Populations. The included trials involved participants diagnosed with ED

The included trials involved participants diagnosed with ED. The total and mean numbers of patients randomly assigned to an intervention or placebo across the 22 trials were 8, 621 and 392, respectively, while the number of randomly assigned patients in each trial ranged from 21¹⁹³ to 1020.¹⁹⁰

The inclusion criteria across most of the included trials were: adult males aged ≥ 18 years, diagnosed with ED for ≥ 6 months in a stable monogamous heterosexual relationship.^{180–184, 189–195, 197–201, 203, 204} In one trial, ²⁰⁵ the inclusion criteria for the patients' age and duration of ED were slightly different (≥ 20 and ≥ 5 years, respectively). In the report of one trial²⁰⁶ the patient inclusion criteria for age and duration of ED were not clear.

The additional inclusion criteria in seven trials were diagnoses for the following conditions: diabetes types I or II, ^{181, 205} diabetes type I, ²⁰⁴ nerve-sparing retropubic prostatectomy, ¹⁸³ history of renal transplant, ²⁰⁶ untreated mild major depressive disorder, ¹⁹⁹ or arterial hypertension.¹⁹⁶ One trial included ED patients who had not responded to previous sildenafil therapy.¹⁸⁴ In three trials, the included patients were sildenafil-naï ve.^{180, 201, 204} In one of these trials, ¹⁸⁰ patients had not received any previous treatment for ED.

In most trials, patients had ED with a broad spectrum of causes (i.e., organic, psychogenic, and mixed).^{180, 182, 184, 189–195, 197, 198, 200, 201, 203} The mean age across the 22 trials ranged from 34 years¹⁹⁵ to 60 years.^{183, 184}

Exclusion criteria were not reported for two trials.^{180, 200} Patients with the following conditions were excluded from the trials: primary hypoactive sexual desire^{181–184, 190–193, 196–199, 201, 203–205} penile/genital anatomical deformity, ^{182, 184, 189–192, 195–199, 201, 203, 204, 206} any medical psychiatric or substance abuse disorder affecting the ability to complete the study, ^{182, 184, 189, 199, 201, 205} ED resulting from spinal cord injury, ^{181–184, 189–199, 201, 203–205} cardiovascular conditions (e.g. coronary artery disease, myocardial infarction, electrocardiographic ischemia, life-threatening arrhythmia, stroke, uncontrolled atrial tachyarrhythmia, unstable angina pectoris, uncontrolled atrial fibrillation), ^{181–184, 189–193, 195–198, 201, 203–206} hyper/hypotension (resting), ^{181–184, 189–193, 195, 196, 201, 203–206} postural hypotension, ^{182, 183, 189, 192, 196, 201, 204, 205} liver disease, ^{181, 183, 189, 191, 192, 196, 198, 201, 204–206} radical prostatectomy, ^{190–199, 201, 203–205} bleeding or hematological disorder, ^{181, 183, 189, 191, 192, 198, 201, 203, 204, 206} retinitis pigmentosa, ^{181–183, 190, 192, 193, 195–199, 203–205} poorly controlled diabetes mellitus, ^{182, 183, 189–195, 198, 203} hepatitis B, ^{189, 192, 194, 195, 198, 203} hepatitis C, ^{189, 192, 194, 196, 201, 204} peptic ulceration, ^{183, 189, 192, 201, 205, 206} major psychiatric disorders, ^{193, 195, 199} endocrine diseases, ^{193, 195} autonomic neuropathy, ¹⁸¹ or prostate cancer.¹⁸³

The following concomitant medications were not allowed: nitrates or nitric oxide donors, ^{181–184, 189, 191–198, 201, 203–206}cimetidine, erythromycin, ketoconazole or trazodone, current use of digoxin derivatives or digitoxin antiarrhythmics, ^{189, 192, 194, 196–198, 201, 204} anticoagulants, ^{181–183, 192, 194, 196–198, 201, 204} androgens, ^{192, 196–198, 201, 203, 204} ketoconazole, ^{194, 196, 197, 204} alpha blockers, ^{196–198, 201} or rifampicin.^{189, 194}

Patients with abnormal hormone profiles such as low serum total testosterone, ^{182–184, 189, 192, 194, 201, 203} elevated serum creatinine, ^{184, 189, 192, 196, 201, 203, 204} serum free thyroxine (T4) out of the normal range, ¹⁸⁹ or thyroid-stimulating hormone (TSH) below the normal range were also excluded.^{189, 194}

Also excluded were sildenafil nonresponders^{189–194, 198, 199, 203} and patients who had discontinued previous sildenafil treatment because of side effects.^{181, 183, 189–191, 198}