What does the needle feel like?
The needle is the smallest part of the experience. The Edex label describes a superfine 29-gauge needle and recommends a half-inch, 27- to 30-gauge needle for these injections; the Caverject label uses a 29- or 30-gauge half-inch needle. That is the same range as many insulin syringes, which people with diabetes use several times a day.
Most men expect the worst and are surprised. The skin on the side of the shaft is thin, the needle goes in quickly, and the injection takes a few seconds. Anxiety before the first one is normal and usually fades once you have done it with your provider watching.
Where on the penis does the injection go?
The injection goes into the side of the shaft, in the third closest to the body. The Caverject label describes injecting along the upper side of the shaft at that level, avoiding visible veins, and switching sides with each use. Staying on the side keeps the needle away from the urethra underneath and the main nerves and vessels on top.
After the injection, you press on the spot for about five minutes with an alcohol swab or gauze, as the Caverject label directs. That pressure is what keeps bruising to a minimum.
Why does Trimix sometimes ache?
The ache, when it happens, comes from the medicine, not the needle. Alprostadil, one of the three Trimix ingredients, is known for causing a dull penile ache during or after the erection. In Edex trials lasting up to two years, men reported pain at least once during the injection (29%), during the erection (35%) or afterward (30%), but only 15% of individual injections were linked to pain, and most was mild to moderate. In Caverject trials, 37% of men reported penile pain at some point and 3% stopped because of it.
Trimix uses a smaller amount of alprostadil alongside papaverine and phentolamine, which is part of its appeal. The evidence on whether that means less pain is mixed. The AUA erectile dysfunction guideline found pain was most common with papaverine or alprostadil used alone and with papaverine plus phentolamine, with few studies on other mixes. A randomized study of 180 men found Trimix and alprostadil alone caused similar pain.
What makes the injection more comfortable?
Good technique and the right dose do most of the work:
- Learn it in the clinic first. The AUA recommends an in-office injection test, which is also where you practice the angle and grip with your provider guiding you.
- Use the side of the shaft and avoid veins. Hitting a vessel is what causes most bruises.
- Alternate sides. Rotating spots gives each one time to heal.
- Report an ache that bothers you. Your provider can change the formula or the dose. Never change the amount yourself.
Our guide on how to self-inject Trimix walks through the routine step by step.
When is pain a warning sign?
A mild ache that fades with the erection is expected. A new hard lump, a bend in the erect penis or pain when you are not erect should be reported, because repeat injections can cause scar tissue.
An erection that is still firm and painful after 4 hours is an emergency. Call 911 or go to the nearest emergency room and tell the staff you used a penile injection. Our page on what to do if an erection lasts more than 4 hours explains the steps.
How Ultimate Male teaches the first injection
Nobody at Ultimate Male is sent home to figure out Trimix alone. After labs and a consultation with a PA-C or MD, your first dose is given in the clinic with a low starting amount, so your provider can see how you respond, show you the injection site and answer questions while you are there.
You leave with written instructions and a plan for a prolonged erection, and follow-up visits fine-tune the dose. Read more on our Trimix injections page, compare it with approved single-drug shots in Trimix versus Caverject, or see all options on our ED medications page.
