Somatropin-injection
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Precautions
Clinical pharmacology
Mechanism Of Action
Somatropin (as well as endogenous growth hormone) binds to dimeric growth hormone receptors located within the cell membranes of target tissue cells resulting in intracellular signal transduction and a host of pharmacodynamic effects. Some of these pharmacodynamic effects are primarily mediated by IGF-1 produced in the liver and also locally (e.g., skeletal growth, protein synthesis), while others are primarily a consequence of the direct effects of somatropin (e.g., lipolysis) [see Pharmacodynamics].
Pharmacodynamics
Tissue GrowthSkeletal Growth: SAIZEN stimulates skeletal growth in prepubertal children with pituitary growth hormone deficiency. Skeletal growth is accomplished at the epiphyseal plates at the ends of long bone. Growth and metabolism of epiphyseal plate cells are directly stimulated by growth hormone and one of its mediators, insulin-like growth factor-1. Serum levels of insulin-like growth factor-1 (IGF-1) are low in children and adolescents who are growth hormone deficient, but increase during treatment with SAIZEN. Linear growth continues until the growth plates fuse at the end of puberty.
Cell Growth: Treatment with pituitary-derived human growth hormone results in an increase in both the number and the size of skeletal muscle cells.
Organ Growth: Somatropin influences the size and function of internal organs and increases red cell mass.
Protein MetabolismLinear growth is facilitated in part by increased cellular protein synthesis. This is reflected by increased cellular uptake of amino acids and nitrogen retention as demonstrated by a decline in urinary nitrogen excretion and blood urea nitrogen during somatropin therapy.
Carbohydrate MetabolismSomatropin is a modulator of carbohydrate metabolism. Children with inadequate secretion of growth hormone sometimes experience fasting hypoglycemia that is improved by treatment with somatropin. SAIZEN therapy may decrease glucose tolerance. Administration of SAIZEN to normal adults and patients with growth hormone deficiency resulted in transient increases in mean serum fasting and postprandial insulin levels. However, glucose levels remained in the normal range.
Lipid MetabolismAcute administration of somatropin to humans results in lipid mobilization. Nonesterified fatty acids increase in plasma within one hour of SAIZEN administration. In growth hormone deficient patients, long-term somatropin administration often decreases body fat. Mean cholesterol levels decreased in patients treated with SAIZEN. The clinical significance of this decrease in cholesterol level is unknown.
Mineral MetabolismSomatropin administration results in the retention of total body potassium, phosphorus, and sodium. Serum calcium levels appear to be unaffected.
Connective Tissue/Bone MetabolismSomatropin stimulates the synthesis of chondroitin sulfate and collagen as well as the urinary excretion of hydroxyproline.
Pharmacokinetics
AbsorptionThe absolute bioavailability of somatropin after subcutaneous administration ranges between 70 to 90%.
DistributionThe steady-state volume of distribution (mean +SD) of somatropin following intravenous administration in healthy volunteers was estimated to be 12.0 ± 1.08 L.
MetabolismThe metabolic fate of somatropin involves classical protein catabolism in both the liver and kidneys. In renal cells, at least a portion of the breakdown products is returned to the systemic circulation. The mean half-life of intravenous somatropin in normal males is around 0.6 hours, whereas subcutaneously and intramuscularly administered somatropin has a half-life of around 2 hours. The longer half-life observed after subcutaneous or intramuscular administration is due to slow absorption from the injection site.
ExcretionThe clearance (mean +SD) of intravenously administered somatropin in six normal male volunteers was 14.6 ± 2.8 L/hr.
Specific Populations
Pediatric - The pharmacokinetics of somatropin is similar in children and adults. However, no pharmacokinetic studies of SAIZEN have been conducted in pediatric patients.
Gender - No gender studies have been performed in children for somatropin. In adults, the clearance of somatropin in both men and women tends to be similar. However, no studies have been conducted to evaluate the effect of gender on pharmacokinetics of SAIZEN.
Race - No studies have been conducted to determine the effect of race on the pharmacokinetics of SAIZEN.
Renal Impairment - Children and adults with chronic renal failure tend to have decreased somatropin clearance compared to those with normal renal function. However, no studies have been conducted to evaluate the effect of renal impairment on the pharmacokinetics of SAIZEN.
