Reviewed on 8/2/2023

What Is Pegvisomant and How Does It Work?

Pegvisomant is a prescription medication used for the treatment of acromegaly in patients who have had an inadequate response to surgery or radiation therapy, or for whom these therapies are not appropriate. The goal of treatment is to normalize serum insulin-like growth factor-I (IGF-I) levels.

  • Pegvisomant is available under the following different brand names: Somavert

What Are Side Effects Associated with Using Pegvisomant?

Common side effects of Pegvisomant include:

  • pain
  • fever, chills, body aches, flu symptoms
  • nausea, diarrhea
  • abnormal liver function tests
  • pain or irritation where the medicine was injected

Serious side effects of Pegvisomant include:

  • hives
  • wheezing
  • difficult breathing
  • light-headedness
  • swelling of the face, lips, tongue, or throat
  • thickening of the skin or a hard lump where you injected the medicine
  • easy bruising
  • liver problems—nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes)

Rare side effects of Pegvisomant include:

  • none

Seek medical care or call 911 at once if you have the following serious side effects:

  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, coordination loss, unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheadedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Are the Dosages of Pegvisomant?

Adult dosage

Powder for injection

  • 10 mg
  • 15 mg
  • 20 mg


Adult dosage

  • Load: 40 mg SC under physician supervision
  • Maintenance: 10 mg SC once a day; titrate by 5 mg increments every 4 to 6 weeks according to IGF-1 levels
  • No more than 30 mg/day maintenance
  • Monitor: Growth hormone (GH), IGF-1, LFTs (see cautions)

Dosage Considerations – Should be Given as Follows:

  • See “Dosages”

What Other Drugs Interact with Pegvisomant?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Pegvisomant has severe interactions with no other drugs
  • Pegvisomant has serious interactions with the following drug:
    • macimorelin
  • Pegvisomant has moderate interactions with at least 31 other drugs
  • Pegvisomant has minor interactions with at least 23 other drugs

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your healthcare professional or doctor for additional medical advice, health questions, or concerns.

What Are Warnings and Precautions for Pegvisomant?


  • Hypersensitivity to pegvisomant or latex (vial stopper contains latex)

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Pegvisomant?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Pegvisomant?”


  • Potential for growth hormone (GH) deficiency; observe patients for signs or symptoms of GH deficiency; monitor serum insulin-like growth factor 1 (IGF-1) every 4 to 6 weeks
  • Lipohypertrophy may occur; rotation of the injection site may reduce the occurrence
  • May increase liver function tests; obtain baseline serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), serum total bilirubin (TBIL), and alkaline phosphatase (ALP) levels before initiating therapy

Pregnancy and Lactation

  • Postmarketing reports of use in pregnant women are insufficient to establish a drug-associated risk for major birth defects, miscarriage, or adverse maternal or fetal outcomes
  • Published data from case reports, case series, and a small interventional study in pregnant women with acromegaly have demonstrated that acromegaly may improve or stabilize without treatment during pregnancy, particularly if acromegaly is treated before pregnancy
  • In rare cases, acromegaly may worsen during pregnancy; since IGF-1 levels may change physiologically during pregnancy and interpreting IGF-1 and growth hormone levels in pregnant women with acromegaly may be unreliable, clinical monitoring is recommended
  • Reproductive potential
    • Discuss the potential for unintended pregnancy with premenopausal women as therapeutic benefits of a reduction in GH levels and normalization of IGF-1 concentration in women with acromegaly treated with Pegvisomant may lead to improved fertility
  • Lactation
    • Limited information from a case report in published literature reported that the level of the drug in human milk was below the level of detection
    • There is no information available on the effects of the drug on breastfed infants or effects on milk production; the developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for therapy and any potential adverse effects on the breastfed child from therapy or underlying maternal condition

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