Short answer: In the label's three placebo-controlled trials of Stendra taken as needed, the most common side effects were headache (5.1% on 50 mg, 6.9% on 100 mg and 10.5% on 200 mg vs 1.7% on placebo), flushing (3.2% to 4.3% vs 0.0%), nasal congestion, nasopharyngitis and back pain. Stopping because of side effects was 1.4% to 2.0% vs 1.7% on placebo. Stendra has no boxed warning.
What Stendra is approved for: Stendra is a PDE5 inhibitor approved to treat erectile dysfunction in adult males (section 1).
Source
STENDRA (avanafil) tablets, for oral use, prescribing information and Patient Information. Metuchen Pharmaceuticals. DailyMed, version published July 24, 2024. DailyMed setid fa7d93e3-b69b-4e02-8146-89760cd8e9d6
No. The current Stendra label has no boxed warning.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Stendra.
| Adverse Reaction | Placebo (N = 349) | STENDRA 50 mg (N = 217) | STENDRA 100 mg (N = 349) | STENDRA 200 mg (N = 352) |
|---|---|---|---|---|
| Headache | 1.7% | 5.1% | 6.9% | 10.5% |
| Flushing | 0.0% | 3.2% | 4.3% | 4.0% |
| Nasal congestion | 1.1% | 1.8% | 2.9% | 2.0% |
| Nasopharyngitis | 2.9% | 0.9% | 2.6% | 3.4% |
| Back pain | 1.1% | 3.2% | 2.0% | 1.1% |
Mean age 56.4 (range 23 to 88); 30.6% had diabetes. Stopping because of side effects: 1.4% on 50 mg, 2.0% on 100 mg and 2.0% on 200 mg vs 1.7% on placebo.
| Adverse Reaction | Placebo (N = 100) | STENDRA 100 mg (N = 99) | STENDRA 200 mg (N = 99) |
|---|---|---|---|
| Headache | 1.0% | 8.1% | 12.1% |
| Flushing | 0.0% | 5.1% | 10.1% |
| Nasopharyngitis | 0.0% | 3.0% | 5.1% |
| Upper respiratory infection | 0.0% | 2.0% | 3.0% |
| Nasal congestion | 1.0% | 3.0% | 1.0% |
| Back pain | 1.0% | 3.0% | 2.0% |
| Electrocardiogram abnormal | 0.0% | 1.0% | 3.0% |
| Dizziness | 0.0% | 1.0% | 2.0% |
298 men after nerve-sparing prostate cancer surgery, mean age 58.4 (range 40 to 70).
In the open-label extension of up to 52 weeks (711 men, most moved up to 200 mg): headache 5.6%, flushing 3.5%, nasopharyngitis 3.4% and nasal congestion 2.1%. Stopping because of side effects was 2.8%.
In the 2-month time-to-onset study (Table 4; placebo, 100 mg, 200 mg): headache 0.7%, 1.4%, 8.9%; nasal congestion 0.0%, 0.7%, 4.1%; viral gastroenteritis 0.0%, 0.0%, 2.1%.
Across all trials at any dose, 1 man reported a change in color vision.
In healthy volunteers, Stendra 200 mg briefly lowered sitting blood pressure by 8.0 mmHg systolic and 3.3 mmHg diastolic, with the largest drop 1 hour after the dose.
Two observational studies suggested about a 2-fold higher risk of NAION (a sudden optic nerve problem) right after PDE5 inhibitor use, with risk estimates of 2.15 (95% CI 1.06, 4.34) and 2.27 (95% CI 0.99, 5.20). The label says this does not establish cause.
Reported after approval: heart attack, sudden cardiac death, stroke and brain bleeding in men who all had heart risk factors (cause could not be determined), transient global amnesia, vitreous detachment, vision problems, NAION and sudden hearing loss.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Do not use with nitrates or riociguat. Stendra must not be used with any organic nitrate, taken regularly or now and then, or with guanylate cyclase stimulators such as riociguat or vericiguat, because blood pressure can drop sharply. If a nitrate is needed in a life-threatening emergency, at least 12 hours should pass after the last Stendra dose, with close monitoring. Allergy to any ingredient is also a contraindication.
Heart risk with sexual activity. Stendra is not for men whose heart condition makes sexual activity inadvisable. It is not recommended after a heart attack, stroke, life-threatening arrhythmia or coronary revascularization in the last 6 months, with blood pressure under 90/50 or over 170/100 mmHg, or with unstable angina, angina during sex, or NYHA Class 2 or greater heart failure.
CYP3A4 inhibitors. Stendra is not used with strong CYP3A4 inhibitors such as ketoconazole, ritonavir or clarithromycin. With moderate ones such as erythromycin, diltiazem, fluconazole or verapamil, the maximum is 50 mg once every 24 hours.
Prolonged erection. Erections over 4 hours and priapism have been reported with other PDE5 inhibitors. An erection lasting more than 4 hours needs immediate medical help, as untreated priapism can permanently damage the penis.
Sudden vision loss. Sudden loss of vision in one or both eyes may be a sign of NAION. The label says to stop all PDE5 inhibitors and get medical attention. It is not recommended with inherited retinal disorders such as retinitis pigmentosa.
Sudden hearing loss. Sudden decrease or loss of hearing, sometimes with ringing in the ears or dizziness, has been linked to PDE5 inhibitors. The label says to stop Stendra and get prompt medical attention.
Alpha-blockers and blood pressure medicines. Stendra can add to the blood-pressure-lowering effect of these medicines and cause dizziness or fainting. Men should be stable on an alpha-blocker first, and Stendra then starts at 50 mg.
Alcohol. Substantial alcohol (for example more than 3 units) with Stendra can raise heart rate, lower standing blood pressure, and cause dizziness and headache.
Other ED treatments, bleeding and STDs. Combining it with other ED treatments is not recommended. Its safety is unknown in people with bleeding disorders or active stomach ulcers. It offers no protection against sexually transmitted diseases, including HIV.
From the Patient Information that comes with Stendra:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.