Pegvisomant

SOMAVERT

Open Pegvisomant in the interactive console ↗

What it isGrowth hormone receptor antagonist; acromegaly.

Why this oneIt normalizes IGF-1 when somatostatin analogues have failed, because it blocks the receptor rather than the hormone.

What limits itMeasured GH rises and becomes uninterpretable — IGF-1 is the only useful marker. Daily injection; transaminase rise.

FDA-approved for

Acromegaly (2003)

FDA label

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FDA dosing	Population	Start	Target	Max
Acromegaly	Adults	40 mg SC loading dose (under HCP supervision), then 10 mg SC QD starting next day	10–30 mg SC QD, titrated to normalize age-adjusted serum IGF-1	30 mg SC QD

Titration Adjust by 5 mg increments/decrements every 4–6 weeks based on serum IGF-1 (measure q4–6 wk); do not adjust on GH levels or symptoms

Renal Undefined

Hepatic Baseline LTs >3× ULN: do not initiate until comprehensive workup establishes cause (r/o cholelithiasis, esp. after somatostatin analogs)

Instructions

Obtain baseline ALT, AST, total bilirubin, alkaline phosphatase before first dose; monitor per label schedule (monthly ×6 mo if normal baseline)
Reconstitute with supplied diluent against vial wall; swirl slowly — do not shake or invert (protein denaturation); use immediately; solution must be clear
Inject SC into upper arm, upper thigh, abdomen, or buttocks at 90°; rotate site daily to prevent lipohypertrophy
Serum GH assays read falsely elevated on therapy — do not use GH to guide dosing

Cautions

Hypoglycemia in diabetes mellitus (GH lowering improves glucose tolerance) — monitor glucose, reduce anti-diabetic drugs as needed
Liver toxicity — discontinue immediately if LTs ≥5× ULN, or ≥3× ULN with any bilirubin rise; weekly LTs for elevations 3–5× ULN
Cross-reactivity with GH assays — measured GH appears falsely elevated
Lipohypertrophy — rotate injection sites daily
Systemic hypersensitivity (anaphylaxis, laryngospasm, angioedema) — close monitoring if re-initiating

Adverse reactions

Infection (23% at 10 mg)
Pain
Nausea
Diarrhea
Abnormal liver tests
Flu syndrome
Injection site reaction
Transaminase elevations (occasionally >10× ULN)
Postmarketing: anaphylaxis, angioedema, urticaria

Pregnancy Insufficient human data; rabbit post-implantation loss at 6× MRHD (BSA); acromegaly itself may improve during pregnancy; normalized IGF-1 may improve fertility — advise on unintended pregnancy

Lactation Case report: pegvisomant below detection level in human milk; infant effects unknown — weigh benefit vs maternal need

NO BOXED WARNINGS

Principal riskMeasured GH becomes uninterpretable; only IGF-1 guides dosing