II. Indications
- Erectile Dysfunction (PDE5 Inhibitor)
- Other indications
- Pulmonary Arterial Hypertension Management (PDE5 Inhibitor)
- COPD (PDE3 and PDE4 Inhibitors)
III. Contraindications
- Absolute Contraindications
- Men using nitrates (causes profound Hypotension)
- Men using alpha blockers (e.g. Hytrin for BPH)
- Relative Contraindications
- Active coronary ischemia in men not on nitrates
- Congestive Heart Failure
- Borderline low Blood Pressure
- Bordrline low volume status
- Multidrug Antihypertensive regimen
- Taking Cytochrome P450-3A4 (CYP3A4) inhibitor
- Areas where PDE5 agents may be used safely
- Safe in stable coronary disease (no nitrates)
IV. Mechanism
- Phosphodiesterase Type 5 Inhibitor
- Phosphodiesterase Type 5 causes Erection to subside
- Blocks Phosphodiesterase Type 5
- Enhances vasodilating effect of Nitrous Oxide
- Normally released during sexual stimulation
V. Medications
- Phosphodiesterase 5 Inhibitors (Erectile Dysfunction, and also used in Pulmonary Hypertension)
- Sildenafil (Viagra)
- Vardenafil (Levitra, Staxyn)
- Tadalafil (Cialis)
- Avanafil (Stendra)
- Released in 2014 with similar activity as Viagra (onset in 30 minutes and duration for 5 hours)
- Similar Drug Interactions as for Vardenafil (Levitra, Staxyn)
- Phosphodiesterase 4 Inhibitors (COPD)
- Roflumilast (Daliresp, only PDE4 activity)
- Ensifentrine (Ohtuvayre, combined PDE3 and PDE4 activity)
VI. Adverse Effects: Viagra (but most apply to the PDE5 Class as a whole)
- Hypotensive effect for men on Nitrates (Avoid)
-
Vision effects
- Light Sensitivity (Photophobia)
- Temporary color Vision disturbance (6%)
- Blue colors may appear to be green
- Blurred Vision or Vision Loss (Retinal Detachment, Optic Neuropathy)
- Higher risk if atherosclerosis
- Vision Loss can be permanent
- Appears to occur with all PDE5 Inhibitors
- Rare occurence (although some recent data as of 2022 suggests Incidence as high as 16 in 10,000)
- Etminan (2022) JAMA Ophthalmol 140(5):480-4 +PMID: 35389459 [PubMed]
- Mild Headache (21%)
- Facial Flushing (27%)
- Indigestion or Dyspepsia (11%)
- Myalgias
- Does not cause Priapism
-
Sensorineural Hearing Loss
- Sudden onset and permanent Hearing Loss
- McGwin (2010) Arch Otolaryngol Head Neck Surg 136(5):488-49 [PubMed]
VII. Drug Interactions
- Decreased effect (or delayed affect) after a fatty meal (esp. Sildenafil, Verdenafil)
- Inhibit breakdown of Viagra via Cytochrome P3A4
- Cimetidine (Tagamet)
- Ketoconazole (Nizoral)
- Itraconazole (Sporonox)
- Mibefradil (Posicor)
- Protease Inhibitors (Ritonavir, Indinavir, Saquinavir, Atazanavir)
- Macrolides (Clarithromycin, Erythromycin)
- Profound Vasodilitation and Hypotension (Avoid)
- Nitroglycerin and other Nitrates (e.g. Nitroglycerin, Isosorbide Dinitrate)
- Avoid Avanafil (Stenda) within 12 hours of nitrates
- Avoid Sildenafil (Viagra) and Verdenadil (Levitra) within 24 hours of nitrates
- Avoid Tadalafil (Cialis) within 48 hours of nitrates
- Alpha-blockers (Flomax or Tamsulosin may be used instead with caution)
- Nitroglycerin and other Nitrates (e.g. Nitroglycerin, Isosorbide Dinitrate)
VIII. Efficacy
IX. References
- (2022) Presc Lett 29(6): 33-4