October 6, 2015
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"By Peter Russell
WebMD Health News
Reviewed by Arefa Cassoobhoy, MD, MPH

They say the research could lead to better treatment, because doctors would be able to know which tumors are more likely to grow and spread.



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

Side Effects


Immediate-Onset Systemic Allergic Reactions: See BOXED WARNINGS and WARNINGS

In the single study of Plenaxis™ conducted in men with advanced symptomatic prostate cancer, adverse events reported by ≥ 10% of patients are listed in Table 4. Adverse events are listed without regard to causality. Causality is often difficult to assess in elderly patients with multiple co-morbidities and prostate cancer.

Table 4: Adverse Events in ≥ 10% of Patients in the Advanced Symptomatic Prostate Cancer Study (without regard for causality).

Preferred Term Plenaxis™
n (%)
Hot flushes* 64 (79)
Sleep disturbance* 36 (44)
Pain 25 (31)
Breast enlargement* 24 (30)
Breast pain/nipple tenderness* 16 (20)
Back pain 14 (17)
Constipation 12 (15)
Peripheral edema 12 (15)
Dizziness 10 (12)
Headache 10 (12)
Upper respiratory tract infection 10 (12)
Diarrhea 9 (11)
Dysuria 8 (10)
Fatigue 8 (10)
Micturition frequency 8 (10)
Nausea 8 (10)
Urinary retention 8 (10)
Urinary tract infection 8 (10)
* Pharmacological consequence of androgen deprivation

Changes in Laboratory Values

Clinically meaningful increases in serum transaminases were seen in a small percentage of patients in both treatment groups in each active-controlled Plenaxis™ study. In Study 1 and Study 2 combined, the percentage of Plenaxis™ patients reporting serum ALT > 2.5 times upper limit of normal or > 200 U./L was 8.2% and 1.8%, respectively. The percentage reporting serum AST > 2.5 times upper limit of normal or > 200 U/L was 3.1% and 0.8%, respectively. Similar results were reported for active comparators.

Slight decrease in hemoglobin, a pharmacological consequence of castration, were observed in patients receiving Plenaxis™ and active comparator. Mean increases in serum triglycerides of approximately 10% were seen in Plenaxis™ -treated patients.

Read the Plenaxis (abarelix) Side Effects Center for a complete guide to possible side effects


No formal drug/drug interaction studies with Plenaxis™ were performed. Cytochrome P-450 is not known to be involved in the metabolism of Plenaxis™ . Plenaxis™ is highly bound to plasma proteins (96 to 99%).

Laboratory Tests

Response to Plenaxis™ should be monitored by measuring serum total testosterone concentrations just prior to administration on Day 29 and every 8 weeks thereafter (see WARNINGS). Serum transaminase levels should be obtained before starting treatment with Plenaxis™ and periodically during treatment. Periodic measurement of serum PSA levels may also be considered.

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

Side Effects

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.


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