SOMAVERT (Pegvisomant)
Growth hormone receptor antagonist for acromegaly treatment
Quick Facts About SOMAVERT
Key Takeaways About SOMAVERT
- Treats acromegaly: SOMAVERT is the only growth hormone receptor antagonist approved for treating acromegaly, particularly when surgery or other therapies have not adequately controlled the disease
- Daily subcutaneous injection: After an initial 80 mg loading dose, patients self-inject 10 mg daily, with dose adjustments every 4–6 weeks based on IGF-1 levels
- Liver monitoring required: Liver function tests must be performed before treatment and every 4–6 weeks during the first 6 months; treatment should stop if persistent liver problems occur
- May affect diabetes management: As acromegaly improves, insulin sensitivity may increase, requiring adjustments to diabetes medications
- Rotate injection sites: To prevent lipohypertrophy (fatty lumps under the skin), injection sites should be varied with each dose
What Is SOMAVERT and What Is It Used For?
SOMAVERT (pegvisomant) is used to treat acromegaly, a rare hormonal disorder characterised by excessive production of growth hormone (GH), usually caused by a benign pituitary tumour (adenoma). It is the only available growth hormone receptor antagonist and works by blocking the action of GH at its receptor, thereby lowering circulating levels of IGF-1.
Acromegaly is a chronic condition that develops when the pituitary gland produces too much growth hormone, typically due to a GH-secreting pituitary adenoma. This excess GH stimulates the liver and other tissues to produce elevated levels of insulin-like growth factor 1 (IGF-1), which in turn causes the characteristic features of the disease: gradual enlargement of the hands, feet and facial features; soft tissue swelling; joint pain; cardiovascular complications; and metabolic disturbances including insulin resistance and diabetes.
The active substance in SOMAVERT is pegvisomant, a genetically engineered analogue of human growth hormone that has been structurally modified so that it binds to the GH receptor without activating it. By occupying the receptor site, pegvisomant acts as a competitive antagonist, preventing endogenous GH from triggering its normal downstream signalling cascade. This mechanism is fundamentally different from somatostatin analogues (such as octreotide or lanreotide), which work by reducing GH secretion from the pituitary.
SOMAVERT is typically prescribed to patients with acromegaly who have had an inadequate response to surgery, radiation therapy, or somatostatin analogue therapy. Clinical trials have demonstrated that pegvisomant normalises IGF-1 levels in approximately 90–97% of patients when the dose is appropriately titrated, making it one of the most effective treatments for biochemical control of acromegaly. According to the Endocrine Society’s clinical practice guidelines, pegvisomant should be considered as second-line medical therapy or in combination with somatostatin analogues when first-line treatment has failed to achieve adequate disease control.
Acromegaly affects approximately 3–14 people per 100,000 worldwide and is typically diagnosed in middle-aged adults. Because the disease progresses slowly, there is often a delay of 5–10 years between symptom onset and diagnosis. If left untreated, acromegaly can lead to serious complications including cardiovascular disease, diabetes, arthritis, sleep apnoea, and an increased risk of colorectal polyps. Early and effective treatment is essential to reduce morbidity and mortality.
What Should You Know Before Taking SOMAVERT?
Before starting SOMAVERT, your physician should evaluate your liver function, monitor your pituitary tumour size, and review all medications you are taking. SOMAVERT is not recommended during pregnancy, and women of childbearing age should use contraception during treatment.
Contraindications
Do not use SOMAVERT if you are allergic (hypersensitive) to pegvisomant or any of the other ingredients in this medicine. The inactive ingredients include glycine, mannitol (E421), anhydrous disodium phosphate, and sodium dihydrogen phosphate monohydrate. The diluent is water for injections. SOMAVERT contains less than 1 mmol (23 mg) of sodium per dose and is considered essentially sodium-free.
Warnings and Precautions
Talk to your physician, pharmacist or nurse before using SOMAVERT. Several important precautions should be observed during treatment:
Liver function monitoring: Your physician will perform liver function tests (LFTs) before starting treatment and at regular intervals during therapy. During the first six months, liver enzyme levels should be checked every 4–6 weeks. Elevations in transaminases (ALT and AST) have been reported in patients receiving pegvisomant, and treatment should be discontinued if there are persistent signs of liver disease. If your liver test values are abnormal before treatment, your physician will discuss alternative treatment options with you.
