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Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

STENDRA was administered to 1923 men during clinical trials. In trials of STENDRA for use as needed, a total of 493 patients were exposed for greater than or equal to 6 months, and 153 patients were treated for greater than or equal to 12 months.

In three randomized, double-blind, placebo-controlled trials lasting up to 3 months in duration, the mean age of patients was 56.4 years (range from 23 to 88 years). 83.9% of patients were White, 13.8% were Black, 1.4% Asian, and < 1% Hispanic. 41.1% were current or previous smokers. 30.6% had diabetes mellitus.

The discontinuation rate due to adverse reactions for patients treated with STENDRA 50 mg, 100 mg, or 200 mg was 1.4%, 2.0%, and 2.0%, respectively, compared to 1.7% for placebo-treated patients.

Table 1 presents the adverse reactions reported when STENDRA was taken as recommended (on an as-needed basis) from these 3 clinical trials.

Table 1: Adverse Reactions Reported by Greater Than or Equal to 2% of Patients Treated with STENDRA From 3 Placebo-Controlled Clinical Trials Lasting 3 Months for STENDRA Use as Needed

Adverse Reaction  Placebo
(N = 349) 
(N = 217) 
STENDRA 100 mg
(N = 349) 
STENDRA 200 mg
(N = 352) 
Headache  1.70% 5.10% 6.90% 10.50%
Flushing  0.00% 3.20% 4.30% 4.00%
Nasal congestion  1.10% 1.80% 2.90% 2.00%
Nasopharyngitis  2.90% 0.90% 2.60% 3.40%
Back pain  1.10% 3.20% 2.00% 1.10%

Adverse reactions reported by greater than or equal to 1%, but less than 2% of patients in any STENDRA dose group, and greater than placebo included: upper respiratory infection (URI), bronchitis, influenza, sinusitis, sinus congestion, hypertension, dyspepsia, nausea, constipation, and rash.

In an, open-label, long-term extension study of two of these randomized, double-blind, placebo-controlled trials, the total duration of treatment was up to 52 weeks. Among the 712 patients who participated in this open-label extension study, the mean age of the population was 56.4 years (range from 23 to 88 years). The discontinuation rate due to adverse reactions for patients treated with STENDRA (50 mg, 100 mg, or 200 mg) was 2.8%.

In this extension trial, all eligible patients were initially assigned to STENDRA 100 mg. At any point during the trial, patients could request to have their dose of STENDRA increased to 200 mg or decreased to 50 mg based on their individual response to treatment. In total, 536 (approximately 75%) patients increased their dose to 200 mg and 5 (less than 1%) patients reduced their dose to 50 mg.

Table 2 presents the adverse reactions reported when STENDRA was taken as recommended (on an as-needed basis) in this open-label extension trial.

Table 2: Adverse Reactions Reported by Greater Than or Equal to 2% of Patients Treated With STENDRA in an Open-Label Extension Trial

 Adverse Reaction  STENDRA
(N = 711) 
Headache  5.60%
Flushing  3.50%
Nasopharyngitis  3.40%
Nasal congestion  2.10%

Adverse reactions reported by greater than or equal to 1%, but less than 2% of patients in the open-label extension study included: upper respiratory infection (URI), influenza, sinusitis, bronchitis, dizziness, back pain, arthralgia, hypertension, and diarrhea.

In an additional, randomized, double-blind, placebo-controlled study lasting up to 3 months in 298 men who had undergone bilateral nerve-sparing radical prostatectomy for prostate cancer, the mean age of patients was 58.4 years (range 40 – 70). Table 3 presents the adverse reactions reported in this study.

Table 3: Adverse Reactions Reported by Greater than or Equal to 2% of Patients Treated with STENDRA in a Placebo-Controlled Clinical Trial Lasting 3 Months in Patients Who Underwent Bilateral Nerve-Sparing Radical Prostatectomy

Adverse Reaction  Placebo
(N = 100) 
STENDRA 100 mg
(N = 99) 
STENDRA 200 mg
(N = 99) 
Headache  1.00% 8.10% 12.10%
Flushing  0.00% 5.10% 10.10%
Nasopharyngitis  0.00% 3.00% 5.10%
Upper respiratory infection  0.00% 2.00% 3.00%
Nasal congestion  1.00% 3.00% 1.00%
Back pain  1.00% 3.00% 2.00%
Electrocardiogram abnormal  0.00% 1.00% 3.00%
Dizziness  0.00% 1.00% 2.00%

Across all trials with any STENDRA dose, 1 patient reported a change in color vision.

