A European multicentre study to evaluate the tolerability of apomorphine sublingual administered in a forced dose-escalation regimen in patients with erectile dysfunction

Objective To determine the risk-benefit ratio of a forced dose-escalation regimen (2 to 3 to 4 mg) in a European clinical study evaluating apomorphine sublingual (SL) in treating erectile dysfunction (ED), by evaluating the overall tolerability and efficacy of the regimen compared with placebo in patients with ED, and evaluating efficacy by assessing the proportion of successful attempts resulting in sexual intercourse. Patients and methods This randomized, double-blind, two-arm, parallel-group study was conducted in 507 patients enrolled at 34 European sites. After a 1-2 week screening period, patients were treated for 8 weeks with either placebo or apomorphine SL administered as a forced dose-escalation regimen. Heterosexual men (aged 18-70 years) were eligible for participation in the study if they were in stable health, a stable relationship of greater than or equal to 6 months duration, had a history of erectile inability, and were diagnosed with ED (successful in fewer than half of attempts to attain and maintain an erection firm enough for intercourse during the 30 days before screening). Patients provided information (recorded on diary cards and reviewed at each study visit) about the frequency and success in achieving erections and of sexual intercourse attempts during both the screening and treatment periods. The dosing regimen required patients to take one tablet of apomorphine SL (2 mg for 2 weeks, then 3 mg for 2 weeks and finally 4 mg for the remaining 4 weeks) or placebo 15-25 min before intercourse, and intercourse was to be attempted at least twice a week. Safety data were collected throughout the 8-week study period, and included recording adverse events, vital signs and changes in laboratory test values for standard haematology and biochemistry variables. The primary efficacy variable was the proportion of successful attempts, defined as an erection rigid enough for sexual intercourse, occurring after dosing (successful intercourse rate). The proportion of erections achieved was a secondary efficacy variable. Results Of the 507 patients, 254 received apomorphine SL and 253 received placebo; 87% of patients in both groups completed the 8-week treatment period. Of the patients receiving apomorphine SL, 24% had hypertension, 11%, had coronary artery disease, 10% had diabetes, and 5.5% had benign prostatic hypertrophy; 62.6% of treated patients received concomitant medications for these maladies. The treatment groups were balanced for demographic and baseline variables, including comorbidity factors. Treatment-emergent adverse events, reported by > 5% of patients in the treated group, were nausea (9.8%), dizziness (7.1%) and headache (6.7%), compared with 0.4%, 2.4% and 4.0%, respectively, in the placebo group. Sixty-six patients withdrew from the study, 16 because of study drug-related adverse events (12 from the apomorphine and four from the placebo group). Six patients (three in each group) reported a total of nine serious treatment-emergent adverse events, all of which resolved by the end of the study. In the intention-to-treat population, the proportion of successful attempts at sexual intercourse and of erections were statistically greater in the apomorphine than in the placebo group (P = 0.001 and 0.021, respectively); analysis of the per-protocol population results confirmed this significant difference. Conclusion This European study supports the safety and tolerability of apomorphine SL despite the forced escalation to a 4-mg dose (exceeding the approved 2-3 mg dose). Adverse effects were not treatment-limiting. These results further support the clinically significant efficacy of apomorphine SL for treating ED at all doses used. The risk/benefit ratio supports apomorphine SL as a safe and effective alternative in managing ED.