Phosphodiesterase inhibitors have been shown to be remarkably safe but all medicines 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 that their use is an absolute contraindication to prescribing or using sildenafil.

Another possible side effect is a change in vision. Some people who use sildenafil see a bluish tint but others suffer a far more serious consequence. It is rare but it is possible for people using sildenafil 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 sildenafil 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.

This may seem obvious but sildenafil doesn’t protect you from getting sexually transmitted diseases like HIV, syphilis, herpes, or gonorrhea. Using a condom for sex after being unable to engage in sexual activity may seem like adding a challenge just when one is being overcome. Nevertheless, the last thing you need after solving one health issue is to acquire another one. Wear a condom.

Taking your medication is just one part of solving the issue of erectile dysfunction, and taking the medicine properly is vital in achieving the best results.

Take the medicine on an empty stomach and avoid fatty foods for at least two hours before taking the pill. Fat interferes with its absorption. Grapefruit juice can possibly affect the absorption of sildenafil, as well. It increases the blood level after an initial delay in absorption. It can increase the possibility of side effects (Clin Pharmacol Ther 2002;71(1):21-29) and can make it difficult to predict the effect with each use. Alcohol may be a means to relax but it can impair achieving and maintaining an erection. Avoid alcohol.

If patients are on an alpha blocker, which can be given for high blood pressure or an enlarged prostate, they should be on a stable regimen of the alpha blocker before starting a reduced dose of a Sildenafil. They should also be started on the lowest dose of an alpha blocker if a patient is already on an effective dose of Sildenafil. Moreover, it is best not to take Sildenafil within four hours of taking an alpha blocker.

As with all erectile dysfunction drugs, follow up is necessary to be certain the medications continue to work and that there has been no change in the patient’s heart status or capacity to engage in sex. If that ever occurs, please contact ALL your healthcare providers including your Roman physician or nurse practitioner. Remember, your medication will do nothing unless you have erotic stimulation to kick off the process. In the box below, the biology of achieving and maintaining an erection is summarized. After reading it, you will understand how your medication works.

One of the best ways to use your medication the first time is alone. It can be very helpful to familiarize yourself with the medication privately. This will allow you to know its effects, its possible side effects, and to be able to eliminate any concern about “performance” with a partner. Also, focusing on yourself before you would be focusing on the dynamics of coupled sexual activity is a great way to gain confidence. It has been shown that the best results with a phosphodiesterase are seen after the patient has tried to use the medication eight times. (Urology 2002;60:28-38) Most people use the medication twice a week for 4 to 8 weeks to find the best dose and to understand their reaction to the medication, including timing its best effect.

While exploring the best dose can be useful, never take more than one prescribed dose (and only the prescribed dose) in 24 hours. Regularity is one of the keys to finding the best regimen.
Occasionally, patients are prescribed two different erectile dysfunction medications. We do not recommend this. If a patient is on two different erectile dysfunction drugs (phosphodiesterase-5 inhibitors), they should never be taken within 48 hours of each other. Therefore, when switching to a new medication, we recommend a similar clearing out period.

Getting an erection is just the start. There is keeping the erection throughout the act of sexual intimacy, and then there is having an orgasm. It is interesting that all the PDE5I’s (phosphodiesterase 5 inhibitors) can lead to an erection but some men still cannot maintain it while having intercourse. That is why sex can be a two person issue best resolved when two people are involved in the solution. For some men, the friction of intercourse doesn’t provide the stimulation they need. For other men, having sex again may be anxiety producing so they have difficulty maintaining an erection. Other couples discover that having sex was not their sole problem and their relationship was in need of repair. Circumstances can vary greatly so a diagnosis and a treatment plan is just a first step.

In a twist that is often unexpected, some men discover that getting an erection becomes easy but reaching orgasm even without being anxious, is difficult. The phosphodiesterases have been found to delay orgasm, even for men without Erectile Dysfunction (ED), and are even used to treat premature ejaculation. So, in some patients the ability to achieve and maintain an erection happens but the new difficulty of reaching orgasm is discovered.

