Plasma testosterone, Inhibin B and sexual function in men on methadone or buprenorphine maintenance for opioid dependence

Abstract

High dose methadone is known to suppress plasma testosterone (T). Buprenorphine is a new drug for the pharmacotherapy of opioid dependence. The influence of B on T and sexual function has not been investigated to date. Therefore, we investigated the incidence of hypogonadism and sexual dysfunction in men on methadone or buprenorphine maintenance. 37 were maintained on methadone (mean 88±16mg/day), 17 on buprenorphine (mean 11.2±4.3mg/day). 51 healthy blood donors served as controls. T analysis was carried out using blood samples obtained directly prior to the next opioide dosage between 08:00 and 10:00 a.m. using a chemiluminescence assay system (Immulite, DPC Los Angeles, USA). In addition LH, FSH, SHBG and Inhibin B were assayed. The impairment of libido and potency was quantified using a rating scale from 0 (not at all) to 6 (extremely). Suggested cut-of values of the sexual function questionnaire are: 0=no impairment of libido or potency; 1–2=mild, 3–4=moderate, 5–6=severe impairment of libido or potency. The Buprenorphine group had significant higher testosterone values compared to the methadone group (5.1±1.2 ng/ml versus 2.8±1.2 ng/ml; P=0,0001) it did not differ significantly from the healthy controls. SHBG levels were in the normal range in the treatment groups. Interestingly, Inhibin B did not differ between all groups. In patients maintained on methadone libido was reduced in 83% and potency in 72%, in the buprenorphine group 23% reported reduced libido and 15% reduced potency. The incidence of sexual dysfunction is high in men on methaodne maintenance and is mainly caused by methadone-induced hypogonadism. Inhibin B – a measure for sertoli-cell function – seemed not to be crucially affected by methadone. Buprenorphine does not appear to cause hypogonadism resulting in significantly less sexual dysfunction compared to addicts maintained on methadone.