Transdermal testosterone delivery: comparison between scrotal and nonscrotal delivery systems

Area of Science:

• Endocrinology
• Dermatology
• Pharmacokinetics

Background:

• Testosterone transdermal delivery systems (T-TDSs) are used for testosterone replacement therapy.
• Understanding the bioequivalence and pharmacokinetic profiles of different T-TDSs is crucial for optimizing treatment.

Purpose of the Study:

• To investigate the bioequivalence of two T-TDSs: Testoderm (scrotal) and Androderm (nonscrotal).
• To compare in vitro permeation and release kinetics, and in vivo pharmacokinetics in a minipig model.

Main Methods:

• In vitro skin permeation and release kinetics studies using minipig dorsal skin.
• In vivo pharmacokinetic studies in castrated Yucatan miniature swine (minipigs).
• Analysis of plasma testosterone profiles, including Cmax, AUC0-28, and time to reach Cmax.

Main Results:

• Testosterone permeated minipig skin via zero-order kinetics from both T-TDSs.
• The nonscrotal T-TDS exhibited a 13-fold higher permeation rate than the scrotal T-TDS.
• Significant differences in daily dose, Cmax, and AUC0-28 were observed, attributed to permeation rate differences.

Conclusions:

• The nonscrotal T-TDS delivers a significantly higher dose of testosterone compared to the scrotal T-TDS.
• Pharmacokinetic profiles differ due to dose delivery variations, not absorption rate differences.
• These findings highlight the importance of T-TDS design in determining therapeutic outcomes.