What is sildenafil?
In the U.S., Sildenafilo, which is the chemical name for generic Viagra®, is a medication that is beneficial to most men who have trouble getting or maintaining an erection during sexual activity. It works by increasing blood flow to the penis when a man is sexually stimulated, which can help him achieve and maintain an erection. But it can help the penis become erect only if sexual stimulation takes place.
U.S. doctors also use sildenafil to treat a condition called pulmonary arterial hypertension (PAH), a type of high blood pressure. It affects the blood vessels in the lungs. Sildenafil helps to relax these blood vessels, so the heart can easily pump blood through the lungs.
The alternatives to sildenafil for the U.S. include tadalafil (chemical name for generic Cialis®), vardenafil (chemical name for generic Levitra®, generic Staxyn®), and avanafil (chemical name for generic Stendra®).
There are also non-oral treatments available for erectile dysfunction. These include self-injections, where medications such as alprostadil are injected directly into the penis to achieve an erection. Another option is an alprostadil urethral suppository, where a tiny suppository is placed inside the penis in the penile urethra. Testosterone replacement therapy may also be recommended for some men with low levels of testosterone. Penis pumps, surgery, and implants are other options for treating erectile dysfunction.
The branded names of sildenafil in the U.S. include Viagra®, Revatio®, Liqrev®. The name “sildenafil” refers to the chemical name, and is the same ingredient in generic versions of Viagra. Per the FDA, the effectiveness of a generic drug is the same as the branded drug.
Of course, while sildenafil can help most men with erectile dysfunction, it may not be able to help some men.
Drugs not to take with sildenafil
Not everyone can take sildenafil. Those who are allergic to sildenafil or any of its ingredients should not take it. Also, people who are taking the following should not take sildenafil:
- nitrates for chest pain or heart problems
- alpha-blockers for prostate problems or high blood pressure
- guanylate cyclase stimulator such as riociguat
- protease inhibitors
- macrolide antibiotics
- antifungal medications
- other erectile dysfunction medications
- seizure medications
Do not take sildenafil with nitrates
Taking sildenafil and a nitrate at the same time causes a significant drop in blood pressure. Then, it can lead to dizziness, lightheadedness, fainting, and other potentially serious or fatal complications.
Patients often use nitrate to relieve chest pain or angina. They take it as a sublingual tablet, spray, or patch.
Nitrates include:
- Nitroglycerin, including brand names such as Nitrostat®, Nitrolingual®, Nitro-Dur®, Nitroquick®, Minitran®, Rectiv®, GoNitro®. Patients often use this to relieve chest pain or angina, especially as a sublingual tablet, spray, or patch.
- Isosorbide dinitrate, including brand names such as Isordil®, ISDN®, Dilatrate-SR®, Isochron®, Sorbitrate®, Isotrate®. Patients often use this to prevent chest pain or angina, especially as as a tablet or capsule.
- Isosorbide mononitrate, including brand names such as Imdur®, ISMO®, Monoket®. Patients use this nitrate to prevent chest pain or angina, and they take it as a tablet or capsule.
- Sodium nitroprusside, including brand names such as Nipride®, Nitropress®. Doctors use this in the hospital setting to treat severe hypertension (high blood pressure) or heart failure. Generally, they give it intravenously (through an IV).
Do not take sildenafil with alpha blockers
Taking sildenafil and an alpha blocker at the same time can cause a significant drop in blood pressure. Then, this can lead to dizziness, lightheadedness, fainting, and other potentially serious complications.
Patients take alpha-blockers to treat high blood pressure or symptoms of an enlarged prostate.
Alpha blockers include:
- Prazosin, including brand names such as Minipress®, Prazopress®
- Terazosin, including brand names such as Hytrin®, Zayasel®
- Doxazosin, including brand names such as Cardura®, Doxadura®, Larbex®, Raporsin®, and Slocin®
- Tamsulosin®, including brand names such as Flomax®, Contiflo®, Harnalidge®, Contiflo XL®, Faramsil MR®, Flomaxtra XL®, Pamsvax XL®, and Tabphyn MR®
- Alfuzosin, including brand names such as Uroxatral®, Xatral®
Do not take sildenafil with calcium channel blockers
Taking sildenafil and a calcium channel blocker at the same time can cause a drop in blood pressure. Then, this can lead to dizziness, lightheadedness, fainting, and other potentially serious complications.
