In dogs, a new compound called L-692,585 caused a big jump in growth hormone (GH) levels—up to 21 times higher than a salty control—and was 2‑2.5 times more powerful than the well‑known peptide GHRP‑6. The GH spike happened within 5‑15 minutes and fell back to normal by about 90 minutes. Giving the drug every day for two weeks kept boosting GH without any sign of the body getting used to it. This shows that GHRP‑6 does raise GH, but newer non‑peptide drugs can do it even stronger.

L-692,585 is a 2-hydroxypropyl derivative of L-692,429, both novel non-peptidyl growth hormone (GH) secretagogues. The effects of single and repeated intravenous administration of L-692,585 on serum or plasma GH and other hormones in beagles were evaluated. In a balanced 8-dog dose-ranging study, compared to the saline control with a mean (+/- S.E.M.) after-dose serum GH peak of 6.1 +/- 1.3 ng/ml, L-692,585 significantly increased (P < 0.05) peak GH concentrations 4.3-fold (32.5 +/- 7.0 ng/ml) at a dose of 0.005 mg/kg, 7-fold (49.4 +/- 10.6 ng/ml) at a dose of 0.02 mg/kg, and 21-fold (134.3 +/- 29.0 ng/ml) at a dose of 0.10 mg/kg. Total GH release, expressed as area under the curve, showed a similar dose-dependent increase. Peak GH levels were recorded at 5 or 15 min after dosing with the levels returning to near baseline by 90 min. Serum cortisol levels were increased above saline control levels in a dose-dependent manner; however, the increases were modest compared to the GH increases. Based on peak responses and total GH release, L-692,585 was 10- to 20-fold and 2- to 2.5-fold more potent than L-692,429 and the growth hormone releasing peptide, GHRP-6, respectively. When L-692,585 was administered once daily for 14 consecutive days at 0, 0.01 or 0.10 mg/kg to each of 6 dogs, peak plasma GH levels and total GH release on days 1, 8 and 15 significantly increased in a dose-dependent manner, and no desensitization was evident.(ABSTRACT TRUNCATED AT 250 WORDS)