Study summary · research use only
Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
This study compared the pharmacokinetics of three new peptidyl growth hormone secretagogues-ipamorelin (NNC 26-0161), NNC 26-0194 and NNC 26-0235-with the hexapeptides GHRP-2 and GHRP-6 in the male rat by different routes. The abstract reports that after i.v. bolus, plasma concentrations declined biexponentially; ipamorelin had a systemic plasma clearance 5-fold lower than GHRP-6 and was mainly excreted in urine, whereas GHRP-6 was predominantly excreted in bile. Ipamorelin and the two NNC peptides were moderately resistant to metabolism, with 60-80% recovered intact from bile and urine. After intranasal application, ipamorelin bioavailability was estimated at approximately 20%, with approximately 50% for NNC 26-0235, NNC 26-0194 and GHRP-2, and lower for GHRP-6. The authors describe the nasal route as promising for systemic delivery.
Abstract
1. The pharmacokinetics of three new peptidyl growth hormone secretagogues, ipamorelin (NNC 26-0161), NNC 26-0194 and NNC 26-0235, were compared with two well-known hexapeptides, GHRP-2 and GHRP-6, in the male rat following different routes of administration. 2. Following i.v. bolus injection, plasma concentrations of the peptides declined biexponentially. Ipamorelin differed markedly from the other peptides investigated, demonstrating a systemic plasma clearance 5-fold lower than that of GHRP-6. Ipamorelin was mainly excreted in the urine, whereas GHRP-6 was predominantly excreted in the bile. NNC 26-0194 and NNC 26-0235 also showed high biliary excretions. Ipamorelin and the two NNC peptides were moderately resistant towards metabolism as 60-80% of the administered dose could be recovered from bile and urine as intact peptide. 3. After intranasal application, the bioavailability of ipamorelin was estimated at approximately 20%. Higher bioavailabilities of approximately 50% were determined for NNC 26-0235, NNC 26-0194 and GHRP-2, whereas the nasal absorption of GHRP-6 was somewhat lower. Thus, the peptides could be easily transported across the nasal epithelium suggesting that the nasal route seems promising for systemic delivery of this family of peptidyl growth hormone secretagogues.
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