Generic drug: mecasermin (rDNA origin)

Brand name: Increlex

What is Increlex, and how does it work?

  • Increlex (mecasermin [rDNA origin]) is a liquid that contains man-made insulin-like growth factor-1 (IGF-1). Increlex is used to treat children who are very short for their age because their bodies do not make enough IGF-1. This condition is called primary IGF-1 deficiency.
  • IGF-1 should not be used instead of growth hormone.
  • It is not known if Increlex is safe and effective in children under 2 years of age.

What are the side effects of Increlex?

Increlex may cause serious side effects, including:

  • Low blood sugar (hypoglycemia). Increlex may lower blood sugar levels. It is important to only give your child Increlex 20 minutes before or 20 minutes after a meal or snack to reduce the chances of low blood sugar. Do not give your child Increlex if your child cannot eat. Signs of low blood sugar include:

Severe hypoglycemia may cause unconsciousness, seizures, or death. If your child receives Increlex, they should avoid participating in high risk activities (e.g. driving, exercise, etc.) within 2 to 3 hours after the Increlex injection, especially at the beginning of Increlex treatment.

Before beginning treatment with Increlex your child's doctor or nurse will explain to you how to treat hypoglycemia. Your child should always have a source of sugar such as orange juice, glucose gel, candy, or milk available in case symptoms of hypoglycemia happen. For severe hypoglycemia, if your child is not responsive and cannot drink sugar-containing fluids, you should get emergency medical help for your child right away. Your doctor or nurse will show you how to give the injection.

  • Allergic reactions. See “Who should not receive Increlex?” Allergic reactions are a serious but common side effect of Increlex. Your child may have a mild or serious allergic reaction with Increlex. Call your child's doctor right away if your child gets a rash or hives. Hives, also known as urticaria, appear as a raised, itchy skin reaction. Hives appear pale in the middle with a red rim around it. Hives generally appear minutes to hours after the injection and may sometimes occur at many places on the skin. Stop taking Increlex and get medical help right away if your child has trouble breathing or goes into shock, with symptoms like dizziness, pale, clammy skin or passing out.
  • Increlex can also cause reactions at the injection site including:
    • loss of fat (lipoatrophy)
    • increase of fat (lipohypertrophy)
    • pain, redness, or bruising

Injection site reactions can be avoided by changing (rotating) the injection site at each injection.

  • Increased pressure in the brain (intracranial hypertension). Increlex, like growth hormone, can sometimes cause a temporary increase in pressure within the brain. The symptoms of intracranial hypertension can include headache, nausea and vomiting. Tell your doctor if your child has a headache with vomiting. Your doctor can then check to see if intracranial hypertension is present. If it is present, your child's doctor may decide to temporarily reduce or stop Increlex therapy.
  • Enlarged tonsils. Some signs of enlarged tonsils include: snoring, difficulty breathing, sleep apnea (a condition where breathing stops briefly during sleep), or fluid in the middle-ear. Sleep apnea can cause excessive daytime sleepiness. Call your child's doctor if these symptoms bother your child. Your child's doctor should do regular exams to check your child's tonsils.
  • A bone problem called slipped capital femoral epiphysis. This happens when the top of the upper leg (femur) slips apart. Get medical help for your child right away if your child develops a limp or has hip or knee pain.
  • Worsened scoliosis (caused by rapid growth). If your child has scoliosis, your child will need to be checked often for an increase in the curve of the spine.
  • Tumor Growths. Several cases of cancerous tumors have been observed in pediatric patients who received treatment with Increlex. Tell your doctor immediately if your child develops any new growths or symptoms of cancer.
  • Benzyl alcohol toxicity. Benzyl alcohol is a preservative in Increlex. Benzyl alcohol can cause serious side effects, including death in infants who have received medicines that contain the benzyl alcohol preservative.

The most common side effects of Increlex include: hypoglycemia (low blood sugar), injection site reactions, allergic reactions and enlarged tonsils.

Call your child's doctor if your child has any side effects that bothers them or that does not go away.

These are not all the possible side effects of Increlex. For more information, ask your child's doctor or pharmacist.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is the dosage for Increlex?

  • Preprandial glucose monitoring is recommended at treatment initiation and until a well-tolerated dose is established. If frequent symptoms of hypoglycemia or severe hypoglycemia occur, preprandial glucose monitoring should continue.
  • The dosage of Increlex should be individualized for each patient. The recommended starting dose of Increlex is 0.04 to 0.08 mg/kg (40 to 80 micrograms/kg) twice daily by subcutaneous injection.
  • If well-tolerated for at least one week, the dose may be increased by 0.04 mg/kg per dose, to the maximum dose of 0.12 mg/kg given twice daily.
  • Doses greater than 0.12 mg/kg given twice daily have not been evaluated in children with Primary IGFD and, due to potential hypoglycemic effects, should not be used.
  • If hypoglycemia occurs with recommended doses despite adequate food intake, the dose should be reduced. Increlex should be administered shortly before or after (± 20 minutes) a meal or snack.
  • If the patient is unable to eat shortly before or after a dose for any reason, that dose of Increlex should be withheld. Subsequent doses of Increlex should never be increased to make up for one or more omitted doses.
  • Treatment with Increlex should be supervised by a physician who is experienced in the diagnosis and management of pediatric patients with short stature associated with severe primary IGF-1 deficiency or with growth hormone gene deletion and who have developed neutralizing antibodies to growth hormone.

What drugs interact with Increlex?

No information provided

Is Increlex safe to use while pregnant or breastfeeding?

  • There are no available data on Increlex use in pregnant women. Exposure to Increlex during pregnancy is unlikely because the drug is not indicated for use after epiphyseal closure.
  • There is no information available on the presence of mecasermin in human or animal milk, the effects of the drug on the breastfed infant, or the effects of the drug on milk production.
  • The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for Increlex and any potential adverse effects on the breast-fed child from Increlex or from the underlying maternal condition.


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Increlex (mecasermin [rDNA origin]) is a liquid that contains man-made insulin-like growth factor-1 (IGF-1). Increlex is used to treat children who are very short for their age because their bodies do not make enough IGF-1. This condition is called primary IGF-1 deficiency. Serious side effects of Increlex include low blood sugar (hypoglycemia), allergic reactions, and injection site reactions.

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You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Medically Reviewed on 6/15/2021
All sections courtesy of the U.S. Food and Drug Administration