Hepatic Impairment - A reduction in somatropin clearance has been noted in patients with hepatic dysfunction as compared with normal controls.
Clinical Studies
Adult Growth Hormone Deficiency (GHD)A multicenter, randomized, double-blind, placebo-controlled clinical trial was conducted in 115 adults with growth hormone deficiency comparing the effects of SAIZEN and placebo on body composition. Patients in the active treatment arm were treated with SAIZEN at an initial dose of 0.005 mg/kg/day for one month which was increased to 0.01 mg/kg/day if tolerated for the remaining five months of the study. The primary endpoint was the change from baseline in lean body mass measured by dual energy X-ray absorptiometry (DXA) after 6 months. Treatment with SAIZEN produced significant (p < 0.001) increases from baseline in LBM compared to placebo (Table 2).
Table 2 : Lean Body Mass (kg) by DXA
| SAIZEN (n=52) | Placebo (n=51) | |
| Baseline (mean) | 47.7 | 54.0 |
| Change from baseline at 6 months (mean) | +1.9 | -0.2 |
| Treatment difference (mean) | 2.1 | |
| 95% confidence interval | (1.3, 2.9) | |
| p-value | < 0.001 | |
Sixty-seven (58%) of the 115 randomized patients were male. The adjusted mean treatment difference on the increase in lean body mass from baseline was significantly greater in males (2.9 kg) than females (0.8 kg).
Ninety-seven (84%) of the 115 randomized patients had adult onset GHD. The adjusted mean treatment differences on the increase in lean body mass from baseline were not significantly different in AO GHD (2.1 kg) compared with childhood onset GHD (1.0 kg) patients. However, there were relatively few patients with childhood onset GHD (n=18) on which to base the comparison.
Analysis of the treatment difference on the change from baseline in total fat mass (by DXA) revealed a significant decrease (p < 0.001) in the SAIZEN-treated group compared to the placebo group. SAIZEN also produced beneficial effects on several bone turnover markers including bone specific alkaline phosphatase, C-terminal propeptide, osteocalcin, urine deoxypyridinoline and iPTH.
One hundred and eleven patients were enrolled in an open label follow up study and treated with SAIZEN for an additional 6-30 months. During this period, the beneficial effects on lean body mass and total fat mass achieved during the initial six months of treatment were maintained.
Side effects
The following important adverse reactions are also described elsewhere in the labeling:
- Increased mortality in patients with acute critical illness [see WARNINGS AND PRECAUTIONS]
- Fatalities in children with Prader-Willi syndrome [see WARNINGS AND PRECAUTIONS]
- Neoplasms [see WARNINGS AND PRECAUTIONS]
- Glucose intolerance and diabetes mellitus [see WARNINGS AND PRECAUTIONS]
- Intracranial hypertension [see WARNINGS AND PRECAUTIONS]
- Severe hypersensitivity [see WARNINGS AND PRECAUTIONS]
- Fluid retention [see WARNINGS AND PRECAUTIONS]
- Hypoadrenalism [see WARNINGS AND PRECAUTIONS]
- Hypothyroidism [see WARNINGS AND PRECAUTIONS]
- Slipped capital femoral epiphysis in pediatric patients [see WARNINGS AND PRECAUTIONS]
- Progression of preexisting scoliosis in pediatric patients [see WARNINGS AND PRECAUTIONS]
- Otitis media and cardiovascular disorders in patients with Turner syndrome [see WARNINGS AND PRECAUTIONS]
- Lipoatrophy [see WARNINGS AND PRECAUTIONS]
- Pancreatitis [see WARNINGS AND PRECAUTIONS]
Clinical Trials Experience
Because clinical trials are conducted under varying conditions, adverse reaction rates observed during the clinical trials performed with one somatropin formulation cannot always be directly compared to the rates observed during the clinical trials performed with a second somatropin formulation, and may not reflect the adverse reaction rates observed in practice.
