Erectile Dysfunction · Medication Guide
TriMix Injections in Thailand
What TriMix injection therapy is, who it helps when erectile dysfunction tablets are unsuitable or stop working, the risks including priapism, and how doctors in Bangkok prescribe it. Reviewed by a licensed physician at a MOPH-registered men's health clinic.
- Works in 5–15 minutes, no arousal signal needed
- Second-line after tablets · first dose taught in clinic
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Medically reviewed by Dr. Noppon Arunkajohnsak (Win)
Menscape Clinic
Last reviewed
11 July 2026
5–15
Minutes to onset
acts directly on penile blood vessels
94%
Injections rated effective
alprostadil home-use trial, NEJM 1996
2nd
Line of ED treatment
after tablets, per AUA and EAU guidance
>4 h
Erection is an emergency
priapism can cause permanent damage
Key takeaways
TriMix is an injectable treatment for erectile dysfunction that combines three medicines (alprostadil, papaverine and phentolamine) in one small-volume injection into the side of the penis.
It is a second-line treatment. Doctors reserve it for men in whom tablets like sildenafil or tadalafil have genuinely failed or are unsuitable, including after prostate surgery and in long-standing diabetes.
TriMix is a compounded preparation made for a named patient against a prescription, not a registered retail product. Menscape does not keep it on a shelf; it is arranged per patient after a urology consultation, and the first dose is given and taught in clinic.
An erection lasting more than 4 hours (priapism) is a medical emergency. It can permanently damage erectile tissue. Go to a hospital immediately; do not wait for it to pass.
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What TriMix is & how it works
TriMix is an injectable prescription treatment for erectile dysfunction. It combines three vasoactive medicines, alprostadil (prostaglandin E1), papaverine and phentolamine, in a single small-volume injection given into the erectile tissue at the side of the penis with a fine, short needle.
It works differently from tablets. Sildenafil and tadalafil amplify a signal that still has to come from the nerves, so they need a reasonably intact nerve supply and sexual stimulation to work. TriMix bypasses that pathway: the three medicines relax the smooth muscle of the penile arteries and erectile tissue directly, so blood flows in and an erection develops within 5–15 minutes whether or not the nerves are sending a signal.¹ That is why injection therapy can work after prostate surgery, in long-standing diabetes and in men who never responded to tablets.
TriMix is one option among several at this stage, alongside single-agent alprostadil, vacuum devices and, as a definitive step, penile implant surgery. Which is appropriate depends on why the tablets failed, your health history and your dexterity and preferences. That is what the urology consultation is for.
Three medicines, one syringe
Alprostadil, papaverine and phentolamine are combined in a tiny volume, drawn up in an insulin-type syringe.
Injected into the erectile tissue
A fine, short needle delivers the dose into the corpus cavernosum at the side of the penis. The technique is taught by the doctor.
Vessels relax directly
The three drugs act on penile smooth muscle through complementary pathways. No intact nerve signal or arousal is required.¹
Erection in 5–15 minutes
A firm erection develops within minutes and, at a correctly titrated dose, subsides within about an hour.²
02
Getting TriMix in Thailand
Thai legal status
TriMix is not a registered off-the-shelf product in Thailand or anywhere else; it is a compounded preparation made for a named patient against a doctor's prescription. Only single-agent alprostadil exists as a registered injectable, sold in some markets under brands such as Caverject. Injectable ED medicines are strictly prescription-only.⁷
How to get it through Menscape
Menscape does not stock TriMix on a shelf. After a urology consultation, the preparation is compounded per prescription, or registered alprostadil is ordered for you individually. Your first injection is given in clinic, where the doctor titrates the dose and teaches you the self-injection technique before any home use.
Avoid grey-market vials
Pre-mixed vials sold online arrive with no sterility guarantee, no cold chain and no way to verify the dose. Injecting an unverified product into the penis risks infection, scarring and priapism. Use only a preparation traceable to a licensed doctor and pharmacy.
