Norditropin FlexPro: Uses, Dosage & Side Effects
Somatropin – Pre-Filled Recombinant Growth Hormone Pen
Quick Facts About Norditropin FlexPro
Key Takeaways About Norditropin FlexPro
- Pre-filled disposable pen: Unlike cartridge-based systems, FlexPro arrives ready to use with no loading required; the pen is discarded after the medicine is finished or after 3–4 weeks in use
- Broad pediatric indication profile: One of the few growth hormones approved for Noonan syndrome (FDA-approved for this indication since 2007) in addition to GHD, Turner syndrome, chronic kidney disease, and SGA
- Half-unit dose precision: The FlexPro pen allows dose adjustments in 0.025 mg increments for the 5 mg pen, supporting precise weight-based dosing in children
- Room-temperature flexibility: Once in use, the pen can be kept at room temperature (below 25 °C) for up to 3 weeks, which helps with travel and daily routine
- Monitoring essential: Regular follow-up is required to assess growth velocity, IGF-1 levels, blood glucose, thyroid function, and, in at-risk patients, bone health and cancer surveillance
What Is Norditropin FlexPro and What Is It Used For?
Norditropin FlexPro is a prescription medicine containing somatropin – a recombinant form of human growth hormone produced by Novo Nordisk using genetically engineered Escherichia coli. Supplied in a pre-filled, disposable multi-dose pen, it is injected once daily under the skin to replace missing growth hormone in children with growth disorders and in adults with growth hormone deficiency.
Growth hormone (GH), also known as somatotropin, is produced in the anterior pituitary gland and orchestrates linear bone growth, body composition, protein synthesis, and the metabolism of carbohydrates, lipids, and minerals. When the body does not produce enough growth hormone – whether due to a congenital pituitary defect, chromosomal condition, injury, surgery, or unknown cause – growth and metabolic regulation are impaired. Somatropin, the active ingredient in Norditropin FlexPro, is identical to the 191-amino-acid sequence of naturally produced human growth hormone and restores these essential functions.
Norditropin itself has been available since the late 1980s, making it one of the longest-marketed recombinant growth hormone products worldwide. FlexPro, introduced around 2010, represents the current generation of pen devices designed to simplify self-injection. The pen is ready to use straight out of the refrigerator, requires no cartridge changes, features a dose memory window, and allows precise dialing in very small increments – important for pediatric patients whose prescribed dose is calculated per kilogram of body weight.
At the cellular level, somatropin binds to growth hormone receptors on hepatocytes and other tissues. This triggers the JAK2-STAT5 signaling cascade and stimulates the liver to release insulin-like growth factor 1 (IGF-1), the primary mediator of longitudinal bone growth and anabolic protein synthesis. Growth hormone also has direct effects on adipose tissue (promoting lipolysis), muscle (supporting lean mass), and bone (increasing bone turnover and mineral content).
Approved Indications in Children
Norditropin FlexPro is approved for several pediatric conditions where growth failure is a key clinical feature. The exact set of indications may vary slightly between regulatory agencies (EMA, FDA, MHRA, Health Canada, TGA), but the following are broadly recognized:
- Growth hormone deficiency (GHD): Congenital, acquired, or idiopathic insufficiency of pituitary growth hormone production, diagnosed through auxological assessment and GH stimulation testing
- Turner syndrome: A chromosomal condition (usually 45,X) affecting females, associated with short stature, ovarian insufficiency, and cardiovascular anomalies. Growth hormone therapy can increase adult height by an average of 5–8 cm
- Noonan syndrome: An autosomal dominant disorder caused by mutations in the RAS–MAPK signaling pathway (PTPN11, SOS1, RAF1, and others). Norditropin holds an FDA-granted indication (since 2007) for short stature associated with Noonan syndrome, based on randomized data demonstrating a meaningful height gain
- Chronic kidney disease (CKD): Pre-transplant chronic renal insufficiency in children with impaired growth velocity. Treatment is typically discontinued at the time of renal transplantation
- Small for gestational age (SGA): Children born with birth weight and/or length below the 3rd percentile for gestational age who do not demonstrate catch-up growth by age 4 (or later in certain jurisdictions)
- Idiopathic short stature (ISS): Approved in some markets (including the U.S.) for non-GHD short stature more than 2.25 standard deviations below the mean for age with poor predicted adult height
Approved Indications in Adults
In adults, Norditropin FlexPro is indicated for the treatment of pronounced growth hormone deficiency arising from either pituitary disease (hypopituitarism from adenoma, surgery, radiation therapy, or traumatic brain injury) or persistent childhood-onset GHD that remains after completion of linear growth. Diagnosis in adults should be confirmed by an appropriate stimulation test such as the insulin tolerance test, glucagon stimulation test, or, where available, macimorelin testing.
