Sildenafil and tadalafil: uses, differences and side effects

Both are phosphodiesterase-5 (PDE5) inhibitors. According to MedlinePlus, they increase blood flow to the penis during sexual stimulation: they don’t cause an erection on their own, they don’t cure erectile dysfunction and they don’t increase desire.

• Sildenafil (brand Viagra): FDA-approved to treat erectile dysfunction.
• Tadalafil (brand Cialis): FDA-approved for erectile dysfunction, for the symptoms of an enlarged prostate (benign prostatic hyperplasia), and for both together.
• Pulmonary hypertension: according to MedlinePlus, sildenafil (brands Revatio and Liqrev) and tadalafil (brand Adcirca) are also used, under other brands and labels, for pulmonary arterial hypertension, high pressure in the arteries of the lungs.

The main difference is how long the effect lasts. According to the FDA labels and MedlinePlus:

Only with a prescription and as your doctor directs. According to the FDA labels, neither is taken more than once a day. The dose depends on your age, kidneys, liver and other medicines, so the doctor decides it.

The AUA guideline recommends explaining how to take them to get the most benefit: they need sexual stimulation, time to act and, with sildenafil, no heavy meal right before. If one didn’t work for you, talk to the doctor before changing the dose on your own.

According to the FDA labels for both medicines:

According to the FDA labels, the most common side effects are headache, flushing, indigestion, stuffy nose, back pain and muscle aches. Sildenafil can also change your vision slightly (for example, a blue tint or blurriness).

Serious side effects are rare, but you should know them. Get care right away if you have:

• Sudden vision loss in one or both eyes: it can be an optic nerve stroke (NAION). Stop taking the medicine.
• Sudden hearing loss, sometimes with ringing or dizziness.
• An erection lasting more than 4 hours (priapism): it can damage the penis if not treated in time.
• Severe dizziness or fainting from low blood pressure.

The FDA warns that many sexual enhancement products are falsely advertised as dietary supplements, foods or “all-natural” treatments, and are likely to contain dangerous hidden ingredients. They are sold online and in stores, often with many positive reviews and through social media.

The danger is real: if a product hides sildenafil or tadalafil and you take nitrates for your heart, your blood pressure can drop dangerously. The FDA says its list of tainted products covers only a fraction of them, so a product that isn’t listed is not safe for that reason. The NIH also advises against ordering these medicines on the internet without talking to a doctor.