VIADUR- leuprolide acetate
Bayer Pharmaceuticals Corporation
Viadur® (leuprolide acetate implant) is a sterile nonbiodegradable, osmotically driven miniaturized implant designed to deliver leuprolide acetate for 12 months at a controlled rate (Figure A). Viadur® incorporates DUROS® technology. The system contains 65 mg of leuprolide (free base). Leuprolide acetate is a synthetic nonapeptide analog of naturally occurring gonadotropin-releasing hormone (GnRH or LH-RH). The analog possesses greater potency than the natural hormone. The implant is inserted subcutaneously in the inner aspect of the upper arm. After 12 months, the implant must be removed. At the time an implant is removed, another implant may be inserted to continue therapy.
Viadur® contains 72 mg of leuprolide acetate (equivalent to 65 mg leuprolide free base) dissolved in 104 mg dimethyl sulfoxide. The 4 mm by 45 mm titanium alloy reservoir houses a polyurethane rate-controlling membrane, an elastomeric piston, and a polyethylene diffusion moderator. The reservoir also contains the osmotic tablets, which are not released with the drug formulation. The osmotic tablets are composed of sodium chloride, sodium carboxymethyl cellulose, povidone, magnesium stearate, and sterile water for injection. Polyethylene glycol fills the space between the osmotic tablets and the reservoir. A minute amount of silicone medical fluid is used during manufacture as a lubricant. The weight of the implant is approximately 1.1g.
Figure A Viadur® (leuprolide acetate implant) (diagram not to scale)
The chemical name is 5-Oxo-L-prolyl-L-histidyl-L-tryptophyl-L-seryl-L-tyrosyl-D-leucyl-L-leucyl-L-arginyl-N-ethyl-L-prolinamide acetate (salt), with the following structural formula:
Leuprolide acetate, an LH-RH agonist, acts as a potent inhibitor of gonadotropin secretion when given continuously and in therapeutic doses. Animal and human studies indicate that after an initial stimulation, chronic administration of leuprolide acetate results in suppression of ovarian and testicular steroidogenesis.
In humans, administration of leuprolide acetate results in an initial increase in circulating levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), leading to a transient increase in concentrations of gonadal steroids (testosterone and dihydrotestosterone in males, and estrone and estradiol in premenopausal females). However, continuous administration of leuprolide acetate results in decreased levels of LH and FSH. In males, testosterone is reduced to castrate levels. These decreases occur within 2 to 4 weeks after initiation of treatment.
One Viadur® Implant nominally delivers 120 micrograms of leuprolide acetate per day over 12 months. Leuprolide acetate is not active when given orally.
After insertion of Viadur® , mean serum leuprolide concentrations were 16.9 ng/mL at 4 hours and 2.4 ng/mL at 24 hours. Thereafter, leuprolide was released at a constant rate. Mean serum leuprolide concentrations were maintained at 0.9 ng/mL (0.3 to 3.1 ng/mL; SD = ±0.4) for 12 months. Upon removal and insertion of a new Viadur® at 12 months, steady-state serum leuprolide concentrations were maintained.
The mean steady-state volume of distribution of leuprolide following 1 mg intravenous (IV) bolus administration to healthy male volunteers was 27 L. In vitro binding to human plasma proteins ranged from 43% to 49%.1
In healthy male volunteers administered a 1 mg IV bolus of leuprolide, the mean systemic clearance was 8.34 L/h, with a terminal elimination half-life of approximately 3 hours, based on a two-compartment model.1
A pentapeptide (M-1) is the major leuprolide metabolite upon administration with different leuprolide acetate formulations. No drug metabolism study was conducted with Viadur®.
No drug excretion study was conducted with Viadur®.
In a study comparing one Viadur® implant to two Viadur® implants, mean serum leuprolide concentrations were proportional to dose.
The majority (88%) of the 131 patients studied in clinical trials were age 65 and over.
The safety and effectiveness of Viadur® in pediatric patients have not been established (see CONTRAINDICATIONS).
In the patients studied (80 Caucasian, 23 Black, 3 Hispanic), mean serum leuprolide concentrations were similar.
