Effect of obesity on recombinant follicle-stimulating hormone absorption: subcutaneous versus intramuscular administration

To determine whether recombinant follicle-stimulating hormone (rFSH) should be administered intramuscularly (IM) or subcutaneously (SC) to obese women. Randomized, single-center, two-way crossover study. Academic clinical research center. Nineteen healthy women of reproductive age with body mass indices of 19.9 kg/m 2–42.8 kg/m 2. Leuprolide acetate 3.75 mg IM to achieve pituitary down-regulation as determined by serum E 2 levels. Subjects were then given a single dose of 300 IU rFSH either IM or SC. Multiple blood sampling was performed over the next two weeks, and after retreatment with leuprolide, a second 300 IU rFSH dose was given via the other administration route. Serum samples were analyzed in duplicate for follicle-stimulating hormone (FSH) using a standard radioimmunoassay in a single run. Maximum concentrations (C max), times to C max (T max), and extent of absorption (area under curve [AUC]) with IM vs. SC administration were compared using paired analysis. Maximal concentrations were achieved within 24 hours with both SC and IM routes. No significant differences were found in C max, T max, or AUC with SC vs. IM administration. A decline of AUC occurred among subjects of higher body mass index (BMI) with rFSH given either SC or IM. Subcutaneous administration achieved AUCs comparable to IM administration in both normal-weight and obese subjects. Our data indicate that the SC administration of rFSH is appropriate for women regardless of body mass.