Sildenafil What You Need to Know

Sildenafil What You Need to Know

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Sildenafil What You Need to Know

Sildenafil comes under a medicinal group known as phosphodiesterase 5 inhibitors (PDE5), inhibiting the quick working of a phosphodiesterase 5 enzyme. Sildenafil is used to prevent pulmonary hypertension and erectile dysfunction.

If you are using it for pulmonary hypertension, it will treat the disease by relaxing your chest’s blood vessels. However, in erectile dysfunction (sexual impotence), Sildenafil increases blood flow to your penis and causes an erection. 

Sildenafil is a prescribed medicine and you can buy it in the form of liquid, standard tablets, or chewable tablets. Are there any side effects of Sildenafil? What precautionary measures should I take before taking Sildenafil? Scroll down and solve all your queries!

Who Can/Cannot Take Sildenafil?

Men at the age of 18 or over can take Sildenafil for the treatment of erectile dysfunction. However, adults and children of 1 year can take Sildenafil to combat pulmonary hypertension. Besides this, you must not take this medicine if you:

Are allergic to Sildenafil

Have stomach ulcer, hemophilia, liver/heart problems, low blood pressure (hypotension), or retinitis pigmentosa (genetic eye disease).

Are taking medicines for angina/chest pain.

Have leukemia, sickle cell anemia (red blood cells abnormality), multiple myeloma (cancer of bone marrow), or curved/deformed penis (Peyronie’s disease).

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Mode of Action of Sildenafil

Sildenafil blocks the working of cGMP-specific phosphodiesterase type-5 enzymes. This enzyme breaks down cGMP molecules, relaxing the smooth muscles.

When Sildenafil inhibits the working of PDE-5, the level of cGMP increases within the smooth muscles, causing vasodilation and muscle relaxation. 

Although PDE-5 is found throughout your body’s smooth muscles, its high level is present in the lungs, penis, and retina. Let’s see how Sildenafil treats erectile dysfunction and pulmonary hypertension:

Erectile Dysfunction

In erectile dysfunction, the penis does not expand and harden when a man is sexually stimulated. Sildenafil controls the phosphodiesterase 5 enzyme, increases the blood flow to the penis, and produces an erection after the penis is stroked. However, during sexual intercourse, Sildenafil does not cause an erection. 

For erectile dysfunction, Sildenafil is known by brand names such as Nipatra, Aronix, Viagra, and Liberize.

Pulmonary Hypertension

Pulmonary hypertension occurs due to high blood pressure in the lungs and heart. So, Sildenafil treats pulmonary hypertension in men and women by inhibiting the action of phosphodiesterase 5 enzyme.

It relaxes the lungs’ blood vessels, causing your heart to pump enough blood to the lungs, and reducing the overall workload.

For pulmonary hypertension, Sildenafil is known by brand names such as Grandipam and Revatio.

Effectiveness of Sildenafil

How quickly does Sildenafil work? Let’s see the facts!

  • For erectile dysfunction, the results are noticeable within 30-60 minutes after a single dose.
  • In the case of pulmonary hypertension, you can see the results within 1-2 hours.
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Precautionary Measures for Taking Sildenafil

While taking Sildenafil, you must consider the following precautionary measures:

  • Grapefruit juice affects the working of Sildenafil, so do not drink it while taking Sildenafil. 
  • If you are taking Sildenafil for pulmonary hypertension, you must visit your doctor regularly to evaluate the progress of the medicine. 
  • Sildenafil does not protect you against HIV or AIDS so if you have any queries, consult your doctor. 
  • If you have allergy problems with Sildenafil or any other medicine, food, animal, dyes, or preservatives, consult your doctor before starting to take Sildenafil. 
  • Smoking also affects the working of Sildenafil, so consult your doctor if you smoke.

How To Use Sildenafil Properly?

Sildenafil is only prescribed by your doctor so do not use it against your doctor’s advice. It also comes with a patient information leaflet so read it and follow instructions to avoid any mishap.

If you have any queries/problems, consult your doctor. However, the general guidelines are:

For Oral Liquid:

You must shake the bottle for 10 seconds and:

  • Remove the cap of the Sildenafil bottle and insert the tip of your syringe by holding the bottle upright.
  • Pull back the plunger carefully after you get the required dose.
  • If you see air bubbles in your syringe, repeat the process.
  • Place the tip of the syringe into your or your child’s mouth and make it point toward your/child’s cheek. 
  • For erectile dysfunction, Sildenafil will start working within 30 minutes and continue to work for four hours.

For Tablets

Simply take a Sildenafil tablet by mouth with water/juice (except grapefruit juice). For erectile dysfunction, take Sildenafil on an empty stomach to enhance its working. 

How And When Should You Take Sildenafil?

How much Sildenafil is too much? You must take Sildenafil according to your doctor’s advice. However: 

Dosage for Erectile Dysfunction

For erectile dysfunction, the strength of Sildenafil tablets ranges from 25-100 mg. The standard dose is 50 mg for adults of 65 years and they must take it once per day.

The increase or decrease of the dose depends on the effects and other factors. For sexual activity, you must take Sildenafil four hours before sex and you need to be sexually excited.

However, adults older than 65 years must take a single dose of 25 mg per day. It is not recommended for children. 

Dosage for Pulmonary Hypertension

For pulmonary hypertension, Sildenafil tablets come in two different strengths such as 10 and 20 mg. The standard dose is 20 mg for adults and they must take it 3 times a day.

