Sildenafil is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. Its effectiveness for treating sexual dysfunction in women has not been demonstrated.Common side effects include headaches and heartburn, as well as flushed skin. Caution is advised in those who have cardiovascular disease. Rare but serious side effects include prolonged erections, which can lead to damage to the penis, and sudden-onset hearing loss. Sildenafil should not be taken by people who take nitrates such as nitroglycerin (glycerin trinitrate), as this may result in a severe and potentially fatal drop in blood pressure.
Sildenafil acts by inhibiting cGMP-specific phosphodiesterase type 5 (phosphodiesterase 5, PDE5), an enzyme that promotes degradation of cGMP, which regulates blood flow in the penis. Sildenafil relaxes muscles found in the walls of blood vessels and increases blood flow to particular areas of the body.
Sildenafil under the name Viagra is used to treat erectile dysfunction (impotence) in men.
Another brand of sildenafil is Revatio, which is used to treat pulmonary arterial hypertension and improve exercise capacity in men and women.
Sildenafil (Viagra Connect, Pfizer) is to be formally reclassified from a prescription only medicine (POM) to a pharmacy medicine (P), the Medicines and Healthcare products Regulatory Agency (MHRA) has announced.
Sildenafil will be available through pharmacy outlets, following a discussion with the pharmacist, for adult men with erectile dysfunction. The drug will be sold at a maximum daily dose of 50mg and a maximum pack size of eight tablets.
The decision to reclassify the drug was made following an assessment of the safety of sildenafil, advice from the Commission on Human Medicines and a public consultation earlier this year. The drug will not be sold to those with severe cardiovascular disorders, liver failure, severe kidney failure or individuals taking certain interacting medicines.
“This decision is good news for men’s health,” said Mick Foy, MHRA group manager in vigilance and risk management of medicines.
“The move to make Viagra Connect more widely accessible will encourage men to seek help within the healthcare system and increase awareness of erectile dysfunction,” he added.
President of the Royal Pharmaceutical Society, Ash Soni, welcomed the MHRA’s decision to switch sildenafil to a P medicine.
“Discussing health problems with patients and advising on the benefits and risks of treatment options is an integral part of the role of a pharmacist,” he said.
“The switch will increase access to a medicine that has been proven safe and effective through over 15 years of use by many millions of men, and provides a genuine and safe source of supply of one of the world’s most counterfeited medicines,” he added.
Pfizer is currently working on plans to launch the drug in the UK in the spring of 2018. According to Pfizer, in the interim the company will be implementing an extensive training and education programme within pharmacies.
“We understand some men may avoid seeking support and treatment for this condition so we believe giving them the option to talk to a pharmacist and buy Viagra Connect could be a real step forward in encouraging more men into the healthcare system,” said Berkeley Phillips, UK medical director at Pfizer Ltd.
“As erectile dysfunction may be a sign of an underlying condition such as diabetes, high blood pressure, or heart disease, there could also be a wider benefit to public health in the long term,” he added.
Before taking this medicine
You should not use sildenafil if you are allergic to it,
- if you take other medicines to treat pulmonary arterial hypertension, such as riociguat (Adempas).
Do not take sildenafil if you are also using a nitrate drug for chest pain or heart problems. This includes nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate. Nitrates are also found in some recreational drugs such as amyl nitrate or nitrite (“poppers”). Taking sildenafil with a nitrate medicine can cause a sudden and serious decrease in blood pressure.
To make sure sildenafil is safe for you, tell your doctor if you have ever had:
- heart disease or heart rhythm problems, coronary artery disease;
- a heart attack, stroke, or congestive heart failure;
- high or low blood pressure;
- liver or kidney disease;
- a blood cell disorder such as sickle cell anemia, multiple myeloma, or leukemia;
- a bleeding disorder such as hemophilia;
- a stomach ulcer;
- retinitis pigmentosa (an inherited condition of the eye);
- a physical deformity of the penis (such as Peyronie’s disease); or
- if you have been told you should not have sexual intercourse for health reasons.
Sildenafil can decrease blood flow to the optic nerve of the eye, causing sudden vision loss. This has occurred in a small number of people taking sildenafil, most of whom also had heart disease, diabetes, high blood pressure, high cholesterol, or certain pre-existing eye problems, and in those who smoked or were over 50 years old. It is not clear whether sildenafil is the actual cause of vision loss.
This medicine is not expected to harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.
It is not known whether sildenafil passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.
Do not give sildenafil to anyone under 18 years old without medical advice.
Before taking sildenafil
Take sildenafil exactly as it was prescribed for you Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.
Revatio is usually taken three times each day, about 4 to 6 hours apart.
Viagra is usually taken only when needed, 30 minutes to 1 hour before sexual activity. You may take it up to 4 hours before sexual activity. Do not take Viagra more than once per day.
