Sildenafil side effects and drug information

Sildenafil is a brand name for Viagra. It is a medication that is utilized to cure erectile dysfunction or ED among men. ED or impotence is a condition where men are unable to achieve or maintain an erection. On another note, Sildenafil (Revatio) is utilized to increase the capacity of patients with pulmonary arterial hypertension or PAH to exercise. PAH is a condition where the patient suffers from high blood pressure in the vessels that are supplying blood towards the lungs, resulting in dizziness, shortness of breath, and tiredness.

Molar Mass 474.5764 g/mol
CAS ID 171599-83-0
ChemSpider ID 56586
Trade names Adcirca, Revatio, Viagra
PubChem CID 5212

Children shouldn’t consume sildenafil unless the doctor decides that it is the most suitable and effective medication to cure the child’s health complications. Viagra or Sildenafil belongs to the category of drugs that are known as phosphodiesterase (PDE) inhibitors. It treats erectile dysfunction by improving blood pressure towards the penis during sexual stimulation. With this, blood pressure is increased, resulting in a better erection. Besides, Sildenafil cures PAH by calming the blood vessels located in the lungs to enable blood to flow smoothly.

Always keep in mind that if you are consuming sildenafil to cure erectile dysfunction, it doesn’t treat erectile dysfunction nor improve sex drive. It only helps men achieve a better erection by increasing blood flow to the penis with the help of sexual stimulation. Sildenafil doesn’t prevent pregnancy nor transmit sexually transmitted diseases like human immunodeficiency virus (HIV).

Side effects

Just like any medications, Sildenafil effects can also be severe or serious. If you experience any of these side effects, call your doctor right away:

  • heartburn
  • flushing (feeling of warmth)
  • difficulty falling asleep or staying asleep
  • headache
  • diarrhea
  • nosebleeds
  • muscle aches
  • sensitivity to light
  • burning, numbness, or tingling in the arms, feet, hands, or legs
  • changes in color vision (seeing a blue tone on objects or having a problem telling the difference between green and blue)

There are also Sildenafil adverse effects can be severe. In the events that you suffer from any of the following adverse facts, reach out to your doctor, or get emergency help right away:

Some people experience chest pain, a sudden loss of all or some of their vision right after they consume sildenafil or other prescription medications. There are rare cases that vision loss or blurred vision was permanent. However, there are still no reported studies or clinical trials that proved that the sudden vision loss was due to Viagra. If you have abrupt vision loss while taking Viagra, contact your doctor or physician right away. Discontinue using any more dosages of Viagra, Sildenafil or other similar medications like vardenafil (Levitra) or tadalafil (Cialis) until you reach out to your doctor.

Besides this, side effects such as stroke, high blood pressure, irregular heartbeat, coronary artery disease, bleeding in the lungs or brain, and sudden death among men who consumed Sildenafil to treat erectile dysfunction. The majority of these people , but not all, suffered from heart complications before drinking Viagra. It is still unknown if these circumstances were due to Viagra, heart failure, sexual intercourse, or a combination of all of these. This is because there are no studies and clinical trials reported that link Viagra into all of these. Talk to your physician or doctor about the side effects of Viagra before taking it.

Furthermore, some individuals suffer from abrupt loss or decrease of hearing right after they consumed sildenafil (Viagra) or any other medications that are associated with Sildenafil. Usually, the hearing loss from Sildenafil only affects one ear and doesn’t always progress once the patient discontinues taking medicine.

It is still unknown whether the sudden hearing loss was due to Viagra since there are no clinical trials and studies that prove it. In the events that you experience abrupt hearing loss, alongside dizziness or ringing in the ears, while you are drinking Viagra or Sildenafil , contact your doctor right away. Always remember that if you are consuming Viagra, Sildenafil , and any other medications such as vardenafil (Levitra) or tadalafil (Cialis) to treat erectile dysfunction, don’t take more dosages unless your doctor says so.