Pituitary tumour monitoring: Your physician will monitor the size of your pituitary adenoma during treatment. Unlike somatostatin analogues, pegvisomant does not reduce tumour size and there have been reports of tumour growth during pegvisomant therapy. Regular imaging (typically with MRI) is recommended, particularly during the first year of treatment and in patients with large tumours situated close to the optic chiasm. If you experience visual disturbances or new headaches, contact your physician immediately.
Diabetes and glucose metabolism: Acromegaly is associated with insulin resistance, and many patients have impaired glucose tolerance or overt diabetes mellitus. As SOMAVERT normalises GH/IGF-1 levels and the disease improves, insulin sensitivity typically increases. This may necessitate dose adjustments of insulin or oral hypoglycaemic agents. Blood glucose levels should be monitored regularly, particularly during the early months of treatment and during dose titration.
Fertility considerations: Female patients may experience increased fertility as acromegaly improves during treatment with SOMAVERT. Women of childbearing potential should be advised to use effective contraception. See the pregnancy section below for further details.
Contact your physician immediately if you experience visual disturbances, severe or unusual headaches, signs of an allergic reaction (swelling of the face, tongue, lips or throat; wheezing or difficulty breathing; generalised skin rash; hives or itching; or dizziness), or signs of liver problems (yellowing of the skin or eyes, dark urine, persistent nausea, or upper abdominal pain).
Pregnancy and Breastfeeding
The use of SOMAVERT during pregnancy is not recommended. Animal studies are insufficient to fully assess the potential risk, and there are no adequate and well-controlled studies in pregnant women. If you are a woman of childbearing potential, you should use effective contraception during treatment with SOMAVERT. If you become pregnant while receiving treatment, inform your physician immediately so that the benefits and risks of continuing therapy can be evaluated.
It is not known whether pegvisomant is excreted in human breast milk. Breastfeeding is not recommended during treatment with SOMAVERT unless the potential benefit to the mother outweighs the potential risk to the infant, as determined by your physician. If you are pregnant or breastfeeding, think you may be pregnant, or are planning to have a baby, consult your physician or pharmacist before using this medicine.
Driving and Operating Machinery
No studies have been conducted on the effects of SOMAVERT on the ability to drive or use machinery. However, some patients may experience dizziness or somnolence during treatment. If affected, patients should exercise caution when driving or operating machinery.
How Does SOMAVERT Interact with Other Drugs?
SOMAVERT may interact with insulin and oral hypoglycaemic agents, as normalisation of GH/IGF-1 levels can improve insulin sensitivity and alter glucose metabolism. Previous treatment with somatostatin analogues or other acromegaly medications should also be discussed with your physician.
Drug interactions with SOMAVERT are primarily related to its pharmacological effects on glucose metabolism. As the disease improves during treatment, the metabolic changes associated with acromegaly may reverse, affecting the pharmacokinetics and pharmacodynamics of co-administered drugs. You should tell your physician about all medications you are taking, have recently taken, or might take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.
Patients with acromegaly frequently have comorbid conditions that require concomitant medication. Studies have shown that pegvisomant can affect the clearance of drugs metabolised by the cytochrome P450 system, as elevated GH levels in acromegaly can alter hepatic enzyme activity. As GH levels are normalised during pegvisomant treatment, the metabolism of these drugs may change, potentially requiring dose adjustments.
| Drug / Drug Class | Interaction Type | Clinical Significance | Recommendation |
|---|---|---|---|
| Insulin | Pharmacodynamic | Improved insulin sensitivity may cause hypoglycaemia | Monitor blood glucose; reduce insulin dose as needed |
| Oral hypoglycaemics (e.g., metformin, sulfonylureas) | Pharmacodynamic | Risk of hypoglycaemia as glucose metabolism normalises | Monitor blood glucose; adjust doses as necessary |
| Somatostatin analogues (octreotide, lanreotide) | Pharmacokinetic | May alter pegvisomant absorption; combination use studied | Can be used in combination under specialist supervision |
| Opioids | Pharmacodynamic | May reduce GH levels and affect disease monitoring | Inform physician if taking opioid medications |
| CYP450 substrates (e.g., certain statins, warfarin) | Pharmacokinetic | Normalisation of GH may alter hepatic enzyme activity | Monitor therapeutic levels of co-administered drugs |
It is important that you continue taking all medications prescribed to you, including SOMAVERT, unless your physician, pharmacist or nurse tells you otherwise. Do not stop or change the dose of any medication without first consulting your healthcare provider.
