Sildenafil vs. Tadalafil (Viagra vs. Cialis): Cost per Dose, Timing and Which Fits You

Same drug class, same basic mechanism, very different day-to-day experience. Here is how generic sildenafil and generic tadalafil compare on timing, food, daily dosing, side effects and cost per dose, plus where Levitra fits and how to get either one filled.

Medically reviewed Medically reviewed by Angelo DeFazio, R.Ph. — NPI 1629115530 · Last updated 2026-10-14

Sildenafil (Viagra) and tadalafil (Cialis) are both PDE5 inhibitors. They work the same way, by improving blood flow when you are sexually aroused, and in head-to-head research they work about equally well. What separates them is everyday use: how long a dose lasts, whether food matters, whether you can take it daily, and which side effects you are more likely to notice. Both have been sold as inexpensive generics since 2017–2018, so the price gap that once mattered is now mostly about brand versus generic, not sildenafil versus tadalafil.

At a glance

The full side-by-side, drawn from the FDA labels:

Timing: onset, food and the 36-hour window

Most of the real-world difference comes down to how long a dose stays useful:

• Onset. Sildenafil is taken about an hour before sex. It can work from 30 minutes, and you have up to about 4 hours. Tadalafil peaks later, at about 2 hours, but stays active much longer, so planning is far less precise.
• Food. A heavy, fatty meal slows sildenafil down by about an hour. Tadalafil does not care what you ate. If your evenings usually involve dinner first, this matters more than most comparisons admit.
• Daily tadalafil. At 2.5 or 5 mg every day, tadalafil reaches a steady level after about 5 days. After that, there is no pill to time at all. Sildenafil has no daily option for ED.

Which works better? What the research says

There are two useful summaries of the evidence, and they agree more than the marketing suggests:

• Head to head (Gong et al., 2017). A meta-analysis of 16 trials that compared the two directly found similar effectiveness and similar overall side-effect rates. Tadalafil did better on sexual confidence and other psychological measures, and patients and their partners preferred it. Tadalafil caused more muscle aches and back pain; sildenafil caused more flushing.
• Trade-off ranking (Chen et al., 2015). A network meta-analysis of 82 trials and more than 47,000 men ranked sildenafil 50 mg highest for effect, but with the highest overall side-effect rate. Tadalafil 10 mg landed in the middle for effect with the lowest side-effect rate. Vardenafil and avanafil had side-effect rates similar to sildenafil but noticeably lower effect.

In practice, preference usually comes down to the window and the side effects you notice, not raw strength. Most men who don't like one try the other.

"Preference" studies have limits: many early crossover trials were funded by a manufacturer, and you cannot blind a patient to a 36-hour window. Treat the preference finding as useful, not decisive.

Side effects and safety, compared

The two drugs share most of their side effects. The differences follow from which other PDE enzymes each one touches:

Alcohol is a smaller issue than people expect: a drink or two is fine with either. The tadalafil label specifically warns that around 5 or more drinks with tadalafil can cause dizziness and fainting on standing.

Cost per dose: generic vs. brand

Once both went generic, the meaningful price difference became brand vs. generic, not sildenafil vs. tadalafil. Here is what pharmacies themselves pay, per tablet, from the federal NADAC survey:

What that means for a month, at those wholesale costs:

• 8 as-needed doses of generic sildenafil 100 mg: about $1.06.
• 8 as-needed doses of generic tadalafil 20 mg: about $1.34.
• 30 days of daily generic tadalafil 5 mg: about $3.10.
• The same 8 doses as brand Viagra: about $670.

Retail cash prices run higher than wholesale and vary a lot by pharmacy and quantity. Typical ranges:

Insurance. Some commercial plans cover generic ED medicine with a monthly limit, such as 6 or 8 tablets. Medicare Part D is barred by law from covering drugs for erectile dysfunction. It can cover the same molecules for other FDA-approved uses, such as tadalafil 5 mg for BPH or sildenafil for pulmonary arterial hypertension. With generics this inexpensive, the cash price is often close to a copay, so always ask for both.

Scorecard: sildenafil vs. tadalafil vs. vardenafil

Which one fits you?

This is a routine question, not a strength contest. If you take nitrates or riociguat, the answer is neither: talk to your prescriber about other options. Otherwise:

If swallowing tablets is the problem, prescribers have other FDA-approved options, including a sildenafil liquid and a melt-on-the-tongue vardenafil tablet. We cover them on our Kamagra page. If the concern is premature ejaculation rather than erections, that is a different drug question; see our dapoxetine page.

What about Levitra (vardenafil) and Stendra?

Vardenafil (Levitra, plus the melt-in-mouth Staxyn) is a third PDE5 inhibitor. It is taken about an hour before sex, works for about 4–5 hours, and like sildenafil is slowed by a high-fat meal. It is also generic, but it costs pharmacies far more: about $2.79 per 20 mg tablet versus 13 to 17 cents for sildenafil or tadalafil. Avanafil (Stendra) is brand-only and is labeled to be taken about 15 minutes before sex at its 100 mg and 200 mg doses. For most people, generic sildenafil or tadalafil is the practical first choice, and the other two are options if neither works or suits you.

Getting either one filled

Both sildenafil and tadalafil need a valid US prescription. That can come from your own doctor or a licensed telehealth service. No legitimate US pharmacy sells either without one, and sites that do are outside the FDA-regulated supply chain (see the FDA's BeSafeRx guidance).

• Generic by default. We fill generic sildenafil and generic tadalafil unless your prescriber writes brand-only. The active ingredient is the same.
• Ask for the cash price too. Generics are cheap enough that paying cash can beat a copay or a plan's tablet limit. We'll quote both.
• Switching is easy. If you want to try the other drug, your prescriber sends a new prescription. You can also move an existing prescription to us with one call.
• Discreet pickup or delivery. Pick up at 500 Farmington Avenue, or use our free next-day delivery in the Hartford area.

Questions about which one to ask your prescriber for, or what your cash price would be? Call us at (860) 522-9289.

Frequently asked questions