VANTAS
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VANTAS (VANTAS).
Gonadotropin-releasing hormone (GnRH) agonist; continuous stimulation suppresses pituitary gonadotropin secretion, resulting in decreased testosterone production.
| Metabolism | Primarily metabolized by peptidases; not dependent on cytochrome P450 enzymes. |
| Excretion | Renal: negligible. Fecal: ~100% (unchanged drug). Histrelin is not metabolized and is excreted unchanged in feces via biliary elimination. |
| Half-life | Terminal elimination half-life approximately 4 weeks (28 days) due to continuous release from the implant; after implant removal, plasma concentrations decline with a half-life of about 3-4 days. |
| Protein binding | Approximately 50-70% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Approximately 4-5 L/kg, indicating extensive distribution into tissues. |
| Bioavailability | Subcutaneous implant: 100% (systemic delivery via continuous release). |
| Onset of Action | Subcutaneous implant: Suppression of testosterone to castrate levels occurs within 2-4 weeks after implantation. |
| Duration of Action | The implant provides continuous therapeutic effect for 12 months; after removal, testosterone levels return to baseline within 4-8 weeks. |
| Molecular Weight | 1323.5 |
10 mg subcutaneously every 24 weeks.
| Dosage form | IMPLANT |
| Renal impairment | No adjustment required for creatinine clearance ≥15 mL/min. Insufficient data for GFR <15 mL/min. |
| Liver impairment | No adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not studied in severe impairment (Child-Pugh C). |
| Pediatric use | Not approved for use in pediatric patients. |
| Geriatric use | No specific dose adjustment required; monitor for cardiovascular effects and bone mineral density loss. |
| 1st trimester | Contraindicated: May cause fetal harm due to androgen suppression. No adequate studies; animal studies show fetal abnormalities. |
| 2nd trimester | Contraindicated: Continued androgen suppression may impair fetal development, including genital development in male fetuses. |
| 3rd trimester | Contraindicated: Risk of fetal harm persists; avoid use throughout pregnancy. |
Clinical note
Comprehensive clinical and safety monograph for VANTAS (VANTAS).
| Placental transfer | Evidence: For histrelin, placental transfer is likely given its molecular size; animal studies demonstrate fetal effects. Specific human data absent, but presumed transfer occurs. |
| Breastfeeding | Excretion into human milk unknown. However, due to potential serious adverse effects in nursing infants (androgen suppression), breastfeeding is not recommended during therapy. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to histrelin or GnRH agonists (e.g., anaphylaxis)Pregnancy (Category X)Undiagnosed vaginal bleeding (potential androgen-sensitive tumor)
| Precautions | Transient increase in serum testosterone during initial treatment may cause worsening of prostate cancer symptoms or ureteral obstruction., Monitor serum testosterone levels periodically., May cause injection site reactions including pain, bruising, and nodule formation., Not indicated for use in women or children. |
| Food/Dietary | No specific food interactions; however, limit alcohol as it may exacerbate liver burden during androgen deprivation therapy. |
Loading safety data…
| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | Category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: Risk of spontaneous abortion and major congenital malformations including urogenital abnormalities. Second and third trimesters: Risk of fetal androgenization, specifically clitoral hypertrophy and labial fusion in female fetuses. |
| Fetal Monitoring | Pregnancy test required prior to initiation and monthly during therapy. Monitor for signs of pregnancy. In case of accidental exposure, immediate discontinuation and fetal ultrasound for genital development. |
| Fertility Effects | Impairs fertility in males and females via suppression of gonadotropins. Males: Oligospermia or azoospermia, testicular atrophy, decreased libido. Females: Anovulation, menstrual irregularities, reversible upon discontinuation. |
| Clinical Pearls |
| Monitor serum testosterone levels 1 month after insertion; if not suppressed, confirm implant presence via palpation or ultrasound. Do not rely on PSA alone for castration efficacy. Handle with care to avoid needle-stick injury; implant contains 50 mg histrelin acetate. Remove after 12 months; failure to remove may lead to prolonged suppression. For insertion, use the provided trocar subcutaneously in the inner upper arm; avoid deep placement to prevent nerve damage. |
| Patient Advice | The implant provides continuous hormone suppression for 12 months; you must return to have it removed before or at 12 months. · Do not attempt to remove or manipulate the implant yourself; it is placed under the skin of your upper arm. · Common side effects include hot flashes, erectile dysfunction, loss of libido, and injection site reactions (bruising, pain). · Report any signs of infection (redness, swelling, pus) or implant migration immediately. · The implant may affect bone density; ensure adequate calcium and vitamin D intake, and discuss bone health monitoring with your doctor. |