Clinical features of adult GHD include reduced muscle and bone mass, increased abdominal and visceral fat, dyslipidemia, reduced exercise capacity, impaired quality of life, and sometimes mood disturbances. Adequate GH replacement has been shown to improve body composition, lipid profile, bone mineral density, cardiac output, and patient-reported outcomes. Treatment is typically lifelong in patients who demonstrate clinical benefit, with periodic reassessment.
Norditropin FlexPro should only be initiated by a physician with expertise in growth hormone therapy – typically a pediatric endocrinologist for children and an adult endocrinologist for adults. The diagnosis must be biochemically and, where relevant, genetically confirmed before starting therapy.
What Should You Know Before Using Norditropin FlexPro?
Before starting Norditropin FlexPro, your physician will confirm the diagnosis, review your medical history for malignancies, check for critical illness, and test thyroid, adrenal, and glucose metabolism. It must not be used by people with active cancer, severe acute critical illness, closed growth plates in children prescribed for height, or known hypersensitivity to somatropin or any excipient.
Contraindications
Norditropin FlexPro must not be used under the following circumstances:
- Hypersensitivity: Known allergy to somatropin or any of the excipients (mannitol, histidine, poloxamer 188, phenol, water for injections). Severe reactions, though rare, have been reported
- Active malignancy (cancer): Tumors must be inactive and cancer therapy completed before starting somatropin. In children treated for intracranial lesions, imaging should confirm stability
- Closed epiphyses: Somatropin prescribed to promote linear growth must not be used in children whose bone growth plates have already fused
- Acute critical illness: Patients with complications following open-heart surgery, abdominal surgery, multiple accidental trauma, acute respiratory failure, or similar acute conditions must not receive somatropin. Increased mortality has been observed in this population
- Active proliferative or severe non-proliferative diabetic retinopathy: Growth hormone should not be initiated until retinopathy is stabilized
If you or your child are admitted to hospital with a serious acute illness, major surgery, trauma, or respiratory failure, tell the healthcare team that Norditropin FlexPro is being used. The treating physician may decide to pause growth hormone therapy, as pharmacological doses during critical illness have been linked to increased mortality.
Warnings and Precautions
Discuss all of the following with your prescribing physician before and during treatment:
- Insulin resistance and diabetes: Somatropin can reduce insulin sensitivity and unmask or worsen type 2 diabetes. Fasting glucose and, where indicated, HbA1c should be monitored. Patients with existing diabetes may need adjustment of their insulin or oral antidiabetic therapy
- Hypoadrenalism: Somatropin can unmask central adrenal insufficiency, especially in patients with hypopituitarism. Glucocorticoid replacement may need to be reviewed and, if used, doses of oral cortisone or hydrocortisone may require adjustment
- Hypothyroidism: Somatropin increases peripheral conversion of T4 to T3, which can reveal underlying hypothyroidism. Thyroid function should be tested before and during therapy; those on thyroid hormone replacement may need dose changes
- Intracranial hypertension (pseudotumor cerebri): Rare cases have been reported, typically within the first 8 weeks of treatment. Symptoms include severe headache, nausea, vomiting, and visual disturbances. Fundoscopy is recommended if suspected, and the dose may need to be reduced or temporarily stopped
- Slipped capital femoral epiphysis (SCFE) and Legg–Calvé–Perthes disease: Children receiving GH who develop a limp or hip/knee pain should be evaluated urgently
- Scoliosis: Rapid growth may accelerate pre-existing scoliosis. Regular orthopedic assessment is advised
- Pancreatitis: Although rare, inflammation of the pancreas has been reported, especially in children with Turner syndrome. Severe abdominal pain warrants prompt evaluation
- Second neoplasms: Long-term safety data suggest an increased risk of second neoplasms in childhood cancer survivors treated with GH, particularly those who received cranial irradiation. Regular surveillance and a careful risk–benefit discussion are essential
- Fluid retention: Peripheral edema, joint stiffness, and carpal tunnel syndrome occur more often in adults. Symptoms usually improve with dose reduction
- Injection site lipoatrophy: Rotate injection sites systematically to prevent local fat tissue changes
Special Populations
Children with Turner syndrome: Cardiac and thyroid evaluation before treatment is essential. Otitis media and hearing changes should be monitored. A higher GH dose than for classical GHD is typically required.
