Sildenafil 101: How It Works, Effectiveness And Side Effects

In this article, we will be explaining what sildenafil is, how it works as a form of erectile dysfunction treatment, how you should take it for the best results and the potential side effects that could occur.

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In this article, we will be explaining what sildenafil is, how it works as a form of erectile dysfunction treatment, how you should take it for the best results and the potential side effects that could occur.

What Is Sildenafil and How Does It Help Treat Erectile Dysfunction

Sildenafil is a prescription oral medication used for erectile dysfunction (ED) treatment. 

Also known as generic Viagra, sildenafil is part of a class of medications called  phosphodiesterase-5 inhibitors (PDE5 inhibitors).These mediations help to restrict the enzyme PDE5 which degrades cGMP, a molecule that helps to relax the muscle tissues in the body. By inhibiting the enzyme PDE5, sildenafil is able to relax the muscle tissues that's present in the blood vessel walls, which results in an improved blood flow to where you need it the most; your penis. 

Contrary to popular belief, erectile dysfunction medications like sildenafil or Viagra won't cause you get random erections or increase your sex drive. They will still require you to be sexually aroused in order for an erection to occur. Thankfully for most healthy men, taking sildenafil will help make getting an erection a much easier task. In a study done by the journal Therapeutics and Clinical Risk Management, researchers found that long-term usage of sildenafil was safe and had low instances of adverse side effects.

It is important to note that sildenafil will not protect you against sexually transmitted diseases like gonorrhea, syphilis, hepatitis B or HV. It is vital that you practice safe sex and use condoms to prevent the spread of these STDs. 

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How Should I Take Sildenafil?

Sildenafil comes in a range of doses from 20mg, 25mg, 50mg and 100mg tablets. Most commonly prescribed is the 50mg dose, however your doctor might recommend that you start taking 25mg at first to see if it's a sufficient enough dose. 

When it comes to treating erectile dysfunction, sildenafil should be taken on an as-needed basis. As sildenafil is absorbed rather quickly into the bloodstream and will reach its maximum concentration within an hour for most users, it is recommended that you take sildenafil an hour before you have sex. However it is possible that sildenafil can start taking effect as early as 30 minutes.

After the 4-hour mark, the effect will begin to taper off. It is recommended that you only take a dose of sildenafil once a day to prevent adverse reactions from occuring. 

You can take sildenafil either with or without a meal, but it is important to note that taking it with a high-fat meal might cause the medication to work more slowly and delay when it starts to take effect. 

Potential Side Effects Of Taking Sildenafil

While taking sildenafil is safe, it might cause some temporary and minor side effects. Here is a list of side effects that could occur after taking sildenafil: 

  • Headaches
  • Dizziness or lightheadedness
  • Muscle aches
  • Heartburn¬†
  • Flushing (warming and reddening of the face)
  • Vision changes (like increased sensitivity to light)
  • Nasal congestion
  • Nausea or an upset stomach

As mentioned earlier, these side effects are mostly temporary and will gradually go away as the medication begins to wear off and exits your body. To help lessen the dizziness and lightheadedness that might occur, you should gradually get up from a lying or sitting position. 

It is important that you contact your doctor promptly or seek medical assistance if you begin to experience the following serious side effects: 

  • The dizziness, lightheadedness, nausea does not go away after having sex. Experiencing chest pain is also a concerning sign and should be checked out by a medical professional immediately.¬†
  • You experience a sudden loss of vision in one or both eyes, or experience a sudden loss of hearing (where tinnitus, or ringing in the ears, might occur)¬†
  • You experience symptoms of a serious allergic reaction such as the itching and swelling of the face, throat and tongue, trouble breathing, rashes and severe dizziness or lightheadedness
  • You experience priapism, a painful erection that persists for more than 4 hours.


Potential Drug Interactions To Look Out For When Taking Sildenafil

Similar to any powerful medication, sildenafil can interact with other drugs and cause adverse reactions. Here is a list of medications that could cause adverse interactions when taken with sildenafil: 

  1. Do Not Take Sildenafil With Heart or Blood Pressure Medication
  • Sildenafil can adversely interact with medications used to treat high blood pressure or angina. When taken with medications like nitrates, diuretics, calcium channel blocker or ACE inhibitors, sildenafil could cause a dangerous drop in blood pressure. This drop in blood pressure could cause headaches, fainting, dizziness and in more severe cases, could result in less oxygen being transported to your organs.

    If you are currently taking heart or high blood pressure medication or have had heart issues in the past 6 months, it is important that you inform your doctor about this before you use sildenafil. 

  1. Do Not Take Sildenafil With Other Kinds of ED Medications
  • Avoid taking sildenafil with any other kinds of erectile dysfunction medication as they could lower your blood pressure which increases the likeliness of dizziness and fainting, and in rare instances, even cause heart attacks.¬†

  1. Avoid Taking Sildenafil With CP450 Medications
  • When taken together with cytochrome P450 (CP45) medications (like modafinil, fluvoxamine, cimetidine and clopidogrel), it can cause sildenafil to work more slowly and delay when it takes effect, as well as increases the likelihood of you experiencing side effects.¬†

  1. Avoid Drinking Alcohol When Taking Sildenafil 
  • While it might be tempting to indulge in a few cheeky brews to get into the mood, the combination of alcohol and sildenafil could lower your blood pressure and can result in you experiencing side effects like dizziness, nausea or blurred vision.¬†

  1. Avoid Eating Grapefruit When Taking Sildenafil  
  • Grapefruit and grapefruit juice are the only foods that interact with sildenafil. While they can increase the levels of sildenafil in your body, they can also cause a delay in when sildenafil takes effect.

If you are experiencing erectile dysfunction, it is advisable that you consult a doctor. Here at Noah, our doctors are best equipped with the knowledge to help you ascertain the root cause of your erectile dysfunction and can determine whether generic sildenafil is right for you. They will be able to advise you on the best treatment suited for you, and can also prescribe you the right medication should you need it.


McMurray, James G et al. ‚ÄúLong-term safety and effectiveness of sildenafil citrate in men with erectile dysfunction.‚ÄĚ Therapeutics and clinical risk management vol. 3,6 (2007): 975-81. (Link)

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Published On
July 26, 2021

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