What is Sildenafil?

Doctor with PatientSildenafil is a medication used to treat erectile dysfunction. Erectile dysfunction is the inability to get and keep an erection in men. Erectile dysfunction, sometimes called impotence, has several causes. Causes of erectile dysfunction include heart disease, high blood pressure, diabetes, low testosterone, stress, depression, and most commonly due to a narrowing of the arteries that take blood to the penis.

What are The Benefits of Sildenafil?

Sildenafil works by preventing the action of a chemical in the body called Phosphodiesterase type 5. This helps relax and widen blood vessels to improve the flow of blood. In erectile dysfunction, Sildenafil improves the blood flow to the penis following sexual stimulation, and helps to maintain an erection. In a study published in the New England Journal of Medicine titled “Oral Sildenafil in the treatment of Erectile Dysfunction”, it was found that “For the men receiving 100 mg of sildenafil, the mean score for the question about achieving erections was 100 percent higher after treatment”. Not only does Sildenafil work, but it has also been found to have a low rate of adverse reactions. During a four year study titled “Long-term safety and effectiveness of sildenafil citrate in men with erectile dysfunction” by the Multicenter Study Group published in the US National Library of Medicine, 979 men used sildenafil and only 37 had “adverse events that led to changes in dosing or to temporary or permanent discontinuation”. Most of the adverse effects that led to change were headache and flushing.

Standing upSildenafil is also used to treat Pulmonary Arterial Hypertension. PAH is a type of high blood pressure that occurs between the heart and the lungs. When hypertension occurs

In the lungs, the heart must work harder to pump enough blood through the lungs.  Sildenafil works by relaxing and dilating the blood vessels in the lungs and decreases the pulmonary blood pressure to the heart and improves its function. This reduces blood pressure in the lungs which generally results in the ability to be more active. Howard C. Herrmann, MD published his findings on sildenafil for primary pulmonary hypertension and found that the ability to exercise, cardiac index, dyspnea, and fatigue all improved with the use of sildenafil.

What are The Side Effects of Sildenafil?

Sildenafil may cause drowsiness, dizziness, fainting, or blurred vision. These effects may be worse if you use it with alcohol or certain medicines. Use Sildenafil with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to the medication. Sildenafil should not be taken by people who take nitrates such as Nitroglycerin, as this may result in a severe and potentially fatal drop in blood pressure.


  • Phosphodiesterase inhibitor – suppresses the enzyme phosphodiesterase, increasing the production of cyclic GMP, which facilitates vasodilation, causing erection in males
  • Pulmonary antihypertensive – medication used to control blood pressure


  • Tablet
  • Solution for injection



  • For erectile dysfunction: Dose 1 hour prior to sexual activity
  • Do not give within 24 hours of taking any medication with nitrates


  • Give undiluted
  • Give as a bolus dose – a large dose of a substance for the purpose of rapidly achieving the needed therapeutic concentration in the bloodstream

Therapeutic Effects

Effective for treatment of:

  • Erectile dysfunction – inability to get or keep an erection in men
  • Pulmonary arterial hypertension – high blood pressure that occurs between the heart and lungs


Sildenafil is recommended for use in individuals with erectile dysfunction whether organic or psychogenic in origin.

Sildenafil produces a significant improvement in arterial oxygenation in pulmonary arterial hypertension


  • Hypersensitivity to Sildenafil
  • Sickle Cell disease

Cautious Use

  • CAD with unstable angina – heart does not get enough blood flow
  • Heart failure
  • Heart attack
  • Cardiac arrhythmias
  • Hypotension and hypertension – low blood pressure and high blood pressure
  • Anatomic deformity of the penis
  • Active bleeding or a peptic ulcer
  • Hepatitis – inflammation of the liver
  • Cirrhosis – late stage of scarring (fibrosis) of the liver
  • Severe renal impairment

Patient Education

  • Do not take sildenafil within 4 hours of taking doxazosin, prazosin, terazosin, or tamsulosin
  • Consuming a high-fat meal before taking drug may cause delay in drug actionImmediately report the following:
  • Headaches
  • Flushing
  • Chest pain
  • Indigestion
  • Blurred vision
  • Sensitivity to light
  • Changes in color vision

Side Effects:

Body – These effects can appear anywhere in the body

  • Face edema
  • Photosensitivity
  • Shock
  • Pain
  • Chills
  • Allergic reaction
  • Arthritis
  • Myalgia – muscle pain

Central Nervous System – These effects impact the brain, spinal cord, and nerve messages throughout the body

  • Headache
  • Dizziness
  • Migraine
  • Tremor
  • Vertigo
  • Depression
  • Insomnia
  • Abnormal dreams
  • Fainting or passing out
  • Cerebral thrombosis – blockage of blood flow through a vessel in the brain by a blood clot
  • Ataxia – lack of muscle control

Cardiovascular – These effects pertain to the heart and circulation

  • Flushing
  • Chest pain
  • Heart Attack
  • Angina
  • Tachycardia – faster than normal heart rate
  • Cardiomyopathy – disease of abnormal heart muscle
  • Heart failure
  • Abnormal ECG – recording of the electrical activity of the heart
  • Edema – swelling

Gastrointestinal – These effects are found in the digestive tract which begins at the mouth, goes through the stomach, and ends with the intestines and rectum

  • Indigestion
  • Diarrhea
  • Abnormal pain
  • Vomiting
  • Dry mouth
  • Thirst
  • Abnormal liver function
  • Gastroenteritis – stomach flu
  • Esophagitis – inflammation of the esophagus
  • Stomatitis – inflammation of the mouth and lips

Skin – These effects impact the skin

  • Rash
  • Sweating
  • Exfoliative – scaling of the skin
  • Dermatitis – inflammation of the skin
  • Itching
  • Hives

Urogenital – These effects impact the reproductive system and urine

  • Urinary Tract Infection

Eyes – These effects impact the eyes

  • Abnormal vision
  • Color changes
  • Photosensitivity
  • Blurred vision
  • Sudden vision loss

Hematologic – These effects are disorders which affect the blood

  • Anemia
  • Leukopenia – decreased number of white blood cells found in the blood

Metabolic – Relating to metabolism, the process your body uses to make energy from food

  • Gout – sudden burning pain, stiffness, and swelling in a joint
  • Hyperglycemia – high blood sugar
  • Hyperuricemia – high levels of uric acid in the blood
  • Hypoglycemia – low blood sugar
  • Hypernatremia – elevated sodium level in the blood

Respiratory – These effects impact the nose, nasal passages, pharynx, larynx, trachea, bronchi, and lungs

  • Dyspnea – shortness of breath
  • Laryngitis – inflammation of the vocal cords
  • Pharyngitis – inflammation of the pharynx, located in the back of the throat
  • Sinusitis – sinus infection
  • Bronchitis – inflammation of the lining of the bronchial tubes
  • Nasal congestion
  • Asthma
  • Cough