Objective: To investigate the acceptability and pharmacokinetics (PK) of SC injection of TU.

Design: Randomized sequence, crossover clinical study of SC vs IM TU injections.

Setting: Ambulatory clinic of an academic andrology center.

Participants: Twenty men (11 hypogonadal, 9 transgender men) who were long-term users of TU. injections. Intervention: Injection of 1000 mg TU (in 4 mL castor oil vehicle) by SC or IM route. Main Outcome Measures: Patient-reported pain, acceptability, and preference scales. PK by measurement of serum testosterone, dihydrotestosterone (DHT), and estradiol (E2) concentrations with application of population PK methods and dried blood spot (DBS) sampling.

Results: Pain was greater after SC compared with IM injection 24 hours (but not immediately) after injection but both routes were equally acceptable. Ultimately 11 preferred IM, 6 preferred SC, and 3 had no preference. The DBS-based PK analysis of serum testosterone revealed a later time of peak testosterone concentration after SC vs IM injection (8.0 vs 3.3 days) but no significant route differences in model-predicted peak testosterone concentration (8.4 vs 9.6 ng/mL) or mean resident time (183 vs 110 days). The PK of venous serum testosterone, DHT, and E2 did not differ according to route of injection.

PATIENTS AND METHODS: A total of 120 men, aged 40-70 years, with TD (serum total testosterone [TT] ≤ 12 nmol/L) were randomised to receive either i.m. TU (1000 mg) or placebo. In all, 58 and 56 men in the placebo and treatment arm, respectively, completed the study. Participants were seen six times in the 48-week period and the following data were collected: physical examination results, haemoglobin, haematocrit, TT, lipid profile, fasting blood glucose, sex hormone-binding globulin, liver function test, prostate- specific antigen (PSA) and adverse events.

RESULTS: The mean (sd) age of the participants was 53.4 (7.6) years. A significant increase in serum TT (P < 0.001), PSA (P = 0.010), haematocrit (P < 0.001), haemoglobin (P < 0.001) and total bilirubin (P = 0.001) were seen in the treatment arm over the 48-week period. Two men in the placebo arm and one man in the treatment arm developed myocardial infarction. Common adverse events observed in the treatment arm included itching/swelling/pain at the site of injection, flushing and acne. Overall, TU injections were well tolerated.

DESIGN: A 4-site, prospective randomized double-blind, placebo-controlled trial was conducted among prison and jail inmates with HIV and OUD transitioning to the community from September 2010 through March 2016.

METHODS: Eligible participants (N = 93) were randomized 2:1 to receive 6 monthly injections of XR-NTX (n = 66) or placebo (n = 27) starting at release and observed for 6 months. The primary outcome was the proportion that maintained or improved VS (<50 copies/mL) from baseline to 6 months.

RESULTS: Participants allocated to XR-NTX significantly improved to VS (<50 copies/mL) from baseline (37.9%) to 6 months (60.6%) (P = 0.002), whereas the placebo group did not (55.6% at baseline to 40.7% at 6 months P = 0.294). There was, however, no statistical significant difference in VS levels at 6 months between XR-NTX (60.6%) vs. placebo (40.7%) (P = 0.087). After controlling for other factors, only allocation to XR-NTX (adjusted odds ratio = 2.90; 95% confidence interval = 1.04 to 8.14, P = 0.043) was associated with the primary outcome. Trajectories in VS from baseline to 6 months differed significantly (P = 0.017) between treatment groups, and the differences in the discordant values were significantly different as well (P = 0.041): the XR-NTX group was more likely than the placebo group to improve VS (30.3% vs. 18.5%), maintain VS (30.3% vs. 27.3), and less likely to lose VS (7.6% vs. 33.3%) by 6 months.