For children 1 year and older weighing 20-45 kg, the dose will be 20 mg and they must take it 3 times per day. But children, 1 year and older weighing less than 20 kg must take 10 mg Sildenafil 3 times per day.

For children younger than 1 year, the dose will be determined by the doctor. 

However, if you forget to take your dose, take it as soon as you remember. If it is too late, leave the missed one and take your next one at its time. Remember, never take two doses/extra doses at the same time to compensate for the forgotten one. 

Over-Dosage of Sildenafil

Over-dosage of Sildenafil will cause unpleasant side effects such as:

  • Dizziness 
  • Headache
  • Indigestion 
  • Changes to your vision
  • Blocked nose

If you experience any of these side effects, talk to your doctor immediately.

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Sildenafil Side Effects

The most common side effects of Sildenafil are:

  • Dyspepsia
  • Diarrhea 
  • Flushing
  • Nausea 
  • Headache 
  • Numbness 
  • Indigestion
  • Visual disturbances
  • Muscle or back pain
  • Low blood pressure
  • Nasal congestion
  • Insomnia
  • Runny nose
  • Heartburn 
  • Nose bleeding
  • Light sensitivity 
  • Sudden hearing loss

Rare/serious side effects of Sildenafil are:

  • Painful erections
  • Sudden loss of hearing 
  • Dizziness/fainting 
  • Chest pain
  • Shortness of breath 
  • Rash
  • Itching 
  • Ringing in ears
  • Sudden death 

If you experience serious side effects, consult your doctor immediately and report to the FDA (food and drug administrations).

Effect of Sildenafil on Pregnancy, Fertility, And Breastfeeding

Let’s discuss the effect of Sildenafil on pregnancy, fertility, and breastfeeding!


If you have pulmonary hypertension, consult your doctor and take Sildenafil throughout your pregnancy. Moreover, you must consult your doctor/pharmacist and ask him to give you additional care and review you in a special heart and pregnancy clinic.  


The effect of Sildenafil on fertility is unknown. It is not clear whether Sildenafil reduces fertility in men or women. So, consult your pharmacist before trying it. 


Sildenafil passes via breast milk in a small amount so it does not cause any side effects. So, you can consume Sildenafil for pulmonary hypertension while breastfeeding.

However, if you feel changes in baby behavior like unusual sleep, pale color, or flushing, consult your doctor. 

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Interaction of Sildenafil with Other Medicines 

Sildenafil can interact with other medicines, resulting in low working and increased side effects. Sildenafil can also inhibit CYP1A2, CYP3A4, and CYP2C9.

Any drug that is a substrate of any of these enzymes can interact with Sildenafil. So to manage drug interaction, consult your doctor. The medicines that react with Sildenafil are:

  • Alpha-blocker (doxazosin, alfuzosin, tamsulosin, prazosin, or terazosin)
  • Nitrates ( isosorbide dinitrate, amyl nitrate, nitroglycerin, or isosorbide mononitrate)
  • Alpha-agonist (methyldopa or clonidine)
  • Antidepressant (sertraline, desipramine, or St. John's Wort)
  • Antibiotics (clarithromycin, azithromycin, erythromycin, norfloxacin, metronidazole, rifabutin, tetracycline, or rifampin)
  • Antifungal medication ( ketoconazole, itraconazole, or voriconazole)
  • Blood thinner (warfarin)
  • Beta-blocker (propranolol/atenolol)
  • Cimetidine
  • Epilepsy medication (oxcarbazepine, carbamazepine, phenytoin, or phenobarbital)
  • Cystic fibrosis medication (ivacaftor)
  • Other erectile dysfunction medication (Cialis, alprostadil, or vardenafil)
  • HIV medication ( delavirdine, atazanavir, efavirenz, indinavir, fosamprenavir, etravirine, nevirapine, ritonavir, or tipranavir)
  • Heart medications (amiodarone, amlodipine, bosentan, atenolol, candesartan, clonidine, or captopril)
  • Others such as butalbital, aprepitant, cimetidine, riociguat, cyclosporine, or imatinib.
Storage and Disposal of Sildenafil

How to store Sildenafil? How to dispose of Sildenafil? Let’s jump into it!


You must store Sildenafil in an air-tight container and out of reach of children. You can store Sildenafil tablets at room temperature and ensure there is no moisture, light,ord heat around them (but not in the bathroom).

For Sildenafil suspension, you must store it in the refrigerator but not in the freezer. 


You must dispose of any unused Sildenafil suspension after 60 days. However, ensure that the disposal is out of reach of pets and other people.

Do not discard the medicine in the toilet, the best way is to dispose of Sildenafil via a medicine take-back program.

The Verdict

Sildenafil is an effective way to treat pulmonary hypertension and erectile dysfunction. However, you must follow some precautionary measures and guidelines for quick action and to avoid any side effects. So, consult your doctor, improve your health, and give your life a new chance!

Frequently Asked Questions 

What Do You Feel When You First Take Sildenafil?

When you take Sildenafil for the first time, you will experience mild side effects such as headache, dizziness, flushing, etc. However, these side effects settle within a few hours. 

What Should You Monitor While Taking Sildenafil?

You should monitor your health while taking Sildenafil. If you face mild side effects, let them settle within a few hours. If you experience serious health issues, consult your doctor. 

How Long Will Sildenafil Keep You Hard?

Sildenafil lasts for 2-4 hours. It makes erection easier during sex.

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