Other men, having sex after a long period of abstinence, find that they have premature ejaculation. As has been found in study after study, simply getting a prescription and taking one of the medications does not solve the problem for everyone, especially if you include the perspective of men’s partners. Education, dialogue, and a cooperative approach creates the best chance of success.

You should be familiar with other treatment options. The solution offered by your healthcare provider may be a great start but remaining open to every option as your life evolves, and as you try the option offered, is vital.

When the brain is stimulated by something erotic, the tissues of the penis release Nitric Oxide (NO), which causes an increase in a chemical called cyclic Guanosine MonoPhosphate (cyclic-GMP). Cyclic GMP then causes the penis muscles to relax. There are two spongy tubes of muscle that run along each side of the penis and, when they are made to relax, blood rushes in. That increased volume (6X normal) causes swelling, and an erection begins. This is called tumescence. All that blood rushing in would just rush out, and nothing much would happen, if the sudden swelling didn’t cause the veins that would carry the blood out of the penis to collapse. The consequence is that the blood is stuck in the penis creating an erection.

Fortunately, the body has a control mechanism that eventually allows all that blood to escape and for the penis to return to its flaccid state. This is called detumescence. It is the presence of chemicals called phosphodiesterases, particularly phosphodiesterase-5, that does the trick. It breaks down the cyclic GMP. That reverses the entire process that all started when Nitric Oxide (NO) increased the amount of cyclic GMP that allowed all the blood into the penis in the first place.

So, how does the drug prescribed work? It is a phosphodiesterase inhibitor. It blocks the natural phosphodiesterases in your body so they cannot get rid of the cyclic GMP, meaning the blood in the penis piles up and hangs around longer. The result is a more full erection that lasts longer.

The various phosphodiesterase inhibitors, though similar, have different effects and side effects. Sildenafil (Viagra) and Vardenafil (Levitra) have relatively rapid onsets compared to Tadalafil (Cialis). Viagra (Sildenafil) and Levitra (Vardenafil) can be effective in as little as 1 hour, while Cialis might not take effect for 2 hours, though for some patients these medicines can work more rapidly. Viagra and Levitra will be out of the body in about 6 to 8 hours, while Cialis can work for 24 to 36 hours. Levitra works about as quickly as Viagra and lasts about as long. The effect of Viagra or Levitra may not be needed beyond 6 or 8 hours and any side effects will fade rapidly as a medication leaves the bloodstream. The differences can make one drug preferred over the others, depending on a person’s circumstance.

Consider two men. One might be able to predict when sexual activity will occur. A drug that works rapidly and leaves his system quickly thereafter would be perfect, as with sildenafil. With Viagra or sildenafil, a fatty meal may delay absorption and the peak of activity may take longer than an hour to begin. This is true of Levitra but to a lesser degree unless the meal contains more than 55% of its calories as fat.

Another man might know sex will occur during the course of a weekend but cannot know exactly when that will occur. For him, a drug with a prolonged period of activity is far more important than how long it takes for a medicine to start working. For him, tadalafil (Cialis) may be the best option.

Above we discussed how phosphodiesterases vary in their effect and how life situations could affect the choice of treatment. Side effects can vary, as well. Since these medications all affect phosphodiesterases, and there are many different types of phosphodiesterases doing various work throughout the body, side effects can vary between medications. To one degree or another, they all cause headaches (10%-16%), nasal stuffiness (1%-10%), flushing (5%-12%), dizziness (~3%), and upset stomach (4%-12%). [Drugs 2005;65:1621-1650]

Vardenafil (Levitra) is almost identical to sildenafil in onset of action and the duration of its effect. It has been shown to be more potent and more selective than Viagra at inhibiting phosphodiesterase 5 biochemically. That doesn’t seem to translate into being more effective in treating Erectile Dysfunction (ED), but it does give Levitra one solid advantage over sildenafil. Though uncommon, sildenafil can cause men to see a bluish tint. That is because sildenafil not only affects phosphodiesterase 5 but also phosphodiesterase 6, which has a role in regulating the retina. Vardenafil has very little impact on phosphodiesterase 6 and significantly decreases the possibility of that side effect.

