Source comparison
MK-677 Absorption Kinetics: Fed vs Fasted State
MK-677 (ibutamoren mesylate) is a non-peptide growth hormone secretagogue with oral bioavailability of approximately 60–70% regardless of fed state. But the rate of absorption changes significantly. A crossover trial comparing fasted vs postprandial dosing fou
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- MK-677 (ibutamoren mesylate) is a non-peptide growth hormone secretagogue with oral bioavailability of approximately 60–70% regardless of fed state. But the rate of absorption changes significantly. A crossover trial comparing fasted vs postprandial dosing found that Tmax (time to peak concentration) decreased from 2.9 hours fed to 2.1 hours fasted, while Cmax increased by 18%. The mechanism: food in the stomach delays gastric emptying, which slows but does not prevent MK-677 transit to the duodenum where absorption occurs.
- The growth hormone response follows plasma concentration closely. Dosing MK-677 on an empty stomach produces sharper, earlier GH pulses. Peak serum GH levels occur 90–120 minutes post-dose fasted vs 150–180 minutes fed. For research applications targeting acute GH elevation (sleep architecture studies, metabolic flux measurement), fasted morning dosing maximises the signal window. For chronic administration focused on IGF-1 elevation over weeks, the fed vs fasted difference in cumulative exposure is negligible. Area under the curve (AUC) over 24 hours differs by less than 8%.
- What changes dramatically is side effect incidence. The same trial noted that nausea scores on a 10-point visual analog scale averaged 1.8 in fed subjects vs 4.2 in fasted subjects during the first two weeks of 25mg daily dosing. This isn't a trivial difference. It's the threshold where dropout rates begin climbing in trials.