Sildenafil (Viagra)
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Sildenafil (Viagra)
Used for Erectile Dysfunction
Sildenafil (Viagra) is taken by mouth as needed before sexual activity.
How Sildenafil (Viagra) works
Sildenafil (Viagra) is a phosphodiesterase-5 enzyme (PDE-5) inhibitor. PDE-5 is an enzyme in your body that breaks down the molecules that normally cause an erection. When it blocks PDE-5, Sildenafil helps an erection occur by allowing smooth muscle in the penis to relax and the penis to fill with blood.
Typical dosing for Sildenafil (Viagra)
- Erectile dysfunction (taken as needed): Available dosages for sildenafil are 20 mg, 25 mg, 50 mg and 100 mg tablets.
- You take it only as needed, typically about an hour before sexual activity, but you can take it anywhere between 30 minutes to 4 hours before sex
mensRxplus Recommendations:
It’s best to take sildenafil (Viagra) about 1 hour before sex, but you can take it anywhere between 30 minutes and 4 hours before you need it.
Sildenafil (Viagra) can be taken with or without food. A large meal, particularly fatty food, or alcohol ingestion can slow the metabolism of sildenafil (Viagra) so it takes longer to start working.
Don’t take more than one dose of sildenafil (Viagra). Doing so could lead to increased risk of side effects like low blood pressure, dizziness, and vision problems, and increased risk of priapism.
Who should not take Sildenafil?
Not recommended if you’ve had a heart attack or a stroke in the past 6 months.
Can’t be used if you’ve recently taken nitrates like isosorbide mononitrate (Monoket) or nitroglycerin (Nitrostat)
Side Effects:
Common Side Effects
- Headache (16-28%)
- Flushing (10-19%)
- Indigestion (3-17%)
- Changes in vision or light sensitivity (1-11%)
- Stuffy nose (4-9%)
Other side effects that are less common:
- Back pain
- Dizziness
- Muscle ache
- Nausea
- Rash
Note: There is a higher incidence for side effects, such as headaches and flushing, for people who are 65 years and older.
Serious Side Effects
Contact your healthcare provider or go to the emergency room immediately if you experience any of the following.
- Priapism – an erection lasting for more than 4 hours
- Vision loss
- Dangerously low blood pressure: feeling faint or weak, dizziness, blurry vision, feeling confused
Sildenafil (Viagra) interactions with other drugs:
See detailed warning section.
Nitrates
Nitrates are a class of medications that treat heart conditions and are taken for chest pain. Examples of nitrates are nitroglycerin (Nitrostat) and isosorbide mononitrate (Monoket). These medications cause blood vessels to dilate in order to increase blood flow to your heart, but can also lower your blood pressure.
Taking sildenafil with nitrates is contraindicated. That means that it should be avoided since it can cause harm. You should not be prescribed sildenafil if you have a prescription for nitrates.
Alpha Blockers
Alpha blockers treat conditions like benign prostatic hyperplasia (BPH) and high blood pressure. Examples of alpha blockers are tamsulosin (Flomax), alfuzosin (Uroxatral), and doxazosin (Cardura). These medications lower blood pressure by relaxing the smooth muscle in blood vessels. Combining alpha blockers with sildenafil can cause low blood pressure.Many men take both medications, but sometimes the dose of one needs to be lowered to avoid dizziness.
Medications and supplements that affect liver metabolism
Some medications affect liver metabolism and can cause higher. sildenafil levels. Examples are ritonavir (Norvir), clarithromycin, and ketoconazole. Taking these with sildenafil can make the side effects of sildenafil, like headaches and flushing, more likely or more severe. Your provider may suggest a lower sildenafil dose to avoid side effects.
Other medications and supplements can have the opposite effect and can result in lower sildenafil levels. These include rifampin (Rifadin), carbamazepine (Tegretol, Carbatrol), and St. John’s wort. When combined with these treatments, sildenafil may not work as well, and your provider may need to prescribe a higher
dose.
Blood pressure medications
Combining sildenafil with any medication that lowers blood pressure can potentially lead to blood pressure getting too low. Examples of blood pressure medications to be aware of are angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), calcium channel blockers like amlodipine (Norvasc), and diuretics. As discussed in above sections, Nitrates and alpha blockers tend to have more severe interactions with sildenafil.
Your healthcare provider may have you check your blood pressure more regularly if you’re taking any of these combinations. And, if you notice that your blood pressure is getting too low, they may need to adjust your dose of sildenafil.
Frequently Asked Questions
When taking sildenafil for ED, you need to take this medication at least 30 minutes before sexual activity. But it might take 1-2 hours for the full effects of this medication to kick in.
Sildenafil can work for up to 8 hours after you take it. But this doesn’t mean that the erection will last the entire time. It just means that you might be able to achieve better erections and sometimes more than one erection within this time frame. Best results will occur 1-4 hours after taking sildenafil. Remember, if an erection lasts for longer than 4 hours, seek emergency medical care as this can lead to permanent damage to the penis.
