Erectile dysfunction

Question 1

What is the Endothelium-Derived Relaxant Factor

Answer 1

Nitric oxide

Question 2

How does NO cause relaxation

Answer 2

Blood vessel is lined by vascular endothelium

• Endothelium converts L-arginine to NO using the enzyme NOS
• NO activates guanylyl cyclase which activates cGMP which has a vasodilatatory effect

Question 3

How are patients with angina treated

Answer 3

Given GTN under tongue which liberates NO2 which activates guanulyl cyclase and activates cGMP which causes vasorelaxation

Question 4

In the penis, what releases NO

Answer 4

Nerves (when the nerve depolarises). This causes vasodilatation

Question 5

How is an erection achieved

Answer 5

Sexual stimulation. Dilatation of an artery in corpus cavernosum which is mediated by arterial vasodilatation. There is also no increased venous flow which leads to Engorgement with blood and so an erection occurs

Question 6

What is cGMP broken down by and what does this mean

Answer 6

PDEV (phosphodiesterase5) which leads to inactivity of nitrous oxide

Question 7

What is the mode of action of Sildenafil (viagara)

Answer 7

Blocks the enzyme PDE5 and so increases action of NO and cGMP (cause vasorelaxation)

Question 8

What are the different management strategies of erectile dysfunction

Answer 8

Injection of alpha- blocker phenoxybenzamine or papaverine into corpus cavernosum

Prostaglandins administered intra-urethra

Sildenafil

Pumps with a ring placed on penis to prevent venous blood flow and maintain erection for 30 mins

Question 9

Side effects of viagara

Answer 9

Headache (because of vasodilatation)
Visual disturbances (because can inhibit some isoforms of PDE5 in the eyes)

Question 10

What works in lower concentrations- viagara or vardenafil?

Answer 10

Vardenafil

Question 11

What drugs should not be taken with Sildenafil and why

Answer 11

Nitrates contraindicated

-BEcause the effect of cGMP is greatly enhanced and will cause severe hypotension

Question 12

When should sildenafil be taken to be effective

What is the half life like

How many doses of sildenafil can be taken In 1 day

Answer 12

• 1 hour before sexual activity because it is in the peak plasma concentration
• Half life is 3.5h
• Only 1 in 24h

Question 13

Benefits of taking Tadalafil instead of Sildenafil

Answer 13

Has a longer half life and so sexual activity does not need to be planned and restricted

Question 14

Causes of erectile dysfunction

Answer 14

Cardiovascular disease
Smoking
Diabetes
Psychogenic

Drugs:

• Thiazides
• Prazosin
• Antidepressants
• Antipsychotics

Question 15

How can you tell if the cause of erectile dysfunction is psychogenic (anxiety)

Answer 15

If the patient still experiences nocturnal erections.

Test this by placing postage stamps on the penis and in the morning, if the postage stamps have come off then it means the patient is capable of experiencing nocturnal erections which means the ED may be psychogenic

Question 16

What conditions does the NHS prescribe viagara for

Answer 16

Diabetes
Multiple sclerosis 
Parkinson's disease
Prostate cancer
SPina bifida 

Viagara can also be bought over the counter