Common Viagra Warnings & Precautions

For decades, Viagra® has held on to the title of the most well-known medication for erectile dysfunction — and for good reason.

Viagra contains the active ingredient sildenafil. Following its approval in 1998, sildenafil's effectiveness in improving erectile function led healthcare providers to write 5.3 million prescriptions for its use. Within two years, around 20 percent of men at risk of erectile dysfunction had been treated with this medication.

However, like any medication, you may find that Viagra usage can come with certain side effects. Likewise, safety measures must be observed to prevent adverse outcomes when using this medication.

We'll be looking into common Viagra warnings to avoid adverse effects, as well precautions to take when using this medication. But first, we'll check out what makes Viagra an effective treatment for erectile dysfunction.

How Does Viagra Work?

Put very simply, Viagra helps to increase blood flow to the penis to produce stronger and longer lasting erections.

It achieves this through its active ingredient, sildenafil —  a PDE-5 inhibitor.

To understand how this medication works, it's important to note that erections are produced when the corpus cavernosum is filled with sufficient amounts of blood. The corpus cavernosum is one of two chambers made up of spongy tissue that run the length of the penis. These chambers provide the structure for erections.

Blood flows into these chambers through smooth muscles. However, this process begins when nitric oxide is produced in the body following sexual arousal. Nitric oxide acts as a vasodilator by encouraging blood vessels to open up or dilate. This compound also has the very important function of stimulating the production of cyclic guanosine monophosphate (cGMP).

The accumulation of cGMP is what makes it possible for the smooth muscles of the corpus cavernosum to relax and get filled with blood. However, this process may be prevented by PDE-5, an enzyme found in these muscles. 

This enzyme hangs on to and degrades cGMP, preventing its accumulation and the achievement of strong erections. This is where PDE-5 inhibitors like Viagra come in.

Viagra binds to PDE-5, preventing the breakdown of cGMP. This allows for an increase in cGMP in the smooth muscles which can lead to stronger, prolonged erections.

Because Viagra primarily acts on PDE-5, it has no direct effects on relaxing the smooth muscles. This means that administering Viagra will not lead to an automatic erection — adequate sexual stimulation must first occur.

Warnings and Precautions When Using Viagra

Viagra’s ability to cause smooth muscle relaxation and vasodilation are what makes it such an effective treatment against erectile dysfunction. However, these vasodilatory properties are also largely responsible for its side effects, some of which include: headaches, flushing and indigestion.

This mechanism of action also means that Viagra may sometimes produce dangerous or even fatal interactions when combined with certain medications. This is why Viagra may not be safe to use when dealing with specific medical conditions.

To prevent adverse outcomes, here are certain warnings and precautions to be noted when using Viagra:

Cardiovascular risk

Viagra is able to produce stronger erections by promoting the activities of nitric oxide, a known vasodilator. You'll remember that nitric oxide stimulates the production of cGMP which helps with smooth muscle relaxation.

However, while nitric oxide encourages the muscles of penile blood vessels to relax, its effects aren't restricted to just the penis.

Nitric oxide may affect blood vessels like arteries all around the body, causing them to widen and increase blood flow. This however has the after-effect of reducing blood pressure.

For people with conditions that involve blood flow obstruction, compounding their ailment with further reduced blood pressure may have dangerous effects.

This includes conditions such as myocardial infarction, which is the blockage of blood flow to the heart muscle. It also covers hypotension or low blood pressure, as well as coronary artery disease, where blood flow to the heart is restricted following damage to major blood vessels.

Individuals with cardiac failure, where the heart is unable to pump blood adequately, may also be sensitive to the effects of Viagra.

Drug Interactions

The vasodilatory properties of Viagra may also lead to dangerous interactions when combined with certain medications. These include:

Antihypertensives

Antihypertensives are intended to lower blood pressure in people living with hypertension — a known cause of erectile dysfunction. However, when antihypertensives are combined with medications such as Viagra which can replicate its effects, this may further lower blood pressure.

However, while caution is important, studies have shown that the combination of sildenafil and hypertensives may not lead to significant decreases in blood pressure, especially where taken in low doses. 

To avoid adverse effects, it is suggested that sildenafil doses higher than 25mg should not be taken within four hours of using an antihypertensive.

Alpha-blockers

Alpha-blockers are also used for the reduction of blood pressure in hypertensive patients. If used in combination with PDE-5 inhibitors, two factors will be at work to reduce blood pressure in the body. Viagra usage may be particularly harmful in patients who experience unstable blood pressure. It may also be unsafe to combine both types of medications when the total volume of blood in a patient is reduced.

Like antihypertensives, alpha-blockers may be safely combined with Viagra in low doses, but only after having a very careful conversation about it with your healthcare provider.

Ritonavir

Anti-retroviral drugs such as ritonavir (Norvir®) are necessary for the management of HIV. With HIV posing an increased risk of erectile dysfunction, medications such as Viagra may be considered for managing this condition.

However, ritonavir has been shown to affect the absorption of sildenafil when used together. It can lead to a significant increase in the concentration of sildenafil in the body.  

It bears mentioning, however, that while this combination may increase sildenafil concentration, it isn’t very likely to raise the chances of adverse effects.

Regardless, users of ritonavir should take extra care when combining the medication with Viagra to avoid negative outcomes.

Hearing loss

Although rare, there is a chance that PDE-5 inhibitors such as Viagra can cause sudden deafness. This may be due to a suspected ototoxicity to the ear.

Viagra users are advised to immediately stop the medication and seek medical assistance where hearing loss is observed.

Vision loss

The loss of sight following Viagra usage is a very rare event, but one that may be linked to its role as a PDE-5 inhibitor. Because PDE-5, the enzyme that prevents the flow of blood to the penis is also found in the eye, administering Viagra can lead to vasodilation in the retina. 

Links have been drawn between Viagra usage and non-arteritic anterior ischaemic optic neuropathy, which is the reduced flow of blood to the optic nerve. This condition may cause sudden blindness in one eye. There’s also concern that PDE-5 inhibitors may also lead to macular detachment, a condition which can lead to blindness in one eye. 

If you notice the loss of vision in one or both eyes following Viagra usage, you should immediately stop the medication and seek medical attention for your vision.

Priapism

A prolonged erection that lasts longer than four hours — otherwise known as priapism — is unsafe and may lead to complications that result in erectile dysfunction. There have been reports that high doses of Viagra, such as its 200mg dosage, may be linked to this condition.

If you experience an erection that lasts longer than four hours, you must seek immediate medical assistance to avoid damage to penile tissue.

Likewise, Viagra comes with a warning for patients with an anatomically deformed penis. This includes patients with conditions such as Peyronie’s disease and angulation.

Closing Off

Viagra is one of the most widely trusted and recognized treatments for erectile dysfunction.

However, to enjoy its full benefits, certain precautions have to be observed. These include taking careful consideration of drugs Viagra may have negative interactions with, or any health conditions it may be unsuitable for.

These precautions may also require stopping its use when adverse side effects such as hearing loss, or the loss of sight occur.

To make sure Viagra is safe and suitable for your use, it's important to first run a plan to use the medication by a healthcare professional for necessary advice.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.