Direct Preventive Care

Important Safety Information for


Confident in her medical abilities

What is the FDA-approved use of sildenafil? 

Sildenafil is a phosphodiesterase-5 (PDE5) inhibitor indicated for the treatment of erectile dysfunction (ED). 


Who should not use sildenafil? 

Do not use sildenafil if: 

  • You are taking a class of medications called nitric oxide donors, including organic nitrates or organic nitrites in any form. Sildenafil can increase the blood pressure-lowering effect of nitrates. 
  • You have a known allergy to sildenafil. 
  • You are taking a class of medications called guanylate cyclase (GC) stimulators, such as riociguat. Sildenafil can increase the blood pressure-lowering effect of these medications. 


How should I take sildenafil? 

Sildenafil can be taken with or without food. Take about 30 minutes to 1 hour before anticipated sexual activity. 

Do not take sildenafil more than once in a 24-hour period or within 24 hours of any other ED medications or PDE-5 inhibitors. 

You should take the medication exactly as prescribed. If your symptoms are not improving or you have any questions about changing or stopping medication, reach out to your DPC-affiliated provider for guidance. 


What should I tell my DPC-affiliated provider before using sildenafil? 

  • Sildenafil has certain drug interactions. It’s important to tell your DPC-affiliated provider all of the medications you are currently taking, including prescription, over-the-counter medications, vitamins, and herbal and dietary supplements.  


Some medications to watch out for include: 

  • Nitrates, alpha-blockers, and antihypertensives: When these medications are taken with sildenafil, a sudden drop in blood pressure can occur. 
  • CYP3A4 inhibitors, such as ritonavir, ketoconazole, itraconazole and erythromycin: These medications increase sildenafil levels in the blood stream, which can cause a sudden drop in blood pressure and prolonged erection. 


It’s important to share your entire medical history with your provider. In particular, tell your provider if you have or have a past history of: 

  • Cardiovascular risk that prevents you from partaking in sexual activity 
  • Chest pain requiring nitroglycerin 
  • Predisposition to priapism (painful erection that lasts >4 hours) 
  • Ventricular outflow obstruction (e.g. aortic stenosis, idiopathic hypertrophic subaortic stenosis) 
  • Severely impaired autonomic control of blood pressure 
  • Myocardial infarction, stroke, or life-threatening arrhythmia  
  • Low or high blood pressure 
  • Cardiac failure or coronary artery disease causing unstable angina 
  • Anterior ischemic optic neuropathy (NAION) or a “crowded” optic disc. 
  • Bleeding disorders or ulcers 
  • Kidney or liver disease 
  • Pulmonary hypertension 
  • Retinitis pigmentosa 


Withholding or providing inaccurate information about your health and medical history in order to obtain treatment may result in harm, including, in some cases, death. 


What are the most serious side effects that I or a caregiver should monitor for when taking sildenafil? 

If you are experiencing a medical emergency, call 911 or seek immediate medical attention. 

You or a caregiver should carefully monitor for these side effects, especially in the beginning of treatment. 

  • Cardiac risk of sexual activity: ED medication should not be used by men for whom sexual activity is not advised because of their underlying cardiovascular status.  
  • Prolonged erections: Seek immediate emergency treatment for an erection lasting more than 4 hours. 
  • Effects on the eye: Seek medical care and stop medication if you experience a sudden loss of vision in one or both eyes. Sudden loss of vision could be a sign of non arteritic anterior ischemic optic neuropathy (NAION). 
  • Sudden hearing loss: Stop medication and seek prompt medical attention if you experience a sudden decrease or loss of hearing, which may be accompanied by ringing in the ears.   
  • Co-administering with alpha-blockers or other blood pressure-lowering drugs: If you are taking a medication to lower your blood pressure or taking an alpha-blocker, sildenafil may increase the blood-pressure-lowering effect, leading to a sudden drop in blood pressure. When starting sildenafil, monitor carefully for signs of low blood pressure, including dizziness, light headedness, or fainting. 
  • Co-administering with ritonavir: If you are taking a medication called ritonavir at the same time as taking sildenafil, ritonavir can increase the amount of sildenafil in your system. Monitor for lowered blood pressure, fainting, and prolonged erection. 
  • Combination with other PDE-5 inhibitors: Do not take sildenafil more than once in a 24-hour period or within 24 hours of any other ED medications or PDE-5 inhibitors. 
  • Effects on bleeding: Sildenafil has no effect on bleeding time when taken alone or with aspirin; however, there have been reports of bleeding with the use of sildenafil. Tell your Ro-affiliated provider if you have a history of bleeding disorders or ulcers. 
  • Sexually transmitted infections: Sildenafil does not protect against sexually transmitted diseases. Use safe sex practices. 


What are the most common side effects of sildenafil? 

  • Headache 
  • Flushing 
  • Indigestion 
  • Vision changes 
  • Nasal congestion 
  • Back pain 
  • Muscle pain 
  • Nausea 
  • Dizziness 
  • Rash 


You are encouraged to report negative side effects of prescription products to the FDA. Visit www.fda.gov/medwatch or call 1-800-FDA-1088.