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U.S. BRAND NAMES — Plenaxis™ [DSC]
PHARMACOLOGIC CATEGORY Gonadotropin Releasing Hormone Antagonist
DOSING: ADULTS — Male prostate cancer: I.M.: 100 mg administered on days 1, 15, 29 (week 4), then every 4 weeks
DOSING: ELDERLY — Refer to adult dosing.
DOSAGE FORMS — Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product.
Injection, powder for reconstitution [preservative free]: 113 mg [provides 100 mg/2 mL depot suspension when reconstituted; packaged with diluent and syringe] [DSC]
GENERIC EQUIVALENT AVAILABLE — No
ADMINISTRATION — Administer intramuscularly (to the buttock).
USE — Palliative treatment of advanced prostate cancer; treatment is limited to men who are not candidates for LHRH therapy, refuse surgical castration, and have one or more of the following complications due to metastases or local encroachment: 1) risk of neurological compromise, 2) ureteral or bladder outlet obstruction, or 3) severe bone pain (persisting despite narcotic analgesia)
ADVERSE REACTIONS SIGNIFICANT >10%: Cardiovascular: Hot flushes (79%), peripheral edema (15%) Central nervous system: Sleep disturbance (44%), pain (31%), dizziness (12%), headache (12%) Endocrine & metabolic: Breast enlargement (30%), nipple discharge/tenderness (20%) Gastrointestinal: Constipation (15%), diarrhea (11%) Neuromuscular & skeletal: Back pain (17%) Respiratory: Upper respiratory infection (12%)
1% to 10%: Central nervous system: Fatigue (10%) Endocrine & metabolic: Serum triglycerides increased (10%) Gastrointestinal: Nausea (10%) Genitourinary: Dysuria (10%), micturition frequency (10%), urinary retention (10%), urinary tract infection (10%) Hepatic: Transaminases increased (2% to 8%) Miscellaneous: Allergic reactions (urticaria, pruritus, syncope, hypotension); risk increases with prolonged treatment
CONTRAINDICATIONS — Hypersensitivity to abarelix or any component of the formulation
WARNINGS / PRECAUTIONS Box warnings: Allergic reactions: See "Concerns related to adverse effects" below. Diminished efficacy: See "Other warnings/precautions" below. Plenaxis™ Plus Program: See "Other warnings/precautions" below.
Special handling: Hazardous agent: Use appropriate precautions for handling and disposal.
Concerns related to adverse effects: Allergic reactions: [U.S. Boxed Warning]: Has been associated with immediate-onset allergic reactions; may occur with initial dose and risk increases with duration of treatment. Observe for signs/symptoms of allergic reactions (which may include hypotension and/or syncope) for at least 30 minutes following each injection. Decreased bone mineral density: Extended treatment may result in a decrease in bone mineral density. QT prolongation: May cause prolongation of the QT interval; consider risk:benefit in patients with baseline QTc values >450 msec or patients receiving concurrent medications which prolong the QTc interval (class Ia and class III antiarrhythmics).
Other warnings/precautions: Diminished efficacy: [U.S. Boxed Warning]: Efficacy may diminish during prolonged treatment, particularly in patients weighing >225 pounds; monitor serum testosterone levels to identify treatment failures. Monitoring: Monitor transaminase levels and hepatic function during therapy. Plenaxis™ Plus Program: [U.S. Boxed Warning]: May only be prescribed by physicians enrolled in the Plenaxis™ Plus Program.
RESTRICTIONS — Abarelix is not distributed through retail pharmacies. Prior to its discontinuation, prescribing and distribution of abarelix was limited to physicians and hospital pharmacies participating in the Plenaxis™ PLUS program. Additional information may be obtained by calling 1-877-772-3247 or 1-866-753-2947.
DRUG INTERACTIONS — No formal drug interaction studies have been conducted.
QTc-prolonging agents: Additive QTc prolongation may occur. Life-threatening ventricular arrhythmias may result. Example drugs include class Ia and class III antiarrhythmics, cisapride, selected quinolones, erythromycin, pimozide, mesoridazine, and thioridazine.
PREGNANCY RISK FACTOR — X (show table)
PREGNANCY IMPLICATIONS — Not indicated for use in women; may cause fetal harm if administered to a pregnant woman.
LACTATION — Excretion in breast milk unknown/not indicated in women
BREAST-FEEDING CONSIDERATIONS — Not indicated for use in women
MONITORING PARAMETERS — Signs/symptoms of allergic reaction (for at least 30 minutes after each injection). Obtain transaminase levels at baseline and periodically during treatment. Serum testosterone (to identify treatment failure) just prior to abarelix administration, beginning on day 29 and every 8 weeks thereafter. PSA and bone mineral density may be monitored as needed.
REFERENCE RANGE — Efficacy may be monitored by suppression of serum testosterone <50 ng/dL
TOXICOLOGY / OVERDOSE COMPREHENSIVE — No experience in overdose. Treatment is symptomatic and supportive.
MECHANISM OF ACTION — Competes with naturally-occurring GnRH for binding on receptors of the pituitary. Suppresses LH and FSH, resulting in decreased testosterone.
PHARMACODYNAMICS / KINETICS Distribution: Vd: 4040 L (+/- 1607)
Metabolism: Hepatic, via peptide hydrolysis
Half-life elimination: 13 days
Time to peak, serum: 3 days (following I.M. administration)
Excretion: Urine (13% as unchanged drug)
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