Children with Noonan syndrome: Cardiac evaluation (particularly for hypertrophic cardiomyopathy and pulmonary valve stenosis) must precede therapy, and cardiac status should be monitored annually. The underlying RAS–MAPK pathway mutation may theoretically increase cancer risk – appropriate vigilance is recommended although clinical evidence remains limited.
Children born SGA: Glucose metabolism should be evaluated before and annually during treatment. If pubertal development begins, co-management with the endocrinologist to plan puberty timing is advised.
Chronic kidney disease: Renal function, blood pressure, and signs of renal osteodystrophy must be monitored. Growth hormone therapy is stopped at the time of renal transplantation to reduce the risk of acute rejection.
Elderly patients: Experience with GH therapy in patients over 60 years is limited. Older adults may be more sensitive to side effects such as edema, carpal tunnel syndrome, and insulin resistance. Doses should therefore be lower and titrated carefully.
Pregnancy and Breastfeeding
Norditropin FlexPro is generally not recommended during pregnancy. Human data on somatropin exposure during pregnancy are limited, and animal studies do not adequately predict human reproductive outcomes. Women of childbearing potential planning pregnancy, or who become pregnant during treatment, should contact their physician to discuss the risks, benefits, and whether therapy should be paused.
It is not known whether somatropin passes into human breast milk in meaningful amounts. As a precaution, and because breastfeeding imposes additional metabolic demands, most guidelines advise discontinuing therapy or avoiding breastfeeding until a medical decision has been made. Always consult your physician before restarting GH therapy postpartum.
Driving and Using Machines
Norditropin FlexPro is not known to impair the ability to drive or operate machinery. However, rare symptoms such as headache, blurred vision, or fatigue – particularly early in therapy – should prompt caution until they have resolved.
How Does Norditropin FlexPro Interact with Other Drugs?
Norditropin FlexPro can interact with glucocorticoids, insulin and oral antidiabetics, thyroid hormones, oral estrogens, anticonvulsants, and drugs metabolized by cytochrome P450 enzymes. Dose adjustments of either somatropin or the co-administered medication may be required, and close monitoring is important whenever a new medicine is started or stopped.
Growth hormone affects several hormonal axes and metabolic pathways. It alters the conversion of cortisol to cortisone, increases the peripheral conversion of thyroxine to triiodothyronine, and modifies glucose handling. It may also influence the activity of CYP3A4, one of the liver's major drug-metabolizing enzymes. These effects can be clinically meaningful when other medications depend on tight hormonal or metabolic balance.
You should always share a complete list of your medications, vitamins, herbal supplements, and over-the-counter products with your prescribing physician and pharmacist. This includes any hormone replacement therapy, corticosteroids for asthma, antiepileptic drugs, and treatments for diabetes. The lists below summarize the main documented interactions; it is not exhaustive.
