Viagra side effects: what sildenafil does and what you notice

The side effects of Viagra are mild and temporary for most men: headache, flushing, a blocked nose and sometimes stomach complaints. They come with the way the medicine works and fade as the effect wears off. There is one combination that is genuinely dangerous, and it appears further down.

Viagra is the brand name of sildenafil. Since the patent expired, generic sildenafil has been the same medicine at a fraction of the price.

What strikes us is that men rarely read the patient leaflet but will trawl forums for hours. That is a shame, because the most important information is short and boring.

How does sildenafil work in your body?

Sildenafil is a PDE5 inhibitor. It blocks an enzyme that narrows the blood vessels in the erectile tissue again, so blood is held longer. It starts working after about 30 to 60 minutes and the effect often lasts 4 to 5 hours.

PDE5 is not only found in the penis. It also sits in the blood vessels of your nose, your head and your digestive tract.

That explains almost the entire list of complaints. A blocked nose is not a coincidence, but the same mechanism somewhere else.

Which side effects are most common?

The frequencies below come from the patient leaflet and the Dutch Farmacotherapeutisch Kompas. Very common means more than 1 in 10 users, common means 1 to 10 in 100. Your own response may differ.

That blue tint is the side effect that surprises men most. It is better known with sildenafil than with tadalafil and disappears along with the effect.

Is Viagra bad for your heart?

For most men with a healthy heart, sildenafil at usual strengths does not strain the heart. It lowers blood pressure slightly, roughly the way brief exertion does. The question changes if you already take heart medication.

If you use nitrates, for example nitroglycerin under the tongue or isosorbide dinitrate, combining them with sildenafil is life threatening. Both lower blood pressure, and together that drop can become extreme.

The same applies to poppers, which also contain nitrates. That is exactly why your GP wants to see your medication list first.

There is another heart angle. In research, erectile dysfunction often appears as an early signal of vascular damage, sometimes years before heart complaints show up. More on that in which blood values point to risk.

Viagra experiences: what do users report?

Experiences vary widely, and that is more often down to circumstances than to the medicine. Satisfied men usually mention that it works reliably and that the nerves around sex fade. Disappointed men often turn out to have overlooked something.

Take a man of 52 who takes the pill during a long dinner with wine. The fats slow absorption, the alcohol dampens stimulation, and an hour and a half later little happens.

He concludes that sildenafil does not work for him. In reality he never tested it under normal conditions.

Other things users frequently mention:

• The first time disappoints, the third time works
• Headache eases with repeated use
• A lower strength sometimes gives enough effect with fewer complaints
• The blocked nose is more annoying than expected

Research into PDE5 inhibitors shows that the number of successful attempts rises with repeated use. That matches what men report themselves.

When is the pill not the problem?

Around 30 to 35 percent of men respond poorly to a PDE5 inhibitor. In some of them a hormonal or metabolic cause is involved that has nothing to do with the pill. A stronger dose then often changes nothing.

Testosterone, blood sugar and thyroid values come up most often in that list. We wrote earlier about the signals of low testosterone.

Medication counts too. Some blood pressure lowering drugs affect your erection, as we discussed in side effects of blood pressure medication.

A testosterone test brings some of those values into view. Discuss the result with your GP.

What is the difference between Viagra and Kamagra?

Viagra is a registered medicine with a controlled amount of sildenafil. Kamagra is not registered in Europe and falls outside that oversight, so the actual contents can differ from batch to batch. That is the whole difference, and it is bigger than it sounds.

We worked that out in our article on Kamagra.

What to do with this information

My advice stays simple: give a medicine a fair chance before deciding it does not work. That means on an empty stomach, without much alcohol, with enough time and enough stimulation.

If nothing happens after a few honest attempts, go back to your GP with those details. That conversation runs differently from the first one, as we described in the GP visit. And look at the other ED medications too, because a different profile sometimes fits better. The role of desire is covered separately in libido and hormones.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

References

• Berner MM, et al. Efficacy of PDE-5-inhibitors for erectile dysfunction. A comparative meta-analysis. Int J Impot Res, 2006. PMID: 16239897
• Corona G, et al. Erectile dysfunction and cardiovascular risk: a review of current findings. Expert Rev Cardiovasc Ther, 2020. PMID: 32192361
• Yafi FA, et al. Non-invasive management options for erectile dysfunction when a phosphodiesterase type 5 inhibitor fails. Drugs Aging, 2018. PMID: 29464656
• Farmacotherapeutisch Kompas, monograph for sildenafil.