Christoph Arth

Comparison of the bioavailability and adhesiveness of different rotigotine transdermal patch formulations

Abstract Objective: Rotigotine transdermal patch is approved for the treatment of early and advanced idiopathic Parkinson’s disease (PD) and moderate-to-severe idiopathic restless legs syndrome (RLS). A cold chain manufacturing and distribution process was temporarily implemented in 2008, as this reduced the crystal formation reported within patches stored at room temperature. In order to overcome the crystallization issue and meet EMA and FDA requirements, a new room temperature stable formulation was developed. The three studies reported here were conducted to determine whether the new room temperature stable patch demonstrated similar bioavailability and adhesiveness to the original and intermediate patches. Methods: Data are reported from three cross-over studies that compared the original, cold chain and room temperature stable patch. Two open-label bioequivalence studies investigated the 2 mg/24 h dosage in healthy individuals (SP951, n = 52 [Clinicaltrials.gov: NCT00881894]; SP0987, n = 50 [NCT01059903]) and a double-blind patch adhesiveness study investigated the 8 mg/24 h dosage in patients with PD (SP1066, n = 56 [NCT01338896]). Results: Plasma concentration–time curves and geometric means for pharmacokinetic parameters were similar for the cold chain vs. original patch in SP951 (AUC(0–tz): 2.68 vs. 2.71 ng/mL*h; point estimate: 0.99 [90% confidence interval (CI): 0.91, 1.07]) (Cmax: 0.131 vs. 0.136 ng/mL; 0.96 [0.89, 1.04]) and for the room temperature stable vs. cold chain patch in SP0987 (AUC(0–tz): 4.51 vs. 4.87 ng/mL*h; 0.90 [0.84, 0.97]) (Cmax: 0.23 vs. 0.23 ng/mL; 0.95 [0.88, 1.02]). In both studies, 90% CIs for ratios of AUC(0–tz) and Cmax were within the bioequivalence acceptance range (0.8–1.25). In SP1066, overall median adhesiveness scores were similar for cold chain (0.5 [range: 0–4]) and room temperature stable (0 [0–4]) formulations. Conclusion: These results demonstrated bioequivalence and indicated similar adhesiveness of the approved room temperature stable rotigotine patch with the original and cold chain patches. Potential limitations include the enrolment of healthy volunteers in the bioequivalence studies, as these individuals were likely to be younger than the general PD or RLS population.

Validation of Freeze-Drying to Visualize Percutaneous 3H-Estradiol Transport: The Influence of Skin Hydration on the Efficacy of the Method

A study was made of the validity of freeze-drying to visualize the distribution of 3H-estradiol in human stratum corneum after topical application of a dry dose, a patch or a buffer solution. Each of these donor formulations was applied to human dermatomed skin for 24 h using Franz permeation cells. Subsequently, small pieces of skin were subjected to cryofixation, freeze-drying, osmium tetroxide vapor fixation, Spurr resin embedding and electron microscopic autoradiography. Stratum corneum from dry dose and patch application experiments was well preserved by freeze-drying, allowing an accurate localization of 3H-estradiol. In contrast, stratum corneum from buffer solution experiments suffered from cryofixation artifacts due to excessive hydration of the skin. The corresponding autoradiographs showed strong redistribution of 3H-estradiol. Thus, the visualization method under investigation has its limitations regarding the hydration level of the skin.