Clinical Trials In Children With Noonan Syndrome
Norditropin was studied in a two-year prospective, randomized, parallel dose group trial in 21 children, 3-14 years old, with Noonan syndrome. Doses were 0.033 and 0.066 mg/kg/day. After the initial two-year randomized trial, children continued Norditropin treatment until final height was achieved; randomized dose groups were not maintained. Final height and adverse event data were later collected retrospectively from 18 children; total follow-up was 11 years. An additional 6 children were not randomized, but followed the protocol and are included in this assessment of adverse events.
Based on the mean dose per treatment group, no significant difference in the incidence of adverse events was seen between the two groups. The most frequent adverse events were the common infections of childhood, including upper respiratory infection, gastroenteritis, ear infection, and influenza. Cardiac disorders was the system organ class with the second most adverse events reported. However, congenital heart disease is an inherent component of Noonan syndrome, and there was no evidence of somatropin-induced ventricular hypertrophy or exacerbation of preexisting ventricular hypertrophy (as judged by echocardiography) during this study. Children who had baseline cardiac disease judged to be significant enough to potentially affect growth were excluded from the study; therefore the safety of Norditropin in children with Noonan syndrome and significant cardiac disease is not known. Among children who received 0.033 mg/kg/day, there was one adverse event of scoliosis; among children who received 0.066 mg/kg/day, there were four adverse events of scoliosis [see WARNINGS AND PRECAUTIONS]. Mean serum IGF-I standard deviation score (SDS) levels did not exceed +1 in response to somatropin treatment. The mean serum IGF-I level was low at baseline and normalized during treatment.
Clinical Trials In Children With Turner Syndrome
In two clinical studies wherein children with Turner syndrome were treated until final height with various doses of Norditropin as described in Clinical Studies (14.2), the most frequently reported adverse events were common childhood diseases including influenza-like illness, otitis media, upper respiratory tract infection, otitis externa, gastroenteritis and eczema. Otitis media adverse events in Study 1 were most frequent in the highest dose groups (86.4% in the 0.045-0.067-0.089 mg/kg/day group vs. 78.3% in the 0.045-0.067 mg/kg/day group vs. 69.6% in the 0.045 mg/kg/day group) suggesting a possible dose-response relationship. Of note, approximately 40-50% of these otitis media adverse events were designated as “serious” [see WARNINGS AND PRECAUTIONS]. No patients in either study developed clearcut overt diabetes mellitus; however, in Study 1, impaired fasting glucose at Month 48 was more frequent in patients in the 0.045-0.067 mg/kg/day group (n=4/18) compared with the 0.045 mg/kg/day group (n=1/20). Transient episodes of fasting blood sugars between 100 and 126 mg/dL, and, on occasion, exceeding 126 mg/dL also occurred more often with larger doses of Norditropin in both studies [see WARNINGS AND PRECAUTIONS and ADVERSE REACTIONS]. Three patients withdrew from the 2 high dose groups in Study 1 because of concern about excessive growth of hands or feet. In addition, in Study 1, exacerbation of preexisting scoliosis was designated a serious adverse reaction in two patients in the 0.045 mg/kg/day group [see WARNINGS AND PRECAUTIONS].
Clinical Trials In Children Born Small For Gestational Age (SGA) With No Catch-Up Growth By Age 2-4 Years
Study 1 (Long-Term)In a multi-center, randomized, double-blind study, 53 non-GHD children with short stature born SGA with failure to catch-up were treated with 2 doses of Norditropin (0.033 or 0.067 mg/kg/day) to final height for up to 13 years (mean duration of treatment 7.9 and 9.5 years for girls and boys, respectively). The most frequently reported adverse events were common childhood diseases including influenza-like illness, upper respiratory tract infection, bronchitis, gastroenteritis, abdominal pain, otitis media, pharyngitis, arthralgia, and headache. Adverse events possibly/probably related to Norditropin were otitis media, arthralgia, headaches (no confirmed diagnoses of benign intracranial hypertension), gynecomastia, and increased sweating. One child treated with 0.067 mg/kg/day for 4 years was reported with disproportionate growth of the lower jaw, and another child treated with 0.067 mg/kg/day developed a melanocytic nevus [see WARNINGS AND PRECAUTIONS]. There were no clear cut reports of exacerbation of preexisting scoliosis or slipped capital femoral epiphysis. No apparent differences between the treatment groups were observed. In addition, the timing of puberty was age-appropriate in boys and girls in both treatment groups. Therefore, it can be concluded that no novel adverse events potentially related to treatment with Norditropin were reported in long-term Study 1.