The following events occurred in less than 1% of patients in the three placebo-controlled 3-month clinical trials and/or the open-label, long-term extension study lasting 12 months. A causal relationship to STENDRA is uncertain. Excluded from this list are those events that were minor, those with no plausible relation to drug use and reports too imprecise to be meaningful.

Body as a whole — edema peripheral, fatigue

Cardiovascular — angina, unstable angina, deep vein thrombosis, palpitations

Digestive — gastritis, gastroesophageal reflux disease, hypoglycemia, blood glucose increased, alanine aminotransferase increased, oropharyngeal pain, stomach discomfort, vomiting

Musculoskeletal — muscle spasms, musculoskeletal pain, myalgia, pain in extremity

Nervous — depression, insomnia, somnolence, vertigo

Respiratory — cough, dyspnea exertional, epistaxis, wheezing

Skin and Appendages – pruritus Urogenital balanitis, erection increased, hematuria, nephrolithiasis, pollakiuria, urinary tract infection

Postmarketing Experience


Non-arteritic anterior ischemic optic neuropathy (NAION), a cause of decreased vision including permanent loss of vision, has been reported rarely post-marketing in temporal association with the use of phosphodiesterase type 5 (PDE5) inhibitors. Most, but not all, of these patients had underlying anatomic or vascular risk factors for developing NAION, including but not necessarily limited to: low cup to disc ratio (“crowded disc”), age over 50, diabetes, hypertension, coronary artery disease, hyperlipidemia and smoking. It is not possible to determine whether these events are related directly to the use of PDE5 inhibitors, to the patient's underlying vascular risk factors or anatomical defects, to a combination of these factors, or to other factors [see WARNINGS AND PRECAUTIONS and PATIENT INFORMATION].

Read the Stendra (avanafil) Side Effects Center for a complete guide to possible side effects


Potential For Pharmacodynamic Interactions With STENDRA


Administration of STENDRA to patients who are using any form of organic nitrate, is contraindicated. In a clinical pharmacology trial, STENDRA was shown to potentiate the hypotensive effect of nitrates. In a patient who has taken STENDRA, where nitrate administration is deemed medically necessary in a life-threatening situation, at least 12 hours should elapse after the last dose of STENDRA before nitrate administration is considered. In such circumstances, nitrates should only be administered under close medical supervision with appropriate hemodynamic monitoring [see CONTRAINDICATIONS, WARNINGS AND PRECAUTIONS, and CLINICAL PHARMACOLOGY].


Caution is advised when PDE5 inhibitors are co-administered with alpha-blockers. PDE5 inhibitors, including STENDRA, and alpha-adrenergic blocking agents are both vasodilators with blood pressure-lowering effects. When vasodilators are used in combination, an additive effect on blood pressure may be anticipated. In some patients, concomitant use of these two drug classes can lower blood pressure significantly leading to symptomatic hypotension (e.g., dizziness, lightheadedness, fainting) [see WARNINGS AND PRECAUTIONS, DOSAGE AND ADMINISTRATION, and CLINICAL PHARMACOLOGY].


PDE5 inhibitors, including STENDRA, are mild systemic vasodilators. A clinical pharmacology trial was conducted to assess the effect of STENDRA on the potentiation of the blood pressure-lowering effects of selected antihypertensive medications (amlodipine and enalapril). Additional reductions in blood pressure of 3 to 5 mmHg occurred following co-administration of a single 200 mg dose STENDRA with these agents compared with placebo [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].


Both alcohol and PDE5 inhibitors, including STENDRA, act as vasodilators. When vasodilators are taken in combination, blood pressure-lowering effects of each individual compound may be increased. Substantial consumption of alcohol (e.g., greater than 3 units) in combination with STENDRA can increase the potential for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache [see CLINICAL PHARMACOLOGY].

Potential For Other Drugs To Affect STENDRA

STENDRA is a substrate of and predominantly metabolized by CYP3A4. Studies have shown that drugs that inhibit CYP3A4 can increase avanafil exposure.