Shake the oral suspension (liquid) well just before you measure a dose. Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.
Viagra can help you have an erection when sexual stimulation occurs. An erection will not occur just by taking a pill. Follow your doctor’s instructions.
During sexual activity, if you become dizzy or nauseated, or have pain, numbness, or tingling in your chest, arms, neck, or jaw, stop and call your doctor right away. You could be having a serious side effect of sildenafil.
Store at room temperature away from moisture and heat.
If I miss a dose
Since Viagra is used as needed, you are not likely to miss a dose.
If you miss a dose of Revatio, take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
Sildenafil Side Effects
Applies to sildenafil: oral powder for suspension, oral tablet
Other dosage forms:
- intravenous solution
Along with its needed effects, sildenafil may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking sildenafil:
- Bladder pain
- burning feeling in the chest or stomach
- burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings
- cloudy or bloody urine
- increased frequency of urination
- pain on urination
- stomach upset
- tenderness in the stomach area
- Abnormal vision
- behavior change similar to drunkenness
- bleeding of the eye
- blurred vision
- bone pain
- breast enlargement
- chest pain
- cold sweats
- convulsions (seizures)
- cool and pale skin
- deafness or hearing loss
- decrease in amount of urine or the frequency of urination
- decreased vision
- difficulty in concentrating
- dizziness or lightheadedness, especially when getting up suddenly from a lying or sitting position
- double vision
- dry eyes
- dry mouth
- dryness, redness, scaling, or peeling of the skin
- excessive hunger
- eye pain
- fainting or faintness
- fast, irregular, or pounding heartbeat
- feeling of something in the eye
- fever or chills
- headache (severe or continuing)
- increase in the size of the pupil
- increased sweating
- increased thirst
- lower back or side pain
- migraine headache
- nausea (severe or continuing)
- numbness of the hands
- painful, swollen joints
- prolonged, painful erection of penis
- redness, burning, or swelling of the eyes
- redness, itching, or tearing of the eyes
- restless sleep
- seeing shades of colors differently than before
- sensitivity to light
- skin lesions with swelling
- skin paleness
- skin rash, hives, or itching
- skin ulcers
- slurred speech
- sore throat
- sudden weakness
- swelling of the face, hands, feet, or lower legs
- trouble breathing
- twitching of the muscles
- unusual feeling of burning or stinging of the skin
- unusual tiredness or weakness
- vision changes
- vision loss, temporary
Incidence not known
Some side effects of sildenafil may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- Aches or pains in the muscles
- bloody nose
- difficult or labored breathing
- pain or tenderness around the eyes and cheekbones
- redness of the skin
- stomach discomfort following meals
- stuffy or runny nose
- trouble sleeping
- unusually warm skin
- Abdominal or stomach pain
- abnormal dreams
- clumsiness or unsteadiness
- diarrhea or stomach cramps (severe or continuing)
- difficulty in swallowing
- ear pain
- increased amount of saliva
- increased skin sensitivity
- lack of coordination
- loss of bladder control
- mental depression
- numbness or tingling of the hands, legs, or feet
Avoid that while taking sildenafil
Drinking alcohol with this medicine can cause side effects.
Grapefruit and grapefruit juice may interact with sildenafil and lead to unwanted side effects. Avoid the use of grapefruit products while taking sildenafil.
Avoid using any other medicines to treat impotence, such as alprostadil or yohimbine, without first talking to your doctor.
Call your doctor at once if you have:
- ringing in your ears, or sudden hearing loss;
- irregular heartbeat;
- swelling in your hands, ankles, or feet;
- shortness of breath;
- seizure (convulsions); or
- a light-headed feeling, like you might pass out.
Common sildenafil side effects may include:
- flushing (warmth, redness, or tingly feeling);
- headache, dizziness;
- abnormal vision (blurred vision, changes in color vision)
- runny or stuffy nose, nosebleeds;
- sleep problems (insomnia);
- muscle pain, back pain; or
- upset stomach.
Sildenafil dosing information
Usual Adult Dose of Sildenafil for Erectile Dysfunction:
Initial dose: 50 mg orally once a day, as needed, 1 hour prior to sexual activity
Maintenance: 25 to 100 mg orally once a day, as needed, 1 hour prior to sexual activity
Comments: This drug may be taken anywhere from 30 minutes to 4 hours before sexual activity.
Use: Treatment of erectile dysfunction
Usual Adult Dose for Pulmonary Hypertension:
-Initial dose: 5 or 20 mg orally three times a day, 4 to 6 hours apart
-Maximum dose: 20 mg orally three times a day
-Initial dose: 2.5 or 10 mg IV bolus three times a day
-No greater efficacy was achieved with oral doses higher than the maximum recommended dose.
-A 10 mg injection dose is predicted to provide pharmacological effect equivalent to the 20 mg oral dose.