What Is the Correct Dosage of SOMAVERT?
SOMAVERT treatment begins with an 80 mg loading dose administered by a healthcare professional, followed by daily subcutaneous self-injections of 10 mg. The dose is then titrated every 4–6 weeks in 5 mg increments based on serum IGF-1 levels to achieve optimal disease control.
Always use SOMAVERT exactly as your physician or pharmacist has instructed. Consult your physician or pharmacist if you are unsure about any aspect of your treatment. The goal of treatment is to normalise serum IGF-1 levels while minimising side effects.
Adults
Loading Dose
Your physician will give you a first subcutaneous injection of 80 mg pegvisomant. This loading dose is necessary to rapidly achieve therapeutic drug levels and is typically administered in a clinical setting under medical supervision.
Maintenance Dose
Starting the day after the loading dose, the daily maintenance dose is 10 mg given as a subcutaneous injection. Your physician will adjust the dose every 4–6 weeks in increments of 5 mg per day, based on your serum IGF-1 levels, to maintain optimal therapeutic response. The maximum recommended dose is 30 mg per day.
| Phase | Dose | Route | Notes |
|---|---|---|---|
| Loading dose (Day 1) | 80 mg | Subcutaneous | Administered by healthcare professional |
| Initial maintenance | 10 mg daily | Subcutaneous | Self-injection; begin day after loading dose |
| Dose titration | ±5 mg adjustments | Subcutaneous | Every 4–6 weeks based on IGF-1 levels |
| Maximum dose | 30 mg daily | Subcutaneous | Do not exceed without medical supervision |
Children and Adolescents
The safety and efficacy of SOMAVERT in children and adolescents under 18 years of age have not been established. There are limited data available, and use in the paediatric population is not recommended unless under the direct supervision of a paediatric endocrinologist experienced in managing growth hormone disorders.
Elderly Patients
No dose adjustment is required for elderly patients. However, as older patients may have reduced hepatic and renal function, dose titration should be performed with care, and liver function tests should be monitored regularly. Clinical experience in patients over 65 years of age is limited.
Missed Dose
If you forget to take a dose of SOMAVERT, inject the next dose as soon as you remember. Then continue to inject SOMAVERT as prescribed by your physician. Do not inject a double dose to make up for a forgotten dose. If you have any further questions about using this medicine, contact your physician, pharmacist or nurse.
Overdose
If you accidentally inject more SOMAVERT than your physician has prescribed, it is unlikely that any serious harm will occur. However, you should contact your physician, pharmacist or nurse immediately. Experience with overdose is limited, but no specific adverse effects beyond exaggerated pharmacological activity would be expected. In clinical studies, single doses of up to 80 mg have been administered without acute toxicity. Treatment of overdose should be supportive and symptomatic.
SOMAVERT must be reconstituted (dissolved) before use. The powder should be mixed with the provided diluent by gently swirling – never shake the vial, as shaking can cause foaming and render the medicine unusable. After reconstitution, the solution should appear clear and free of particles. It should be used immediately. Rotate injection sites (abdomen, thighs, upper arms) with each dose to prevent lipohypertrophy. Detailed injection instructions are provided with your medication.
What Are the Side Effects of SOMAVERT?
Like all medicines, SOMAVERT can cause side effects, although not everyone experiences them. The most common side effects include headache, diarrhoea, and joint pain. Injection site reactions and elevated liver enzymes are also frequently reported. Rare but serious allergic reactions may occur.
Mild to severe allergic (anaphylactic) reactions have been reported in some patients receiving SOMAVERT. Symptoms of a severe allergic reaction may include one or more of the following: swelling of the face, tongue, lips or throat; wheezing or difficulty breathing (laryngospasm); generalised skin rash; hives (urticaria) or itching; or dizziness. Contact your physician immediately if you develop any of these symptoms.
