Sildenafil vs Vardenafil vs Tadalafil vs Udenafil vs Avanafil — which one for which guy?

You're on sildenafil. It works. But the 4-hour window keeps biting you, the headache is annoying, and you keep reading "tadalafil is better" on Reddit. The Reddit answer is half right.

There are five PDE5 inhibitors on the planet. You've heard of four. The fifth (udenafil) is sold mostly in Korea — Dong-A's brand Zydena never got a US or EU filing — but Indian ED-export specialist Sunrise Remedies makes a generic version (Zudena) and a udenafil + dapoxetine combo (Super Zudena), both routable through us. So our lane is the full five.

Most comparison articles pick one axis (usually half-life) and call it a day. That's lazy. The real decision is five-dimensional, and the right molecule for you is decided by which axis you care about.

The five molecules and where they live

Udenafil never got a US or EU filing. The brand (Zydena) is developed and marketed by Dong-A Pharmaceutical (동아제약), one of Korea's oldest pharma companies. It remains the molecule a Korean urologist would reach for first because it has interesting on-paper advantages we'll get to. We don't ship Dong-A's brand Zydena — but we route Sunrise Remedies' Indian generic equivalent (Zudena 100mg, Super Zudena 100/60 combo) through the same lane as our other molecules.

For a half-life-only deep dive on the four globally-available molecules, see our PDE5 half-life article. This one is the full five-axis comparison.

Axis 1 — onset (how fast does it kick in)

If "fast" is your primary need (you don't want to plan, you want a 15-minute pre-game), avanafil is the only molecule that delivers that reliably. The trade is dose cost.

For everyone else, onset differences in the 30-60 minute range are clinically smaller than they sound — by the time both partners are actually ready, an extra 15 minutes is rarely the failure point.

Axis 2 — duration (how long does it last)

This is where the molecules truly diverge.

Tadalafil's 17.5-hour half-life isn't a marketing number — it's why a Friday-evening dose still has clinical activity Sunday morning. Roughly 25% of peak concentration remains at 36 hours.

Udenafil sits in an interesting middle zone — too long for a single event (you'll have residual effect the next day), too short for the "weekender" play. In Korea it's prescribed both as PRN and as a low daily 25-50mg tablet, partly because that intermediate window matches some patients better than tadalafil's all-weekend behavior.

If your decision driver is "I want to stop planning sex," tadalafil daily 5mg or PRN 20mg is what changes the conversation. If your decision driver is "I want one event covered cleanly without a 36-hour tail," sildenafil or vardenafil is honest. Avanafil and udenafil are middle-ground.

Axis 3 — food sensitivity (the steak problem)

This one matters more than men think. The pivotal trial data:

The men who complain "sildenafil didn't work last night" most often did one of two things: ate a heavy meal first, or measured the effect at hour 5+. Both are setups for failure. If you're going out to dinner and don't know what's on the menu, the food-insensitive molecules (tadalafil, avanafil, udenafil) are operationally easier.

Axis 4 — side effect signature (selectivity)

All PDE5 inhibitors hit PDE5 in vascular smooth muscle — that's the point. The differentiator is what else they hit.

There are 11 different PDE enzymes in the body — your eye uses PDE6, your back muscles use PDE11, your heart uses PDE3. Cross-reactivity (how much the molecule bleeds into PDEs other than the target PDE5) is what gives each molecule its side effect personality.

Avanafil's selectivity is the strongest case for it. The molecule was designed in 2001-2008 specifically to outperform on this axis, and the data backs it up — though head-to-head comparisons against the older molecules are sparse and mostly funded by the avanafil developer.

Common side effects across all five — headache (10-15%), flushing (10%), dyspepsia (5-10%), nasal congestion (4%) — track with the underlying vasodilation and don't differ enormously molecule to molecule. The differences live in the cross-reactivity column above.

If you got the blue tinge on sildenafil, vardenafil or udenafil is the molecule to try. If you got back pain on tadalafil, sildenafil or avanafil is the move. Avanafil is the cleanest if you've reacted to two or more.

If you only read one section: skip to The three real decisions → Most men are solving one of three problems and the answer takes 60 seconds.

Axis 5 — access (where can you actually get this)

Here's where the article gets honest.

Udenafil is the molecule we get asked about by Korean-American customers who used Zydena before they moved to the US. The honest situation is:

1. Brand Zydena (Dong-A Pharmaceutical): Korean/Russian/Philippine prescription only. We don't ship Dong-A's branded product — Dong-A holds those patents in the markets where it's approved.
2. Indian generic udenafil (Sunrise Remedies): routable through us. The two SKUs are Zudena (udenafil 100mg standalone) and Super Zudena (udenafil 100mg + dapoxetine 60mg combo). Same molecule, Indian-manufactured, our standard 2-week shipping lane.
3. What it means in practice: if you used Zydena in Korea and want continuity, Sunrise's Zudena gives you the same molecule at the same 100mg dose without the brand's price tag. If you want a tada+dapox or sild+dapox combo, the Super Zudena combo is the udenafil-based equivalent in the same category.

The class has five members. Our lane has all five. We just don't carry the original Korean brand — that's a Dong-A licensing problem, not a molecule-availability one.

The three real decisions

Forget the 5-axis grid for a second. Most men come to this question with one of three problems.

Problem 1: Sildenafil works but the timing is annoying. You've had the 9pm-success-2am-failure experience. The answer is tadalafil. PRN 10-20mg gives you 24-36 hours of usable window. Daily 5mg gives you steady-state continuous response with no pre-loading. This is the single biggest quality-of-life upgrade in the class.

