Sildenafil (the active ingredient in Viagra) and vardenafil (Levitra) are both PDE5 inhibitors. They work the same way: by preventing the breakdown of cGMP, they allow blood vessels in the penis to relax and fill in response to arousal. Neither creates arousal — both require it.
Chemically they are close, and the practical differences between them are smaller than the marketing implies.
Onset
- Sildenafil: typically 30 to 60 minutes
- Vardenafil: typically 25 to 60 minutes, with some people finding it slightly faster
The difference is modest and easily swamped by individual variation.
Duration
Both last roughly four to five hours. This is where they differ most clearly from tadalafil, which lasts far longer — if duration is your priority, the meaningful comparison is with tadalafil rather than between these two.
Food and Alcohol
Sildenafil is noticeably affected by food, particularly a heavy or fatty meal, which slows absorption and delays onset. Vardenafil is affected too but somewhat less so.
Alcohol works against both, and not through a pharmacological interaction so much as through the obvious: alcohol impairs erectile function directly. A large drink is more likely to be the problem than the tablet is.
Potency and Dose
Vardenafil is more potent milligram for milligram, which is why its doses are numerically smaller — 5mg, 10mg and 20mg, against sildenafil's 25mg, 50mg and 100mg. A 10mg vardenafil tablet is not a lower dose than a 50mg sildenafil tablet in any meaningful sense. Comparing the numbers directly is a common and misleading error.
Side Effects
Largely shared: headache, flushing, nasal congestion, indigestion and dizziness. Sildenafil is more associated with visual effects — a blue tinge to vision or light sensitivity — because of its action on a related enzyme in the retina. Vardenafil has less of this.
Both carry the same absolute contraindication: they must not be taken with nitrates, or with recreational poppers, because the combined effect on blood pressure can be life-threatening.
Which Works Better?
For most men, similarly. Response is individual, and a poor response to one does not predict a poor response to the other — which is the main clinical reason to switch.
Before concluding that a medicine has failed, check the basics: was the dose adequate, was it taken far enough in advance, was there a heavy meal or significant alcohol, and was there genuine sexual stimulation? A fair trial usually means several attempts at an adequate dose, not one disappointing evening.
Availability and Cost in the UK
Sildenafil is the more widely available and generally the cheaper of the two, with generic versions from many suppliers, and sildenafil 50mg is available over the counter as Viagra Connect after a pharmacist consultation. Vardenafil is prescription-only and typically more expensive, partly because fewer suppliers stock it.
For most people starting treatment, generic sildenafil is the sensible first choice on cost alone. Vardenafil earns its place when sildenafil has been tried properly and has not suited — either through side effects or inadequate response.
The Short Answer
Start with sildenafil unless there is a reason not to. Move to vardenafil if sildenafil has had a fair trial and disappointed. Consider tadalafil if the four-to-five hour window is the thing that does not fit your life.