Approximately 17% of patients develop antibodies to growth hormone during treatment. These antibodies do not appear to interfere with the efficacy of the medication.
Very Common
- Headache
- Diarrhoea
- Joint pain (arthralgia)
Common
- Injection site reactions (bruising, bleeding, tenderness, swelling, lipohypertrophy)
- Elevated liver enzymes (visible in blood test results)
- Shortness of breath
- Blood in the urine (haematuria)
- Elevated blood pressure (hypertension)
- Constipation, nausea, vomiting, bloating, indigestion, flatulence
- Dizziness, drowsiness, involuntary tremor, reduced sense of touch
- Excessive sweating, itching, rash, increased tendency to bruise
- Muscle pain (myalgia), arthritis
- Elevated cholesterol, weight gain, elevated or reduced blood glucose
- Flu-like symptoms, fatigue, weakness, fever
- Swollen arms and legs (peripheral oedema)
- Abnormal dreams, eye pain
Uncommon
- Allergic reactions after drug administration (fever, rash, itching, and in severe cases breathing difficulties, rapid tissue swelling requiring immediate medical attention)
- Protein in the urine, increased urine volume, kidney problems
- Apathy, confusion, increased libido, panic attacks, memory loss, sleep disturbances
- Decreased platelet count; increased or decreased white blood cell count; bleeding tendency
- Feeling of being abnormal, impaired wound healing
- Eye strain, inner ear problems
- Facial swelling, dry skin, night sweats, skin redness (erythema), raised itchy bumps (urticaria)
- Elevated blood lipids, increased appetite
- Dry mouth, increased salivation, dental problems, haemorrhoids
- Altered taste, migraine
Reported (frequency unknown)
- Anger
- Severe shortness of breath (laryngospasm)
- Rapid swelling of skin and underlying tissues (angioedema)
It is important to report suspected side effects after the medicine has been authorised. This allows continued monitoring of the benefit-risk balance of the medicine. Healthcare professionals and patients are encouraged to report any suspected adverse reactions to their national regulatory authority.
How Should You Store SOMAVERT?
SOMAVERT powder vials should be stored in a refrigerator at 2–8°C, protected from light. They can be stored at room temperature (up to 25°C) for up to 30 days if kept away from light. Once reconstituted, the solution must be used immediately.
Keep this medicine out of the sight and reach of children. Do not use after the expiry date stated on the vial and carton after “EXP”. The expiry date refers to the last day of the stated month.
Powder vials: Store in the original carton in a refrigerator (2°C–8°C) to protect from light. Do not freeze. The carton containing SOMAVERT powder vials may be stored at room temperature at a maximum of 25°C for a single period of up to 30 days. The new use-by date must be written on the carton in the format day/month/year (no more than 30 days from the date removed from the refrigerator). The vials must be protected from light. This medicine should not be returned to the refrigerator after room temperature storage. Discard if not used by the new use-by date or the printed expiry date, whichever comes first.
Pre-filled diluent syringes: Store at a maximum of 30°C or in a refrigerator (2°C–8°C). Do not freeze.
Reconstituted solution: After dissolving the powder, the solution should be used immediately. Do not use the solution if it is cloudy or contains particles.
Do not throw away any medicines via household waste or wastewater. Ask your pharmacist how to dispose of medicines you no longer use. These measures help protect the environment.
What Does SOMAVERT Contain?
The active substance in SOMAVERT is pegvisomant, available in 10, 15, 20, 25 and 30 mg vials. Each vial is reconstituted with 1 ml of water for injections to produce a solution containing the corresponding concentration of pegvisomant.
