Eligard’s active ingredient, leuprolide, clears from your bloodstream within days of the depot running out, but its effects on testosterone suppression last far longer. The drug itself has a terminal half-life of about 3 hours once it reaches your blood. However, Eligard is a slow-release injection designed to continuously deliver leuprolide over 1, 3, 4, or 6 months depending on your formulation. So the real answer depends on whether you’re asking about the drug molecule itself or the hormonal suppression it causes.
How the Slow-Release System Works
Eligard isn’t a simple injection that enters your bloodstream all at once. It uses a polymer-based delivery system that forms a small solid implant under the skin at the injection site. This implant gradually breaks down and releases leuprolide at a controlled rate throughout the dosing period. At the end of a 6-month cycle with the 45 mg formulation, studies show that 99% to 100% of the leuprolide has been released from the implant. The implant itself, though, can still be felt as a firm lump under the skin even after the drug has fully released. It continues to biodegrade on its own over time.
The four available formulations and their designed release periods are:
- 7.5 mg: 1 month
- 22.5 mg: 3 months
- 30 mg: 4 months
- 45 mg: 6 months
How Quickly Leuprolide Leaves Your Blood
Once leuprolide enters the bloodstream, it’s broken down rapidly by enzymes called peptidases, the same type of enzymes your body uses to digest proteins. The terminal elimination half-life is approximately 3 hours. That means after the depot stops releasing drug, blood levels drop to near zero within about a day. Traces of a leuprolide metabolite have been detected in urine up to 29 days after a dose, but at extremely low concentrations.
Less than 50% of leuprolide in the blood is bound to plasma proteins, which means it circulates mostly in free form and is cleared relatively quickly. No formal studies have been done on how kidney or liver problems affect Eligard clearance specifically, so if you have significant issues with either organ, that’s worth discussing with your treatment team.
Why the Effects Last Much Longer Than the Drug
Here’s the part that matters most to people asking this question: even after leuprolide is completely gone from your body, its impact on testosterone production persists for months or even years. Eligard works by continuously stimulating the pituitary gland’s hormone signaling, which paradoxically shuts it down. This suppression doesn’t just flip back on when the drug disappears. Your hormonal system needs time to reboot.
With the 45 mg formulation, clinical trials confirmed that testosterone stays suppressed below the castration threshold (50 ng/dL) in 100% of patients for the full 6-month dosing period. A second dose maintained that suppression without causing a new testosterone spike.
Testosterone Recovery After Stopping Eligard
This is where the timeline gets much longer than most people expect. A study of 208 men who stopped androgen deprivation therapy (the class of treatment Eligard belongs to) tracked how long it took for testosterone to recover to two different thresholds.
For recovery to 50 ng/dL, the castration threshold, the median time was 11 months. A quarter of men recovered by 7 months, while another quarter took 13 months or longer. About 75% of men in the study eventually reached this level.
Recovery to a normal testosterone level (350 ng/dL) took dramatically longer. The median time was 93 months, roughly 7.5 years. A quarter of men didn’t reach that level until about 8.5 years after stopping treatment. And 81% of the men in the study never recovered to normal testosterone at all during a median follow-up of over 6 years.
Several factors influence how quickly your testosterone recovers. Younger men tend to recover faster. The total duration of treatment matters significantly: someone who was on Eligard for 6 months will generally recover much sooner than someone who received it for 2 or 3 years. Baseline testosterone levels before treatment also play a role.
What This Means in Practical Terms
If you’re scheduled for a procedure like surgery or imaging and wondering about drug clearance, the leuprolide molecule itself will be undetectable in your blood within a few days of the depot running dry. If you’re stopping treatment and wondering when side effects like hot flashes, fatigue, or low libido will ease, the answer depends on testosterone recovery, which typically begins within several months but may take much longer to reach levels where you feel meaningfully different.
The physical depot under your skin is the longest-lasting physical remnant. It remains as a palpable lump at the injection site for weeks to months after the drug has fully released, gradually dissolving on its own without needing removal. It’s harmless but can be noticeable, especially with the larger-dose formulations.