Calcium channel blockers relaxes the blood vessels and lowers blood pressure.
Calcium channel blockers include:
- Amlodipine, including brand names such as Norvasc®
- Diltiazem, including brand names such as Cardizem®, Cartia®, Diltzac®, Taztia®, Tiazac®
- Felodipine, including brand names such as Plendil®
- Isradipine, including brand names such as DynaCirc®
- Nicardipine, including brand names such as Cardene®
- Nifedipine, including brand names such as Procardia®, Adalat®
- Nisoldipine, including brand names such as Sular®
- Verapamil, including brand names such as Calan®, Isoptin®, Verelan®
Do not take sildenafil with angiotensin II receptor antagonists (ARB)
Taking sildenafil and an angiotensin II receptor antagonist at the same time can cause a drop in blood pressure. Then, this can lead to dizziness, lightheadedness, fainting, and other potentially serious complications.
Angiotensin II receptor antagonists relax veins and arteries to lower blood pressure. Therefore, it makes it easier for the heart to pump blood. For example, people often use this if they have heart disease.
Angiotensin II receptor antagonists include:
- Losartan, including brand names such as Cozaar®
- Valsartan, including brand names such as Diovan®
- Irbesartan, including brand names such as Avapro®
- Candesartan, including brand names such as Atacand®
- Olmesartan, including brand names such as Benicar®
- Telmisartan, including brand names such as Micardis®
- Eprosartan, including brand names such as Teveten®
Do not take sildenafil with alcohol
Taking sildenafil and alcohol at the same time can increase the risk of certain side effects, such as dizziness, lightheadedness, fainting, and headache. Consuming alcohol while taking sildenafil may also increase the risk of certain side effects associated with the medication. For example, these include flushing, stomach upset, and changes in vision. Additionally, alcohol can reduce sildenafil’s effectiveness. Because the same enzymes that your body uses to metabolize alcohol work to break down medications as well.
Do not take sildenafil with guanylate cyclase stimulator
Taking sildenafil and guanylate cyclase stimulator such as riociguat at the same time can increase the risk of serious side effects, especially hypotension (very low blood pressure), fainting, and pulmonary hypertension.
Riociguat, including brand names such as Adempas®, Riociguat Bayer®, is used to treat pulmonary hypertension. This is a condition in which the blood vessels in the lungs are narrowed, making it difficult for blood to flow through them.
Do not take sildenafil with protease inhibitors
Taking sildenafil and protease inhibitors at the same time can increase the levels of sildenafil in the blood. This can then increase the risk of side effects associated with sildenafil.
Protease inhibitors (PIs) are a class of medications used to treat viral infections, specifically HIV and hepatitis C. Examples of protease inhibitors used in medicine include:
- HIV protease inhibitors: Atazanavir (Reyataz®), Darunavir (Prezista®), Fosamprenavir (Lexiva®), Indinavir (Crixivan®), Lopinavir/ritonavir (Kaletra®), Nelfinavir (Viracept®), Saquinavir (Invirase®, Fortovase®), Tipranavir (Aptivus®), Atazanavir/cobicistat (Evotaz®), Darunavir/cobicistat (Prezcobix®), Lopinavir/ritonavir (Aluvia®), Ritonavir (Norvir®)
- Hepatitis C protease inhibitors: Glecaprevir/pibrentasvir (Mavyret®), Grazoprevir/elbasvir (Zepatier®), Paritaprevir/ritonavir/ombitasvir/dasabuvir (Viekira Pak®, Viekira XR®), Simeprevir (Olysio®), Voxilaprevir (Vosevi®)
Do not take sildenafil with ACE inhibitors
An ACE inhibitor is used to treat high blood pressure, diabetic kidney disease, and heart failure. But, if taken with sildenafil, it may lead to a drop in blood pressure.