Injectable erectile dysfunction medicines are prescription-only in Thailand. Compounded preparations are made for a named patient against a physician's prescription and are not registered retail products. This page describes treatment of a medical condition and is not an advertisement for any specific product.
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Does it work? The evidence
Intracavernosal injection therapy is one of the best-documented treatments in urology. In the pivotal randomised trials of injectable alprostadil (1,861 men studied, including a 6-month home-use phase in 683 men), 94% of home injections produced an erection satisfactory for intercourse.¹ The three-drug combination was developed to push effectiveness further at lower doses of each component: in the original pharmacologic erection programs it restored usable erections in a majority of men who had not responded to single agents, which is why urology guidelines position injections as the standard second-line step after tablets.³ ⁴ ⁵ ⁶
Two honest caveats. First, per-injection success is high, but many men stop injection therapy over time, because of penile ache, the routine itself, or a preference for another option; reviews report substantial attrition within the first year.⁴ Second, dose matters: the response is titrated in clinic precisely because too little does nothing and too much risks a prolonged erection. Injection therapy managed with a doctor is very different from guessing with a grey-market vial.
94%
Alprostadil injections
rated satisfactory for intercourse in the 6-month home-use trial
37%
Reported penile pain
most common side effect in the same trial program
Linet & Ogrinc, New England Journal of Medicine, 1996; U.S. prescribing information for injectable alprostadil. Individual results vary.
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Side effects & who shouldn't take it
Common side effects
Penile ache or burning after injection is the most common complaint, reported by 37% of men on alprostadil alone; the lower alprostadil dose in TriMix is often better tolerated.² Small bruises or a haematoma at the injection site and brief light-headedness also occur.
Priapism, the serious one
In the alprostadil trials, prolonged erections of 4–6 hours occurred in about 4% of men and true priapism in 0.4%.² An erection lasting more than 4 hours is a medical emergency: untreated, it can permanently damage erectile tissue. Go to a hospital immediately. In-clinic dose titration exists to make this rare.
Not suitable for
Men with sickle cell disease or trait, leukaemia, multiple myeloma or other conditions predisposing to priapism; men with a penile implant or significant penile curvature or scarring; and men who cannot inject safely (poor vision or hand control) without a trained partner.²
Long-term & interactions
Penile scarring or nodules developed in about 3% of trial patients, so scheduled injection-site checks matter.² Papaverine has been linked to liver-enzyme rises. Tell your doctor everything you take; alcohol and blood-pressure medicines can add to dizziness, and injections are not combined with PDE5 tablets unless your doctor explicitly directs it.
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Alternatives & combinations
Tablet · first-line
Sildenafil & tadalafil
PDE5 tablets remain the first-line treatment for erectile dysfunction. Before moving to injections, the doctor checks the tablets were genuinely given a fair trial: right dose, right timing, enough attempts.
Injection · single agent
Alprostadil alone
A registered single-medicine injectable with standardised dosing, sometimes tried before a compounded mix. It causes penile ache more often than TriMix but is the most studied injection option.¹
Device & surgery · third-line
Vacuum device or penile implant
A vacuum erection device is a drug-free option some men prefer. For men who fail or dislike injections, a penile implant is the definitive surgical treatment, and it is a service Menscape's urology team provides.
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How prescription works at Menscape
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Book your urology consultation today.
Message us on WhatsApp or LINE
A few minutes on your phone: health history, current medicines including nitrates and blood thinners, and which tablets you have already tried. PDPA-protected.
Urology consultation
A licensed Thai doctor reviews your case in clinic at Asoke, examines you, confirms tablets have genuinely failed or are unsuitable, and screens for conditions that make injections unsafe.
First dose, taught in clinic
If injection therapy is appropriate, the preparation is compounded per prescription or registered alprostadil is ordered for you. The first injection happens in clinic: the doctor finds your dose and teaches the technique step by step.
