Key points to remember

  • Six months of daily treatment with tadalafil (Cialis), an agent that treats erectile dysfunction (ED), in men with both erectile dysfunction and type 2 diabetes resulted in significant improvement in blood sugar control compared to placebo in a prospective randomized study involving 68 patients who completed the study.

  • Tadalafil was well tolerated and no participants discontinued the study due to treatment-related adverse reactions.

  • The study was conducted at a single center in South Korea.

  • The study is currently a pre-publication and has not been peer reviewed.

Why it matters

  • Low dose tadalafil has been shown to be effective and safe in improving both blood sugar control and erectile function in men with type 2 diabetes and erectile dysfunction.

  • Evidence shows that men with diabetes are more than three times more likely to have erectile dysfunction than men without diabetes.

  • The results of an earlier study showed that treating men with type 2 diabetes and erectile dysfunction with 5 mg of tadalafil by mouth once daily is effective in improving erectile dysfunction and is safe and well tolerated. The new results show how this treatment affects blood sugar control.

Study design

  • Researchers recruited eligible men from the outpatient clinic at Myongji Hospital, South Korea, in January 2017 and November 2018.

  • The men enrolled were between the ages of 35 and 75 with a diagnosis of type 2 diabetes and ED for over a year.

  • The enrolled patients had a regular sexual partner and had had sexual intercourse at least once in the previous month, but also had a history of persistent inability to achieve or maintain an erection sufficient for satisfactory sexual performance.

  • All included patients had an A1c level below 9% and no history of treatment with a phosphodiesterase type 5 (PDE-5) inhibitor (the class of drugs that includes tadalafil) in the past 3 months.

  • Outcomes evaluated included a change from baseline A1c, a change in fasting blood sugar, and changes in two measures of erectile dysfunction, the International Index of Erectile Function (IIEF-5) and the international prostate symptom index (IPSS).

  • Baseline IIEF-5 score and IPSS did not differ between the two treatment groups.

  • Researchers randomized 50 patients to receive 5 mg of oral tadalafil per day and 25 patients to receive placebo. After 6 months, 45 patients in the tadalafil group and 23 in the placebo group had completed the full treatment protocol and their assessment at 6 months.

Key results

  • At the end of the study, A1c levels decreased from baseline by an average of 0.137% in the tadalafil group and increased by an average of 0.196% in the placebo group (P = .030).

  • After 6 months, the mean fasting glucose was 6.40 mg / dL below baseline in the tadalafil group and 5.35 mg / dL above baseline in the placebo group (P = .046).

  • The improvement in the IIEF-5 score was significantly greater in the tadalafil group than in the placebo group at 6 months, with a mean score of 6.56 with tadalafil and of 2.22 with the placebo (P = 0.003).

  • IPSS showed a numerical improvement in patients taking tadalafil compared to those taking placebo, which was not significant.


  • A relatively small, single-center study.

  • The analyzes did not adjust for confounding variables that might affect the results, such as lifestyle changes.

  • The possible mechanisms of the observed effects of tadalafil on blood sugar control are unclear.

  • Larger, long-term randomized controlled trials are needed to further document the hypothetical effects of tadalafil on blood sugar control.


  • The study was supported by Hanmi Pharmaceutical, a company that markets a formulation of tamsulosin and tadalafil (Gugutams), which is indicated for erectile dysfunction.

  • Hanmi Pharmaceutical did not play any role in the design, conduct or analysis of the trial.

  • None of the authors made any disclosures.

This is a summary of a preprinted research study authored by researchers at Myongji Hospital in Goyang, Korea and Hanyang University Medical Center in Seoul, Korea on Research Square provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study is available on

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