ACE inhibitors include:
- Benazepril (Lotensin®)
- Captopril (Capoten®)
- Enalapril (Vasotec®)
- Fosinopril (Monopril®)
- Lisinopril (Prinivil®, Zestril®)
- Moexipril (Univasc®)
- Perindopril (Aceon®)
- Quinapril (Accupril®)
- Ramipril (Altace®)
- Trandolapril (Mavik®)
Do not take sildenafil with beta blockers
A beta blocker is used to treat high blood pressure. But, if taken with sildenafil, it may lead to a drop in blood pressure that can have serious complications.
Beta blockers include:
- Acebutolol (Sectral®)
- Atenolol (Tenormin®)
- Bisoprolol (Zebeta®)
- Carvedilol (Coreg®)
- Esmolol (Brevibloc®)
- Labetalol (Normodyne®, Trandate®)
- Metoprolol (Lopressor®, Toprol-XL®)
- Nadolol (Corgard®)
- Nebivolol (Bystolic®)
- Penbutolol (Levatol®)
- Pindolol
- Propranolol (Inderal LA®, InnoPran XL®)
Do not take sildenafil with macrolide antibiotics
Taking sildenafil and certain macrolide antibiotics at the same time may cause a drug interaction that can increase the levels of sildenafil in the body, potentially leading to an increased risk of side effects.
Examples of macrolide antibiotics include:
- Azithromycin (Zithromax®, Z-Pak®)
- Clarithromycin (Biaxin®, Biaxin XL®)
- Erythromycin (E-Mycin®, Eryc®, Ery-Tab®, PCE®)
- Fidaxomicin (Dificid®)
- Telithromycin (Ketek®)
Do not take sildenafil with antifungal medications
Taking sildenafil and certain antifungal medications at the same time may cause a drug interaction that can increase the levels of sildenafil in the body. This can potentially lead to an increased risk of side effects.
Examples of antifungal medications include:
- Ketoconazole (Nizoral®)
- Itraconazole (Sporanox®)
- Fluconazole (Diflucan®)
Do not take sildenafil with other erectile dysfunction medications
Taking sildenafil with other medications used to treat erectile dysfunction, including tadalafil (generic Cialis®) or vardenafil (Levitra® and Staxyn®), can increase the risk of side effects associated with these medications.
Do not take sildenafil with seizure medications
Taking sildenafil and seizure medicine, such as carbamazepine phenytoin, phenobarbital, and valproate, may lower the threshold for seizures. Also, this decreases the effectiveness of sildenafil.
Do not take sildenafil with cimetidine
Cimetidine is used to treat heartburn or stomach discomfort. But, if taken with erectile dysfunction drugs, it can increase the risk of serious side effects associated with erectile dysfunction drugs.
Brand names for cimetidine include:
- Tagamet®
- Tagamet HB®
- Acid Reducer-Cimetidin®
- Leader Heartburn Relief®
- Equaline Acid Reducer®
Do not take sildenafil with these other drugs
- Bosentan (Tracleer). Used to treat pulmonary arterial hypertension (PAH). May make sildenafil less effective.
- Etravirine (Intelence). Used to treat HIV. May make sildenafil less effective.
When to stop taking sildenafil and seek immediate medical attention or call 911?
If you have:
- Symptoms of an allergic reaction to sildenafil, including hives, difficulty breathing, or swelling of your face, lips, tongue, or throat
- Symptoms of a heart attack, such as chest pain, chest pressure, difficulty breathing, nausea, vomiting, dizziness, excessive sweating, cold sweats, pain or discomfort in the arms, jaw, back, or neck
- An erection that is painful or lasts longer than 4 hours, because prolonged erection can damage the penis
- Vision changes or sudden vision loss or blurred vision
- Sudden hearing loss or sudden decrease in hearing or ringing in the ears
- Feeling of fainting or actually passing out
People with what current or past conditions cannot take sildenafil for erectile dysfunction?
