ORIGINAL RESEARCH—PSYCHOLOGY: Sensitivity of the Psychological and Interpersonal Relationship Scales to Oral Therapies for Erectile Dysfunction


Ann Cameron, PhD, Eli Lilly & Company—Outcomes Research, Lilly Corporate Center Drop Code 5024, Indianapolis, IN 46285 USA. Tel: (317) 651-5419; Fax: (317) 277-7444; E-mail: cameronae@lilly.com


Introduction.  Studies of erectile dysfunction (ED) therapies typically assess erectile function end- points, although other treatment outcomes may also be of value to men and their partners.

Aim.  To examine the treatment sensitivity of the Psychological and Interpersonal Relationship Scales (PAIRS) associated with the use of two phosphodiesterase type 5 (PDE5) inhibitors with different duration of action.

Methods.  Men with ED were recruited from three clinical trials of tadalafil and sildenafil citrate to complete post-treatment questionnaires that included the PAIRS. In study 1, the PAIRS was assessed after 6 months of open-label tadalafil (20 mg) treatment and after 2 months of real-world sildenafil use (25–100 mg). In studies 2 and 3, the PAIRS was assessed at the end of the trial assessment phase. In study 2, men with a 6–24 week history of sildenafil use (25–100 mg) received 3 weeks of open-label sildenafil treatment (dosage at study entry), and then switched to 9 weeks of tadalafil treatment. In study 3, a double-blind, crossover study, men were randomized to 12 weeks of either tadalafil (20 mg) or sildenafil (50 mg) treatment, followed by 12 weeks of the alternate treatment; PAIRS scores for the second treatment period were evaluated.

Main Outcome Measure.  Treatment outcomes were assessed with the PAIRS, a new reliable and valid self-report measure of sexual self-confidence, spontaneity, and time concerns before sex.

Results.  Significant mean differences were observed on all PAIRS domain scores associated with tadalafil and sildenafil treatment. Across studies, men had significantly higher sexual self-confidence and spontaneity scores, and lower time concerns scores in reference to tadalafil compared with their scores in reference to sildenafil.

Conclusions.  Mean differences observed on PAIRS domains across studies support the sensitivity of the measure to differentiate between these two ED treatments.