Histrelin Acetate

Pronunciation: (hiss-TREL-in AS-e-tate)Class: Gonadotropin-releasing hormone analog

Trade Names:Supprelin LA- Implant 50 mg

Trade Names:Vantas- Implant 50 mg

Pharmacology

Inhibits gonadotropin secretion.

Pharmacokinetics

Absorption

C max is 1.1 ng/mL, occurring in 12 h. Bioavailability is 92%. Average rate of subcutaneous drug release is 56.7 mcg/day.

Distribution

Vd following subcutaneous bolus of 500 mcg is 58 L. Unbound drug in plasma is 29.5%.

Metabolism

One single metabolite resulting from C-terminal dealkylation and possible fragments resulting from hydrolysis. Apparent Cl after a 50 mg subcutaneous implant is approximately 174 mL/min.

Elimination

Terminal t ½ is 3.92 h.

Special Populations

Renal Function Impairment

Average serum histrelin concentrations are approximately 50% higher in patients with renal function impairment.

Hepatic Function Impairment

No data.

Indications and Usage

Supprelin LA

Treatment of children with central precocious puberty.

Vantas

Palliative treatment of advanced prostate cancer.

Contraindications

Women who are or may become pregnant while receiving this drug; patients hypersensitive to gonadotropin-releasing hormone (GnRH), GnRH agonist analogs, or any component of the product; women and children ( Vantas ).

Dosage and Administration

Adults ( Supprelin LA – 2 yr of age and older)

Subcutaneous 1 implant (50 mg) for 12 mo. Implant must be removed after 12 mo, at which time another implant may be inserted to continue therapy.

General Advice

For subcutaneous implantation only. Not for intradermal, IM, or oral administration.
Follow manufacturer's instructions regarding preparation of injection site, preparation of insertion tool, insertion of implant, and closing of the incision site.

Storage/Stability

Store implant in refrigerator (36° to 46°F). Protect from light. Do not freeze.

Drug Interactions

None well documented.

Laboratory Test Interactions

Results of diagnostic tests of pituitary gonadotropic and gonadal function may be affected.

Adverse Reactions

Cardiovascular

Palpitations, ventricular extrasystoles (less than 2%).

CNS

Fatigue (10%); headache, insomnia (3%); decreased libido (2%); depression, dizziness, irritability, lethargy, malaise, tremor, weakness (less than 2%).

Dermatologic

Contusion, hematoma, hypotrichosis, increased sweating, night sweats, pruritus (less than 2%).

GI

Constipation (4%); abdominal discomfort, nausea (less than 2%).

Genitourinary

Renal function impairment, testicular atrophy (5%); erectile dysfunction, gynecomastia (4%); aggravated gynecomastia, aggravated hematuria, aggravated renal failure, aggravated urinary frequency, breast pain, breast tenderness, dysuria, genital pruritus (male), renal calculus, sexual dysfunction, urinary frequency, urinary retention (less than 2%).

Hematologic-Lymphatic

Anemia (less than 2%).

Hepatic

Hepatic disorder (less than 2%).

Lab Tests

Increased AST, blood glucose, blood LDH, blood testosterone, and prostatic acid phosphatase, decreased CrCl (less than 2%).

Local

Implant-site reactions (51%); keloid scar, scar, suture-related complication (6%); application-site pain, postprocedural pain (4%); wound infection.

Metabolic-Nutritional

Weight increase (2%); fluid retention, food craving, hypercalcemia, hypercholesterolemia, increased appetite, peripheral edema, weight decrease (less than 2%).

Musculoskeletal

Aggravated back pain, arthralgia, back pain, bone pain, muscle twitching, myalgia, neck pain, pain in limb (less than 2%).

Respiratory

Exertional dyspnea (less than 2%).

Miscellaneous

Hot flashes (66%); exacerbated pain, feeling cold, flushing, pain, stent occlusion (less than 2%).

Precautions

Monitor

Supprelin LA

Monitor luteinizing hormone, follicle stimulating hormone, and estradiol or testosterone at 1 mo post implantation then every 6 mo thereafter. Assess height and bone age every 6 to 12 mo.

Vantas

Ensure serum testosterone and prostate-specific antigen are periodically measured to monitor response to therapy, especially if anticipated clinical or biochemical response to therapy has not been achieved.

Pregnancy

Category X .

Lactation

Undetermined.

Children

Supprelin LA

Safety and efficacy not established in children younger than 2 yr of age.

Vantas

Contraindicated.

Worsening symptoms

Patients may experience worsening of symptoms or onset of new symptoms during the first week of treatment.

Patient Information

Advise patient that implant containing medication will be prepared and implanted by health care provider in a health care setting.
Review the treatment regimen, including implantation and removal of implant, dosing schedule, duration of treatment, and monitoring that will be required.
Advise patient to read the patient information leaflet before the insert is implanted and each time another histrelin implant is inserted.
Advise patient that some pain, redness, and/or bruising at the implant insertion site may occur but that these usually go away without treatment within 2 wk. Instruct patient to contact health care provider immediately if unusual bleeding or persistent or worsening pain or redness at the insertion site occur.
Caution patient not to wet the arm where implant was inserted for 24 h following implantation, at which time the pressure bandage can be removed. Caution patient not to remove surgical strips but to allow the strips to fall off on their own (may take several days). Caution patient to avoid heavy lifting or strenuous exertion of the inserted arm for 7 days following implant insertion.
Advise patient that histrelin implant infrequently can be expelled from the body through the original insertion site. Advise patient to contact health care provider if the implant has been expelled.
Advise patient that pellet will deliver histrelin to the body for 12 mo, and then the implant must be removed. Inform patient that a new histrelin implant may be implanted at that time by health care provider if therapy is to be continued.
Advise patient to contact health care provider immediately if new or worsening bone pain, weakness or loss of feeling in legs, blood in the urine, or difficulty urinating occur.