title: Long-term pharmacokinetics of transdermal testosterone gel in hypogonadal men.
abstract: Transdermal delivery of testosterone (T) represents an effective alternative to injectable androgens. Transdermal T patches normalize serum T levels and reverse the symptoms of androgen deficiency in hypogonadal men. However, the acceptance of the closed system T patches has been limited by skin irritation and/or lack of adherence. T gels have been proposed as delivery modes that minimize these problems. In this study we examined the pharmacokinetic profiles after 1, 30, 90, and 180 days of daily application of 2 doses of T gel (50 and 100 mg T in 5 and 10 g gel, delivering 5 and 10 mg T/day, respectively) and a permeation-enhanced T patch (2 patches delivering 5 mg T/day) in 227 hypogonadal men. This new 1% hydroalcoholic T gel formulation when applied to the upper arms, shoulders, and abdomen dried within a few minutes, and about 9-14% of the T applied was bioavailable. After 90 days of T gel treatment, the dose was titrated up (50 mg to 75 mg) or down (100 mg to 75 mg) if the preapplication serum T levels were outside the normal adult male range. Serum T rose rapidly into the normal adult male range on day 1 with the first T gel or patch application. Our previous study showed that steady state T levels were achieved 48-72 h after first application of the gel. The pharmacokinetic parameters for serum total and free T were very similar on days 30, 90, and 180 in all treatment groups. After repeated daily application of the T formulations for 180 days, the average serum T level over the 24-h sampling period (C(avg)) was highest in the 100 mg T gel group (1.4- and 1.9-fold higher than the C(avg) in the 50 mg T gel and T patch groups, respectively). Mean serum steady state T levels remained stable over the 180 days of T gel application. Upward dose adjustment from T gel 50 to 75 mg/day did not significantly increase the C(avg), whereas downward dose adjustment from 100 to 75 mg/day reduced serum T levels to the normal range for most patients. Serum free T levels paralleled those of serum total T, and the percent free T was not changed with transdermal T preparations. The serum dihydrotestosterone C(avg) rose 1.3-fold above baseline after T patch application, but was more significantly increased by 3.6- and 4.6-fold with T gel 50 and 100 mg/day, respectively, resulting in a small, but significant, increase in the serum dihydrotestosterone/T ratios in the two T gel groups. Serum estradiol rose, and serum LH and FSH levels were suppressed proportionately with serum T in all study groups; serum sex hormone-binding globulin showed small decreases that were significant only in the 100 mg T gel group. We conclude that transdermal T gel application can efficiently and rapidly increase serum T and free T levels in hypogonadal men to within the normal range. Transdermal T gel provided flexibility in dosing with little skin irritation and a low discontinuation rate.
authors.affiliation: Divisions of Endocrinology, Departments of Medicine/Pediatrics, Harbor-University of California-Los Angeles Medical Center, Torrance, California 90509, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Swerdloff
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.forename: G
authors.initials: G
authors.lastname: Cunningham
authors.forename: A
authors.initials: A
authors.lastname: Dobs
authors.forename: A
authors.initials: A
authors.lastname: Iranmanesh
authors.forename: A M
authors.initials: AM
authors.lastname: Matsumoto
authors.forename: P J
authors.initials: PJ
authors.lastname: Snyder
authors.forename: T
authors.initials: T
authors.lastname: Weber
authors.forename: J
authors.initials: J
authors.lastname: Longstreth
authors.forename: N
authors.initials: N
authors.lastname: Berman
mesh_terms: D000279:Administration, Cutaneous; D000328:Adult; D000368:Aged; D001682:Biological Availability; D013196:Dihydrotestosterone / Q000097:blood; D004958:Estradiol / Q000097:blood; D005782:Gels; D006801:Humans; D007006:Hypogonadism / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D013739:Testosterone / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D005782:Gels; D012738:Sex Hormone-Binding Globulin; D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol; D007986:Luteinizing Hormone