Tadalafil was compared with cilodoxineand placebo in a prospective randomized trial that evaluated the ease of ureteroscopic navigation in the treatment of ureteral calculi [19c]. Compared with placebo, patients treated with tadalafil had better ureteral dilation, better ureteroscopy, and longer surgery. The tadalafil group reported more frequent headaches and back pain compared to the cilodoxine and placebo groups. The incidence of dizziness abnormal ejaculation and orthostatic hypotension did not differ significantly among the three groups.

Tadalafil 5 mg was studied as a combination with tamlosin 0.4 mg or 0.2 mg, compared with tadalafil 5 mg for lower urinary tract symptoms (LUTS) and erectile dysfunction associated with benign prostatic hyperplasia (BPH). The study demonstrated enhanced efficacy for BPH-associated LUTS, combined erectile dysfunction complaints, a lower rate of side effects, and simplified and convenient treatment for patients taking this combination product. However, the lack of a control group for tamlosin monotherapy was a limitation of this study. Adverse reactions were similar in different treatment groups. An independent trial evaluating the combination of tadalafil and tamsulosin in 171 Japanese patients found improved urination scores and no clinically significant changes in blood pressure. In addition, pooled analysis was performed on the age stratification of tadara nonusers (≥ 75 years vs < 75 years). Safety in older adults was similar to that in younger adults, with no increase in cardiovascular adverse events.

Tadalafil has been extensively studied in several clinical trials that do not involve pain management. The most common side effects were headache, gastrointestinal discomfort (including pain, indigestion, gas, and reflux), back pain, myalgia, flushing, and rhinorrhea. Although most of these side effects are short-lived, myalgia and back pain can last up to 24 hours.

In 2005, a post-marketing analysis showed a possible association between tadalafil and visual impairment caused by non-arteritis anterior ischemic optic neuropathy (NAION). Patients who developed complications had increased risk factors for underlying anatomical or vascular disease, including low cup/dish ratio, older than 50 years, hypertension, coronary artery disease, smoking, and hyperlipidemia. Because of NAION's low incidence and widespread use of tadalafil, the FDA does not issue an official warning, but it does require a warning on drug labeling. In addition, post-marketing analysis showed an increased risk of sudden hearing loss, which is also a warning on the drug's packaging.