Short answer: Somapacitan has a half-life of about 2 to 3 days in adults (about 34 to 37 hours in children). Levels peak 4 to 24 hours in adults (8 to 25 hours in children) after a dose. People vary, so treat these as estimates.
Somapacitan is a long-acting form of growth hormone. It is human growth hormone with a small fatty side chain that binds to albumin in the blood, which slows its removal so one injection lasts a week. It is sold as Sogroya (Novo Nordisk), injected under the skin once a week.
Also known as: Sogroya, somapacitan-beco.
Sogroya comes as ready-to-use prefilled pens in three strengths: 5 mg/1.5 mL (dialed in 0.025 mg steps up to 2 mg), 10 mg/1.5 mL (0.05 mg steps up to 4 mg) and 15 mg/1.5 mL (0.1 mg steps up to 8 mg). It is injected under the skin of the upper arm, thigh, belly or buttocks once a week, at any time of day, rotating the site each week. A missed dose can be given within 3 days; after that it is skipped and the next dose is taken on the usual day.
If you also use a powder peptide, the free peptide reconstitution calculator handles the vial math.
The Sogroya label approves somapacitan for children 2.5 years and older with growth failure from growth hormone deficiency, short stature after being born small for gestational age (SGA) with no catch-up growth by age 2, Noonan syndrome, or idiopathic short stature, and to replace growth hormone in adults with growth hormone deficiency. Label dosing: 0.16 mg/kg once a week for children with growth hormone deficiency and 0.24 mg/kg for SGA, Noonan syndrome and idiopathic short stature. Adults start at 1.5 mg once a week (1 mg over age 65, 2 mg for women on oral estrogen) and step up by about 0.5 to 1.5 mg every 2 to 4 weeks by IGF-1 and response, to at most 8 mg.
The label has no boxed warning. Its warnings, shared with daily growth hormone, cover higher death rates when started during acute critical illness (where it is not used), severe allergic reactions, growth of existing tumors and second tumors in childhood cancer survivors, higher blood sugar, raised pressure in the skull, fluid retention, low cortisol and thyroid changes, hip problems and scoliosis in children, pancreatitis, fat changes at injection sites, and sudden death in children with Prader-Willi syndrome. An eye exam is done before starting. In the adult trial, back pain was 10% vs 3.3% on placebo and joint pain 6.7% vs 1.6%. Full numbers are on the Sogroya side effects, Sogroya dosing schedule, missed Sogroya dose and Sogroya storage pages. Comparisons: Sogroya vs Ngenla, Skytrofa vs Sogroya and Sogroya vs daily growth hormone.
The Sogroya label gives an elimination half-life of about 2 to 3 days in adults with growth hormone deficiency, and a terminal half-life of about 34 hours in children with growth hormone deficiency (36 to 37 hours at 0.24 mg/kg in SGA, Noonan syndrome and idiopathic short stature). Peak levels come 4 to 24 hours after a dose in adults and 8 to 25 hours in children. Steady levels are reached after 1 to 2 weekly doses. Binding to albumin is what slows its removal.
Numbers shown are taken from the source above. Half-life varies from person to person and with injection site.
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