which increases coronary flow.

20
Q

List 2 unwanted effects of calcium channel blockers.

A

1 - Flushing.

2 - Decreased GIT activity.

21
Q

Why don’t calcium channel blockers affect skeletal muscle activity?

A
  • In the heart, Ca2+ release from the sarcoplasmic reticulum is Ca2+ induced, which is controlled by voltage gated Ca2+ channels.
  • In the skeletal muscle, Ca2+ release from the sarcoplasmic reticulum is triggered by action potentials which penetrate the myocyte and act on the sarcoplasmic reticulum directly.
22
Q

What is Raynaud’s syndrome?

A

A peripheral vascular disease which causes spasm in peripheral vessels induced by cold weather.

23
Q

Give an example of a drug treatment for Raynaud’s syndrome.

To which drug class does this drug belong?

A
  • Nifedipine.

- Dihydropyridines (calcium channel blockers).

24
Q

Describe the mechanisms by which smooth muscle relaxation occurs in the corpora cavernosa of the penis to produce erections.

A
  • Nitric oxide release increases cGMP production.

- cGMP inhibits the contraction of smooth muscle in the corpora cavernosa, producing an erection.

25
Q

Which drug class is used to treat male impotence?

Give an example of a drug within this class.

A
  • Phosphodiesterase inhibitors.

- Sildenafil (Viagra).

26
Q

Describe the mechanism of action for phosphodiesterase inhibitors for treatment of male impotence.

A
  • Phosphodiesterases degrade cGMP (type 5 phosphodiesterases are present in genital tissue).
  • Inhibition of type 5 phosphodiesterase in genital tissue results in an increase in cGMP.
  • Increased cGMP increases inhibition of smooth muscle contraction in the corpora cavernosa, producing an erection.
27
Q

Why do drugs that are used to treat male impotence not have many side effects?

A

Because they are selective for type 5 phosphodiesterases which are only found in genital tissue.

28
Q

What is minoxidil used for?

How is it administered?

A
  • To decrease hair loss.

- It is applied topically.

29
Q

Describe the mechanism of action for minoxidil.

A
  • Minoxidil opens K+ channels on the myocytes in local vessels.
  • This hyperpolarises the cells, decreasing Ca2+ influx and therefore calcium induced calcium release.
  • This reduces contraction, resulting in local vasodilation, improving blood flow to hair follicles.
30
Q

How can calcium channel blockers be used to treat poor cerebral function?

A

1 - Ca2+ channel blockers can be used to treat post-haemorrhagic vasospasm by causing vasodilation in the vessels supplying the brain.

2 - The same mechanism can be used to treat dementia.