Problem 2: Sildenafil at 100mg didn't work twice. You're a non-responder, which is real — about 30-40% of men in unselected populations don't respond robustly to sildenafil (Carson 2004 PROVEN trial). The mistake is escalating dose. The right move is switching molecule. Vardenafil rescues a meaningful fraction of sildenafil non-responders — Carson's PROVEN trial reported 46.1% successful intercourse rate and 61.8% GAQ-improved erections after switching. Avanafil and tadalafil rescue similar fractions through different selectivity profiles. The order to try: sildenafil → vardenafil OR tadalafil → avanafil.

Problem 3: Side effects, not efficacy. You got the blue tinge, the back pain, the headache that lasted 6 hours. The answer is selectivity-driven swap, not dose reduction. Match the side effect to the molecule's known cross-reactivity (Axis 4 above) and switch.

The single-question cheat sheet

Multi-tier price reality

The middle columns matter. Hims and Roman are sildenafil + tadalafil specialists — they don't routinely carry vardenafil or avanafil, which is why those molecules show "not carried" in their columns and you're stuck with either Stendra brand or CVS retail cash if you need them. TRT clinics typically bundle a PDE5 add-on at $150-200/mo into a testosterone subscription — economic only if you're already there for testosterone, bad as a standalone PDE5 lane. CVS retail without insurance is the cleanest US comparator for the four globally-available molecules — for sildenafil and tadalafil it's within 1.5-2x of LiberaCure on a per-pill basis, especially when you factor in our 2-week lead time on personal import. Where the price gap re-opens is high-dose strengths, daily-tadalafil long-term refills, vardenafil and avanafil specifically (where the US lanes are thin), and patients without insurance or a stable US address.

The metaphor: PDE5s are knife sets

You don't pick the best knife. You pick the right one for what you're cutting.

Sildenafil is the chef's knife. Default. Most-used. Cheapest to replace.

Tadalafil is the bread knife — looks weird, lives in a different geometry, and once you have one you stop using the chef's knife for bread.

Vardenafil is the utility knife. Slightly different from the chef's knife but mostly does the same thing.

Avanafil is the ceramic paring knife — sharp, fast, expensive, narrow use case.

Udenafil is the Korean santoku. Excellent at what it does, hard to source as the original Korean brand outside Korea (we route the Indian generic Zudena instead), the people who use one tend to keep using one.

Most men get handed the chef's knife by the telehealth default and never know the bread knife existed.

What to do this month

If you're new to PDE5: start with sildenafil 50mg. Cheap, well-studied, predictable. Most men respond. If 50mg works, stay there. If 100mg twice doesn't work, switch molecule (don't escalate dose).

If sildenafil works but timing is the problem: try tadalafil 10mg PRN once. The 36-hour window is the upgrade most men are actually looking for and don't realize.

If you've got specific side effects: match them to Axis 4 and pick the cleanest molecule for your reaction profile. Avanafil is the safest first switch when sildenafil's side effects are the issue.

If you're the Korean expat who misses Zydena: same molecule, different label. We route Zudena (Sunrise Remedies, Indian generic udenafil 100mg) and Super Zudena (udenafil + dapoxetine combo) through our standard lane. Brand Zydena from Dong-A we don't carry — that's a licensing/distribution thing — but the molecule itself is in our catalog.

A note on bias.

We route all five PDE5 inhibitors — sildenafil, vardenafil, tadalafil, avanafil, and udenafil (via Sunrise Remedies' Zudena, since Dong-A's brand Zydena isn't in our supply chain). Be aware of that.

LiberaCure routes orders to licensed personal-import pharmacies. Our sildenafil line comes primarily from Cipla (Suhagra) and other Tier S Indian giants. Tadalafil comes from Cipla (Tadacip, Tadaflo), Dr. Reddy's (Tazzle), and Macleods (Megalis). Vardenafil and avanafil come through ED-specialist Indian manufacturers because the global giants don't currently produce them at scale. So we have a financial reason to want this article to push you toward the four molecules we do route — and we deliberately included udenafil anyway because pretending the class only has four members would be a worse article.

Read this with that in mind. The protocol above is what I'd tell a friend, not what maximizes reorder rate.

Sources:

• Yuan J et al. Comparative effectiveness and safety of oral phosphodiesterase type 5 inhibitors for erectile dysfunction: a systematic review and network meta-analysis. Eur Urol 2013;63(5):902-912.
• Carson CC et al. Long-term safety and efficacy of vardenafil (PROVEN trial). BJU Int 2004;94:1301-1309. (PMID 15610110)
• Goldstein I et al. Oral sildenafil in the treatment of erectile dysfunction. N Engl J Med 1998;338:1397-1404.
• Goldstein I et al. A randomized, double-blind, placebo-controlled evaluation of the safety and efficacy of avanafil. J Sex Med 2012;9(4):1122-1133.
• Paick JS et al. Efficacy and safety of udenafil for the treatment of erectile dysfunction. J Sex Med 2008;5(4):946-953. (Korean phase III)
• Kim BH et al. Pharmacokinetic profile of udenafil in healthy Korean male volunteers. Br J Clin Pharmacol 2008;65(6):848-854.
• Salonia A et al. European Association of Urology Guidelines on Sexual and Reproductive Health 2021: Erectile Dysfunction. Eur Urol 2021;80(3):333-357.
• FDA labels: Viagra (NDA 20-895), Cialis (NDA 21-368), Levitra (NDA 21-400), Stendra (NDA 202-276).
• Dong-A Pharmaceutical Zydena (udenafil) prescribing information (KFDA, Korean label, current revision).

— LiberaCure editorial. We route generic medication through licensed personal-import pharmacies. We don't dispense, prescribe, or warehouse. Read more about why.