On another note, if you are consuming Revatio Sildenafil to treat PAH, never discontinue your usage until you discuss it with your physician or doctor. Viagra or Sildenafil may also cause other forms of side effects. So if you experience unusual symptoms while consuming Sildenafil , talk to your doctor right away. In case you experience any severe side effect, your doctor, physician, or you could send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event.

Indication and dosage

Viagra or Sildenafil is indicated for the cure of erectile dysfunction or ED. All potential drug forms and doses may not be listed here. Your drug treatment, and how often you drink the medication is solely dependent on these factors:

  • the complication being treated
  • your age
  • how severe your condition is
  • how you react to the first dose
  • other medical complications that you have

Here are the recommended dosages for taking Viagra or Sildenafil for erectile dysfunction:

  • Generic: Sildenafil
  • Form: oral tablet
  • Strengths: 100 mg, 50 mg, 25 mg
  • Brand: Viagra
  • Form: oral tablet
  • Strengths: 100 mg, 50 mg, 25 mg

Here are the recommended dosages for patients that are 18-64 years old:

  • Minimum dosage: 50 mg consumed as needed approximately 1 hour before sexual intercourse. It can be consumed 30 minutes to 4 hours before any sexual activity.
  • Maximum dosage: 100 mg once a day

For children ages 0 to 17 years old:

  • Viagra or Sildenafil hasn’t confirmed whether or not it is useful or safe for children below 18 years old.

For patients that are 65 years and older:

The heart, liver, and kidneys of older individuals taking Sildenafil might not function as high as they used to. With this organ impairment, their body would have difficulties processing the medications. This often leads to a more significant amount of Sildenafil drug accumulation in their body that stays there for a prolonged period. When this happens, their risk of suffering from side effects might increase. For seniors, doctors or physicians might decrease the dosage of Sildenafil to prevent higher levels of drugs from accumulating in the body.

Drug Interaction

Sildenafil oral tablet can interact with other types of medications, supplements, vitamins, and herbs that you might be consuming. Sildenafil Interaction happens when a substance alters the mechanism of a particular drug. When an interaction occurs, this can be hazardous or impeded the medication from taking its full potential. To prevent interactions from happening, you should only allow your physician or doctor to handle all your drugs, especially Sildenafil . Make sure you inform them about the all vitamins, medications, and supplements that you are consuming. You should also ask your pharmacist or doctor how Viagra or Sildenafil might interact with any medication, vitamins, supplements, or herbs that you’re taking.

Here are examples of drugs that can result in interactions with Viagra or Sildenafil .

Do not consume these drugs alongside sildenafil. Taking these can lead to hazardous side effects in the body.


Examples of these drugs are:

  • Nitrates like isosorbide dinitrate, isosorbide mononitrate, or nitroglycerin.

Consuming these drugs alongside Viagra or Sildenafil can lead to a sudden drop in your blood pressure to the point that it might reach an unsafe level.

  • Guanylate cyclase stimulators like riociguat.

Drinking these drugs, together with Viagra or Sildenafil , can result in a sudden drop in your blood pressure to the point that it might reach an unsafe level.

Moreover, consuming Viagra or Sildenafil with particular medications might increase your risk of side effects from Viagra. This is because the levels of Viagra or Sildenafil in your body is raised. Some of these drugs are:

  • HIV drugs like indinavir, atazanavir, saquinavir, or atazanavir

Improved side effects can range from dizziness, low blood pressure, or problems with vision. They can also result in erections that last longer than the reasonable period.

  • Particular antibiotics like erythromycin or clarithromycin

Improved side effects can range from dizziness, low blood pressure, or problems with vision. They can also result in erections that last longer than a reasonable period.

  • Particular antifungals like itraconazole or ketoconazole

Improved side effects can range from dizziness, low blood pressure, or problems with vision. They can also result in erections that last longer than the average period.

  • Alpha-blockers like tamsulosin, alfuzosin, terazosin, doxazosin, or silodosin.