Tadalafil (Cialis), for reasons not known, seems to cause more back pain and muscle aches (~6%). Nasal stuffiness may be more common with sildenafil.

Avanafil (Stendra) has a very rapid onset of action: as little as 15 minutes. Moreover, while the other medications on the market should not be taken after a fatty meal, this is not an issue with Avanafil. It may also have a decreased likelihood of affecting vision. However, it may not be as effective as the other drugs in the group.

Your healthcare provider has written a prescription and provided education as the first approach to erectile dysfunction. It is possible that the diagnosis is not correct, though the risk that you do not have the problem you have identified is unlikely. Your doctor or nurse practitioner relied on the accuracy of your answers but, even with the most precise information, it is possible that something else is wrong. This treatment is part of the diagnostic process, which is why you must identify the effects and side effects as carefully as possible. Contact your healthcare provider with any new or unexpected information.

And remember, even under the best of circumstances with a perfect diagnosis and ideal patient compliance in a study setting, the phosphodiesterases are ineffective for about 15% of patients. Besides underlying vascular disease due to cardiovascular disease, or nerve damage due to diabetes, an abundance of other issues can be involved. A low testosterone level, or an abnormal thyroid, or even a brain tumor, may make it medically less likely that desire will be present, thus preventing an erection. Psychological reasons can interfere with the initiation of desire, as can relationship issues.

Damage to nerve tissue from trauma, surgery, or from radiation therapy could also interfere with getting an erection. Desire may be present but the signals needed to transmit the message are damaged. This can occur with neurological diseases like multiple sclerosis (MS).

Most men with prostate cancer who have had surgery will have some issues with maintaining good erectile function. One article (Urology 1998;52:963-966), noted that 12 of 15 patients with erectile dysfunction (ED), who had a radical prostatectomy that spared both of the nearby nerves, were able to regain erections with the use of sildenafil, which was the phosphodiesterase inhibitor used in the study. Nevertheless, patients who undergo radical prostatectomy may lose that capacity.

For all of those who experience erectile dysfunction that is resistant to phosphodiesterase inhibitor therapy (including those suffering from hormone deficiencies, e.g., testosterone), it is fortunate that other options exist. Hormones can be replaced, for example. What is included below is a brief overview of just some of the other options patients have at their disposal with healthcare providers you can see in person.

The simplest non-medication treatment is the use of a vacuum device. By creating a vacuum in a tube around the penis, blood is forced into the penis. This causes it to swell and an erection results. The placement of a ring at the base of the penis makes the blood in the penis stay even when the vacuum tube is removed. When the ring is later removed, the penis can release its blood volume and return to a relaxed state. The ring should be removed after 30 minutes to prevent damage to the tissue of the penis. Some men find that the use of a ring, or tourniquet, alone helps them keep erections longer without the use of any other device.

If that is not sufficient, a medication called alprostadil can be used, either as a penile suppository or as a penile injection. It is a vasodilator and causes blood to rush into the penis. It can be inserted as a pellet directly into the urethra, which is the tube that carries urine. It is called MUSE for Medicated Urethral System for Erections. It is not easily used, has a number of contraindications including causing very low blood pressure, and is painful for many patients. Nevertheless, for some properly chosen patients, it works well and is satisfactory.

Alprostadil can also be injected directly into the tissue of the penis. There are potential problems such as scarring or prolonged erections, pain, bleeding, etc., but many well chosen patients do well when well-educated and are carefully followed.

Surgery is a last resort but many patients find that the placement of a rod, semirigid implant, or a newer, inflatable implant, gives satisfactory results.

One of the simplest and most underrated interventions people who experience ED can make is to alter their lifestyle. Take the time to read about everything provided to improve your general health. It will improve your sexual health, as well.

So many things have to go right for you to achieve a strong erection. For starters, your hormones must be released on demand, your arteries need to carry blood to the penis with perfect efficiency, your nervous system must transmit its signals without a hitch, and your mind must be working in perfect harmony with your body. That’s a lot to ask. If you are having difficulty getting the kind of erection you and your partner expect, it may be because a problem is brewing and ED is the first sign.

