Dosing and uses of Somavert (pegvisomant)
Adult dosage forms and strengths
powder for injection
- 10mg
- 15mg
- 20mg
Acromegaly
Load: 40 mg SC under physician supervision
Maintenance: 10 mg SC qDay; titrate by 5 mg increments q4-6Weeks according to IGF-1 levels
No more than 30 mg/day maintenance
Monitor: Growth hormone (GH), IGF-1, LFTs (see cautions)
Administration
- Reconstitiute with 1 mL supplied diluent (sterile water for injection)
- Inject within 6 hours of reconstitution
- Rotate injection sites daily
Hepatic Impairment
Obtain baseline LFTs
- WNL: monitor qMonth for 6 months, then quarterly for 6 months, then bianually for 1yr
- Elevated, but ≤ 3 times ULN: monitor qMonth for 1 yr, then bianually for 1 yr
- >3 times ULN: Do not use pegvisomant until full workup for cause of liver dysfunction; if decision made to initiate treatment, monitor LFTs very closely
LFTs During Treatment
- ≥3 times, but less than 5 times ULN: continue treatment; monitor LFTs qWk and perform comprehensive hepatic workup
- ≥5 times ULN: Discontinue pegvisomant; perform hepatic workup & monitor serial LFTs; if LFTs normalize, may re-initiate treatment with frequent monitoring
- Signs or symptoms of hepatitis or other liver injury: hepatic workup; if liver injury confirmed, discontinue pegvisomant
Pediatric dosage forms and strengths
Safety and efficacy not established
Somavert (pegvisomant) adverse (side) effects
>10%
Pain
Injection site reaction
Diarrhea
Nausea
Flu syndrome
1-10%
Injury
Back pain
Chest pain
Dizziness
Paresthesia
Edema
Hypertension
Sinusitis
Lipohypertrophy
Postmarketing Reports
Elevated transaminases
Systemic hypersensitivity reactions including anaphylactic/anaphylactoid reactions, laryngospasm, angioedema, generalized skin reactions (rash, erythema, pruritus, urticaria)
Warnings
Contraindications
Hypersensitivity to pegvisomant or latex (vial stopper contains latex)
Cautions
Potential for GH deficiency; observe patients for signs or symptoms of GH deficiency; monitor serum IGF-1 q4-6wk
Lipohypertrophy may occur; rotation of injection site may reduce occurence
May increase liver function tests
Pregnancy and lactation
Pregnancy category: B
Lactation: not known if crosses in to breast milk, use caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Somavert (pegvisomant)
Mechanism of action
Recombinant human growth hormone receptor antagonist, with several polyethylene glycol (PEG) polymers covalently bound
Pharmacokinetics
Half-Life: 6 days
Onset: within 2 wk
Peak Plasma Time: 33-77 hr
Bioavailability: 57% (SC)
Vd: 7 L
Clearance: Total body: 28-36 mL/hr
Excretion: unknown