Study 2 (Short-Term)In a multi-center, randomized, double-blind, parallel-group study, 98 Japanese non-GHD children with short stature born SGA with failure to catch-up were treated with 2 doses of Norditropin (0.033 or 0.067 mg/kg/day) for 2 years or were untreated for 1 year. The most frequently reported adverse events were common childhood diseases almost identical to those reported above for Study 1. Adverse events possibly/probably related to Norditropin were otitis media, arthralgia and impaired glucose tolerance. No apparent differences between the treatment groups were observed. However, arthralgia and transiently impaired glucose tolerance were only reported in the 0.067 mg/kg/day treatment group. Therefore, it can also be concluded that no novel adverse events potentially related to treatment with rhGH were reported in short-term Study 2.
As with all protein drugs, some patients may develop antibodies to the protein. Eighteen of the 76 children (~24%) treated with Norditropin developed anti-rhGH antibodies. However, these antibodies did not appear to be neutralizing in that the change from baseline in height SDS at Year 2 was similar in antibody positive and antibody negative children by treatment group.
In both Study 1 and Study 2, there were no clear cut cases of new onset diabetes mellitus, no children treated for hyperglycemia, and no adverse event withdrawals due to abnormalities in glucose tolerance. In Study 2, after treatment with either dose of Norditropin for 2 years, there were no children with consecutive fasting blood glucose levels between 100 and 126 mg/dL, or with fasting blood glucose levels > 126 mg/dL. Furthermore, mean hemoglobin A1c levels tended to decrease during long-term treatment in Study 1, and remained normal in Study 2. However, in Study 1, 4 children treated with 0.067 mg/kg/day of Norditropin and 2 children treated with 0.033 mg/kg/day of Norditropin shifted from normal fasting blood glucose levels at baseline to increased levels after 1 year of treatment (100 to 126 mg/dL or > 126 mg/dL). In addition, small increases in mean fasting blood glucose and insulin levels (within the normal reference range) after 1 and 2 years of Norditropin treatment appeared to be dose-dependent [see WARNINGS AND PRECAUTIONS and ADVERSE REACTIONS].
In both Study 1 and Study 2, there was no acceleration of bone maturation. A dose-dependent increase in mean serum IGF-I SDS levels within the reference range (but including a substantial number of children with serum IGF-1 SDS > +2) was observed after both longterm (Study 1) and short-term (Study 2) Norditropin treatment.
Clinical Trials In Adult GHD Patients
Adverse events with an incidence of ≥5% occurring in patients with AO GHD during the 6 month placebo-controlled portion of the largest of the six adult GHD Norditropin trials are presented in Table 1. Peripheral edema, other types of edema, arthralgia, myalgia, and paraesthesia were common in the Norditropin-treated patients, and reported much more frequently than in the placebo group. These types of adverse events are thought to be related to the fluid accumulating effects of somatropin. In general, these adverse events were mild and transient in nature. During the placebo-controlled portion of this study, approximately 5% of patients without preexisting diabetes mellitus treated with Norditropin were diagnosed with overt type 2 diabetes mellitus compared with none in the placebo group [see WARNINGS AND PRECAUTIONS and ADVERSE REACTIONS]. Anti-GH antibodies were not detected.
Of note, the doses of Norditropin employed during this study (completed in the mid 1990s) were substantially larger than those currently recommended by the Growth Hormone Research Society, and, more than likely, resulted in a greater than expected incidence of fluid retention-and glucose intolerance-related adverse events. A similar incidence and pattern of adverse events were observed during the other three placebo-controlled AO GHD trials and during the two placebo-controlled CO GHD trials.
