What they have in common
Viagra (sildenafil), Cialis (tadalafil) and Levitra (vardenafil) belong to the same drug class — PDE5 inhibitors. They all work the same basic way: by blocking the PDE5 enzyme, they preserve the molecule (cGMP) that relaxes penile blood vessels, improving blood flow in response to sexual stimulation. None creates an erection on its own, all are prescription-only, and all share the same critical safety rule: never combine them with nitrate heart medications. In head-to-head research, the three are broadly similar in overall effectiveness — so the differences that matter are practical.
The key differences at a glance
| Feature | Viagra (sildenafil) | Cialis (tadalafil) | Levitra (vardenafil) |
|---|---|---|---|
| FDA approval | 1998 | 2003 | 2003 |
| Typical onset | ~30–60 min | ~30–45 min | ~30–60 min |
| Duration of effect | ~4–6 hours | up to ~36 hours | ~4–6 hours |
| Effect of food | Delayed by high-fat meal | Not significantly affected | Delayed by high-fat meal |
| Daily-use option | No | Yes (low dose) | No |
| Also treats BPH | No | Yes | No |
| Best suited to | Planned, on-demand use | Spontaneity / frequent activity | On-demand use; some tolerability profiles |
General approximations from prescribing information and clinical literature; individual response varies.
Viagra (sildenafil): the advantage
The proven original with the longest track record. Approved in 1998, sildenafil is the most extensively studied ED medication, with decades of real-world data and the widest familiarity among patients and physicians. It is dependable for planned, on-demand use and now comes in an inexpensive generic form.
- Best for: men who plan sexual activity and want a well-understood, time-tested option.
- Trade-off: shorter window (4–6 hours) and best taken on a relatively empty stomach, since a heavy, fatty meal can delay it.
- Full guide to Viagra →
Cialis (tadalafil): the advantage
Long duration and flexibility. Tadalafil's standout feature is how long it lasts — up to about 36 hours, earning the nickname "the weekend pill." It isn't meaningfully affected by food, and it uniquely offers a low-dose daily option for readiness without timing each dose. It's also the only one of the three approved to treat enlarged-prostate (BPH) symptoms, so it can handle two issues at once.
- Best for: men who value spontaneity, are frequently active, dislike planning around a dose, or also have urinary/BPH symptoms.
- Trade-off: the long duration means the nitrate-interaction caution lasts longer; back or muscle aches are a bit more characteristic of tadalafil.
- Full guide to Cialis →
Levitra (vardenafil): the advantage
A potent alternative when another pill disappoints. Vardenafil is a highly potent PDE5 inhibitor and behaves similarly to sildenafil (fast onset, 4–6 hour window). For some men it is better tolerated than sildenafil, and it has been studied specifically in harder-to-treat groups such as men with diabetes. It gives physicians a useful second option when the first choice isn't a good fit.
- Best for: men who want an on-demand pill and may not have done well on sildenafil, or who tolerate vardenafil better.
- Trade-off: shorter duration like Viagra, food can delay it, and it can affect the heart's QT interval — so it may be avoided with certain rhythm conditions or medications.
- Full guide to Levitra →
How to choose the right one
Since the three are similar in raw effectiveness, the decision usually comes down to your life and health, not a "winner." Consider:
- Frequency & spontaneity: occasional, planned activity favors an on-demand pill (Viagra or Levitra); frequent or unplanned activity favors Cialis, especially the daily dose.
- Duration you want: a few hours vs a day-and-a-half window.
- Food & timing: if you dislike planning around meals, tadalafil is the most forgiving.
- Other conditions: BPH symptoms tip the balance toward tadalafil.
- Your other medications & heart health: these can make one option safer than another.
- Tolerability: if side effects bother you on one, another may suit you better.
Many men try more than one before settling on a favorite. Because response and safety are individual, this choice is best made with a physician.
Also worth reading: brand vs generic
All three are available as FDA-approved generics at much lower cost. See generic Viagra, generic Cialis and generic Levitra for safety and quality checks.
Frequently asked questions
Which one is the strongest?
Vardenafil is the most potent in the lab, but higher lab potency does not translate into clearly better real-world results — the three are broadly comparable in effectiveness.
Can I switch between them?
Many men do, under a physician's guidance, to find the best fit. Never take more than one PDE5 inhibitor at the same time.
Which lasts the longest?
Cialis (tadalafil), by far — up to about 36 hours, versus roughly 4–6 hours for Viagra and Levitra.
Do they have the same safety warnings?
Largely yes — most importantly, none should be combined with nitrates. Vardenafil has an added QT-interval caution, and all require a physician's assessment of your heart health and medications.
Related reading: ED medications overview · About erectile dysfunction