GU: PDE-5 inhibitor, 5-alpha-reductase inhibitor Flashcards
Indications of PDE-5 inhibitor (phosphodiesterase type 5 inhibitors)?
Erectile dysfunction
Primary pulmonary hypertension.
MOA of of PDE-5 inhibitor?
Selective for PDE type-5 (PDE-5) - found in smooth muscle of the:
- Corpus cavenosum of the penis
- Arteries of the lung
Normally:
Sexual stimulation releases nitric oxide (NO)
→ stimulates cGMP (cyclic guanosine monophosphate) production
→ causing arterial smooth muscle relaxation, vasodilation, and penile engorgement
Sildenafil inhibits cGMP, which increases the conc of cGMP.
→ improves penile blood flow
→ improves erection quality
Sildenafil does NOT cause an erection without sexual stimulation.
In primary pulmonary hypertension, sildenafil causes ARTERIAL VASODILATION.
Adverse effects of PDE-5 inhibitor?
Flushing
Headache
Dizziness
Nasal congestion
Hypotension
Tachycardia
Palpitations
MI, STROKE
Visual disorders -seek urgent medical review.
Seek medical advice if an erection fails to subside despite absence of stimulation.
Example of PDE-5 inhibitor?
sildenafil
Warnings of PDE-5 inhibitor?
Avoid in pts whom vasodilation could be dangerous to, e.g.:
- stroke
- ACS
- hx of CVD
Avoid or reduce dose in:
- hepatic impairment
- renal impairment
Interactions of PDE-5 inhibitor?
Avoid combining with nitrates or nicorandil.
Caution in prescribing alongside other vasodilators (e.g. alpha blockers, CCB)
Plasma conc and adverse effects increase by cytochrome P450 inhibitors.
Monitoring of PDE-5 inhibitor?
Erectile dysfunction:
- Review symptoms and side effects
Pulmonary hypertension:
- Regular monitoring for by a specialist.
Pt education of PDE-5 inhibitor?
Aims to help you have and maintain an erection BUT not produce an erection without sexual stimulation.
Take 1 hour before sex to allow sufficient time for absorption.
Seek medical advice if the erection does not subside within 2 hours after sexual activity has finished.
Report any vision changes
Taking it with food can delay its effect.
Indications of 5-alpha-reductase inhibitor?
Benign prostatic enlargement (2nd LINE; 1st: alpha blockers)
Adverse effects of 5-alpha-reductase inhibitor?
SEs relate to their antiandrogen action:
- Impotence (transient)
- Reduced libido (transient)
- Breast tenderness
- Gynecomastia
- Hair growth
Rare:
- Breast cancer in men
Warnings of 5-alpha-reductase inhibitor?
Avoid in pregnant women and make sure they are not exposed during unprotected sex with a man taking these drugs.
→ exposure of the drug to male fetus may cause abnormal development of the external genitalia.
Interactions of 5-alpha-reductase inhibitor?
None significant.
Monitoring of 5-alpha-reductase inhibitor?
Follow up appointment in 3-6 months to review changes in:
- lower urinary tract symptoms
- development of adverse effects
Continue check ups every 6-12 months while tx continues.
Pt education of 5-alpha-reductase inhibitor?
Explain to the patient that the reason he is having difficulty passing urine is because his prostate has grown and is squashing the tube coming out of the bladder.
Aim is to reduce the bulk of the prostate gland.
→ this relieves compression on the tube
→ makes it easier to pass urine
May take up to 6 months for symptoms to improve.
Main SEs (temporary, but improve as tx continues):
- less interest in sex
- may not be able to maintain an erection
See a Dr if:
- tenderness or growth in the tissue under the nipples (risk of breast cancer)
If pt’s partner is or could become pregnant, advise him that if the drug is exposed to her it could harm the baby. Must use condom during sex.
Example of 5-alpha-reductase inhibitor?
Finasteride