Major Interactions
| Interacting Drug / Class | Mechanism | Clinical Action |
|---|---|---|
| Glucocorticoids (hydrocortisone, prednisolone, dexamethasone) | Somatropin inhibits 11β-HSD1, reducing cortisol to cortisone conversion; may unmask central adrenal insufficiency. Supraphysiologic steroid doses attenuate growth | Reassess replacement dose; start at the lowest effective steroid dose; monitor clinical signs of adrenal crisis |
| Insulin & oral antidiabetics (metformin, sulfonylureas, DPP-4 inhibitors) | GH reduces insulin sensitivity, raising glucose and HbA1c | Monitor fasting glucose and HbA1c regularly; adjust antidiabetic therapy; in children, evaluate glucose at baseline and annually |
| Thyroid hormone replacement (levothyroxine) | GH accelerates T4 → T3 conversion; may unmask central hypothyroidism | Check free T4, TSH before and every 6–12 months; uptitrate levothyroxine as required |
| Oral estrogens (combined OCP, HRT) | Oral estrogen undergoes hepatic first-pass metabolism, reducing IGF-1 response to GH | Women on oral estrogen may require higher somatropin doses than men or women using transdermal estrogen |
| Anticonvulsants (carbamazepine, phenytoin, phenobarbital) | GH-induced changes in CYP3A4 may alter anticonvulsant metabolism | Monitor serum levels of anticonvulsants; watch for breakthrough seizures or toxicity |
| Ciclosporin | Possible alteration of ciclosporin pharmacokinetics | Measure trough levels; adjust dose to maintain therapeutic range, especially in transplant patients |
Minor and Contextual Interactions
| Interacting Drug / Class | Mechanism | Clinical Action |
|---|---|---|
| CYP3A4 substrates (certain statins, calcium channel blockers, macrolides) | GH-induced changes in CYP3A4 may reduce plasma levels | Monitor clinical efficacy and adjust dose case-by-case |
| Androgens (testosterone) | Synergistic growth-promoting effect | Coordinate endocrine follow-up; anticipate additive growth velocity |
| GnRH analogues (leuprorelin, triptorelin) | Used together to delay puberty and maximize height gain | Intentional combination under specialist supervision; adhere to growth plans |
| Alcohol | No direct interaction, but alcohol influences glucose homeostasis | Moderation advised, especially in adults at risk of insulin resistance |
Women who switch from oral to transdermal estrogen therapy often require a lower somatropin dose to maintain the same IGF-1 level, because transdermal estrogen avoids first-pass hepatic metabolism. This effect should be anticipated and monitored during any route change.
What Is the Correct Dosage of Norditropin FlexPro?
Norditropin FlexPro is dosed individually, based on body weight (or body surface area), the indication, pubertal status, and clinical response. Typical pediatric doses range from 0.025 to 0.067 mg/kg/day, and adult doses from 0.1 to 0.5 mg/day. It is injected subcutaneously once daily, preferably in the evening, using the FlexPro pen.
Dosing must be personalized by the prescribing endocrinologist. The pen's half-unit dose precision (0.025 mg steps on the 5 mg FlexPro) allows fine weight-based titration in small children. Dose escalation is often gradual over the first weeks to minimize fluid retention and other dose-dependent effects. Regular follow-up every 3–6 months assesses height velocity (children), IGF-1 levels (both age groups), and tolerability.
Children
| Indication | Typical Daily Dose | Equivalent per Week | Notes |
|---|---|---|---|
| Growth hormone deficiency (GHD) | 0.025–0.035 mg/kg/day | 0.175–0.245 mg/kg/week | Start at the lower end; escalate based on IGF-1 and growth response |
| Turner syndrome | 0.045–0.050 mg/kg/day | 0.315–0.350 mg/kg/week | Higher dose than classical GHD; consider early initiation for maximal height gain |
| Noonan syndrome | Up to 0.066 mg/kg/day | Up to 0.462 mg/kg/week | FDA-approved dose; cardiac surveillance recommended |
| Chronic kidney disease | 0.045–0.050 mg/kg/day | 0.315–0.350 mg/kg/week | Stop at the time of renal transplantation |
| Small for gestational age (SGA) | 0.035–0.067 mg/kg/day | 0.245–0.469 mg/kg/week | Evaluate glucose tolerance before and annually during therapy |
| Idiopathic short stature (ISS, where approved) | Up to 0.067 mg/kg/day | Up to 0.469 mg/kg/week | Individualized; review annually for response |
Pediatric treatment continues until near final adult height is reached or the epiphyses close. Annual reassessment of growth velocity, bone age, pubertal staging, and IGF-1 guides dose adjustments. If growth velocity is inadequate after 6–12 months at optimum dosing, adherence, diagnosis, and concomitant therapy should be reviewed.
