pegvisomant

pegvisomant,

a rarely used miscellaneous agent.

indications This drug is used to treat acromegaly in those patients who have an inadequate response to other treatment.

contraindications Latex allergy and known hypersensitivity to this drug prohibit its use.

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pegvisomant

Somavert

Pharmacologic class: Growth hormone (GH) receptor antagonist

Therapeutic class: GH analog

Pregnancy risk category B

Action

Selectively binds to GH receptors on cell surfaces, where it blocks binding of endogenous GH and interferes with GH signal transduction. This action decreases blood levels of insulin-like growth factor-1 (IGF-1) and other GH-responsive serum proteins.

Availability

Solution: 10-mg, 15-mg, and 20-mg vials

⊘Indications and dosages

➣ Acromegaly

Adults: Initial subcutaneous loading dose of 40 mg, followed by 10 mg/day subcutaneously. May adjust in 5-mg increments after serum IGF-1 measurement q 4 to 6 weeks; don't exceed maximum daily maintenance dosage of 30 mg.

Contraindications

• Hypersensitivity to drug, its components, or latex (in vial stopper)

Precautions

Use cautiously in:
• GH-excreting tumors, diabetes mellitus, hepatic dysfunction
• pregnant or breastfeeding patients
• children.

Administration

• Reconstitute in vial with 1 ml of sterile water for injection.
• Roll vial gently between palms to mix; don't shake. Withdraw prescribed dosage and administer subcutaneously.

Route	Onset	Peak	Duration
Subcut.	Unknown	Unknown	24 hr

Adverse reactions

CNS: dizziness, paresthesia

CV: chest pain, hypertension, peripheral edema

EENT: sinusitis

GI: nausea, diarrhea, abdominal pain

Musculoskeletal: back pain

Other: infection, pain, injection site reaction, accidental injury, flulike symptoms

Interactions

Drug-drug. Insulin, oral hypoglycemics: decreased insulin sensitivity, reduced requirements for these drugs

Opioids: increased pegvisomant requirement

Drug-diagnostic tests. GH assays: interference with GH measurement

Liver function tests: abnormal results

Drug-behaviors. Opioid addiction: increased pegvisomant requirement

Patient monitoring

• Assess liver function tests; watch for signs and symptoms of hepatic dysfunction.
• Monitor serum IGF-1 level. If appropriate, discuss dosage adjustments with prescriber.
• Monitor vital signs; check for hypertension, chest pain, and peripheral edema.
• Measure temperature. Watch for signs and symptoms of infection, especially sinusitis or flulike symptoms.
• Assess blood glucose level closely in diabetic patient. Notify prescriber of significant decrease.

Patient teaching

• Teach patient proper technique for reconstituting and administering drug subcutaneously.
☞ Instruct patient to immediately report chest pain, peripheral edema, or signs or symptoms of infection.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects him.
• Teach diabetic patient to monitor blood glucose level closely and report significant decrease.
☞ Instruct patient to report yellowing of skin or eyes and other signs and symptoms of hepatic dysfunction. Tell him he'll undergo frequent liver function tests.
• As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.