A multi-institutional observational study of testosterone levels after testosterone pellet (Testopel(®)) insertion

Implantable testosterone pellets were approved by the Food and Drug Administration in 1972 for the treatment of testosterone deficiency syndrome (TDS). Clinical use of this testosterone delivery modality has been limited until its recent reintroduction (Testopel(®) , Slate Pharmaceuticals, Durham, NC, USA). Six academic institutions collaborated and combined their databases to more fully characterize serum testosterone levels after the pellet implantations.

To assess the time-dependent serum testosterone levels after subcutaneous testosterone pellets in clinical practice for the treatment of TDS.

Data were retrospectively pooled and analyzed from data in six academic institutions. Variables included patient age, total testosterone concentrations before and after implantation, the number of testosterone pellets implanted, and the time from implantation to measurement of serum testosterone concentrations. Three hundred eighty men undergoing 702 insertions were included for analysis using JMP (version 4.0.4; SAS Institute, Cary, NC, USA).

Main outcome measures were postimplantation total testosterone levels and investigator-reported adverse events. Testosterone levels as a function of the number of pellets implanted and time from implantation were assessed.

Implantation of six to ≥10 testosterone pellets (450 to ≥750 mg) increased total testosterone into the therapeutic range at 1 month postimplantation and sustained therapeutic levels (>300) for 4-6 months. Higher pellet numbers (10-12 pellets) were associated with higher, more consistent, and longer maintenance of testosterone levels within the therapeutic range. Four extrusions and three hematomas were reported early in our experience; other investigator-reported adverse events were generally mild to moderate in nature and transient in duration. No subjects required analgesics.

Testosterone pellets (Testopel(®) , Slate Pharmaceuticals) provide sustained levels of testosterone for at least 4 months and up to 6 months in men with TDS. Implantation of ≥8 pellets achieved optimal results with respect to peak mean testosterone level and duration of effect. Testosterone pellets were generally well tolerated.