Safety

Side effects, and the erection that will not go down

Most reactions to PDE5 inhibitors are vascular and temporary: a headache, a flushed face, a stuffy nose, an upset stomach. A smaller set is an emergency. The skill is telling those apart before you decide to sleep it off.

Reactions that are usually uncomfortable, not dangerous

• Headache and flushing. Blood vessels have widened. These track with the dose and fade as the drug leaves. A prescriber may lower the dose or change the drug. Adding a new painkiller without asking is how people accidentally stack blood-pressure effects or stomach irritation.
• Nasal congestion. The same vasodilation in the nose. It is annoying and expected.
• Indigestion. Common with sildenafil and tadalafil. Taking the dose with a large fatty meal is a poor fix for sildenafil, because that meal also delays absorption.
• Back pain and muscle aches. More typical of tadalafil. They often start 12 to 24 hours later and resolve within 48 hours. The delay is on the label, so a Saturday backache after a Thursday dose can still be the drug.
• Blue-tinted vision or light sensitivity. More typical of sildenafil, because it has some effect on PDE6 in the retina. It is usually temporary. It is not the same as sudden vision loss.
• Dizziness. More likely with alcohol, alpha-blockers, blood-pressure medicines, or dehydration. Sit or lie down. If you faint or have chest pain, that is no longer a “common” side effect. Use emergency services.

Red flags that stop the medicine

• Sudden vision loss in one or both eyes. This can be NAION, a stroke of the optic nerve. Stop the drug and get same-day eye or emergency care. A prior episode of NAION belongs in the chart before any PDE5 inhibitor is prescribed. A crowded optic disc, age over 50, diabetes, hypertension, and smoking are risk factors the labels list. Causation is not settled. The action is.
• Sudden hearing decrease or loss, sometimes with tinnitus or vertigo. Stop and get prompt care.
• Chest pain, fainting, or a severe allergic reaction (swelling of the face or throat, widespread hives, trouble breathing). Emergency care. Allergic reactions, including rare severe skin reactions with tadalafil, have been reported after approval.
• An erection still present at 4 hours, painful or not.

Who is at higher risk of a prolonged erection

Labels advise caution with anatomic deformity such as Peyronie’s disease, angulation, or cavernosal fibrosis, and with conditions that predispose to priapism: sickle cell disease, multiple myeloma, and leukemia. There are no controlled trials establishing safety in sickle cell disease. Other drugs can also cause priapism, including some mental-health medicines and injected erectile treatments. Tell the emergency clinician everything you took, including supplements. A gas-station pill can contain a hidden PDE5 inhibitor and be the actual cause.

What emergency care is for

Clinicians drain blood and, when needed, use medicines injected into the penis to constrict vessels. Time matters because the tissue is starved of oxygen. That is why home remedies are not a substitute for the emergency department. Afterward, the prescribing clinician should hear about the episode before any further ED treatment. A second tablet “to see” is the wrong experiment.

Common reactions are also a reason to review the dose rather than to quit in silence or to double up. The comparison shows how side-effect patterns differ across the four drugs.

Sources

• Patient counseling sections of the sildenafil, tadalafil, vardenafil, and avanafil prescribing information: 4-hour erection, NAION, and sudden hearing loss.