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Abarelix

GnRH Antagonist

Also known as: Plenaxis

The first GnRH antagonist approved in the US for prostate cancer, providing immediate testosterone suppression without flare. Withdrawn from market but historically significant.

Typical Dose

100 mg IM on days 1, 15, 29; then monthly

Route

Intramuscular depot

Cycle

Monthly maintenance

Half-life

~13 days

Storage

Per manufacturer

Overview

Abarelix was the first GnRH antagonist approved by the FDA for prostate cancer (2003), predating degarelix. It was withdrawn from the US market in 2005 due to serious hypersensitivity reactions (anaphylaxis in ~1% of patients). Degarelix has largely replaced it clinically with a better safety profile.

Quick Start Guide

1

Withdrawn from US market. Historical reference only.

Research Indications

Prostate cancer

Most Effective

Approved for symptom palliation where GnRH agonist flare is clinically unacceptable.

Side Effects & Safety

Common

  • Hot flashes
  • Injection site pain
  • Breast enlargement

Uncommon

  • Anaphylaxis (~1% — reason for market withdrawal)
  • QT prolongation

When to Stop

  • Hypersensitivity reaction — carry epinephrine

How to Reconstitute

1

Historical product. Not currently available.

Dosing math: Not commercially available in most markets.

What to Expect

Days 1–3

Testosterone suppression without flare.

Community Insights

Self-reported. Reflects user experience, not clinical outcomes.

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Information on this page applies to pharmaceutical-grade peptides. Purity & identity of research-grade products vary. Certipep provides independent ESI-TOF-MS & HPLC analysis with a signed analytical report.

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