As funny as it sounds, paying more attention to the strength of your erection could save your life. Because the blood vessels of the penis are small compared to the job they have to do, serious underlying conditions often manifest themselves with ED first. ED could be an indication of high cholesterol, diabetes, hypertension, sleep disorders, heart disease, hormone issues, or even depression.

Think of ED as your body’s Check Engine light turning on.

How do you turn that light off? Or prevent it from even turning on?

Seeing your general healthcare provider is a great start, but so is living a healthier life.

Exercise

Exercise is the best way to strengthen your heart (and your erection). It increases stamina, strength, and flexibility.

The average heart beats 100,000 times, pumping about 2,000 gallons of blood throughout your body per day. Your heart pumps enough blood to fill an Olympic pool each year for your entire life.

For blood to fill the penis to its capacity (i.e., achieve a firm erection), it requires approximately 6 times its normal flow. Basically, the stronger your heart is, and the cleaner your arteries are, the more blood you can pump with each beat for a longer period of time and with less effort.

But where should you start? Just walk! An underrated form of exercise is walking. Walking uses almost every bone and muscle in your body. A great, and achievable, daily goal is 10,000 steps per day.

Eating

Obesity is a primary risk factor for diabetes, high cholesterol, high blood pressure, certain cancers, gallstones, degenerative arthritis, and erectile dysfunction.

Excess belly fat can interfere with the body’s ability to send enough blood to the penis. It can also cause testosterone production to decrease.

When you’re aroused, nitric oxide is released from the endothelial cells in the penis, which causes the muscles to relax, which enables blood to flow. Obesity damages the endothelium, which prevents the penis from receiving sufficient blood flow for sustained periods of time.

A small decrease in body fat improves erectile dysfunction (among many other things).

Lifestyle habits

Erectile dysfunction is extremely common in those who consume more than 3 drinks daily or in those who smoke at least 10 cigarettes per day.

Men who smoke are twice as likely to experience ED as non smokers. Smoking damages your blood vessels. Even if your nervous system is functioning well, an erection still might be difficult to achieve if your blood vessels have been damaged by smoking. However, quitting can improve your health immediately; your chance of a cardiac event decreases, your blood pressure improves, and your circulation improves within 2-12 weeks, which is incredibly helpful in preventing ED.

Alcohol is a nervous system depressant and can actually block messages between the brain and the body.

In the short term, alcohol relaxes the muscles in the penis enabling blood to flow in, but it also prevents those blood vessels from closing and trapping all the added blood that is vital in maintaining an erection. In the long run, excessive alcohol consumption can cause scarring in the liver, high blood pressure, and can damage your blood vessels (causing ED).

Reducing alcohol consumption and quitting smoking will improve your overall health and sexual performance; you know this.

Sleep

The value of sleep cannot be overstated. A lack of sleep can increase your risk for a cardiac event, slow your metabolism, weaken your immune system, and diminish cognitive abilities. It can also decrease your testosterone, which increases the likelihood of experiencing ED. Worse yet, a decrease in testosterone will most likely decrease your libido so your diminished sexual function may be less noticeable.

Stress

Unchecked stress can lead to high blood pressure, heart disease, obesity, and diabetes. Being in a high stress environment can affect the way your brain sends messages to your body, which can affect blood flow and your ability to achieve and maintain an erection.

There are many potential causes for stress induced ED (e.g., nervousness and anxiety, professional stress, loss of a loved one, changes in health, and financial burden).

It’s important for your overall (and sexual) health to manage your stress.

For many, starting an ED medication means increasing or returning to sexual activity. With that comes the positive aspects of sexual intimacy. However, it also comes with potentially uncomfortable conversations about sexually transmitted infections. Sharing your STI status is an important part of allowing your partner to make a truly informed decision about having sex.

If you have a sexually transmitted infection, you must inform any potential sexual partner. Moreover, this should be done before engaging in any activity that risks giving them an infection. It is also important to ask any prospective partner about their status. Lastly, while condoms are helpful in reducing the risk of pregnancy, transmitting, or acquiring an infection, they can never be 100% effective. That is why informed consent is such an important part of sharing sexual intimacy with honesty and clarity.