- Females (obviously)
- Anyone younger than 18 years old
- Anyone prone to seizures
- Kidney disease
- On dialysis
- Liver disease
- Problems of the heart, including ventricular dysfunction
- Heart obstruction problems, including valve problems, outflow obstruction, aortic stenosis, other types of stenosis
- Diseases of the heart, including restrictive or congestive cardiomyopathy or pericardial constriction
- Heart rhythm problems
- History of heart attacks, heart failures
- History of chest pain or chest discomfort during sex or unstable angina
- High blood pressure (we consider anything greater than 130/85 to be high)
- Low blood pressure (we consider anything less than 90/60 to be low)
- Impaired autonomic control of blood pressure
- History of stroke
- Arterial disease (including coronary artery disease)
- Pulmonary hypertension (high blood pressure in the lungs)
- Pulmonary veno-occlusive disease (PVOD)
- History of sudden vision loss
- Nonarteritic anterior ischemic optic neuropathy (NAION)
- Retinitis pigmentosa
- Blood cell problems, such as sickle cell anemia
- Blood cancer problems, such as multiple myeloma, or leukemia
- Physical deformity of the penis, including angulation, cavernosal fibrosis, Peyronie’s disease
- History of an erection lasting longer than 4 hours
- Bleeding disorder, such as acquired platelet function defects, congenital platelet function defects, disseminated intravascular coagulation (DIC), prothrombin deficiency, factor V deficiency, factor VII deficiency, factor X deficiency, factor XI deficiency, hemophilia C
- Stomach or intestinal ulcer
- Any other medical problems that make sex unsafe
What are common side effects with sildenafil?
- Headaches
- Indigestion
- Flushing
- Back pains
- Muscle aches
- Stuffy nose, congestion
- Runny nose
What are the side effects with less common, or unknown, rates of occurrence?
- Head: headaches, drowsiness, vertigo, insomnia
- Eyes: Visual impairment or loss of sight, seeing double, red inflamed eyes, tender eyes, dry itchy eyes, watery eyes, painful eyes, swelling, permanent loss of vision
- Throat and mouth: coughing, difficulty talking, difficulty swallowing, ulcers, dry mouth, hoarse voice, burning
- Nose: bleeding, congestion
- Ears: decreased hearing, permanent loss of hearing
- Nerves: numbness, tingling, burning sensation
- Muscles: difficulty moving, pain, aches, feeling weak, cramps
- Skin: Formation of skin blisters, shedding of skin, Fissures in skin, inflamed skin, hives, skin covered with scales or flakes,
- Gastrointestinal: discomfort or ache in the abdomen, diarrhea, heartburn
- Heart: heart attack and death, fast arrhythmic beats
- Extremities: swelling, pain
What are the rare side effects?
- Fainting
- Seizures
- Swelling of the eyelids
- Hearing problems
- Skin rashes
- Penile bleeding
- Blood in semen
- Increased sweating
- Blurred vision
- Painful or prolonged erection of the penis
- Loss or change of color vision
- Permanent deafness
How to take sildenafil?
Sildenafil should only be taken under the guidance of a healthcare provider and as prescribed. Do not take more than the recommended dose or take it more frequently than prescribed.
If you are taking sildenafil to treat ED, it’s typically recommended to take it about 30-60 minutes before sexual activity. The medication can be taken with or without food, but it may take longer to work if taken with a high-fat meal. Sildenafil is usually taken only once per day. It’s important to follow the dosage instructions provided by your healthcare provider and not to exceed the recommended dose.
How to store sildenafil?
Store in a cool area without sunlight or heat or moisture.
What if I forgot to take a dose?
You can take a dose when you remembered it unless taking this dose is close to the next dose in which case you should wait to take the next dose. Sildenafil is taken as needed, so you do not need to take it everyday if you do not need it that day.
What if I overdose?
If you overdose, you need emergency medical help or call the Poison Help line at 1-800-222-1222.
What foods to avoid
Alcohol