You should only take one dose per day. The effects of sildenafil should last for up to 8 hours after a dose, but the medication remains in your system a bit longer. Taking this medication more than once per day can increase the amount of drug in your system and raise your risk for serious side effects, such as priapism or vision changes. Instead of taking more than one dose in a day, consider discussing a different dosing option with your provider.
Alcohol can make it harder for you to get and/or maintain an erection, which might worsen ED. Alcohol also slightly lowers your blood pressure, so when combined with sildenafil men have a higher chance of headache and dizziness. Also, both alcohol and sildenafil are metabolized by the liver, so alcohol consumption can result in a longer delay before sildenafil starts to work.
Warnings
Heart problems
Risk factors: Existing heart condition | Recent heart attack or stroke in past 6 months | High or low blood pressure
Let your provider know if you have any heart conditions before starting sildenafil (Viagra). Sexual activity, and therefore sildenafil (Viagra), isn’t recommended for people with certain heart-related conditions, such as very serious heart failure. Also, sildenafil (Viagra) hasn’t been studied in people who have certain conditions, such as recent heart attacks or strokes. If you have a heart condition, ask your provider whether sildenafil (Viagra) is safe for you.
Low blood pressure
Risk factors: Taking alpha blockers | Taking medications for high blood pressure or chest pain (angina) | Taking ritonavir (Norvir)
Taking sildenafil (Viagra) with certain medications, such as alpha blockers, medications for high blood pressure, or the anti viral ritonavir (Norvir) can cause your blood pressure to drop too low. If you take any of these medications, talk with your provider to see if sildenafil (Viagra) is safe for you. If your provider says that you can take sildenafil (Viagra), they might recommend that you check your blood pressure regularly. Be very careful getting up from a sitting or lying down position since this can make you feel dizzy and more likely to fall. You should never take sildenafil (Viagra) when taking nitrate medication for chest pain (angina) because it can cause your blood pressure to drop suddenly to unsafe levels. low blood pressure. Many men take both medications, but sometimes the dose of one needs to be lowered to avoid dizziness.
Prolonged or painful erection (priapism)
Risk factors: Medical conditions that affect the penis | Sickle cell anemia | Multiple myeloma | Leukemia
Some people who took sildenafil (Viagra) reported having an erection that lasted for more than 4 hours (priapism). This side effect is rare. But if it’s not treated in time, it can lead to permanent damage to your penis. You’re at higher risk for these side effects if you have other conditions affecting your penis, or if you have sickle cell anemia, multiple myeloma, or leukemia. Get medical help right away if you have an erection that lasts longer than 4 hours or if you feel pain during an erection.
Interactions with other medications
Risk factors: Age 65 years or older | Liver problems | Kidney problems | Taking nitrate medications | Taking blood pressure medications | Taking alpha blockers | Taking certain antifungals or antivirals
Sildenafil (Viagra) can have serious interactions with certain medications. It’s important that you let your provider know about all the medications you’re taking before you start sildenafil (Viagra). For example, you shouldn’t take sildenafil (Viagra) with nitrate medications because this combination can cause your blood pressure to drop dangerously low. If you’re taking other blood pressure medications, your provider might not recommend sildenafil (Viagra) until your blood pressure is under control. Taking sildenafil (Viagra) with medications, like oral azole antifungals and ritonavir (Norvir), can put you at higher risk for side effects, such as headaches, flushing, and vision changes.
Hearing loss
Some people who took sildenafil (Viagra) reported experiencing hearing loss. And it sometimes happens along with ringing in the ears (tinnitus) and dizziness. Go to the emergency room or call your provider right away if you notice changes in your hearing in one or both ears.
Vision changes
Risk factors: Age 50 years or older | “Crowded” optic disc | Blood vessel problems in the eye
If you suddenly notice changes in your vision in one or both eyes, go to the emergency room or call your provider right away. Although this is rare, sildenafil (Viagra) can cause permanent eye damage. If your provider has told you that you have a “crowded” optic disc, you might be at higher risk for vision changes with sildenafil (Viagra).
Contraindications
Do not take sildenafil if you are:
- Taking a nitrate medication for chest pain (angina)
- Taking guanylate cyclase (GC) stimulators, such as Adempas (riociguat)
Watch out for the fake stuff!
You could encounter a sildenafil (Viagra) counterfeit while clicking on emails or shopping online. Counterfeit medications have ingredients that differ, which may result in a pill that does not work or has other side effects. You want your medications from a legit US pharmacy. mensRxplus providers only prescribe through established US pharmacies to ensure the quality of medication that our patients receive. For the sildenafil (Viagra) to be legit, look for:
- A prescription from a healthcare provider is always required
- A U.S. address and phone number are listed on website
- A licensed pharmacist is available for questions
- The pharmacy is licensed with a state board of pharmacy
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