CH 69 Drugs for ED and BPH Flashcards
PDE5 Inhibitor Contraindications
Contraindications:
* Severe cardiovascular disease (e.g., recent stroke, myocardial infarction).
* Hypotension (low blood pressure).
* Severe liver or kidney impairment.
* Retinitis pigmentosa (an inherited eye disease).
* Concurrent use of nitrates (e.g., nitroglycerin).
Consequence of PDE5 Inhibitor + cytochrome P450 inhibitors (e.g. CYP34A)
- Increased plasma levels of PDE5 inhibitors due to slower metabolism.
- Potential for enhanced or prolonged effects of PDE5 inhibitors, increasing the risk of side effects (e.g., hypotension, dizziness, priapism).
Drugs such as ketoconazole, erythromycin, and protease inhibitors may cause this interaction.
Guidelines of PDE5 Inhibitor in patients taking nitrates
Guidelines:
* Contraindicated to use PDE5 inhibitors with nitrates due to the risk of severe hypotension.
* A minimum of 24 hours should elapse between taking PDE5 inhibitors and short-acting nitrates, and 48 hours for long-acting nitrates.
Likely Outcome if Ignored:
* Severe hypotension, leading to dizziness, fainting, heart attack, or stroke.
Drug: sildenafil (Viagra, Revatio)
Class: PDE5 Inhibitor
MOA: Inhibits PDE5, enhancing normal erectile response to stimuli by increasing cGMP and promoting smooth muscle relaxation
CI: nitrates (nitroglycerine, isosorbide mono/dinitrate) - life threatening hypotension
Note:
* can prolong QT interval
* use w/ alpha blockers can cause symptomatic postural hypotension
* cytochrome P450 (CYP3A4) inhibitors can suppress metabolism
Drug: vardenafil (Levitra, Staxyn)
Class: PDE5 Inhibitor
MOA: Inhibits PDE5, relaxing arterial and trabecular smooth muscle in the penis
CI: nitrates (nitroglycerine, isosorbide mono/dinitrate) - life threatening hypotension
Note:
* can prolong QT interval
* use w/ alpha blockers can cause symptomatic postural hypotension
* cytochrome P450 (CYP3A4) inhibitors can suppress metabolism
Drug: tadalafil (Cialis)
Class: PDE5 Inhibitor
MOA: Inhibits PDE5, relaxing penile arterial and trabecular smooth muscle
CI: nitrates (nitroglycerine, isosorbide mono/dinitrate) - life threatening hypotension
Note:
* can prolong QT interval
* use w/ alpha blockers can cause symptomatic postural hypotension
* cytochrome P450 (CYP3A4) inhibitors can suppress metabolism
* Lasts up to 36 hours; also approved for daily dosing (if intercourse expected 2-3x weekly)
* used daily for BPH
Drug: papaverine + phentolamine
Class: Smooth Muscle Relaxant + Alpha-adrenergic Blocker
MOA: Increases arterial flow and decreases venous outflow in the penis
Note: Administered via injection directly into the corpus cavernosum.
Drug: alprostadil (Prostaglandin E₁)
Class: Prostaglandin E₁
MOA: Increases arterial flow and decreases venous outflow in the penis
Note: Can be injected or administered as a transurethral pellet
Pathophysiology of BPH
caused by the enlargement of the prostate gland due to increased cell growth, primarily driven by dihydrotestosterone (DHT).
DHT is produced from testosterone by the enzyme 5-alpha-reductase.
Use of 5-alpha-reductase inhibitors in BPH
5-alpha-reductase inhibitors (e.g., finasteride) reduce DHT levels, slowing prostate growth and reducing symptoms.
Drug: finasteride (Proscar)
Class: 5-Alpha-reductase Inhibitor
Indication: mechanical obstruction from large prostate
MOA: Inhibits the enzyme 5-alpha-reductase, reducing prostate size
Note: Decreases PSA levels.
Drug: dutasteride (Avodart)
Class: 5-Alpha-reductase Inhibitor
Indication: mechanical obstruction from large prostate
MOA: Inhibits 5-alpha-reductase more completely than finasteride
Note:
* Very long half-life (5 weeks)
* should not be handled by women who are or may become pregnant
Use of alpha blockers in BPH
Alpha blockers (e.g., tamsulosin) relax the smooth muscle in the prostate and bladder neck, improving urine flow and reducing symptoms of urinary obstruction.
Drug: tamsulosin (Flomax)
Class: Selective Alpha₁a-Adrenergic Antagonist
Indication: dynamic obstruction (smaller, but still enlarged prostate)
MOA: Selectively blocks alpha₁a receptors in the prostate/bladder neck, relaxing smooth muscle
Note:
* Associated with ‘floppy-iris syndrome’ during cataract surgery.
* Does not decrease PSA levels.
Drug: tamsulosin + dutasteride (Jalyn)
Class: Combination: Alpha₁a-Blocker / 5-ARI
MOA: Combines MOAs of tamsulosin (smooth muscle relaxation) and dutasteride (prostate size reduction)
Drug: terazosin (Hytrin)
Class: non-selective alpha-1 adrenergic antagonist
Indication: dynamic obstruction (smaller, but still enlarged prostate)
MOA: blocks alpha-1 receptors, relaxing smooth muscle in the bladder neck/prostate and blood vessels
Note: useful for HTN & BPH
Drug: doxazosin (Cardur)
Class: non-selective alpha-1 adrenergic antagonist
Indication: dynamic obstruction (smaller, but still enlarged prostate)
MOA: blocks alpha-1 receptors, relaxing smooth muscle in the bladder neck/prostate and blood vessels
Note: useful for HTN & BPH
Drug: alfuzosin (Uroxatral)
Class: non-selective alpha-1 adrenergic antagonist
Indication: dynamic obstruction (smaller, but still enlarged prostate)
MOA: blocks alpha-1 receptors, relaxing smooth muscle in the bladder neck/prostate and blood vessels
Note: can lower BP. Does not decrease PSA levels
Drug: silodosin (Rapaflo)
Class: non-selective alpha-1 adrenergic antagonist
Indication: dynamic obstruction (smaller, but still enlarged prostate)
MOA: selectively blocks alpha-1 receptors, relaxing smooth muscle in the bladder neck/prostate
Note: has less effect on BP than non-selective agents, but can cause abnormal ejaculation. Does not decrease PSA levels