Strong CYP3A4 Inhibitors

Ketoconazole (400 mg daily), a selective and strong inhibitor of CYP3A4, increased STENDRA 50 mg single-dose systemic exposure (AUC) and maximum concentration (C max ) equal to 13-fold and 3-fold, respectively and prolonged the half-life of avanafil to approximately 9 hours. Other potent inhibitors of CYP3A4 (e.g. , itraconazole, clarithromycin, nefazadone, ritonavir, saquinavir, nelfinavir, indinavir, atanazavir and telithromycin) would be expected to have similar effects. Do not use STENDRA in patients taking strong CYP3A4 inhibitors [see WARNINGS AND PRECAUTIONS and DOSAGE AND ADMINISTRATION].

HIV Protease inhibitor Ritonavir (600 mg twice daily), a strong CYP3A4 inhibitor, which also inhibits CYP2C9, increased STENDRA 50 mg single-dose C max and AUC equal to approximately 2-fold and 13-fold, and prolonged the half-life of avanafil to approximately 9 hours in healthy volunteers. Do not use STENDRA in patients taking ritonavir.

Moderate CYP 3A4 Inhibitors

Erythromycin (500 mg twice daily) increased STENDRA 200 mg single-dose C max and AUC equal to approximately 2-fold and 3fold, respectively, and prolonged the half-life of avanafil to approximately 8 hours in healthy volunteers. Moderate CYP3A4 inhibitors (e.g., erythromycin, amprenavir, aprepitant, diltiazem, fluconazole, fosamprenavir, and verapamil) would be expected to have similar effects. Consequently, the maximum recommended dose of STENDRA is 50 mg, not to exceed once every 24 hours for patients taking concomitant moderate CYP3A4 inhibitors [see WARNINGS AND PRECAUTIONS].

Although specific interactions have not been studied, other CYP3A4 inhibitors, including grapefruit juice are likely to increase avanafil exposure.

Weak CYP3A4 Inhibitors

No in vivo drug-drug interaction studies with weak CYP3A4 inhibitors were conducted.

CYP3A4 Substrate

When administered with STENDRA 200 mg, amlodipine (5 mg daily) increased the C max and AUC of avanafil by approximately 22% and 70%, respectively. The half-life of STENDRA was prolonged to approximately 10 hrs. The C max and AUC of amlodipine decreased by approximately 9% and 4%, respectively [see DOSAGE AND ADMINISTRATION].

Cytochrome P450 Inducers

The potential effect of CYP inducers on the pharmacokinetics of avanafil was not evaluated. The concomitant use of STENDRA and CYP inducers is not recommended.

Potential For STENDRA To Affect Other Drugs

In vitro studies

Avanafil had no effect on CYP1A1/2, 2A6, 2B6, and 2E1 (IC 50 greater than 100 micromolar) and weak inhibitory effects toward other isoforms (CYP2C8, 2C9, 2C19, 2D6, 3A4). Major circulating metabolites of avanafil (M4 and M16) had no effect on CYPs 1A, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4. Avanafil and its metabolites (M4 and M16) are unlikely to cause clinically significant inhibition of CYPs 1A, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, or 3A4.

In vivo studies

Warfarin A single 200 mg dose of STENDRA did not alter the changes in PT or INR induced by warfarin, and did not affect collagen-induced platelet aggregation or the AUC or C max of R-or S-warfarin, a 2C9 substrate.

Desipramine A single STENDRA 200 mg dose increased AUC and C max of a single 50 mg dose of desipramine, a CYP2D6 substrate, by 5.7% and 5.2%, respectively.

Omeprazole A single STENDRA 200 mg dose increased AUC and C max of a single 40 mg dose of omeprazole, a CYP2C19 substrate, given once daily for 8 days by 5.9% and 8.6%, respectively.

Rosiglitazone A single STENDRA 200 mg dose increased AUC by 2.0% and decreased Cmax by 14% of a single 8 mg dose of rosiglitazone, a CYP2C8 substrate.

Amlodipine A single STENDRA 200 mg dose did not affect the pharmacokinetics of amlodipine (5 mg daily), a CYP3A4 substrate [see DOSAGE AND ADMINISTRATION].

Alcohol — A single oral dose of STENDRA 200 mg did not affect alcohol (0.5 g ethanol/kg) plasma concentrations [see WARNINGS AND PRECAUTIONS].

Last reviewed on RxList: 5/20/2014
This monograph has been modified to include the generic and brand name in many instances.


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