Improved side effects can range from fainting or low blood pressure.

  • Blood pressure drugs like amlodipine

Improved side effects include a dip in blood pressure.

  • Other medications for erectile dysfunction like vardenafil, tadalafil, avanafil.

Improved side effects can range from prolonged erections or low blood pressure.

Sildenafil Warnings and Precautions

Cardiovascular warning

There is a high possibility of cardiac risk of sexual activity among patients who are diagnosed with existing cardiovascular disease. This is why the cure for erectile dysfunction, such as Viagra or Sildenafil , shouldn’t be generally utilized among men who are advised to refrain from sexual activity because of their existing cardiovascular condition.

Viagraor Sildenafil is notorious for having systemic vasodilatory properties that lead to dramatic decreases in the supine blood pressure among healthy patients (mean maximum decrease of 8.4/5.5 mmHg). Though this is usually expected to be one of the side effects among patients associated with prescribing Viagra or Sildenafil , doctors need to carefully think about whether or not patients with the pre-existing cardiovascular disease might be affected dramatically by such vasodilatory effects, specifically in combination with sexual intercourse.

Patients should take Viagra or Sildenafil with caution if they have left ventricular outflow obstruction such as idiopathic hypertrophic subaortic stenosis, aortic stenosis, and individuals with severely damaged autonomic control of blood flow. There are no clinical trials and studies with the following existing complication that can specifically affect the mechanism of vasodilators, such as Viagra or Sildenafil , in these groups of individuals. If prescribed, this should be consumed with caution.

  • Patients who suffer from stroke, myocardial infarction, or life-threatening arrhythmia within the last six months.
  • Patients that have resting hypertension (BP >170/110 mmHg) or hypotension (BP <90/50 mmHg)
  • Patients who developed coronary artery disease or cardiac failure resulting in unstable chest pain.

Priapism warning

Viagra or Sildenafil can result in priapism, a condition wherein prolonged erection is experienced by men. If you encounter an erection that stays for more than 4 hours, consult your doctor or call 911 right away. If it is not given instant medical attention, this could lead to permanent damage to the penis.

Moreover, prolonged erection that are more than 4 hours or popularly known as priapism can lead to painful erections. In case an erection stays for more than 4 hours, the person has to look for instant medical help. If priapism is not immediately cured, this could result in permanent loss of potency or penile tissue damage. Viagra or Sildenafil should also be utilized with caution among person that has anatomical deformation of the penis like Peyronie’s disease, cavernosal fibrosis, or angulation. Individuals who suffer from complications that are related to priapism like leukemia, multiple myeloma, or sickle cell anemia should also consume Viagra with caution.

There are still no studies or clinical trials on the effectiveness or safety of Viagra among individuals with sickle cell or other related anemias.

Sudden vision loss warning

Viagra can lead to an abrupt loss of vision in one or two or both eyes. This is an indication of a severe eye problem. When this happens, discontinue drinking Viagra and consult your doctor immediately. Doctors advise patients to stop using all phosphodiesterase type 5 (PDE5) inhibitors, such as Viagra and look for instant medical help in the event of abrupt vision loss. Such even could be an indication of non-arteritic anterior ischemic optic neuropathy (NAION) – a rare condition and a result of lowered vision such as permanent vision loss. According to a published study, the yearly incidence of NAION is 2.5–11.8 cases per 100,000 in males aged ≥ 50.

Moreover, an observational case-crossover study observed the evaluated risk of non-arteritic anterior ischemic optic neuropathy if a PDE5 inhibitor is utilized. The outcome suggested the 2-fold rise in the risk of NAION, alongside an estimated risk of 2.15 (95% CI 1.06, 4.34). Moreover, a similar study discovered a consistent outcome, with a calculated risk of 2.27 (95% CI 0.99, 5.20). There are other risks that are associated with NAION, like the proximity of “crowded” optic disc, might have impacted the visibility of NAION in all these studies. However, there are still no studies or clinical trials regarding the effectiveness or safety of Viagra among patients with retinitis pigmentosa, unless the doctor prescribed, this has to be consumed with caution.