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.

General information

It should not be used in anyone 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. It has not been studied.

The use of Sildenafil is not recommended in patients with Pulmonary Veno-Occlusive Disease (PVOD).

Nitrate/Nitrite Therapy

ABSOLUTELY no one should take sildenafil if they “are currently on nitrate/nitrite therapy.” That includes even if the patient uses of 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 the elderly, or in patients who suffer from liver disease, or in those whose kidney function is reduced by illness or age. Therefore, it is recommended “not to exceed a maximum single dose of 25 mg sildenafil in a 48 hour period.”

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 follow the same regimen.

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)

“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 or nurse practitioner 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? There have been more than 75 deaths due to cardiac events “reported in association with sildenafil use.” It may not seem like many deaths but you don’t want to be the person who bumps that number over 100.]

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 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 discussed.

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.

The list below is long and not one drug on the list is meaningless. That is why we need to know every drug you take and every healthcare provider needs to know you take sildenafil.

Note: Some medications are not on the list but are included in the PDR, which is why it must be read as well. In addition, the list changes as medications may be added over time.

• Alfuzosin (Uroxatral) (Treats High Blood Pressure or Enlarged Prostate)

• Aliskiren (Tekturna, Rasilez) (Treats High Blood Pressure)

• Alpha-blockers (e.g., Cardura, Coreg Flomax, Hytrin, Minipress, Oravase, Rapaflo, Regitine,Trandate) (Treats High Blood Pressure or Enlarged Prostate)

• Ambrisentan (Letairis) (Treats PAH–High Blood Pressure in the Arteries of the Lungs)

• Amlodipine (Norvasc) (Treats High Blood Pressure)

• Amprenavir (Agenerase) (Treats HIV)

• Amyl Nitrite (Amyl nitrite Systemic, Poppers, Rush) (Recreational Drug)

• Aprepitant (Emend) (Treats Nausea)

• Atazanavir (Reyataz) (Treats HIV)

• Atropine (Isopto Atropine) (Treats Eye Conditions)

• Boceprevir (Pegasys, Pegintron) (Treats PAH and Hepatitis C)

• Butyl Nitrate (Poppers, Rush, Liquid Gold) (It is a recreational drug)

• Brigatinib (Alunbrig) (Cancer)

• Capecitabine (Xeloda) (Cancer)

• Cariprazine (Vraylar) (Psychiatric Disorders)

• Ceritinib (Zykadia) (Cancer)

• Cimetidine (Tagamet) (Stomach Ulcers)

• Ciprofloxacin (Proquin, Cipro) (Antibiotic)

• Clarithromycin (Biaxin) (Antibiotic)

• Clopidogrel (Plavix) (Blood Thinner)

• Cobicistat (Stribild, Tybost) (Treats HIV)

• Conivaptan (Vaprisol) (Treats Low Sodium in the blood)

• Crizotinib (Xalkori) (Cancer)

• Darunavir (Prezista) (Treats HIV)

• Dasabuvir (Viekira XR, Viekira Pak–contains Ritonavir*) (Treats Hepatitis C)

• Delavirdine (Treats HIV)

• Dihydroergotamine (Migranal) (Treats Migraines)

• Diltiazem (e.g., Cartia, Cardizem, Dilacor XR, Tiazac,) (Treats High Blood Pressure)

• Doxazosin (Cardura, Carduran) (Treats High Blood Pressure or Enlarged Prostate)

• Dronedarone (Multaq) (Irregular Heartbeats)

• Duloxetine (Cymbalta) (Treats Depression and certain nerve pain disorders)

• Erythromycin (Erythrocin, Ery-Tab, E-Mycin, Eryc) (Antibiotic)

• Fluconazole (Diflucan) (Treats Fungal and Yeast Infections)

• Fluoxetine (e.g., Prozac, Sarafem) (Treats Psychiatric disorders like depression)

