Sildenafil (Please Read the PDR for a Full Discussion)
Read everything below. It is a summary of some of the information in the PDR and other sources. It is by no means complete. You must read the full package insert when it arrives with your medicine. You can access the PDR directly, as well. Keep all the literature handy in case your medical status changes and you need to refer back to it.
How Does Sildenafil Work?
Sildenafil is primarily thought of as an erectile dysfunction (ED) medication, but it can be effective for PE, as well. What is most interesting is that ED often is an underlying cause of PE. Sometimes, the same stress that causes either one can cause both. However, ED itself can begin a cascade of changes that results in PE.
Men with ED often attempt to keep themselves erect with increasing levels of stimulation either with a partner or when masturbating. This intense stimulation can inadvertently result in ejaculation before they would like and can occur even when the penis is not fully erect. When a full erection is supported by a PDE5i like sildenafil, the need to maintain an erection with overly energetic stimulation is no longer necessary and a more well-timed orgasm can follow.
Many men who take sildenafil for ED and who do not have PE also report that they will find it takes longer to orgasm than they might have anticipated.
What are Some Important Things My Doctor Should Know?
- History of problems getting or maintaining erections
- Thoughts of doing harm to yourself at any point in the past
- Shortness of breath
- History of mental illness in you or your family (e.g., depression, psychosis, bipolar disorder, manic depression)
- Diabetes requiring medication
- Low blood pressure
- Recent Heart Attack, congestive heart failure, unstable heart disease
- Irregular heartbeats (arrhythmia)
- Slow heart rate
- High blood pressure
- All medications taken now and within the past two weeks
- History of illicit drug use
- History of drug addiction
- History of serotonin syndrome
- A list of your current medications
- A list of all your current medical problems, including, but not limited to, liver disease, kidney disease, heart disease, and bleeding disorders
- Allergy or negative reaction to sildenafil or other phosphodiesterase 5 inhibitors (PDE5i) under different names or any components (e.g. Viagra, Cialis, Levitra, Stendra, Staxxyn, Revatio, tadalafil, vardenafil, avanafil)
If you have any of the aforementioned conditions—or any others that are not listed—make sure to share this information with your Ro physician, as well as all of your other healthcare providers.
Why is it so important that all your healthcare providers, including your pharmacists, are fully informed and coordinated about every aspect of your care?
There are hundreds of medications that can interact with sildenafil. Most are not severe but some can be life-threatening, as with any nitrates, nitrites, or nitroglycerin. Even simple over the counter medications should be checked for interactions. Remember, something as safe as grapefruit can alter how your body handles sildenafil. All your providers should be kept informed of any medication that is added, dropped, or changed in your regimen.
The Physician Desk Reference (PDR) lists the medications that can interact with sildenafil, along with the contraindications to its use. The PDR is included because it is comprehensive and must be read in its entirety. Contraindications can be absolute, as with nitrates/nitrites, act as relative warnings about drug interactions, and inform patients and healthcare providers how certain conditions can affect the metabolism of sildenafil, either increasing or decreasing the amount in the blood. A few relevant sections are summarized below concerning contraindications and drug interactions, but it is not a complete overview. Please, read the entire package insert, as well.
Contraindications (Who Should Never Take Sildenafil)
- Patients who take nitrates or even carry nitrates in case they’re needed in response to chest pain
- Patients with a history of tinnitus
- Allergy or negative reaction to sildenafil or other phosphodiesterase 5 inhibitors (PDE5i) under different names or any components (e.g. Viagra, Cialis, Levitra, Staxxyn, Stendra, Revatio, tadalafil, vardenafil, avanafil)
- Patients who feel “winded” or too weak or tired to walk up 2 flights of stairs relatively briskly
- Patients who have unstable heart disease or have been told they are not healthy enough for sex
- Patients who have nonarteritic anterior ischemic optic neuropathy (NAION) or retinitis pigmentosa
- Patients with idiopathic hypertrophic subaortic stenosis (IHSS).
- Patients with very low blood pressure
Contraindications and Precautions in More Detail
Sildenafil should not be used if you are allergic to any of the components used to make sildenafil tablets. Also, as discussed above, the use of multiple phosphodiesterase inhibitors at the same time is not recommended.
The use of sildenafil is not recommended in patients with Pulmonary Veno-Occlusive Disease (PVOD).