Sudden hearing loss warning

Viagra can result in abrupt loss of hearing, dizziness, or ringing in the ears/tinnitus. If you experience the sudden loss of hearing with or without ringing in the ears or dizziness, discontinue using Viagra once and for all and consult your doctor immediately.

Physicians and doctors need to advise patients to discontinue the usage of PDE5 inhibitors, such as Viagra, and look for instant medical help in case of abrupt loss or decrease of hearing. These circumstances, which are usually accompanied by dizziness and ringing in the ears, have been reported to be linked to the consumption of PDE5 inhibitors like Viagra. However, it is still impossible to point out whether or not these circumstances are associated with the direct usage of PDE inhibitors and other factors.

Use in children warning

Children with PAH who consume Sildenafil might be at risk of death. That’s why it is highly advisable that children shouldn’t take Sildenafil.

Hypotension with Anti-blockers or Anti-hypertensives warning

caution is suggested when patients with Hypotension consume alpha-blockers with PDE5 inhibitors such as Viagra. When vasodilators are utilized together, an additive effect might occur in the blood pressure. In several patients, continued use of these two medications can decrease blood pressure effectively, resulting in symptoms of symptomatic hypotension such as fainting, lightheadedness, or dizziness. Here are other considerations to be aware of:

  • People who show hemodynamic instability on alpha-blocker therapy alone might potentially suffer from the improved risk of symptomatic hypotension with continued use of PDE5 inhibitors.
  • People should be stable on alpha-blocker with regards to the usage of a PDE5 inhibitor.
  • Among people who depend on alpha-blocker therapy, the PDE5 inhibitors need to be given at the lowest dosage.
  • Among people who are already consuming a maximum dosage of PDE5 inhibitors, such as Viagra, alpha-blocker therapy needs to be presented at the lowest dosage. The dramatic increase in the dosage of alpha-blockers might be linked to the progressive lowering of blood pressure when consuming PDE5 inhibitors.
  • The safety and effectiveness of combined usage of alpha-blockers and PDE5 inhibitors might impact other variables, such as intravascular volume depletion and many other anti-hypertensive drugs.

Overdose and Contraindications

The following person shouldn’t consume Viagra or Sildenafil, or should consult with their physician or doctor first:

  • Men who are recommended to avoid sexual activity due to cardiovascular risk factors
  • People taking nitrates, nitric oxide donors, or organic nitrites
  • People who are diagnosed with kidney disease
  • People with serious liver impairment
  • Those with hereditary degenerative retinal disorders
  • Those who recently suffered from a stroke or heart attack
  • Those that suffer from hypertension or low blood pressure

There are several athletes who consume Sildenafil to improve their ability to exercise. However, there are limited pieces of evidence that back up this use. Individuals who acquire HIV and destroy protease inhibitors need to talk to their doctors before taking Viagra. Protease inhibitors improve the severity and risk of the effects of Viagra. These people shouldn’t take more than 25 milligrams (mg) of Viagra at a specific time or more often every 48 hours.

Moreover, those who consume alpha-blockers need to ensure that they drink Viagra about 4 hours before or after taking alpha-blockers. Doing this will combat the effects of Viagra, which includes low blood pressure. Though death cases that are linked to Viagra are rare, it is possible that patients can die from consuming such drugs.

Clinical Pharmacology

Erectile dysfunction is a widespread and multi-factorial illness that dramatically damages the quality of life among men. Over the past years, there are a lot of innovative methods that have been developed. However, the most effective was the utilization of oral treatment. This was strongly backed up with the introduction of Sildenafil or Viagra in the market. The medication functions by improving the smooth muscle relaxant effect of the nitric oxide or NO. There have been a plethora of clinical studies that supported and proved the effectiveness and safety of Viagra. This medication made a significant impact in different parts of the world, and it is even considered as the “magic pill” by some people.