Phosphodiesterase type 5 inhibitors Flashcards
Give the 2 main common clinical indications for the use of phosphodiesterase type 5 inhibitors.
1) Erectile dysfunction
2) Primary pulmonary hypertension.
1) Name an example of a phosphodiesterase type 5 inhibitor.
2) Phosphodiesterase type 5 inhibitors are selective for what and where is this commonly found?
1) Sildenafil.
2) They are selective for PDE type 5 which is found predominantly in the smooth muscle of the corpus cavernosum and arteries of the lung.
Describe how an erection occurs.
Sexual stimulation > NO released > production of cGMP stimulated > causes arterial smooth muscle relaxation, vasodilation and penile engorgement.
1) What is PDE5 responsible for?
2) Therefore, what does inhibition of PDE5 cause?
1) Break down of cGMP.
2) Increases in cGMP concentrations, improving penile blood flow and erection quality.
What does Sildenafil do in the pulmonary vasculature?
Sildenafil causes arterial vasodilation in pulmonary vasculature by similar mechanisms to in the penis, so can be used to treat primary pulmonary hypertension.
1) What do most of the adverse effects of Sildenafil relate to?
2) Name 4 of the common adverse effects of Sildenafil.
3) Name 4 more serious adverse effects that can occur with Sildenafil.
4) What might be needed if priapism occurs?
1) Its actions as a vasodilator.
2) Flushing, headache, dizziness and nasal congestion.
3) Hypotension, tachycardia, palpitations and a small increased risk of vascular events (e.g. MI and stroke).
4) Urgent medical assistance may be required in order to prevent penile damage.
1) When might visual disturbances including colour distortion occur?
2) Who should you not prescribe Sildenafil for?
3) Why should Sildenafil be avoided or used at lower doses in people with severe hepatic or renal impairment?
1) They occur due to inhibition of PDE6 in the retina and if they occur, they should prompt urgent medical review.
2) Patients in whom vasodilation could be dangerous, including those with recent stroke or ACS or with a. significant Hx of CVD.
3) Because in these cases, metabolism and excretion of Sildenafil is reduced.
1) Name the 2 P-drugs that are alpha-blockers.
2) Name the 2 P-drugs that are 5-alpha reductase inhibitors
3) Name the 2 P drugs that are phosphodiesterase type 5 inhibitors.
4) Name the P-drug prostaglandin E1 analogue.
1) Doxazosin and Tamsulosin (BPH/ HTN)
2) Finasteride and Dutasteride (BPH)
3) Sildenafil and Tadalafil (erectile dysfunction)
4) Alprostadil (erectile dysfunction)
1) Who should you not prescribe Sildenafil for and why?
2) In which patients should you prescribe Sildenafil with caution in and why?
3) Plasma concentrations and adverse effects of Sildenafil are increased by what?
1) People taking any drug that increases nitric oxide, particularly nitrates or nicorandil, as their combined effects on cGMP can cause marked arterial vasodilation and CV collapse.
2) Patients taking other vasodilators including alpha-blockers and CCBs as there is an increased risk of hypotension (alpha blockers should not be taken within 4 hours of sildenafil).
3) CYP450 inhibitors (e.g. Amiodarone, Diltiazem and Fluconazole).
1) Name the 2 preparations of Sildenafil and state which conditions they are used for.
2) When will absorption and onset of action of Sildenafil be delayed?
3) How long before intercourse should Sildenafil be taken and why?
1) Viagra is used for erectile dysfunction and Revatio is used for pulmonary hypertension.
2) If it is taken with food.
3) An hour before intercourse in order to allow sufficient time for absorption.
1) When might a patient need to seek medical advice when taking Sildenafil?
2) What else might a patient need to report if it happens when taking Sildenafil?
3) The combination of Sildenafil and what recreational drug might cause patients to collapse?
1) If the erection does not subside within 2 hours after sexual activity has finished.
2) If they have any eyesight changes.
3) Amyl nitrate (poppers).