Table 1 - Adverse Reactions with ≥5% Overall Incidence in Adult Onset Growth Hormone Deficient Patients Treated with Norditropin During a Six Month Placebo-Controlled Clinical Trial
| Norditropin (N=53) | Placebo (N=52) | |||
| Adverse Reactions | n | % | n | % |
| Peripheral Edema | 22 | 42 | 4 | 8 |
| Edema | 13 | 25 | 0 | 0 |
| Arthralgia | 10 | 19 | 8 | 15 |
| Leg Edema | 8 | 15 | 2 | 4 |
| Myalgia | 8 | 15 | 4 | 8 |
| Infection (non-viral) | 7 | 13 | 4 | 8 |
| Paraesthesia | 6 | 11 | 3 | 6 |
| Skeletal Pain | 6 | 11 | 1 | 2 |
| Headache | 5 | 9 | 3 | 6 |
| Bronchitis | 5 | 9 | 0 | 0 |
| Flu-like symptoms | 4 | 8 | 2 | 4 |
| Hypertension | 4 | 8 | 1 | 2 |
| Gastroenteritis | 4 | 8 | 4 | 8 |
| Other Non-Classifiable Disorders (excludes accidental injury) | 4 | 8 | 3 | 6 |
| Increased sweating | 4 | 8 | 1 | 2 |
| Glucose tolerance abnormal | 3 | 6 | 1 | 2 |
| Laryngitis | 3 | 6 | 3 | 6 |
| The adverse event pattern observed during the open label phase of the study was similar to the one presented above. | ||||
As with all therapeutic proteins, there is potential for immunogenicity. The detection of antibody formation is highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of antibody (including neutralizing antibody) positivity in an assay may be influenced by several factors including assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of the incidence of antibodies to Norditropin with the incidence of antibodies to other products may be misleading. In the case of growth hormone, antibodies with binding capacities lower than 2 mg/mL have not been associated with growth attenuation. In a very small number of patients treated with somatropin, when binding capacity was greater than 2 mg/mL, interference with the growth response was observed.
In clinical trials, GHD pediatric patients receiving Norditropin for up to 12 months were tested for induction of antibodies, and 0/358 patients developed antibodies with binding capacities above 2 mg/L. Amongst these patients, 165 had previously been treated with other somatropin formulations, and 193 were previously untreated naive patients.
Post-Marketing Experience
Because these adverse events are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. The adverse events reported during post-marketing surveillance do not differ from those listed/discussed above in Sections 6 and 6.1 in children and adults.
Serious systemic hypersensitivity reactions including anaphylactic reactions and angioedema have been reported with postmarketing use of somatropin products [see WARNINGS AND PRECAUTIONS].
Leukemia has been reported in a small number of GH deficient children treated with somatropin, somatrem (methionylated rhGH) and GH of pituitary origin. It is uncertain whether these cases of leukemia are related to GH therapy, the pathology of GHD itself, or other associated treatments such as radiation therapy. On the basis of current evidence, experts have not been able to conclude that GH therapy per se was responsible for these cases of leukemia. The risk for children with GHD, if any, remains to be established [see CONTRAINDICATIONS and WARNINGS AND PRECAUTIONS].
The following additional adverse reactions have been observed during the appropriate use of somatropin: headaches (children and adults), gynecomastia (children), and pancreatitis (children and adults [see WARNINGS AND PRECAUTIONS ).
New-onset type 2 diabetes mellitus has been reported.
Read the entire FDA prescribing information for Norditropin (Somatropin Injection)
Read More »What is the most important information i should know about somatropin?
Before you receive somatropin, tell your doctor about all your past and present medical conditions, especially allergies, trauma, surgery, diabetes, cancer, breathing problems, liver or kidney disease, scoliosis, high blood pressure, pancreas disorder, underactive thyroid, or a brain tumor.
Also tell your doctor about all other medications you use, especially steroids or diabetes medications. Your dosages of these medicines may need to be changed when you start using somatropin. Do not stop using a steroid suddenly or change any of your medication doses without your doctor's advice.
If you have Prader-Willi syndrome and are using somatropin, call your doctor promptly if you develop signs of lung or breathing problems such as shortness of breath, coughing, or new or increased snoring.
Call your doctor at once if you have sudden and severe pain in your upper stomach with nausea and vomiting, fast heartbeat, increased thirst or urination, weight loss, or vision changes and sudden, severe pain behind your eyes.