# Sermorelin Dosage in the Clinical Research Literature > Sermorelin dosage as documented in published clinical research: pediatric GHD regimens, adult research doses, the ~12-minute plasma half-life, and subcutaneous administration in trials. ## Sermorelin Dosage in the Clinical Research Literature Sermorelin dosage as reported in the published clinical research falls into three distinct registers: pediatric treatment, pediatric provocative testing, and adult research. This section documents what was administered in published trials. It is not a recommendation and not a prescription; clinical decisions belong to clinicians and the regulatory environment surrounding compounded preparations is non-trivial. The canonical pediatric treatment dose is 30 mcg/kg subcutaneously at bedtime, once daily, as administered to 110 prepubertal children with idiopathic GHD by the Thorner / international multi-site study group [3]. The canonical pediatric diagnostic dose is 1 mcg/kg IV as a single provocative test bolus [6]. Adult research has used either weight-based doses — Khorram's 10 mcg/kg subcutaneously nightly for 16 weeks in nineteen adults aged 55-71 [9] — or fixed-microgram regimens reported in the range of 0.2-0.5 mg subcutaneously nightly in older-adult studies. #### Dosing in the Clinical Research Literature Pediatric GHD trials used 30 mcg/kg subcutaneously at bedtime [3]. Adult research has explored fixed-microgram doses; framing here is studied-at, not prescriptive. Vittone's elderly-male cohort used single nightly GHRH (1-29) injections [10]; Khorram's mixed-sex cohort used 10 mcg/kg subcutaneously nightly for 16 weeks [9]. ## Sermorelin Half-Life and Pharmacokinetics Sermorelin half-life in human plasma is short — approximately 11-12 minutes after intravenous or subcutaneous administration, with clearance of approximately 2.4-2.8 L/min, per Frohman and colleagues [5]. Tmax after subcutaneous dosing is roughly 5-20 minutes. Clearance is via rapid renal ultrafiltration and N-terminal proteolytic degradation. The key pharmacokinetic-pharmacodynamic finding: the GH-secretory effect substantially outlasts the peptide's plasma presence. Ishida and colleagues documented that the GH pulse continues 2-4 hours after a single subcutaneous Sermorelin injection, despite plasma Sermorelin clearing within approximately one hour [12]. The persistence reflects receptor-level signaling and downstream synthesis-release coupling, not continued circulating drug. PEGylation and D-Ala2 substitution have been the principal strategies for extending plasma half-life across the GHRH-analog class — the modified analogs of Esposito and colleagues and the trans-3-hexenoic acid stabilization that defines tesamorelin both addressed the rapid-clearance ceiling [13][16]. #### Sermorelin Half-Life Plasma half-life is short, on the order of 10-20 minutes, due to rapid proteolytic degradation; the GH-secretory effect persists longer than plasma levels would suggest [5][12]. The pharmacodynamic-pharmacokinetic mismatch is the central feature of Sermorelin pharmacology and the reason a 12-minute plasma half-life produces a 2-4-hour GH pulse. ## Subcutaneous Injection in Clinical Studies Sermorelin injection in published trials is overwhelmingly subcutaneous and overwhelmingly administered at bedtime. The mechanistic reason: endogenous GH release is largely nocturnal and pulsatile, and dosing at bedtime aligns the amplified GHRH signal with the body's intrinsic secretory rhythm. A second mechanistic constraint: continuous (non-pulsatile) administration produces tachyphylaxis at the somatotroph — the cell rapidly downregulates its response — while intermittent bedtime dosing preserves responsiveness over the course of months of treatment [18]. This is why pediatric GHD trials used nightly single subcutaneous injections rather than continuous infusion or twice-daily dosing. #### Route of Administration Subcutaneous injection, typically into the abdomen or thigh, administered at bedtime to align with the body's nocturnal GH pulse [3][9]. The provocative-testing literature uses the intravenous route for the 1 mcg/kg diagnostic bolus to obtain a rapid, time-defined GH response [6]. ## Editorial Pause: Why the Bedtime Pulsatile Regimen The bedtime intermittent regimen is not an accident of convention. It is the mechanistic consequence of two facts: GHRH-receptor tachyphylaxis under continuous exposure [18], and the nocturnal-dominant phase of endogenous GH release. Continuous-infusion GHRH analogs blunt the somatotroph response within hours; intermittent dosing aligned with the nocturnal pulse window preserves both responsiveness and physiological rhythm. This is also the mechanistic boundary that separates Sermorelin from longer-acting GHRH analogs. A longer half-life is not, in this class, an unambiguous improvement — it has to be matched against the tachyphylaxis constraint. Tesamorelin's longer half-life is paired with daily dosing in the HIV-lipodystrophy indication for the same physiological reason [13][18]. The pediatric Thorner cohort's bedtime regimen was not improvised either — it derived from the prior 1980s clinical pharmacology of GHRH, in which Vance and colleagues established that intermittent dosing schedules better preserve the somatotroph response than continuous infusion [18]. This is the rationale that survives across the entire GHRH-analog class: the timing of the signal matters as much as the amplitude. Adult research has occasionally explored alternative schedules — twice-daily dosing, morning dosing — but the bedtime nightly schedule remains the published-trial default for the same mechanistic reason. The Khorram 16-week adult cohort used 10 mcg/kg subcutaneously nightly at bedtime for this reason [9]; the Vittone elderly-male cohort used single nightly injections [10]. A clinician designing a research protocol around Sermorelin without engaging the tachyphylaxis and nocturnal-pulse constraints is likely to repeat avoidable methodological errors that the 1980s GHRH-analog literature already worked through. --- A bioluminescent reading room for the Sermorelin and GHRH (1-29) research record — pulsatile pharmacology read in the dark, cited line by line, and signed by no clinic and no vendor.