• Fluvoxamine (Faverin, Fevarin, Floxyfral, Dumyrox, Luvox) (Treats OCD)

• Fosamprenavir (Lexiva) (Treats HIV)

• Grapefruit juice

• Idelalisib (Zydelig) (Treats Cancer–Leukemia)

• Imatinib (Gleevec) (Treats Cancer–Leukemia)

• Indinavir (Crixivan) (Treats HIV)

• Isavuconazonium (Cresemba) (Treats Fungal Infections)

• Isocarboxazid (Marplan) (Treats Depression)

• Isosorbide Dinitrate or Monohydrate (Isordil Titradose, Dilatrate-SR, Imdur, Imdur ER, Ismo, Monoket, IsoDitrate) (Treats Heart Disease and Chest Pain)

• Itraconazole (Sporanox, Onmel) (Treats Fungus and Yeast)

• Ivacaftor (Kalydeco) (Treats Cystic Fibrosis)

• Ketoconazole (Nizoral, Extina, Ketodan Kit, Kuric, Nizoral A-D, Xolegel) (Treats Fungal Infections)

• Lopinavir; Ritonavir (Kaletra) (Contains Ritonavir and Treats HIV)

• Lorcaserin (Belviq) (Weight Control)

• Lurasidone (Latuda) (Treats Depression)

• Mifepristone, RU-486 (Korlym, Mifeprex) (Treats Cushing’s Syndrome and Ends Pregnancy)

• Mitotane (Lysodren) (Treats Cancer and Cushing‘s Syndrome)

• Monoamine oxidase inhibitors (e.g., Azilect, Marplan, Nardil, Parnate) (Treats Depression)

• Nebivolol (Bystolic) (Treats High Blood Pressure)

• Nelfinavir (Viracept) (Treats HIV)

• Nesiritide (Natrecor) (Treats Heart Failure but is an IV drug)

• Netupitant (Akynzeo) (Prevents Nausea and Vomiting)

• Nifedipine (Procardia, Nifedical XL, Adalat, Procardia XL) (Heart Disease among others)

• Nilotinib (Tasigna) (Treats Cancer–Leukemia)

• Nitrates (Isordil Titradose, Dilatrate-SR, Imdur, Imdur ER, Ismo, Monoket, IsoDitrate) (Treats Heart Disease and Chest Pain)

• Nitroglycerin (Nitro-bid, Nitrocot SA Capsule, Nitro-dur, Nitrostat, Nitrodisc, Nitrek transdermal, Minitran, Nitrol ointment, Transderm-Nitro, Nitro-Time, Nitrotab, NitroMist, Nitro-Par, Nitrolingual, Nitroquick, Transderm-Nitro, Nitrogard, Nitroglyn, Nitrong) (Treats Chest Pain and Heart Conditions)

• Nitroprusside (Nipride RTU, Nitropress) (Heart Failure and High Blood Pressure)

• Ombitasvir; Paritaprevir; Ritonavir (Technivie, Viekira Pak) (Treat Hepatitis C)

• Phenoxybenzamine (Dibenzyline) (Treat High Blood Pressure and Pheochromocytoma)

• Phentolamine (Regitine, Oraverse) (Erectile Dysfunction, High Blood Pressure)

• Phenylephrine (e.g.,Sudafed) (Decongestant)

• Posaconazole (Noxafil) (Treats Fungal Infections)

• Prazosin (e.g., Minipress, Vasoflex, Lentopres, Hypovase) (Treats High Blood Pressure, PTSD, and Anxiety)

• Ribociclib (Kisqali) (Treats Cancer)

• Riociguat (Adempas) (Treats High Blood Pressure in the Arteries of the Lung)

• Ritonavir (Norvir) (Also found in Technivie and Viekira Pak) (Treats HIV and Hepatitis C)

• Sapropterin (Kuvan) (Treats a disorder that causes amino acid buildup in the brain)

• Saquinavir (Invirase, Fortovase) (Treats HIV)

• Silodosin (Rapaflo) (Treats an Enlarged Prostate)

