Tadalafil in the Treatment of Erectile Dysfunction: EFFICACY

In: Drug

24 May 2010

The Padman-Nathan Study and Manufacturer’s Data

Tadalafil tablet was studied in the general ED population in seven randomized, multicenter, double-blind, placebo-controlled trials of 12 weeks’ duration. Two of the studies were conducted in the U.S., and five were conducted in centers outside the U.S.

The patients took tadalafil as needed, at doses ranging from 2.5 to 20 mg, up to once a day. They were free to choose the time of sexual attempts and the time interval between dosage administrations.

The three outcome measures were the erectile function (EF) domain of the International Index of Erectile Function (IIEF) and two questions from the Sexual Encounter Profile (SEP).

The IIEF questionnaire was administered over four weeks at the end of a treatment-free baseline period and subsequently at follow-up visits. In the IIEF erectile function domain, there is a 30-point total score, with higher scores reflecting better functioning.

The SEP is a diary in which patients record each sexual attempt made throughout the study. SEP Question 2 asks: “Were you able to insert your penis into your partner’s vagina?” SEP Question 3 asks, “Did your erection last long enough for you to have successful inter-course?”

The two U.S. efficacy and safety trials included 402 men with ED. Their average age was 59 years (range, ages 27 to 87). In these patients, ED was attributed to various causes, including organic and psychogenic disorders and those of mixed origin. The patients also had multiple comorbid conditions, including diabetes mellitus, hypertension, and other cardiovascular diseases.

Study A was conducted in academic centers, and Study B was conducted in community-based urology practices. In both trials, a 20-mg dose of tadalafil displayed clinically meaningful and statistically significant improvements in all of the efficacy variables.

The five efficacy and safety studies conducted in the general ED population outside the U.S. included 1,112 patients

(average age, 59 years; range, 21 to 82). The etiologic mechanisms were similar to those of the other group, and these patients also had various comorbid conditions. In the five trials, 5-, 10-, and 20-mg doses of tadalafil brought about statistically significant improvements.

The Govier Study

Govier et al. conducted a multicenter, randomized, double-blind, crossover study to compare patients’ preferences for tadalafil 20 mg or during the initial treatment of ED; 190 patients completed the study. The men were between 18 and 65 years of age. None of them had ever received tadalafil or sildenafil for ED or had undergone an inadequate trial of tadalafil at a maximum dose of 50 mg.

After a treatment-free screening period of one week, patients were randomly assigned to the first week treatment period with tadalafil 20 mg or sildenafil 50 mg. After a one-week to two-week washout period following the first treatment, they were switched to the alternative treatment for the second four-week period.

After completing the second treatment, the patients were asked: “Which treatment did you prefer?” Of the 190 patients, 66.3% preferred tadalafil 20 mg and 33.7% preferred sildenafil 50 mg.

The Porst Study

Porst and colleagues conducted a multicenter, randomized, double-blind, placebo-controlled, parallel-group study of 348 men (average age, 57 years) in Europe and the U.S. to examine the therapeutic effects of tadalafil on ED at 24 and 36 hours after dosing. The participants were randomly assigned to two four-week treatment intervals, during which they were asked to attempt sexual intercourse approximately 24 and 36 hours after taking or placebo.

The main outcome measure was the number of successful sexual intercourse attempts (completed to ejaculation) according to the patients’ self-report using the SEP diary. At 24 hours, for the tadalafil group, 52.9% of intercourse attempts were successful; for the placebo group, 29.1% of attempts succeeded. At approximately 36 hours after treatment, the proportion of successful intercourse attempts for the tadalafil patients was 59.2%; it was 28.3% for the placebo patients.

The results indicate that tadalafil 20 mg is effective for ED, with a period of responsiveness of up to 36 hours.

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