What tests are required before prescribing phosphodiesterase type 5 inhibitors (PDE5Is) for a new patient presenting with erectile dysfunction (ED) and low libido?

Testing Requirements Before Prescribing PDE5 Inhibitors for ED with Low Libido

For a new patient presenting with erectile dysfunction and low libido, testosterone levels should be measured before prescribing PDE5 inhibitors, as low testosterone is present in 12.5-36% of men with ED and may predict treatment response, though routine hormonal testing is not required for all ED patients without symptoms of hypogonadism. 1

Divergent Guideline Recommendations on Hormonal Testing

The evidence presents conflicting guidance on testosterone testing:

American College of Physicians Position (2009)

• Does not recommend routine hormonal blood tests for all ED patients 1
• Recommends individualizing the decision to measure testosterone based on clinical presentation suggesting hormonal abnormality 1:
  • Decreased libido (as in your patient)
  • Premature ejaculation
  • Fatigue
  • Physical findings: testicular atrophy, muscle atrophy

Princeton III Consensus & International Guidelines (2012)

• Recommends measuring testosterone in all men with organic ED, especially those for whom PDE5 inhibitor therapy failed 1
• This recommendation is supported by the British Society for Sexual Medicine and International Society for Sexual Medicine 1
• Based on evidence linking low testosterone to both ED and cardiovascular disease, with 36% of men seeking consultation for sexual dysfunction having hypogonadism 1

Recommended Testing Approach for Your Patient

Given your patient presents with both ED and low libido (a symptom suggesting hormonal dysfunction), testosterone testing is clearly indicated even by the more conservative ACP guidelines 1:

Essential Tests

• Testosterone levels (total testosterone, ideally measured in morning) 1
• Cardiovascular risk assessment including 1:
  • Blood pressure
  • Waist circumference and BMI
  • Lipid panel
  • Fasting glucose or HbA1c
  • Resting electrocardiogram (especially if hypertension or diabetes present)

Clinical History Elements

• Age and duration of ED 1
• Presence of cardiovascular symptoms 1
• Family history of premature cardiovascular disease (father <55 years, mother <65 years) 1
• Lifestyle factors: smoking, alcohol use, physical activity, diet 1
• Current medications, particularly nitrate use (absolute contraindication to PDE5 inhibitors) 1, 2

Physical Examination Findings

• Testicular size/atrophy 1
• Muscle atrophy 1
• Fundal arterial changes, cardiac auscultation, carotid bruits, peripheral pulses 1

PDE5 Inhibitor Prescribing Without Delay

You can initiate PDE5 inhibitor therapy immediately without waiting for testosterone results, as long as there are no contraindications 1:

Absolute Contraindications to Check

• Nitrate therapy (any form) - causes dangerous hypotension 1, 2
• Severe hepatic impairment (Child-Pugh Class C) 2

Cardiovascular Risk Stratification

• Patients unable to walk 1 mile in 20 minutes or climb 2 flights of stairs in 20 seconds without symptoms should be referred to cardiology before treatment 3
• Men with organic ED should be considered at increased cardiovascular risk until proven otherwise 1

Clinical Significance of Low Testosterone

If testosterone is low (12.5-36% prevalence in ED patients) 1:

• PDE5 inhibitors alone may have reduced efficacy 1
• Low testosterone is associated with increased all-cause and cardiovascular mortality (hazard ratios 1.24-2.56) 1
• Testosterone supplementation combined with PDE5 inhibitors may improve outcomes in hypogonadal men, though evidence quality is limited 1
• Testosterone therapy is not indicated for ED in men with normal testosterone levels 1, 4

Common Pitfalls to Avoid

• Do not delay PDE5 inhibitor initiation waiting for testosterone results in symptomatic patients without contraindications 1
• Always screen for nitrate use before prescribing - this is the most critical safety check 1, 2
• Do not assume PDE5 inhibitor failure without ensuring proper use: at least 5 attempts at maximum dose with adequate sexual stimulation 3, 4
• In patients on alpha-blockers, ensure they are stable on alpha-blocker therapy before initiating PDE5 inhibitors at the lowest dose 2

Practical Algorithm

1. Screen for nitrate use - if present, PDE5 inhibitors are contraindicated 1, 2
2. Assess cardiovascular risk - refer high-risk patients to cardiology first 1, 3
3. Order testosterone level (given low libido symptom) 1
4. Initiate PDE5 inhibitor at standard starting dose (e.g., sildenafil 50mg, tadalafil 10mg) 1, 2
5. Provide proper usage instructions - sexual stimulation required, multiple attempts needed 1, 4
6. Follow up to review testosterone results and adjust therapy if hypogonadism confirmed 1