Divalproex sodium attenuates growth hormone response to baclofen in healthy human males

The effect of divalproex sodium (DVP) on gamma-aminobutyric acid-B (GABAB) receptor function in humans was assessed by measuring growth hormone (GH) responses to a challenge with a GABAB receptor agonist, baclofen, in 10 male healthy volunteers. Each subject received 20 mg of baclofen at 10:00 A.M., and blood samples were collected for measuring GH before and 30, 60, 90, 120, 150, 180 min after baclofen administration. The baclofen challenge test was repeated after 1 week of treatment with DVP (1000 mg/day). The results showed that the plasma GH response to baclofen was significantly attenuated by the DVP treatment and that the degree of attenuation was positively correlated with the blood levels of valproic acid. Our findings suggest that DVP downregulates hypothalamic GABAB receptor function in humans.