Drugs For Erectile Dysfunction Flashcards
Drugs for ED:
Prostaglandin E1
Alprostadil
Drugs for ED:
Alpha- adrenoreceptor antagonists
Phentolamine
Yohimbine
Replaced by efficacious, safe, and easy to use PDE5 inhibitors
Drugs for ED:
Others
Methyltestosterone- use limited to men with hypo gonadal impotence
Trazodone- a SSRI antidepressant agent with alpha- adrenoreceptor blocking properties- priapism side effect- enhance libido & prolongs nocturnal erections
PDE5 inhibitors MOA
Selectively inhibit PDE5- increases cGMP- increase SM relaxation- increase sinusoidal compliance- increase engorgement of penis with blood- INCREASE erection
Treatment of pulmonary hypertension
PDE5 inhibitor contraindication
Patients taking organic nitrate vasodilators (e.g. isosorbid dinitrate or nitroglycerin)
Dosage adjustments in patients with hepatic dysfunction and CYP3A4 inhibiting drugs (clarithromycin, erythromycin)
PDE5 inhibitor adverse effects
Headaches, flushing due to cerebral & cutaneous effects respectively
Inhibit PDE6 isoform- color vision disturbances (loss of blue/green discrimination)
Nasal congestion
Dyspepsia
Sildenafil & tadalafil also inhibit PDE1 & PDE11 isoforms, respectively; these PDE’s play a role in sperm development & function
PDE5 inhibitors drug interaction
Co-administration with NO donor (e.g. nitroglycerin- potentially catastrophic hypotension)
CYP3A4 inhibiting drugs (clarithromycin, erythromycin)
PDE5 time to peak, half life & food interactions
Peak concentration:
Sildenafil- 60 min.
Vardenafil- 60
Tadalafil- 120
Half life:
Sildenafil- 3-4hrs.
Vardenafil- 4-5
Tadalafil- 18
Food interaction:
Sildenafil- Yes
Vardenafil- Yes
Tadalafil- No
Yohimbine MOA
Alpha-2 adrenoreceptor antagonist
Indolealkylamine alkaloid found in bark of the plant Pausinystalia yohimbe and in root of Rauwalfia spp
Relatively selective alpha-2 antagonist
Stimulation of NE receptors in locus coeruleus- central activation of sexual arousal
Blockade of central alpha-2 autoreceptors- increased NE release centrally- increased sexual arousal
Antagonizes 5-HT1 & 5-HT2A- increased mood (antidepressant & aphrodisiac properties- leads to erection)
Phentolamine MOA
Alpha-2 adrenoreceptor antagonist
Competitive alpha-1/2 antagonist- increased penile vasodilation- increased penile blood flow- leads to erection
Beta blockers
High blood pressure medications
Propranolol
Alpha-2 adrenoreceptor agonist
High blood pressure medication
Clonidine
Adrenergic neuron blockers
High blood pressure medication
Guanethidine
ACE inhibitors
High blood pressure medication
Captopril
Calcium channel blockers
High blood pressure medication
Nifedipine