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Plenaxis

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Plenaxis

Discontinued Warning IconPlease Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

Plenaxis™
(abarelix) for Injectable Suspension

WARNING

Immediate-onset systemic allergic reactions, some resulting in hypotension and syncope, have occurred after administration of Plenaxis™ . These immediate-onset reactions have been reported to occur following any administration of Plenaxis™ , including after the initial dose. The cumulative risk of such a reaction increases with the duration of treatment (see WARNINGS). Following each injection of Plenaxis™ , patients should be observed for at least 30 minutes in the office and in the event of an allergic reaction, managed appropriately.

  • Only physicians who have enrolled in the Plenaxis™ PLUS Program (Plenaxis™ User Safety Program), based on their attestation of qualifications and acceptance of prescribing responsibilities, may prescribe Plenaxis™ (See DOSAGE AND ADMINISTRATION and HOW SUPPLIED).
  • Plenaxis™ is indicated for the palliative treatment of men with advanced symptomatic prostate cancer, in whom LHRH agonist therapy is not appropriate and who refuse surgical castration, and have one or more of the following: (1) risk of neurological compromise due to metastases, (2) ureteral or bladder outlet obstruction due to local encroachment or metastatic disease, or (3) severe bone pain from skeletal metastases persisting on narcotic analgesia.
  • The effectiveness of Plenaxis™ in suppressing serum testosterone to castrate levels decreases with continued dosing in some patients (see CLINICAL PHARMACOLOGY, Pharmacodynamics). Effectiveness beyond 12 months has not been established. Treatment failure can be detected by measuring serum total testosterone concentrations just prior to administration on Day 29 and every 8 weeks thereafter (see WARNINGS).

DRUG DESCRIPTION

Abarelix for injectable suspension (Plenaxis™ ) is a synthetic decapeptide with potent antagonistic activity against naturally occurring gonadotropin releasing-hormone (GnRH). Plenaxis™ inhibits gonadotropin and related androgen production by directly and competitively blocking GnRH receptors in the pituitary.

Abarelix is chemically described as acetyl-D-β-naphthylalanyl-D-4-chlorophenylalanyl- D-3-pyridylalanyl-L-seryl-L-N-methyl-tyrosyl-D-asparagyl-L-leucyl-L-N(ε)-isopropyllysyl- L-prolyl-D-alanyl-amide. It is initially manufactured as an acetate water complex and converted to a carboxymethylcellulose (CMC) water complex in manufacturing the drug product. The molecular weight for abarelix anhydrous free base is 1416.06.

The structural formula for abarelix peptide is:

Plenaxis™  (abarelix) Structural Formula Illustration

Abarelix for injectable suspension is supplied as a white to off-white sterile dry powder which, when mixed with the diluent, 0.9% Sodium Chloride Injection, USP, becomes a depot suspension intended for intramuscular (IM) injection. The single-dose vial contains 113 mg of anhydrous free base abarelix peptide (net) supplied in an abarelix CMC complex. This complex also contains 19.1 to 31 mg of CMC. After the vial is reconstituted with 2.2 mL of 0.9% sodium chloride injection, 2 mL is administered to deliver a dose of 100 mg of abarelix (net) as the abarelix CMC complex at a pH of 5±1.

Last reviewed on RxList: 5/26/2011
This monograph has been modified to include the generic and brand name in many instances.

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