SOMAVERT is supplied as a powder and solvent for solution for injection. The powder is white, and the solvent (water for injections) is clear and colourless. It is supplied in pack sizes of 1 and/or 30 vials. Not all pack sizes may be marketed in all countries.
| Strength | Pegvisomant per Vial | Diluent Volume | Final Concentration |
|---|---|---|---|
| SOMAVERT 10 mg | 10 mg | 1 ml | 10 mg/ml |
| SOMAVERT 15 mg | 15 mg | 1 ml | 15 mg/ml |
| SOMAVERT 20 mg | 20 mg | 1 ml | 20 mg/ml |
| SOMAVERT 25 mg | 25 mg | 1 ml | 25 mg/ml |
| SOMAVERT 30 mg | 30 mg | 1 ml | 30 mg/ml |
Inactive ingredients (excipients): glycine, mannitol (E421), anhydrous disodium phosphate, and sodium dihydrogen phosphate monohydrate. The diluent is water for injections. SOMAVERT contains less than 1 mmol (23 mg) of sodium per dose and is considered essentially sodium-free.
The marketing authorisation holder is Pfizer Europe MA EEIG, Brussels, Belgium. The medicine is manufactured by Pfizer Manufacturing Belgium NV, Puurs-Sint-Amands, Belgium. Additional information about SOMAVERT is available on the European Medicines Agency (EMA) website.
How Do You Prepare and Inject SOMAVERT?
SOMAVERT is supplied as a powder that must be reconstituted with the provided diluent before injection. The reconstituted solution is injected subcutaneously (under the skin) daily. You should receive training from a healthcare professional before attempting self-injection.
It is important that you do not attempt to give yourself or someone else an injection unless you have received training from a healthcare professional. SOMAVERT is provided in a vial as a white powder block. You must mix SOMAVERT with the diluent (solvent) provided in the pre-filled syringe before use. Do not use any other liquid to mix with SOMAVERT, and do not mix SOMAVERT with other medicines in the same syringe or vial.
Step-by-Step Preparation
- Gather your supplies: You will need the SOMAVERT powder vial, the pre-filled diluent syringe, the injection needle with safety shield, an alcohol swab, a cotton ball, and a sharps disposal container.
- Prepare the vial: Remove the pack from the refrigerator and allow it to reach room temperature naturally. Wash your hands thoroughly with soap and water. Do not use the vial or syringe if they appear damaged, expired, or if the syringe has been frozen.
- Choose an injection site: Suitable sites include the abdomen, thigh or upper arm. Rotate the injection site with each dose to prevent lipohypertrophy. Avoid areas with bruising, redness, sores, hardness, scars or skin problems. Clean the injection site with an alcohol swab and allow it to dry.
- Remove the vial cap: Remove the flip-off cap from the powder vial and discard it. Do not let anything touch the vial stopper.
- Prepare the syringe: Break off the syringe cap, attach the needle with safety shield by screwing it firmly onto the syringe, and then carefully remove the needle cover.
- Add diluent to the vial: Push the needle through the centre of the vial stopper. Tilt both the vial and syringe slightly, then push the plunger slowly to empty all the diluent into the vial. Do not spray the liquid directly onto the powder, as this causes foaming that renders the medicine unusable.
- Dissolve the powder: Keeping the needle in the vial, hold both with one hand and gently swirl the liquid by moving the vial in a circular motion on a flat surface. Continue swirling until all the powder has completely dissolved. This may take up to 5 minutes. Never shake the vial.
- Check the solution: With the needle still in the vial, inspect the medicine carefully. It must be clear and free of particles. Do not use if the medicine is cloudy, coloured, or contains particles or a layer of foam.
- Withdraw the dose: Invert the vial and reposition the needle tip to the lowest point in the liquid. Pull the plunger back slowly to draw out as much medicine as possible. If you see air in the syringe, tap the barrel so bubbles rise to the top, then gently push them back into the vial.
- Inject the medicine: Gently pinch the skin at the injection site. Insert the needle fully into the skin fold. Push the plunger slowly until the syringe barrel is empty. Release the skin fold and withdraw the needle straight out.
- Secure and dispose: Fold the needle safety shield over the needle and press gently against a hard surface to lock it in place (you will hear a click). Dispose of the syringe and needle in a sharps container. Never reuse syringes or needles. If needed, gently press a clean cotton ball on the injection site without rubbing.
What if something touches the vial stopper? Clean it with a new alcohol swab and let it dry completely. Do not use the vial if you cannot clean the stopper.
What if I drop the syringe? Do not use it, even if it appears undamaged. Dispose of it properly and use a new syringe.
