Table 1 Eligibility criteria for patients

Inclusion criteria

Age ranging from 25 to 65 years.

Type 1 or type 2 diabetes with an HbA1c ≤ 10%.

History of diabetes ≥ 5 years.

Body mass index between 20 and 30.

Baseline International Index of erectile function (IIEF-5) score of < 22.

History of chronic erectile dysfunction for at least 6 months.

Exclusion criteria

penile anatomical deformities (e.g., Peyronie’s disease).

Penile skin irritation, infection, or wound in the immediate areas of skin entry for penile injection.

Bleeding or clotting disorders.

Current urinary tract infection, current or previous infection with human immuno- deficiency or hepatitis viruses.

Previous penile implant, penile vascular surgery, or radical prostatectomy.

Current or previous malignancy.

Prostate-Specific Antigen (PSA) (> 4 ng/mL).

Untreated hypogonadism or low serum total testosterone (< 200 ng/dL).

Uncontrolled hypertension or hypotension (systolic blood pressure > 170 or < 90 mm Hg, and diastolic blood pressure > 100 or < 50 mm Hg).

Cardiovascular disease (e.g., unstable angina, myocardial infarction within past 6 months, cardiac failure or life-threatening arrhythmia, and congestive heart failure) or symptomatic postural hypotension within 6 months before screening.

Systemic autoimmune disorder.

The following laboratory screening results also had to be normal: luteinizing hormone, testosterone and prolactin, liver function tests (ALT, AST, and GGT), kidney function tests and/or electrolytes (urea, creatinine, Na, K, and Ca), complete blood count with differential, coagulation profile (INR, PT, and PTT), lipid profile (HDL, LDL, TG, and total cholesterol), urinalysis and culture, hepatitis B and C (HBs Ag and hepatitis C antibodies), human immune deficiency, and lues serology (VDRL).