Implantable Puberty Blocker: Type and Dosing
The implantable puberty blocker used clinically is histrelin acetate (Vantas), which is administered as a 50 mg subcutaneous implant that releases approximately 65 μg/day and lasts for one year. 1, 2
Mechanism and Administration
- Histrelin is a synthetic gonadotropin-releasing hormone (GnRH) agonist that suppresses gonadotropin release from the anterior pituitary when administered continuously 3
- The implant is inserted subcutaneously under local anesthesia, typically in the inner upper arm 1
- The implant provides continuous slow release of histrelin, eliminating the need for monthly injections 1, 2
Efficacy
- Histrelin implants achieve suppression of gonadotropins (LH and FSH) and sex steroids (estradiol/testosterone) within 1 month of insertion 2
- Suppression is maintained throughout the entire year of implant use 2, 4
- Clinical effects include regression of secondary sexual characteristics, decreased growth velocity, and slowed bone age advancement 1
Duration and Replacement
- Each implant is effective for 12 months and requires replacement annually 2, 4
- Long-term studies have shown that continuous suppression can be maintained for up to 6 years with annual implant replacement 4
- Some preliminary data suggest the implant may remain effective for up to 2 years, though the standard recommendation is annual replacement 5
Advantages Over Injectable GnRH Analogs
- Eliminates the pain and discomfort associated with monthly injections 1
- Provides more consistent hormone suppression than monthly depot injections 2
- Reduces the need for frequent clinic visits, potentially improving treatment compliance 1
Considerations and Side Effects
- The most common adverse event is a skin reaction at the insertion site 3
- The implant requires a minor surgical procedure for both insertion and removal 1
- Removal may be difficult in some cases, particularly after extended use 5
- After discontinuation, the hypothalamic-pituitary-gonadal axis recovers without adverse effects 4
Comparative Costs
- The annual cost of the histrelin implant (Vantas) is approximately $4,350.02 6
- This compares to other GnRH analogs such as leuprolide depot (Lupron) which costs between $1,235.22-$3,025.80 for 6 months depending on dosing schedule 6
The histrelin implant represents an effective option for puberty suppression with the convenience of once-yearly administration, though at a higher cost than some injectable alternatives.