Follow-up & injection-site checks
Scheduled reviews cover dose adjustments, examination of the injection sites for scarring, and a written plan for what to do if an erection lasts too long.
The doctor decides. Injection therapy is prescribed only after an in-person urology assessment, and only when tablets are unsuitable or have genuinely failed. If TriMix is not right for you, your doctor will say so and discuss alternatives.
Medically reviewed by
Dr. Noppon Arunkajohnsak (Win)
Menscape Clinic, Bangkok
“When tablets fail, many men assume they are out of options. They are not. Taught properly and dosed in clinic, injection therapy is quick and reliable, and the teaching matters as much as the medicine.”
- Reviewed
- 11 July 2026
- Next review
- January 2027
- Editorial standard
- Each guide is checked against the Thai FDA label and the primary literature, then reviewed by a licensed physician.
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Frequently asked questions
Can I buy TriMix over the counter in Thailand?
No. TriMix is not a registered retail product anywhere; it is a compounded preparation made for a named patient against a doctor's prescription. Pre-mixed vials sold online are unregistered, unverifiable and unsafe to inject.
Does the injection hurt?
Most men say the needle is less painful than they feared; it is a fine, short insulin-type needle. The more common complaint is an ache in the penis after injection, which is linked to alprostadil and is usually milder with TriMix's lower alprostadil dose.
How often can I use it?
Standard guidance is no more than one injection in 24 hours and no more than about three per week, rotating the injection site. Your doctor sets your exact schedule and dose.
What if my erection won't go down?
An erection lasting more than 4 hours is a medical emergency called priapism. Go to a hospital emergency department immediately; do not wait for it to resolve. Your doctor gives you a written plan for this before you ever inject at home.
Why would I need injections when tablets exist?
Tablets amplify a nerve signal, so they need a working nerve supply and stimulation. Injections relax the blood vessels directly. That is why they can work after prostate surgery, in long-standing diabetes, and in men who never responded to sildenafil or tadalafil.
Will I be taught to inject myself?
Yes. The first injection is always done in clinic, where the doctor titrates your dose and teaches the technique. Most men are comfortable self-injecting after one or two supervised sessions.
What is the difference between TriMix and alprostadil alone?
Alprostadil is a registered single-medicine injectable. TriMix combines three medicines at lower individual doses, which often means less penile ache and a response in some men who did not respond to alprostadil alone. The doctor decides which fits your case.
I'm visiting Bangkok. Can I start injection therapy as a medical tourist?
Yes, after an in-person consultation. Because the preparation is compounded or ordered per patient, allow a few days between the consultation and your first supervised dose. Note that TriMix needs refrigeration, which matters if you plan to travel with it.
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References
1. Linet OI, Ogrinc FG. Efficacy and safety of intracavernosal alprostadil in men with erectile dysfunction. N Engl J Med. 1996;334(14):873-877.
2. U.S. FDA. Caverject® (alprostadil for injection) prescribing information. Pfizer. Accessed July 2026.
3. Bennett AH, Carpenter AJ, Barada JH. An improved vasoactive drug combination for a pharmacological erection program. J Urol. 1991;146(6):1564-1565.
4. Belew D, Klaassen Z, Lewis RW. Intracavernosal injection for the diagnosis, evaluation, and treatment of erectile dysfunction: a review. Sex Med Rev. 2015;3(1):11-23.
5. Burnett AL, et al. Erectile dysfunction: AUA guideline. J Urol. 2018;200(3):633-641.
6. Salonia A, et al. EAU guidelines on sexual and reproductive health. European Association of Urology. 2023.
7. Thai Food and Drug Administration — drug registration database, ndi.fda.moph.go.th. Accessed July 2026.
This guide is educational information, not medical advice. TriMix is a compounded prescription treatment that must be prescribed, titrated and monitored by a licensed physician, with the first dose given under supervision in clinic.
This guide is part of the Menscape ED library
Explore the condition hubTablets stopped working? Ask a urologist, not a forum.
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