Testosterone Cypionate 150 mg Every Two Weeks Conversion to Xyosted
Testosterone cypionate 150 mg every two weeks is approximately equivalent to Xyosted 75 mg administered subcutaneously once weekly.
Dosing Rationale
The conversion is based on both total weekly testosterone delivery and the pharmacokinetic profiles of these formulations:
- Testosterone cypionate 150 mg every 2 weeks delivers approximately 75 mg per week on average
- Xyosted starting dose is 75 mg weekly 1
This represents a straightforward 1:1 weekly dose equivalence when converting from the biweekly intramuscular cypionate regimen.
Important Pharmacokinetic Differences
While the weekly doses are equivalent, Xyosted provides more stable testosterone levels throughout the dosing interval compared to traditional intramuscular testosterone cypionate 2, 3. The subcutaneous auto-injector formulation was specifically designed to minimize peak-to-trough fluctuations that occur with intramuscular injections 4.
Key advantages of Xyosted's pharmacokinetic profile:
- Mean total testosterone levels remain stable between 487-553 ng/dL at trough 2
- Less than 5% of patients experience supraphysiological peaks (>1,500 ng/dL) 2
- Associated with lower post-therapy estradiol and hematocrit compared to intramuscular testosterone cypionate 4
Dose Titration Protocol
After initiating Xyosted at 75 mg weekly, measure trough testosterone levels (drawn 7 days after the most recent dose) at 6 weeks 1:
- If trough ≥650 ng/dL: Decrease to 50 mg weekly
- If trough <350 ng/dL: Increase to 100 mg weekly
- If trough 350-650 ng/dL: Maintain 75 mg weekly
This target range of 350-650 ng/dL at trough ensures testosterone exposures remain in the normal range throughout the entire weekly dosing interval 1.
Clinical Monitoring
The Endocrine Society guidelines recommend monitoring at 3 months and annually thereafter 5, 6:
- Testosterone levels: Measured at trough (day 7 post-injection for Xyosted)
- Hematocrit: At 3-6 months, then annually; discontinue if >54% 6, 1
- PSA and digital rectal exam: At 3-12 months for men 40-69 years at increased risk who choose prostate monitoring 6
Common Pitfalls to Avoid
Do not assume direct dose equivalence without monitoring. Individual patient response varies significantly, and the subcutaneous route may produce different testosterone exposure than intramuscular administration in some patients 7. The 75 mg starting dose should be viewed as an initial estimate requiring confirmation with serum levels at 6 weeks.
Avoid intramuscular administration of Xyosted. This formulation is specifically designed for subcutaneous injection in the abdominal region only 1. The pharmacokinetic profile and safety data are based on subcutaneous administration.