Use: Treatment of PAH (WHO Group I) in adults to improve exercise ability and delay clinical worsening
Usual Geriatric Dose of Sildenafil for Erectile Dysfunction:
Initial dose: 25 mg orally once a day 1 hour prior to sexual activity
Use: Treatment of erectile dysfunction
What other drugs will affect sildenafil?
Do not take sildenafil with similar medications such as avanafil (Stendra), tadalafil (Cialis) or vardenafil (Levitra). Tell your doctor about all other medications you use for erectile dysfunction.
Tell your doctor about all your current medicines and any you start or stop using, especially:
- drugs to treat high blood pressure or a prostate disorder;
- an antibiotic – clarithromycin, erythromycin, or telithromycin;
- antifungal medicine – ketoconazole or itraconazole; or
- medicine to treat HIV/AIDS – atazanavir, indinavir, ritonavir, or saquinavir.
This list is not complete. Other drugs may interact with sildenafil, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.
- If you are taking sildenafil (Viagra) for ED, do not take more than once a day. If you are taking sildenafil (Revatio) for PAH, take as directed (usual dosage is three times daily).
- Do not consume grapefruit or grapefruit products while taking sildenafil.
- Always talk to your doctor before taking ANY medication for ED. Some ED medications are not suitable for men with certain medical conditions, and your doctor can advise you on an alternative.
- Call your doctor immediately if you experience dizziness or feel nauseous during sexual activity, or develop pain, numbness, tingling in your chest, arms, neck, or jaw.
- Do not take sildenafil if you are also taking a nitrate drug (such as nitroglycerin or isosorbide dinitrate/mononitrate) for chest pain or heart problems. Do not take sildenafil with recreational drugs such as “poppers”. Taking these substances together can cause a sudden and dangerous drop in blood pressure.
- Always buy your ED medications from a reputable supplier as there are a lot of counterfeit products on the market.
- Certain lifestyle and psychological factors, such as smoking, drinking, and stress, can impact on ED. Eliminating these – for example, staying more active, losing weight if you are overweight, reducing alcohol intake, stopping smoking and reducing stress – may also help improve ED.
- Never take other ED medications at the same time as taking sildenafil. Do not take Viagra while taking Revatio and vice-versa.
- Seek urgent medical advice if an allergic reaction, sudden vision loss or painful erections lasting more than four hours occur.
- Drinking alcohol after taking sildenafil may lower blood pressure and decrease sexual performance.
- Nichols, DJ; Muirhead, GJ; Harness, JA (6 March 2002). “Pharmacokinetics of Sildenafil after Single Oral Doses in Healthy Male Subjects: Absolute Bioavailability, Food Effects and Dose Proportionality”. British Journal of Clinical Pharmacology. 53: 5S–12S. doi:10.1046/j.0306-5251.2001.00027.x. PMC . PMID 11879254.
- “Viagra (sildenafil citrate) Tablets, for Oral Use. Full Prescribing Information”. Pfizer Labs. Division of Pfizer, Inc., NY, NY 10017. Retrieved 5 November 2016.
- Venhuis BJ, Blok-Tip L, de Kaste D (2008). “Designer drugs in herbal aphrodisiacs”. Forensic Science International. 177 (2–3): 25–27. doi:10.1016/j.forsciint.2007.11.007. PMID 18178354.
- FDA letter to Libidus distributor
- FDA Warns Consumers About Dangerous Ingredients in “Dietary Supplements” Promoted for Sexual Enhancement
- Hidden Risks of Erectile Dysfunction “Treatments” Sold Online
- “Pfizer Wins Viagra Patent Infringement Case Against Teva Pharmaceuticals”. Bloomberg. 15 August 2011. Retrieved 1 April 2012.
- “Revation patent ruled invalid for lack of sound prediction and obviousness”. Canadian Technology & IP Law. Stikeman Elliott. 18 June 2010. Retrieved 14 November 2012.
- “Pfizer Canada Inc. v. Ratiopharm Inc., 2010 FC 612″. CanLII.
- Teva Canada Ltd. v. Pfizer Canada Inc. 2012 SCC 60 at par. 80 (8 November 2012)
- John Spears (8 November 2012). “Supreme Court ruling could lead to cheaper versions of Viagra”. Toronto Star. Retrieved 14 November 2012.
- Ken Hanly (8 November 2012). “Canadian Supreme court rules Viagra patent invalid”. Digital Journal.
- “Viagra patent tossed out by Supreme Court: Decision allows generic versions of drug to be produced”. CBC News. 8 November 2012. Retrieved 14 November 2012.
- “Pfizer Canada drops Viagra price after generic versions get Supreme Court green light”. Financial Post. 22 November 2012. Retrieved 9 February 2013.
- “SCC Case Information, Docket No. 33951”. Retrieved 14 November2012.