Adults
Adult-Onset GHD
Start at 0.1–0.3 mg per day (approximately 0.15–0.30 mg/day in women, 0.1–0.2 mg/day in men), with titration based on IGF-1 levels, clinical response, and tolerability. The typical maintenance dose rarely exceeds 1.0 mg per day.
Continuing from Childhood-Onset GHD
Start at 0.2–0.5 mg per day. Patients transitioning from pediatric to adult care should be retested to confirm persistent severe GHD before continuing therapy in adulthood.
Elderly (Over 60 years)
Start at 0.1–0.2 mg per day, with slow titration. Elderly patients are more sensitive to side effects; the lowest effective dose should be used and rarely exceed 0.5 mg per day.
Dose Adjustment by Sex and Estrogen Route
Women on oral estrogen therapy typically need higher doses than women on transdermal estrogen or men; reassess when changing estrogen route. IGF-1 should be kept within the age- and sex-adjusted reference range.
How to Administer with the FlexPro Pen
Norditropin FlexPro is designed for subcutaneous injection using the integrated pen. Follow the step-by-step instructions provided in the package insert and demonstrated by your healthcare provider. A summary of the key steps:
- Wash hands and inspect the pen – the solution should be clear and colorless
- Attach a new NovoFine or NovoTwist needle to the pen and remove both caps
- Prime the pen by dialing 0.1 mg (the first time you use a new pen), then press the dose button until a drop appears at the needle tip
- Dial your prescribed dose using the clear dose scale; the FlexPro 5 mg pen allows 0.025 mg increments
- Insert the needle into the thigh or abdomen at a 90-degree angle; for very thin children, a skin pinch may be used
- Inject by fully depressing the dose button; keep the needle in place for at least 6 seconds
- Remove and dispose of the needle in a sharps container; replace the pen cap
- Rotate the injection site (thigh, abdomen, upper arm) daily to prevent lipoatrophy or lipohypertrophy
Inject at approximately the same time each day, preferably in the evening to mirror the natural nocturnal pulse of growth hormone secretion. Never share your FlexPro pen with another person, even after a needle change, due to the risk of cross-infection.
Missed Dose
If you forget an injection, skip the missed dose and take the next dose at your usual time – do not take a double dose to compensate. Consistent daily administration is important for predictable effects. If doses are missed regularly, discuss practical strategies with your healthcare provider and keep a treatment diary.
Overdose
Acute overdose of somatropin can cause initial hypoglycemia (low blood sugar) followed by hyperglycemia (high blood sugar). Symptoms of hypoglycemia include sweating, trembling, confusion, weakness, and fainting. Long-term overdose may lead to acromegaly-like changes such as enlarged hands, feet, and facial features, as well as fluid retention and joint pain. Contact your healthcare provider, emergency department, or national poison control center immediately if overdose is suspected.
Do not stop Norditropin FlexPro without consulting your physician. In children still growing, unplanned discontinuation can limit final height potential. In adults, stopping can lead to a rebound of GHD symptoms such as increased adiposity, reduced energy, and impaired quality of life.
What Are the Side Effects of Norditropin FlexPro?
Like all medicines, Norditropin FlexPro can cause side effects, though not everyone experiences them. Adults most commonly report fluid retention, joint and muscle pain, and paresthesia. Children typically experience injection site reactions, headaches, and occasional joint pain. Most effects are dose-dependent and usually resolve with dose reduction or as therapy continues.
The overall safety profile of somatropin is well established after more than three decades of clinical use. The vast majority of side effects are mild to moderate, dose-dependent, and reversible. Serious events are rare but warrant awareness, especially in specific patient groups such as children with underlying syndromic conditions or adults with pre-existing metabolic disease. Your endocrinologist will monitor for these effects through scheduled visits, physical examination, and laboratory tests.