The pharmacokinetics of the drug in hepatically and renally impaired patients have not been determined.
No pharmacokinetic drug-drug interaction studies were conducted with Viadur®.
In two open-label, non-comparative, multicenter studies, 131 patients with prostatic cancer were treated with Viadur® and evaluated for up to two years. Two-thirds of the patients had stage C or less advanced disease. The dose-ranging study assessed serum testosterone as the primary efficacy endpoint in 51 patients treated with either one [n=27] or two [n=24] implants for 12 months. The confirmatory study evaluated achievement and maintenance of serum testosterone suppression in 80 patients each treated with one implant for 12 months. Both studies included a removal procedure and insertion of a new implant with evaluation for 12 additional months.
Following the initial insertion in patients receiving one implant, mean serum testosterone concentrations increased from 422 ng/dL at baseline to 690 ng/dL on Day 3, then decreased to below baseline by week two (Figure B). Serum testosterone decreased below the 50 ng/dL castrate threshold by week four in all but one patient [106 of 107 patients, 99%]. Once serum testosterone suppression was achieved [one patient was not continuously suppressed until week 28], testosterone remained suppressed below the castrate threshold for the duration of the treatment phase.
Figure B Mean (+SD) Serum Total Testosterone Concentrations – All Patients (n=107) Who Received One Implant
Most patients [n=118] had a new implant inserted for a second year of therapy following removal of the first implant(s). No patient experienced a clinically significant increase in serum testosterone [acute-on-chronic phenomenon] upon removal of the original implant(s) and insertion of a new implant. Suppression of serum testosterone was maintained in all patients through the two-month follow-up period following removal of the first implant(s) and insertion of a new implant.
Serum Prostate Specific Antigen (PSA) was monitored as a secondary endpoint in the clinical studies with Viadur®. Serum PSA decreased in all patients after they began treatment with Viadur®. At six months, PSA concentrations decreased from baseline by at least 90% in 74.2% of the 97 evaluable patients.
Periodic monitoring of serum testosterone and PSA concentrations is recommended, especially if the anticipated clinical or biochemical response to treatment has not been achieved.
Viadur® is indicated in the palliative treatment of advanced prostate cancer.
- Viadur® is contraindicated in patients with hypersensitivity to GnRH, GnRH agonist analogs, or any of the components in Viadur®. Anaphylactic reactions to synthetic GnRH or GnRH agonist analogs have been reported in the literature.2
- Viadur® is contraindicated in women and in pediatric patients and was not studied in women or children. Moreover, leuprolide acetate can cause fetal harm when administered to a pregnant woman. Major fetal abnormalities were observed in rabbits but not in rats after administration of leuprolide acetate throughout gestation. There were increased fetal mortality and decreased fetal weights in rats and rabbits. The effects on fetal mortality are expected consequences of the alterations in hormonal levels brought about by this drug. The possibility exists that spontaneous abortion may occur.
Viadur® , like other LH-RH agonists, causes a transient increase in serum concentrations of testosterone during the first week of treatment. Patients may experience worsening of symptoms or onset of new symptoms, including bone pain, neuropathy, hematuria, or ureteral or bladder outlet obstruction (see PRECAUTIONS).
Cases of ureteral obstruction and spinal cord compression, which may contribute to paralysis with or without fatal complications, have been reported with LH-RH agonists.
If spinal cord compression or renal impairment develops, standard treatment of these complications should be instituted.
Patients with metastatic vertebral lesions and/or with urinary tract obstruction should be closely observed during the first few weeks of therapy (see WARNINGS).
X-rays do not affect Viadur® functionality. Viadur® is radio-opaque and is well visualized on X-rays.
The titanium alloy reservoir of Viadur® is nonferromagnetic and is not affected by magnetic resonance imaging (MRI). Slight image distortion around Viadur® may occur during MRI procedures.
An information leaflet for patients is included with the product.
Response to Viadur® should be monitored by measuring serum concentrations of testosterone and prostate-specific antigen periodically.
Results of testosterone determinations are dependent on assay methodology. It is advisable to be aware of the type and precision of the assay methodology to make appropriate clinical and therapeutic decisions.
