Treatment Options · 5 min read
Intracavernosal Injections (TriMix)
When pills aren't enough, injection therapy is a highly effective next step — reliable, fast-acting, and learnable, even though the idea sounds intimidating.
What Are Intracavernosal Injections?
The needle is tiny and the technique is quickly learned. Here's what Dr. Mutter tells patients: if ten men come in for teaching, after the first injection about half say they barely felt it — and the other half say, 'that's not as big a deal as I thought.'
Results are among the most reliable of any non-surgical option, producing erections in over 80% of men — including many for whom pills failed. The medication is injected directly into the erectile chambers, so it works locally and bypasses the nerve signaling that pills depend on.
Formulations
What's in the Syringe
The most common formulation, TriMix, combines three medicines that each relax penile blood vessels through a different route. Because the three work together, lower doses of each can be used, which keeps side effects down.
Alprostadil (PGE1)
Single-agent (Caverject / Edex)Mechanism
A direct smooth-muscle relaxant — prostaglandin E1 analog
Onset / Duration
5–20 min / 30–60 min
Notes
FDA-approved single-agent option. Covered by most insurance.
BiMix
Compounded (two-drug)Mechanism
Papaverine + phentolamine — dual smooth-muscle relaxation
Onset / Duration
5–20 min / 30–90 min
Notes
Used when alprostadil alone is insufficient or causes discomfort.
TriMix
Compounded (most common)Mechanism
Alprostadil + papaverine + phentolamine — three synergistic pathways
Onset / Duration
5–20 min / 30–90 min
Notes
Most effective formulation. Lower doses of each drug reduce side effects. Requires compounding pharmacy.
Dosing Is Set by Your Clinician — Not by You
The first dose is given and titrated in the office. Your clinician starts low (often 0.05–0.1 mL) and increases in small steps over visits until you reach an erection that's firm and lasts roughly 30–60 minutes.
Once your dose is established, you self-inject at home. Never increase the dose on your own. For the detailed titration process, see the separate Titration Guide.
Injection Safety Checklist
Priapism Warning — 4-Hour Rule
Seek emergency care immediately if an erection lasts more than 4 hours. Priapism is a urologic emergency. This risk is minimized with proper dose calibration in the office.
- Titrate the dose only under clinical supervision — never increase it yourself
- Alternate sides of the penis with each injection to prevent scarring (fibrosis)
- Seek emergency care for any erection lasting more than 4 hours
- Store TriMix refrigerated; discard after the period your pharmacy specifies (often ~30 days)
- Do not inject more than 3 times per week, or within 24 hours of a previous injection
Strengths & Trade-offs
Strengths
- Very high success rate — over 80%, including men for whom pills failed
- Fast onset — erection within 5–20 minutes
- Works independent of the arousal/nerve pathway
- Useful when pills are contraindicated or ineffective
Trade-offs
- Requires self-injection — a hurdle for some men initially
- Correct technique and storage are essential
- Can cause mild aching or bruising at the injection site
- Real risk of prolonged erection (priapism) if dose is too high
- Frequent use without alternating sites can cause scar tissue
Key Takeaways
- Injection therapy works in over 80% of men, including many for whom pills failed.
- TriMix combines three vessel-relaxing drugs; your clinician sets and titrates the dose — never increase it yourself.
- Seek emergency care for any erection lasting over 4 hours.
- Alternate injection sites to prevent scarring, and log each dose to help fine-tune it.
Learn If Injection Therapy Is Right for You
Dr. Mutter will walk you through the injection technique in the office and calibrate your dose for safety and effectiveness.