Side Effects in Adults
Very Common
- Peripheral edema (swelling of hands, ankles, feet)
- Joint pain (arthralgia) and joint stiffness
Common
- Muscle pain (myalgia)
- Paresthesia (numbness, tingling in fingers or feet)
- Carpal tunnel syndrome
- Headache
- Impaired glucose tolerance / elevated blood sugar
- Hypothyroidism (unmasked or worsened)
Uncommon
- Type 2 diabetes mellitus
- Gynecomastia (breast enlargement in men)
- Injection site reactions (redness, itching, swelling)
- Rash or urticaria (hives)
Rare
- Benign intracranial hypertension (pseudotumor cerebri)
- Pancreatitis
- Hypersensitivity reactions (including angioedema)
Side Effects in Children
Common
- Transient injection site reactions (redness, itching, mild pain)
- Headache
- Joint or limb pain
Uncommon
- Rash, urticaria
- Benign intracranial hypertension (more frequent in Turner syndrome and CKD)
- Impaired glucose tolerance, insulin resistance
- Hypothyroidism (subclinical or clinical)
- Gynecomastia (prepubertal or pubertal boys)
Rare
- Slipped capital femoral epiphysis (SCFE)
- Legg–Calvé–Perthes disease
- Progression of pre-existing scoliosis
- Pancreatitis (more often reported in Turner syndrome)
Frequency Not Known
- Second neoplasms in survivors of childhood cancer previously treated with radiation
- Adrenal insufficiency unmasked in patients with multiple pituitary hormone deficiencies
- Anti-somatropin antibody formation (usually without clinical impact)
Device-Related Considerations
Because Norditropin FlexPro is a pre-filled pen, device-specific issues are occasionally reported. These include rare mechanical dose-counter failures, needle leakage if the needle is attached incorrectly, and skin irritation caused by alcohol swab residue rather than the medicine itself. If you notice the pen is not delivering the expected dose, the solution appears cloudy or discolored, or the dose button is hard to press, stop using that pen and contact your pharmacy or Novo Nordisk patient support.
If you experience any side effects, even those not listed here, report them to your healthcare provider. In most countries you can also submit reports directly to the national pharmacovigilance authority (for example, the Yellow Card Scheme in the UK, FDA MedWatch in the U.S., or EudraVigilance via EMA). Reporting helps improve the safety knowledge of the medicine.
How Should You Store Norditropin FlexPro?
Before first use, store Norditropin FlexPro refrigerated at 2–8 °C (36–46 °F), protected from light, until the expiry date. After first use, you can keep the pen in the refrigerator for up to 4 weeks, or at room temperature below 25 °C (77 °F) for up to 3 weeks. Never freeze the pen and never shake it vigorously.
Somatropin is a protein that is sensitive to heat, freezing, vigorous agitation, and prolonged light exposure. Correct storage preserves the potency of the medicine and ensures safety. The FlexPro pen is a single patient-use device; once opened, use-by dates apply.
- Before first use: Refrigerate at 2–8 °C (36–46 °F). Keep the pen in the original carton to protect from light. Do not freeze
- After first use (refrigerated): Keep the pen in the refrigerator at 2–8 °C for up to 4 weeks. Discard any remaining medicine after this period
- After first use (at room temperature): Keep the pen at room temperature below 25 °C (77 °F) for up to 3 weeks. Do not switch between refrigerated and room-temperature storage repeatedly
- Travel: Use an insulated cooling wallet when carrying the pen between environments. Airport security may require a doctor's letter identifying the medication as a prescription biologic
- Heat, cold, and light: Avoid temperatures above 25 °C, direct sunlight, and freezing. If the pen has been frozen, do not use it
- Replace the needle: Always remove the needle after each injection and store the pen with the cap in place
Do not use Norditropin FlexPro after the expiry date printed on the carton (EXP) – the date refers to the last day of the month shown. Keep the pen out of the sight and reach of children. Dispose of used pens and needles according to local regulations; most pharmacies accept sharps containers for safe disposal. Do not put the pen or needles into household waste or wastewater.
