Pharmacokinetics and pharmacodynamics of a single dose of recombinant human growth hormone after subcutaneous administration by jet-injection: comparison with conventional needle-injection.

The pharmacokinetics and pharmacodynamics of recombinant human growth hormone (rhGH) were studied after a single subcutaneous dose given by jet-injection, and have been compared with the results obtained after conventional needle-injection. Twelve healthy male volunteers completed an open label, randomised, two-way crossover study, with a 7-day washout period between the two single sc doses. Pharmacokinetic parameters were derived from rhGH concentrations in blood samples collected regularly over 24 h after dosing on Day 1 of each period. To investigate the pharmacodynamics, additional samples were taken for the analysis of somatomedin C (IGF-I) and free fatty acids (FFA). A higher and earlier Cmax was found after jet-injection (ratio (%) jet-injected/needle-injected 124; 90%-confidence interval 108-142). The AUC0-infinity for rhGH were similar (ratio (%) jet-injected/needle-injected 98; 90%-confidence interval 93-103). Both treatments were associated with a significant and similar rise in IGF-I. Both administrations of rhGH were associated with identical rhythmical changes in FFA. The study indicates that jet-injected and needle-injected rhGH are bioequivalent with respect to the amount absorbed. The criterion for bioequivalence is not met for the rate of absorption. It is unlikely that the latter finding will influence the pharmacodynamics of rhGH, since bioequipotency was established for the effect on IGF-I generation. Jet-injection was safe in use and was generally well tolerated.