• Tacrolimus (Prograft, Advagraf XL, Protopic, Hecoria) (Treats Organ Transplants)

• Tamsulosin (Flomax) (Treats an Enlarged Prostate)

• Telaprevir (Incivek, Incivo) (Treats Hepatitis C)

• Telithromycin (Ketek, Ketek Pak) (Antibiotic)

• Telotristat Ethyl (Xermelo) (Treats diarrhea in cancer patients)

• Terazosin (Hytrin) (Treats High Blood Pressure)

• Tipranavir (Aptivus) (Treats HIV)

• Verapamil (Calan, Isoptin) (Treats High Blood Pressure, Angina, Irregular Heart Beats)

• Vigabatrin (Sabril) (Treats Seizure Disorders)

• Voriconazole (Vfend) (Treats Fungal Infection)

The side effects of sildenafil (Viagra) are typically mild. Common side effects can include: 

• Headache -  ED medications can cause headaches by widening blood vessels and increasing blood flow, but these are usually mild and ease as the medication wears off (about 4 hours) and with continued use. To help:

  • Drink more water to reduce headache intensity.

  • Take over-the-counter Tylenol or Motrin 1 hour before your medication to lessen or prevent headaches.

• Indigestion/heartburn -  Heartburn is a common side effect of ED medications, affecting about 1 in 10 patients. To help:

  • Limit caffeine and avoid trigger foods (acidic, spicy, or alcohol) before taking your medication.

  • Drink plenty of water.

  • Avoid eating 2 hours before bed and elevate your head while sleeping.

  • Try over-the-counter remedies like Tums.

• Flushing or redness/warmth in the face - This is a common side effect of ED medications, caused by increased blood flow and dilation of blood vessels, including those in your skin. While it may result in a red, flushed appearance, it’s not dangerous and can even indicate the medication is working. To help:

  • Use a cold compress on your face.

  • Keep the room cool by opening a window or using a fan.

• Stuffy or runny nose - This side effect tends to fade within a few hours of using the medication. To help:

  • Use an over-the-counter nasal spray like Flonase when you take your medication to prevent congestion.

  • Take a warm shower after your dose; the steam can help relieve congestion.

• Lightheadedness or dizziness - Lightheadedness can happen due to a decrease in your blood pressure. Severe or persistent lightheadedness, and especially fainting, can be dangerous and should be evaluated in person. To help mild lightheadedness

  • Lie down until the sensation passes and stand up slowly.

  • Stay hydrated by drinking water.

  • If you take blood pressure medication, avoid taking it at the same time as your ED medication.

• Back pain or muscle aches - Muscle aches and back pain may appear 12-24 hours after taking the medication and go away as the medication wears off. To help:

  • Drink more water to reduce their intensity.

  • Take an over-the-counter pain reliever, like Tylenol or Motrin, 1 hour before your ED medication to lessen or prevent discomfort.

If you experience any of these common side effects and find them to be persistent, bothersome, or preventing you from taking your medication, please reach out to your Ro-affiliated healthcare provider.  

Rare side effects of sildenafil can include: 

• An erection that lasts longer than four hours and won’t go away (priapism).

• Sudden loss of vision

• Sudden loss or decrease/change in hearing

• Chest pain or shortness of breath

• Fainting

If you experience any of these symptoms, stop your medication and seek immediate medical attention. If you experience a sudden loss of vision or a decrease/change in hearing, your evaluation must include a vision and/or hearing test and possibly a specialist evaluation by a vision (ophthalmologist or optometrist, or hearing specialist (ENT/audiologist)).

Rarely, patients using sildenafil may experience blue-tinged vision. This is not typically dangerous, but if you experience changes to your vision, stop using your medication and make an appointment with an ophthalmologist. 

IMPORTANT: Please report any side effects you experience to your Ro-affiliated healthcare provider. This list is not exhaustive. A complete list of side effects can be found here.  If you are experiencing a medical emergency, seek immediate medical attention or call 9-1-1. Symptoms such as chest pain, shortness of breath, severe headache, fainting, visual changes, hearing loss, or any other severe side effect warrant a visit to the emergency room.