ABSOLUTELY no one should take sildenafil if they “are currently on nitrate/nitrite therapy.” This is the case even if the patient uses nitrates/nitrite therapy intermittently. Also, no one who uses recreational nitrates/nitrites (poppers, etc.) should use sildenafil.
Geriatric (The Elderly), Hepatic (Liver) Disease, Renal (Kidney) Impairment
Sildenafil is metabolized by a complex system that can be compromised in men over 65 years of age, or in patients who suffer from liver disease, or those whose kidney function is reduced by illness or age. Therefore, a starting dose of 25 mg sildenafil should be considered in elderly patients, those with severe renal disease, and in men with any degree of liver impairment.
Moreover, certain drugs have a dramatic effect on the metabolism of sildenafil similarly increasing the blood level dramatically. Therefore, those taking erythromycin, itraconazole, ketoconazole, saquinavir, and ritonavir should not take more than 25 mg in a 48 hour period.
See the PDR for a comprehensive list of drugs with which sildenafil interacts.
Angina (Chest Pain), Aortic Stenosis, Cardiac Arrhythmias (Irregular Heartbeats), Cardiac Disease (Heart Disease), Coronary Artery Disease (Narrowing of the Heart Arteries), Heart Failure, Hypertension (High Blood Pressure), Hypotension (Low Blood Pressure), IHSS (Idiopathic Hypertrophic Subaortic Stenosis–a Heart Defect), Myocardial Infarction (Heart Attack), Stroke (like a heart attack but affecting the brain)
The PDR states, “There is a degree of cardiac risk associated with sexual activity; therefore, prescribers should evaluate the cardiovascular status of their patients prior to initiating any treatment for erectile dysfunction.”
NOTE: This means that if you and your provider have a reason to believe after diagnosing erectile dysfunction that you are not healthy enough for sex, you shouldn’t use anything that will help you have sex until you are healthier. Your doctor counts on an honest answer about your health and your capacity to be sexually active. It may seem overly cautious but think about it; if you aren’t healthy enough for sex, shouldn’t you take care of your health before trying to regain your sex life?
The PDR advises that “caution should be used if sildenafil is prescribed in the following groups: patients who have suffered a myocardial infarct, stroke, or life-threatening arrhythmias in the last 6 months; patients with resting hypotension (BP<90/50) or resting hypertension (BP>170/100); patients with fluid depletion; patients with cardiac disease, heart failure, or coronary artery disease which causes unstable angina.”
The PDR notes that the American College of Cardiology recommends that sildenafil be used in caution with patients (not on nitrates, of course) with active coronary ischemia, meaning they have blocked heart arteries that is compromising the function of their heart, such as would show by having symptoms like chest pain or by failing a stress test. They also advise caution in anyone with low blood pressure or low blood volume or in anyone with high blood pressure on a “complicated, multidrug, antihypertensive program.” Patients with “Left Ventricular Outflow Obstruction (e.g., aortic stenosis, idiopathic hypertrophic subaortic stenosis)” should be approached with caution as they, and patients with poor control of the swings in their blood pressure, can be very sensitive to sildenafil and other vasodilators (drugs that open up the blood vessels). They also recommend that doses of sildenafil over 25 mg not be given within 4 hours of taking an alpha-blocker (e.g. doxazosin).
Leukemia, Multiple Myeloma, Penile Structural Abnormality, Polycythemia, Priapism, Sickle Cell Disease
Priapism is an erection lasting more than 4 hours and it can occur with the use of sildenafil. Priapism can be painful but, with or without pain, an erection that lasts over 4 hours could result in damage to the tissues of the penis. People with the above conditions are at greater risk of suffering from priapism with the use of sildenafil. The PDR states, “sildenafil and other agents for the treatment of erectile dysfunction, should be used with caution in patients with penile structural abnormality (such as angulation, cavernosal fibrosis, or Peyronie’s disease), or in patients who have conditions which may predispose them to priapism (such as sickle cell disease, leukemia, multiple myeloma, polycythemia, or history of priapism).”
Human Immunodeficiency Virus (HIV) Infection
The PDR states, “Patients should be reminded that sildenafil, when used for erectile dysfunction, offers no protection against sexually transmitted disease.”
Coagulopathy (Bleeding Abnormalities), Peptic Ulcer Disease (Stomach Ulcer)
There is no safety information yet accumulated on how sildenafil affects patients with bleeding disorders or active stomach ulcers so caution is recommended.
