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Viagra Patient Tips

Medically reviewed on May 8, 2017 by C. Fookes, BPharm.

How it works

  • Viagra is a brand (trade) name for the drug sildenafil. Sildenafil blocks the action of an enzyme known as cGMP-specific phosphodiesterase type-5 (PDE-5). This enzyme breaks down cGMP, a substance that induces smooth muscles to relax. Blocking PDE-5 means increased levels of cGMP within the smooth muscles which promotes muscle relaxation and vasodilation (a widening of blood vessels).
  • High levels of PDE-5 are found in the penis, lungs, and retina. PDE-5 is also found throughout the body within the smooth muscle cells of blood vessels and muscles. Viagra is approved to treat erectile dysfunction (impotence) in men. Another brand of sildenafil (Revatio) is approved to treat high blood pressure associated with pulmonary arterial hypertension (PAH).
  • Viagra belongs to the class of medicines known as PDE-5 inhibitors.

Upsides

  • Viagra is approved to treat erectile dysfunction (ED), also known as impotence, in men. It increases blood flow to the penis following sexual stimulation and allows men to keep an erection hard enough for sex.
  • Viagra only works following sexual stimulation. It works within 30 to 60 minutes, but may be taken up to four hours before sexual activity.
  • Viagra works within 30 to 60 minutes, but it may be taken up to four hours before sexual activity.

Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Dyspepsia, flushing, headache, indigestion, muscle or back pain and visual disturbances are commonly reported.
  • Other side effects include a drop in blood pressure, insomnia, nasal congestion or a runny nose and nosebleeds.
  • Rarely, may decrease blood flow to the optic nerve causing sudden vision loss. The risk is greater in people aged older than 50, or with diabetes, heart disease, high blood pressure, high cholesterol, who smoke, or with certain pre-existing eye problems.
  • Rarely, may cause other side effects or lead to painful erections lasting longer than four hours. See your doctor immediately if this happens.
  • May not be suitable for some people including those with angina, chest pain, or other heart conditions, liver or kidney problems, blood or bleeding disorders, stomach ulcers, certain eye conditions, or a physical deformity of the penis (such as Peyronie's disease).
  • May interact with some medications including certain antibiotics and antifungals, herbal remedies, HIV medicines and drugs used in the treatment of high blood pressure or prostate disorders.
  • There is currently no approved generic version of Viagra available in the U.S.; however, one is expected to become available soon.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

Bottom Line

Viagra is used to treat erectile dysfunction (ED), but will not have any effect in the absence of sexual stimulation. A headache, stomach upsets, and flushing are the main side effects.

Tips

  • Do not take Viagra more than once daily.
  • The usual recommended dosage is 50mg (range 25mg to 100mg), taken when needed, an hour before sexual activity. However, it may be taken anywhere from 30 minutes to four hours before sexual activity. Do not exceed the maximum recommended dose.
  • Do not consume grapefruit or grapefruit products while taking Viagra.
  • 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 Viagra if you are also taking a nitrate drug (such as nitroglycerin or isosorbide dinitrate/mononitrate) for chest pain or heart problems. Do not take Viagra 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 Viagra. 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 Viagra may lower blood pressure and decrease sexual performance.

Response and Effectiveness

  • Peak plasma concentrations of Viagra are reached within 30 to 120 minutes of a single dose. The onset of effect takes about 30 to 60 minutes alongside sexual stimulation.

References

Viagra [Package Insert]. Revised 11/2015. Pfizer Laboratories Div Pfizer Inc. https://www.drugs.com/pro/viagra.html

  • Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Viagra only for the indication prescribed.
  • Disclaimer: Every effort has been made to ensure that this information is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. This drug information does not endorse drugs, diagnose patients or recommend therapy. It is an informational resource designed as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Drugs.com does not assume any responsibility for any aspect of healthcare administered with the aid of this information. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2017 Drugs.com. Revision Date: 2017-11-28 23:56:30

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