Therapy with leuprolide results in suppression of the pituitary-gonadal system. Results of diagnostic tests of pituitary gonadotropic and gonadal functions conducted during and after leuprolide therapy may be affected.
Two-year carcinogenicity studies were conducted in rats and mice. In rats, dose-related increases of benign pituitary hyperplasia and benign pituitary adenomas were noted at 24 months when the drug was administered subcutaneously at high daily doses (4 to 24 mg/m2 , 50 to 300 times the daily human exposure based on body surface area). There were significant but not dose-related increases of pancreatic islet-cell adenomas in females and of testicular interstitial cell adenomas in males (highest incidence in the low dose group). In mice no pituitary abnormalities were observed at up to 180 mg/m2 (over 2000 times the daily human exposure based on body surface area) for 2 years.
Mutagenicity studies were performed with leuprolide acetate using bacterial and mammalian systems. These studies provided no evidence of a mutagenic potential.
Pregnancy Category X (see CONTRAINDICATIONS).
Viadur® is contraindicated in pediatric patients and was not studied in children
The safety of Viadur® was evaluated in 131 patients with prostate cancer treated for up to 24 months in two clinical trials. Viadur® , like other LHRH analogs, caused a transient increase in serum testosterone concentrations during the first 2 weeks of treatment. Therefore, potential exacerbations of signs and symptoms of the disease during the first few weeks of treatment are of concern in patients with vertebral metastases and/or urinary obstruction or hematuria. If these conditions are aggravated, it may lead to neurological problems such as weakness and/or paresthesia of the lower limbs or worsening of urinary symptoms (see WARNINGS and PRECAUTIONS).
In the above-described clinical trials, the transient increase in serum testosterone concentrations was associated with an exacerbation of disease symptoms, manifested by pain or bladder outlet obstructive symptoms (urinary retention or frequency) in 6 (4.6%) patients.
The majority of local reactions associated with initial insertion or removal and insertion of a new implant began and resolved within the first two weeks. Reactions persisted in 9.3% of patients. 10.3% of patients developed application-site reactions after the first two weeks following insertion.
Local reactions after initial insertion of a single implant included bruising (34.6%) and burning (5.6%). Other, less frequently reported, reactions included pulling, pressure, itching, erythema, pain, edema, and bleeding.
In these two clinical trials, four patients had local infection/inflammations that resolved after treatment with oral antibiotics.
Local reactions following insertion of a subsequent implant were comparable to those seen after initial insertion.
In the first 12 months after initial insertion of the implant(s), an implant extruded through the incision site in three of 131 patients (see INSERTION AND REMOVAL PROCEDURES for correct implant placement).
The following possibly or probably related systemic adverse events occurred during clinical trials within 24 months of treatment with Viadur® , and were reported in ≥2% of patients (Table 1).
* Expected pharmacologic consequences of testosterone suppression.
|Body System||Adverse Event||Number (%)|
|Body as a Whole||Asthenia||10 (7.6%)|
|Extremity pain||4 (3.1%)|
|Cardiovascular||Vasodilatation (hot flashes)*||89 (67.9%)|
|Hematology and Lymphatic||Ecchymosis||6 (4.6%)|
|Metabolic and Nutritional||Peripheral edema||4 (3.1%)|
|Weight gain||3 (2.3%)|
|Urogenital||Gynecomastia/breast enlargement*||9 (6.9%)|
|Urinary frequency||5 (3.8%)|
|Testis atrophy or pain*||5 (3.8%)|
|Breast pain*||4 (3.1%)|
In addition, the following possibly or probably related systemic adverse events were reported by <2% of patients using Viadur® in clinical studies.
General: General pain, chills, abdominal pain, malaise, dry mucous membranes
Gastrointestinal: Constipation, nausea
Hematologic: Iron deficiency anemia
Metabolic: Edema, weight loss
Musculoskeletal: Bone pain, arthritis
Nervous: Dizziness, insomnia, paresthesia, amnesia, anxiety
Skin: Pruritus, rash, hirsutism
Urogenital: Urinary urgency, prostatic disorder, urinary tract infection, dysuria, urinary incontinence, urinary retention
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