Can I shake the vial? No. Shaking can destroy the medicine and cause foaming. Continue gently swirling until the liquid is completely clear.
Is a small amount of air in the syringe OK? Small air bubbles in the liquid are normal and safe to inject. However, larger bubbles or air gaps should be pushed back into the vial before injection.
Frequently Asked Questions About SOMAVERT
SOMAVERT (pegvisomant) is used to treat acromegaly, a hormonal disorder caused by excess growth hormone production, usually from a benign pituitary tumour. It works by blocking growth hormone receptors, reducing elevated IGF-1 levels and alleviating symptoms such as excessive bone and soft tissue growth, cardiovascular complications, and metabolic disturbances. It is typically prescribed when surgery, radiation, or somatostatin analogue therapy has not provided adequate disease control.
SOMAVERT is injected once daily as a subcutaneous (under the skin) injection. Treatment starts with an 80 mg loading dose given by your healthcare provider, followed by daily self-injections of 10 mg. The dose is then adjusted every 4–6 weeks based on your blood IGF-1 levels. It is important to inject at approximately the same time each day and to rotate injection sites to prevent skin problems at the injection area.
If you miss a dose, inject it as soon as you remember. Then continue with your regular daily injection schedule as prescribed by your physician. Do not inject a double dose to make up for a missed one. If you are unsure about what to do, contact your physician, pharmacist or nurse for guidance.
SOMAVERT is not recommended during pregnancy. Women of childbearing age should use effective contraception during treatment, as fertility may increase as acromegaly symptoms improve. It is not known whether pegvisomant passes into breast milk, so breastfeeding is generally not recommended during treatment. If you become pregnant or are planning a pregnancy, consult your physician immediately to evaluate the best course of action.
Pegvisomant can cause elevations in liver enzymes (transaminases), which in rare cases may indicate liver injury. Regular monitoring allows your physician to detect any changes early and take appropriate action, which may include adjusting the dose or discontinuing the medication. During the first 6 months, liver function should be tested every 4–6 weeks. After this initial period, your physician will determine the appropriate monitoring schedule based on your individual response.
Yes, SOMAVERT may affect blood glucose control. As acromegaly improves during treatment, insulin sensitivity typically increases, which can lead to lower blood sugar levels. This may require adjustments to your insulin dose or oral diabetes medications. Regular blood glucose monitoring is recommended, particularly during the early months of treatment. Always inform your physician about all diabetes medications you are taking.
References and Medical Sources
This article is based on evidence from the following internationally recognised medical sources:
- European Medicines Agency (EMA). SOMAVERT (pegvisomant) – Summary of Product Characteristics (SmPC). Last updated 2025. Available at: EMA EPAR – SOMAVERT.
- Katznelson L, Laws ER Jr, Melmed S, et al. Acromegaly: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2014;99(11):3933–3951. doi:10.1210/jc.2014-2700.
- Trainer PJ, Drake WM, Katznelson L, et al. Treatment of acromegaly with the growth hormone-receptor antagonist pegvisomant. N Engl J Med. 2000;342(16):1171–1177. doi:10.1056/NEJM200004203421604.
- van der Lely AJ, Biller BM, Brue T, et al. Long-term safety of pegvisomant in patients with acromegaly: comprehensive review of 1288 subjects in ACROSTUDY. J Clin Endocrinol Metab. 2012;97(5):1589–1597. doi:10.1210/jc.2011-2508.
- Melmed S, Bronstein MD, Chanson P, et al. A Consensus Statement on acromegaly therapeutic outcomes. Nat Rev Endocrinol. 2018;14(9):552–561. doi:10.1038/s41574-018-0058-5.
- World Health Organization (WHO). WHO Model List of Essential Medicines. 23rd List, 2023.
- British National Formulary (BNF). Pegvisomant. National Institute for Health and Care Excellence (NICE). 2025.
- U.S. Food and Drug Administration (FDA). SOMAVERT Prescribing Information. Revised 2024.
About the Medical Editorial Team
This article has been written and reviewed by the iMedic Medical Editorial Team, which consists of licensed specialist physicians and pharmacists with expertise in endocrinology, pharmacology, and evidence-based medicine.
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iMedic Medical Editorial Team
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