Do not take Sildenafil (sildenafil citrate) or Tadalafil if you:

• Take medication containing nitrates or guanylate cyclase stimulators for pulmonary hypertension as this could cause an unsafe drop in blood pressure.
• If you are allergic to sildenafil, tadalafil or any ingredients in either medication.

Discuss your health with your doctor to ensure that you are healthy enough for sex.

If you experience chest pain, dizziness, or nausea during sex, seek immediate medical help

Sildenafil and Tadalafil can cause serious side effects. Some side effects include:

• An erection lasting more than 4 hours. If you experience this get medical help right away as this can cause permanent damage if not treated.
• Sudden vision loss in one or both eyes. This can be a sign of a serious eye problem. Stop taking the medication and call your healthcare provider right away if you experience this.- Sudden hearing decrease, hearing loss, ringing in their ears (tinnitus) or dizziness. If you have these symptoms, stop taking the medication and contact a doctor right away.

Before you take Sildenafil, tell your healthcare provider if you:

• Have or have had heart problems such as a heart attack, irregular heartbeat, angina, chest pain, narrowing of the aortic valve, or heart failure
• Have had heart surgery within the last 6 months
• Have pulmonary hypertension
• Have had a stroke
• Have low blood pressure, or high blood pressure that is not controlled
• Have a deformed penis shape
• Have had an erection that lasted for more than 4 hours
• Have problems with your blood cells such as sickle cell anemia, multiple myeloma, or leukemia
• Have retinitis pigmentosa, a rare genetic (runs in families) eye disease
• Have ever had severe vision loss, including an eye problem called NAION
• Have bleeding problems
• Have or have had stomach ulcers
• Have liver problems
• Have kidney problems or are having kidney dialysis have any other medical conditions

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

Sildenafil may affect the way other medicines work, and other medicines may affect the way Sildenafil works, causing side effects. Especially tell your healthcare provider if you take any of the following:

• Nitrates- Guanylate cyclase stimulators such as Adempas (riociguat)
• Alpha-blockers such as Hytrin (terazosin HCl), Flomax (tamsulosin HCl), Cardura (doxazosin mesylate), Minipress (prazosin HCl), Uroxatral (alfuzosin HCl), Jalyn (dutasteride and tamsulosin HCl), or Rapaflo (silodosin).
• HIV protease inhibitors, such as ritonavir (Norvir), indinavir sulfate (Crixivan), saquinavir (Fortovase or Invirase), or atazanavir sulfate (Reyataz)
• Some types of oral antifungal medicines, such as ketoconazole (Nizoral) and itraconazole (Sporanox)
• Some types of antibiotics, such as clarithromycin (Biaxin), telithromycin (Ketek), or erythromycin
• Other medicines that treat high blood pressure
• Other medicines or treatments for ED
• Sildenafil and Tadalafil should not be used with REVATIO or with other PAH treatments containing sildenafil, tadalafil or any other PDE5 inhibitors (such as Adcirca tadalafil)

Sildenafil and Tadalafil do not protect against sexually transmitted diseases, including HIV.

The most common side effects of Sildenafil and Tadalafil include: headache; flushing; upset stomach; abnormal vision, such as changes in color vision(such as having a blue color tinge) and blurred vision; stuffy or runny nose; back pain; muscle pain; nausea; dizziness; rash.