What is the recommended initial approach to injected therapy for erectile dysfunction?

Initial Approach to Intracavernous Injection Therapy for Erectile Dysfunction

The first dose of intracavernous injection (ICI) therapy must be administered under direct healthcare provider supervision in the office to determine the effective dose, teach proper injection technique, and monitor for adverse effects—particularly prolonged erection. 1, 2

Medication Selection

FDA-Approved vs. Compounded Options

• Alprostadil (prostaglandin E1) is the only FDA-approved medication for intracavernous injection in the United States and is typically used as monotherapy 1
• Combination therapy ("bimix" or "trimix") using papaverine, phentolamine, alprostadil, and/or atropine can increase efficacy or reduce side effects but requires compounding pharmacy services 1
• Physician preference guides initial medication choice, with final selection based on efficacy, side effects, and cost 1

Starting with Alprostadil Monotherapy

• Alprostadil monotherapy is readily available at most pharmacies, making it the most practical first-line choice 1
• The dose-response relationship is significant, with response rates increasing from 2.5 to 20 mcg 3
• In clinical trials, 94% of injections resulted in successful sexual activity, with 87% rated satisfactory by patients 3

In-Office Test Dose Protocol

Essential Components of First Visit

• Healthcare provider must be present to instruct on proper intracavernous drug administration technique 1, 2
• Dose titration occurs during this visit to establish the minimal effective dose 1
• Monitor vital signs, particularly blood pressure and heart rate, especially in patients with cardiovascular disease 1
• Observe for adverse effects, with special attention to prolonged erection 1, 2

Dose Finding Strategy

• For alprostadil monotherapy, the minimal effective dose is ≤2 mcg in 23% of men with neurogenic ED, 20% with vasculogenic ED, 38% with psychogenic ED, and 23% with mixed causes 3
• Start with lower doses and titrate upward based on response 3
• The goal is an erection lasting no longer than 1 hour 4

Critical Safety Counseling

Priapism Management Plan

Before prescribing ICI therapy, physicians must: (1) inform patients about prolonged erections, (2) establish a plan for urgent treatment of prolonged erections, and (3) communicate this plan clearly to the patient 1, 2

• Priapism is defined as erection lasting >4 hours and requires prompt intervention to avoid corporal tissue damage 1
• Patients must report erections lasting ≥4 hours immediately 1, 2
• For prolonged erections <4 hours following ICI, intracavernous phenylephrine is the initial treatment 1, 2
• The incidence of priapism with alprostadil is <1% with long-term use 4

Frequency Limitations

• ICI therapy should not be used more than once in a 24-hour period 1, 2
• This restriction minimizes complications and prevents tissue damage 1

Patient Education Requirements

Injection Technique Training

• Thorough instruction and training in self-injection technique is mandatory before home use 1, 4
• Effective training and periodic follow-up decrease improper injection and treatment failure 1, 2
• Patients should be able to adjust dose within specific bounds to match their needs after initial titration 1, 2

Injection Site Selection

• Choose mid-shaft location on alternating sides of the penis 4
• Avoid visible blood vessels 4
• Vary the injection site with each use to prevent fibrosis 4

Expected Timeline

• Erection should occur within 5-20 minutes after injection 4
• Use a 29-gauge superfine needle to minimize discomfort 4
• Apply firm pressure to injection site for 5 minutes after injection to prevent bruising 4

Common Adverse Effects to Discuss

Penile Pain

• Occurs in 29-35% of patients at some point during treatment but only 15% of individual injections 4
• Pain is mild in 80% of cases, moderate in 16%, and severe in only 4% 4
• Frequency decreases over time: 41% experience pain in first 2 months vs. 3% at 21-24 months 4

Local Complications

• Penile fibrosis occurs in 7.8% of patients over 24 months, including Peyronie's disease in 1% 4
• Treatment should be discontinued if penile angulation, cavernosal fibrosis, or Peyronie's disease develops 4
• Local bleeding, hematoma, and ecchymosis occur in 15%, 5%, and 4% respectively, mostly from faulty injection technique 4

Special Precautions

• Patients on anticoagulants (warfarin, heparin) have increased bleeding risk and require compression of injection site for full 5 minutes 4
• Cardiovascular risk assessment is essential—ICI therapy should not be used when sexual activity is inadvisable due to underlying cardiovascular status 4

Follow-Up Strategy

Regular Monitoring

• Regular follow-up with careful penile examination at treatment start and at 3-month intervals is strongly recommended to identify penile changes 4
• Periodic reassessment ensures proper technique and appropriate dosing 1, 2
• Review between 4 weeks and 6 months allows for treatment modification or cessation 1

Efficacy Expectations

Success Rates

• ICI therapy is the most effective non-surgical treatment for ED 1
• With alprostadil, 66% of patients self-injecting at home achieve erections adequate for intercourse 1
• Patient and partner satisfaction rates reach 80-90% 1
• Even patients who failed prior ICI therapy may respond to alternative formulations: 58% of "non-responders" to previous ICI achieved adequate erections with transurethral alprostadil 5