Gastroesophageal Reflux Disease (GERD–heartburn due to reflux of acid), Hiatal Hernia (part of stomach slips upward through the diaphragm)
Sildenafil decreases the pressure of the valve that stops acid from coming back up from the stomach and into the esophagus. It also inhibits the movement of the esophagus itself. It could make symptoms worse for people with GERD or a hiatal hernia so it is recommended that it be used with caution in these patients.
Non-arteritic Anterior Ischemic Optic Neuropathy (NAION), Retinitis Pigmentosa, Visual Disturbance
The PDR states, “Use sildenafil cautiously in patients with preexisting visual disturbance. Post-marketing reports of sudden vision loss have occurred with phosphodiesterase inhibitors. Vision loss is attributed to a condition known as non-arteritic anterior ischemic optic neuropathy (NAION), where blood flow is blocked to the optic nerve. Patients with a history of NAION are at increased risk for recurrence. Only use a PDE5 inhibitor in these individuals if the anticipated benefit outweighs the risk.” It is never recommended for patients with known hereditary degenerative retinal disorders, including retinitis pigmentosa.
There are other situations that would give a healthcare provider pause. Some examples would be if you have lightheadedness, fainting spells, leg cramping when you walk, inability to climb stairs or walk a few blocks without getting short of breath, or if you have allergies to any of the other phosphodiesterases or their components. These, and any other symptoms, must be revealed to your healthcare providers.
A Special Warning for Pilots and Air Traffic Controllers
Some people experience visual side effects when taking PDE5 inhibitors for erectile dysfunction. Due to the sensitive nature of their work, pilots and air traffic controllers should not take Viagra or sildenafil within 6 hours of aviation related duties. Cialis (tadalafil) is a much longer acting medication. Pilots and air traffic controllers should not take Cialis within 36 hours of aviation related duties. Daily Cialis use, at any dose, is not an option for men with these professions.
Some Other Warnings
Phosphodiesterase inhibitors have been shown to be remarkably safe but, like all medicines, they have the potential for causing side effects. Rarely, these can be serious, and you need to know about them.
A phosphodiesterase inhibitor was developed as a blood pressure medication long before it was used to treat erectile dysfunction. In some situations, it can cause dangerously low blood pressure. That is why we spent so much energy asking you about other medications that can lower blood pressure, especially nitrites/nitrates. Nitrites/Nitrates (found in nitroglycerin and other medications, as well as recreational “poppers”) are so dangerous when used at the same time as PDE5i like sildenafil that their use is an absolute contraindication to prescribing or using Viagra (sildenafil).
Another possible side effect is a change in vision. Some people who use Viagra see a bluish tint but others suffer a far more serious consequence. It is rare but it is possible for people using Viagra to suffer complete, permanent blindness in one or both eyes. If this happens, go immediately to an emergency room. It does not matter if it is rare if it happens to you. Be prepared to act immediately if your vision is affected.
Sometimes Viagra works too well and an erection can last far longer than it should. If the penis remains engorged (priapism), it can be painful but, more importantly, the tissue and vessels of the penis can be damaged (even permanently). If you have an erection lasting longer than 4 hours, painful or not, seek immediate medical attention.
Again, to one degree or another, all the phosphodiesterase inhibitors have common or not unusual side effects They can cause headaches (10%-16%), nasal stuffiness (1%-10%), flushing (5%-12%), dizziness (~3%), and upset stomach (4%-12%). [Drugs 2005;65:1621-1650] Some can cause blue-tinted vision as a side effect. If you experience ringing in one or both ears, also called tinnitus, you should immediately discontinue sildenafil and let your provider know.
The medicine prescribed is safe but some rare side effects can occur, as well. Please take a few minutes to familiarize yourself with the list of both common and rare side effects provided here.
IMPORTANT: If any unusual side effect happens, contact us; however, if there is anything severe or emergent go immediately to an emergency room. Any new symptom is worth pursuing. Any severe symptom must be pursued as an emergency. Symptoms such as chest pain, shortness of breath, severe headache, fainting, visual changes, or anything out of the ordinary, even lightheadedness, warrant a visit to the ER. Contact us after it is addressed. Again, take the time to read the list of potential side effects. It doesn’t matter how rare a side effect is if you are experiencing it.
See the PDR