What Does Norditropin FlexPro Contain?
The active substance in Norditropin FlexPro is somatropin, a recombinant human growth hormone produced in genetically engineered Escherichia coli. Each formulation also contains buffer agents, a stabilizer, the preservative phenol, and water for injections. The pen itself is made from medical-grade plastic and glass with a rubber stopper.
All Norditropin FlexPro strengths share the same qualitative excipient profile, differing only in somatropin concentration and total volume. This consistency simplifies handling and reduces the risk of errors when patients change between pen strengths.
Strength and Volume Options
| Presentation | Somatropin per ml | Total Somatropin | Equivalent IU |
|---|---|---|---|
| 5 mg / 1.5 ml | 3.3 mg | 5 mg | 15 IU |
| 10 mg / 1.5 ml | 6.7 mg | 10 mg | 30 IU |
| 15 mg / 1.5 ml | 10 mg | 15 mg | 45 IU |
| 30 mg / 3 ml | 10 mg | 30 mg | 90 IU |
Active Substance
Somatropin (INN): a recombinant protein with 191 amino acids identical in sequence to endogenous human pituitary growth hormone. It is produced through fermentation in a strain of Escherichia coli carrying a plasmid with the human growth hormone gene.
Excipients
- Mannitol: Tonicity adjuster and stabilizer
- Histidine: Buffer to maintain pH stability
- Poloxamer 188: Surfactant that prevents protein aggregation
- Phenol: Preservative allowing multi-dose use
- Hydrochloric acid / sodium hydroxide: pH adjustment
- Water for injections: Solvent
Norditropin FlexPro does not contain benzyl alcohol, making it suitable for use in neonates and infants when prescribed under specialist supervision. However, phenol is a small-molecule preservative and in rare cases may cause local skin reactions. Patients with a documented phenol allergy should discuss alternative formulations with their endocrinologist.
Appearance and Packaging
Each FlexPro pen contains a clear, colorless to slightly opalescent solution for subcutaneous injection. The pen is disposable and ready to use, with a transparent window for dose verification and a click indicator that confirms dose delivery. Pack sizes vary by market, typically 1 or 3 pens per carton. The pen is designed for use with NovoFine or NovoTwist pen needles (sold separately).
Frequently Asked Questions About Norditropin FlexPro
Norditropin FlexPro (somatropin) is a recombinant human growth hormone used to treat growth disorders in children, including growth hormone deficiency, Turner syndrome, Noonan syndrome, chronic kidney disease, and children born small for gestational age. In adults, it treats confirmed severe growth hormone deficiency, whether it originated in childhood or developed later (for example, after pituitary surgery or radiation therapy). Diagnosis should be confirmed by biochemical testing before therapy is initiated.
The FlexPro pen is pre-filled and disposable. Attach a new NovoFine or NovoTwist needle, prime the pen with 0.1 mg when using it for the first time, dial your prescribed dose, and inject subcutaneously into the thigh or abdomen, keeping the needle in for at least 6 seconds. Inject once daily, preferably in the evening. Rotate injection sites and remove the needle after every injection. A healthcare professional will demonstrate the correct technique before you start self-injection.
In adults, the most common side effects are peripheral edema (swollen hands or feet), joint and muscle pain, paresthesia, and sometimes carpal tunnel symptoms. In children, the most common effects are transient injection site reactions, headaches, and joint pain. Most side effects are dose-dependent and often improve with dose reduction or as treatment continues. Less common but important effects include impaired glucose tolerance, hypothyroidism, and, very rarely, benign intracranial hypertension.
Before first use, store the pen in a refrigerator at 2–8 °C (36–46 °F) and keep it in the original carton to protect from light. After first use, the pen can remain in the refrigerator for up to 4 weeks, or be kept at room temperature below 25 °C (77 °F) for up to 3 weeks. Do not freeze the pen, do not shake it, and do not use it if the solution looks cloudy or contains particles. Always replace the needle after each injection.
