Testosterone undecanoate: a useful tool for testosterone administration in rats

Area of Science:

• Pharmacology
• Endocrinology
• Animal Models

Background:

• Maintaining stable serum testosterone levels in experimental animals is challenging.
• Exogenous testosterone administration requires optimized formulations for sustained release.

Purpose of the Study:

• To investigate the pharmacokinetic properties of different testosterone formulations in male rats.
• To compare the efficacy of testosterone undecanoate (TUD), testosterone pellets (TP), and testosterone propionate (Tprop) for sustained testosterone delivery.

Main Methods:

• Two studies were conducted in male Wistar rats (orchiectomised and non-orchiectomised).
• Rats received various doses of TUD (s.c. or i.m.), TP (s.c. pellets), or Tprop (s.c. injection).
• Serum testosterone levels were measured periodically over 4-6 weeks.

Main Results:

• Testosterone undecanoate (TUD) demonstrated favorable, continuous steady-state serum levels for several weeks.
• Testosterone pellets (TP) showed shorter-than-expected duration of elevated testosterone with high inter-individual variability.
• Testosterone propionate (Tprop) resulted in only a transient increase in serum testosterone.

Conclusions:

• A single TUD injection (100 mg/kg s.c.) effectively induces physiological testosterone levels in orchiectomised rats for at least four weeks.
• High-dose TUD (500 mg/kg i.m.) achieves supraphysiological anabolic testosterone concentrations for up to six weeks in non-orchiectomised rats.
• TUD is superior to other tested formulations, offering a convenient and effective method for testosterone administration in experimental animals.