Three studies were performed using a fast dissolving formulation of selegiline hydrochloride designed for buccal absorption "Zydis Selegiline". The aim of the first study was to compare the therapeutic efficacy of Zydis Selegiline (1.25 mg or 10 mg) with conventional selegiline hydrochloride tablets "conventional selegiline tablets" (10 mg) in patients with Parkinson's disease (PD) who were previously treated with conventional selegiline tablets as an adjunct to levodopa/dopamine agonist therapy. Patients were observed for 4 weeks to ensure that they were stable. Stable patients (n=197) were then randomised to continue with conventional selegiline tablets 10 mg (n=68), or to treatment with Zydis Selegiline 1.25 mg (n=64) or Zydis Selegiline 10 mg (n=62) for 12 weeks in this randomised, parallel group study. A further aim was to establish the acceptability of Zydis Selegiline compared with conventional selegiline tablets. Patient preference for Zydis Selegiline was also evaluated in a second study, a single-dose, randomised, two-way crossover study conducted in patients with PD (n=148). Patients were stratified by the presence or absence of swallowing and salivation problems and were randomised to either Zydis Selegiline 5 mg or a placebo fast-dissolving formulation. In a third study, the degree of potentiation of the tyramine pressor effect following Zydis Selegiline was compared with that following conventional selegiline tablets in healthy volunteers. A total of 24 healthy volunteers were randomised to receive Zydis Selegiline 1.25 mg or conventional selegiline tablets 10 mg for 14-16 days in an open-label, randomised parallel group study. Both Zydis Selegiline (1.25 mg and 10 mg) treatments were shown to be therapeutically equivalent to conventional selegiline tablets 10 mg based on comparison of mean total Unified Parkinson's Disease Rating Scale (UPDRS) scores. Therapeutic equivalence was defined a priori as the 90% confidence interval (CI) for the difference in total UPDRS scores between groups to lie entirely within the range +/-5. The difference (90% CI) in mean adjusted total UPDRS between Zydis Selegiline 1.25 mg and conventional selegiline tablets 10 mg was -2.50 (-4.84, -0.17), and for Zydis Selegiline 10 mg and conventional selegiline tablets 10 mg, 0.04 (-2.30, 2.38). For the motor subscores of the UPDRS, differences between adjusted means (90% CI) compared with the conventional selegiline tablets group were: Zydis Selegiline 1.25 mg, -2.14 (-3.94, -0.33) and Zydis Selegiline 10 mg, -0.90 (-2.70, +0.91). Patients who switched from conventional selegiline tablets to Zydis Selegiline 1.25 mg showed a slight improvement in UPDRS scores following 12 weeks of treatment (standard error of difference 1.039; p=0.01). In the single-dose crossover study, most (61%) patients liked Zydis Selegiline 5 mg; a significantly greater proportion than the null hypothesis of 50% (p<0.002). However, only 62 patients (46%) indicated that they liked the taste of Zydis Selegiline. Nevertheless, the proportion of patients who preferred Zydis Selegiline (65%) to their usual medication was significantly greater than the null hypothesis of 50% (p<0.001). Similar findings were demonstrated in the 12-week study where a higher proportion of patients who received up to 3 months of treatment indicated a preference for either Zydis Selegiline 1.25 mg (90%) or Zydis Selegiline 10 mg (86%) over conventional selegiline tablets 10 mg. More than 90% of patients found Zydis Selegiline easy to take, with 61% rating it as extremely easy. Most (81%) patients taking Zydis Selegiline 1.25 mg liked the taste compared with 45% taking Zydis Selegiline 5 mg (in the previous study). Zydis Selegiline did not potentiate the tyramine effect: a pressor effect was elicited after 400 mg tyramine both before and after 14 days of treatment with Zydis Selegiline 1.25 mg. In contrast, after 14 days treatment with conventional selegiline tablets 10 mg, the threshold dose required to elicit the tyramine pressor response was significantly (p<0.0001) reduced from 400 mg to 200 mg. In summary, Zydis Selegiline at doses of 1.25 mg and 10 mg was therapeutically equivalent to conventional selegiline tablets 10 mg. The Zydis Selegiline formulation was well-liked by all patients, with most preferring Zydis Selegiline 1.25 mg to their usual selegiline tablet. Furthermore, Zydis Selegiline was well tolerated and, unlike conventional selegiline tablets, appeared to retain specificity for inhibition of monoamine oxidase type B (MAO-B), since it did not potentiate the pressor response to tyramine.