Can a male patient with hypogonadism, who has shown improvement in symptoms and increased total testosterone (TT) and free testosterone (FT) levels from 4 to 18 and 147 to 660 respectively, be switched from biweekly testosterone injections to a monthly schedule?

Switching to Monthly Testosterone Injections is Not Recommended

Based on current guidelines, switching from biweekly to monthly testosterone injections is not advisable because the pharmacokinetics of testosterone cypionate/enanthate result in peak levels at 2-5 days post-injection with return to baseline by days 10-14, making monthly dosing intervals too long to maintain stable therapeutic levels. 1

Why Monthly Dosing is Problematic

The standard FDA-approved dosing for testosterone cypionate/enanthate is 50-400 mg every 2-4 weeks, not monthly. 1 The pharmacokinetic profile shows:

• Peak serum testosterone occurs 2-5 days after injection 1
• Testosterone levels return to baseline by days 13-14 after injection 1
• This creates a predictable cycle where levels are supraphysiologic early and subtherapeutic late in the dosing interval 1

Extending to monthly injections would result in 2-3 weeks of subtherapeutic testosterone levels each cycle, potentially causing symptom recurrence and defeating the purpose of treatment. 1

Current Dosing is Already Suboptimal

Your patient's testosterone levels suggest they may already be experiencing significant fluctuations:

• Total testosterone of 18 ng/dL (assuming units are ng/dL, which would be 180 ng/dL if you meant 18 x 10) is actually quite low if measured mid-cycle 1
• For patients on biweekly injections, testosterone should be measured midway between injections (days 5-7), targeting mid-normal values of 500-600 ng/dL 1

Better Alternatives to Consider

Option 1: Switch to Weekly Injections (Preferred)

Weekly dosing provides more stable testosterone levels and reduces the peaks and troughs associated with biweekly dosing. 1 This approach:

• Uses 100 mg weekly instead of 200 mg every 2 weeks 1
• Maintains more consistent therapeutic levels 1
• Reduces risk of erythrocytosis compared to higher-dose biweekly injections 1

Option 2: Switch to Transdermal Preparations

Transdermal testosterone (gels, patches) provides the most stable day-to-day testosterone levels and is often favored over intramuscular injections for this reason. 1, 2 Benefits include:

• Relative stability of testosterone levels from day-to-day 1
• Lower risk of erythrocytosis (3-18%) compared to injections (up to 44%) 2
• Easier dose titration 1

The main drawback is significantly higher cost ($2,135.32 annually vs. $156.24 for injections). 2

Option 3: Consider Extra-Long-Acting Testosterone Undecanoate

Testosterone undecanoate can be dosed every 10 weeks after initial loading, providing fewer yearly injections with more stable levels. 1 Dosing protocol:

• 750 mg initially
• Repeat at 4 weeks
• Then every 10 weeks thereafter 1

Critical Monitoring Needed

Before making any changes, verify the patient's current testosterone levels are appropriate:

• Measure testosterone midway between injections (not at trough) 1
• Target mid-normal range of 500-600 ng/dL 1
• Check hematocrit (withhold if >54%) 1
• Monitor PSA in men over 40 years 1

Common Pitfall to Avoid

Never extend dosing intervals beyond what the pharmacokinetics support simply for patient convenience. 1 The goal is stable, therapeutic testosterone levels throughout the dosing interval, not just achieving normal levels briefly after each injection. Monthly dosing with standard testosterone esters would result in prolonged periods of hypogonadal symptoms between injections, negating the benefits of treatment. 1