Yes. Norditropin was the first recombinant growth hormone approved by the U.S. FDA for short stature associated with Noonan syndrome (approved in 2007). It is also recognized for this indication in several other regions. The typical approved dose is up to 0.066 mg/kg/day. Because Noonan syndrome can involve cardiac anomalies (particularly hypertrophic cardiomyopathy and pulmonary valve stenosis), cardiac evaluation is recommended before and during treatment. The underlying RAS–MAPK pathway alterations also call for appropriate clinical vigilance during long-term therapy.
Norditropin FlexPro is generally not recommended during pregnancy. Data on human pregnancy outcomes are limited, and most guidelines advise pausing treatment once pregnancy is confirmed. If you become pregnant while using the medicine, contact your endocrinologist as soon as possible to discuss next steps. Breastfeeding women should likewise seek medical advice before starting or continuing therapy. Women of childbearing potential should use effective contraception if pregnancy must be avoided during treatment.
All three are delivery devices from Novo Nordisk for Norditropin somatropin. FlexPro is the current pre-filled disposable pen, with half-unit dose steps (0.025 mg increments on the 5 mg pen) and a built-in dose memory. NordiFlex was the previous-generation pre-filled pen, largely replaced by FlexPro in most markets. NordiPen is a durable, reusable pen that uses Norditropin SimpleXx cartridges. FlexPro offers the simplest handling, especially for families and new users, because no cartridge loading is required.
Unopened pens should always be kept refrigerated. Once in use, the pen can stay at room temperature below 25 °C (77 °F) for up to 3 weeks – which typically covers most holidays. Use an insulated cooler wallet when moving between environments and avoid direct sunlight, the glove compartment of a car, or freezing conditions. Carry the medicine in your hand luggage when flying, together with a letter from your prescribing physician confirming the diagnosis and the need for refrigerated biologic therapy.
References
- European Medicines Agency (EMA). Norditropin SimpleXx / FlexPro Product Information. Available at: www.ema.europa.eu
- U.S. Food and Drug Administration (FDA). Norditropin [somatropin] Prescribing Information. Silver Spring, MD: FDA. Available at: accessdata.fda.gov
- Grimberg A, DiVall SA, Polychronakos C, et al. Guidelines for Growth Hormone and Insulin-Like Growth Factor-I Treatment in Children and Adolescents: Growth Hormone Deficiency, Idiopathic Short Stature, and Primary Insulin-Like Growth Factor-I Deficiency. Horm Res Paediatr. 2016;86(6):361-397. doi:10.1159/000452150
- Molitch ME, Clemmons DR, Malozowski S, et al. Evaluation and Treatment of Adult Growth Hormone Deficiency: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2011;96(6):1587-1609. doi:10.1210/jc.2011-0179
- Fleseriu M, Hashim IA, Karavitaki N, et al. Hormonal Replacement in Hypopituitarism in Adults: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2016;101(11):3888-3921. doi:10.1210/jc.2016-2118
- Osio D, Dahlgren J, Wikland KA, Westphal O. Improved Final Height with Long-Term Growth Hormone Treatment in Noonan Syndrome. Acta Paediatr. 2005;94(9):1232-1237. doi:10.1080/08035250510031502
- Gravholt CH, Andersen NH, Conway GS, et al. Clinical Practice Guidelines for the Care of Girls and Women with Turner Syndrome. Eur J Endocrinol. 2017;177(3):G1-G70. doi:10.1530/EJE-17-0430
- World Health Organization (WHO). WHO Model List of Essential Medicines – 23rd list, 2023. Geneva: WHO; 2023.
- British National Formulary (BNF). Somatropin. National Institute for Health and Care Excellence (NICE). Updated 2025.
- Novo Nordisk. Norditropin FlexPro Patient Information and Instructions for Use. Bagsværd, Denmark: Novo Nordisk A/S. Current version available from your pharmacy and at www.novonordisk.com
About Our Medical Editorial Team
This article has been written and reviewed by the iMedic Medical Editorial Team, comprising licensed specialist physicians with expertise in endocrinology, pediatrics, and clinical pharmacology. Our team follows the GRADE evidence framework and adheres to international guidelines from the WHO, EMA, FDA, NICE, and the Endocrine Society.
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