Sildenafil and Vardenafil Together: What the Timing Actually Involves
No. Sildenafil and vardenafil should not be taken together, or used close together, unless a prescriber has specifically advised it. Both are PDE5 inhibitors, and combining them can increase the risk of adverse effects without any established added benefit.
For adults in the UK who have been prescribed either medicine, the issue is not only whether they can be taken together, but how long each stays in the body, how switching differs from combining, and when other medicines or health factors increase the risk.
Sildenafil and vardenafil clear on a broadly similar, relatively short timescale, which can make a short gap seem acceptable. It is still not a decision to make without individual clinical advice.
The Short Answer
Sildenafil and vardenafil should not be combined, and you should not assume a short gap between doses makes using both safe.
Both act on the PDE5 pathway, so taking them close together increases the risk of side effects such as low blood pressure.
Both also happen to clear the body over a broadly similar, relatively short timescale. But a shorter clearance time changes how long any overlap might last, not whether deliberately creating that overlap is advisable. It still is not.
Why You Cannot Simply Combine Two PDE5 Inhibitors
Sildenafil and vardenafil are both PDE5 inhibitors used to treat erectile dysfunction.
They work by blocking the same enzyme to support the same natural response, increasing blood flow to the penis during sexual stimulation rather than causing an automatic erection.
Taking a second PDE5 inhibitor while the first is still active is not an established way to improve erectile function. It simply exposes you to the effects and side effects of both medicines at once.
How Long Each Stays in Your System
Sildenafil
Sildenafil tablets have a half-life of around 4 hours. Most of the medicine is eliminated over several half-lives, although the exact time it takes to leave your system varies between people.
Vardenafil
Vardenafil tablets have a terminal half-life of approximately 4 to 5 hours. Like sildenafil, it is eliminated over several half-lives, with the exact timing varying between individuals.
Why They Are More Alike Than You Might Expect
Some PDE5 inhibitors clear the body far more slowly than others, over several days rather than within a day. Sildenafil and vardenafil are not one of those mismatched pairs.
Their clearance timescales are broadly similar, both measured in hours rather than days, which is a genuinely different picture from combinations involving a much longer acting medicine.
That is worth naming rather than glossing over, because it is easy to assume that two chemically distinct medicines must also clear at very different speeds. Here, that assumption does not hold.
The similarity does not change the underlying advice. Do not combine them.
A Worked Example
Consider two situations.
In the first, someone takes sildenafil in the evening and, the following morning, wonders whether it would be fine to try vardenafil instead, since it has been hours. Based on the clearance principle above, sildenafil is still likely to be meaningfully present at that point, so that is not a safe assumption to act on independently.
In the second, someone took sildenafil several days earlier and has not taken anything since. That is a genuinely different starting point, since far more time has passed relative to the clearance window. It is still not a reason to skip an individual assessment before starting vardenafil.
The difference between those two scenarios is exactly why a general principle and a personal green light are not the same thing.
Does a Shorter Clearance Time Make a Short Gap Safer?
Not necessarily. A shorter clearance time may mean the medicines overlap for less time, but it does not make taking them close together a safe choice.
Using two PDE5 inhibitors can increase the risk of side effects, including low blood pressure, without any proven added benefit.
If you are switching from one to the other, do not assume a short gap is enough. Some of the first medicine may still be in your body depending on when you took it, so follow your prescriber's advice rather than working out the timing yourself.
Neither Has a Daily-Dose Version
Some PDE5 inhibitors can be taken every day at a lower dose. Sildenafil and vardenafil are generally used when needed rather than as continuous daily treatment.
That means there is usually no ongoing daily dose in the background to consider, so the timing question is mainly about how much of the previous dose may still be present.
It does not mean the two can be safely combined.
If You Are Prescribed One and Curious About the Other
This is a genuinely different question from combining, and it has a straightforward path.
Switching from sildenafil to vardenafil, or the other way round, is a normal clinical decision, made with proper timing guidance from a prescriber based on your specific situation.
What is not advisable is making that switch independently, by adding the new medicine on top of the old one, or assuming a same-day or next-day gap is automatically fine because both clear relatively quickly.
Not everyone is suited to the same treatment, and the right option depends on your health conditions and medical history. The clearance timescales explained above are a general principle, not a personal green light.
Common Scenarios
These are illustrative only, to show how the underlying principle applies. They are not a substitute for individual advice.
| Situation | What the general principle suggests |
|---|---|
| Took sildenafil today, wants to take vardenafil tomorrow | Do not assume the next day automatically makes switching safe. Follow the timing advice given by your prescriber |
| Took vardenafil today, wants to take sildenafil tomorrow | Likely still within the clearance window for vardenafil, so not advisable without individual guidance |
| Took one several days ago, wants to try the other now | Several days is a much longer interval than either medicine's half-life, but individual circumstances and other medicines still need considering |
| Unsure which medicine, if either, is still active | Worth confirming directly at assessment rather than guessing based on how you feel |
| Currently prescribed one, curious about switching | A straightforward question for a prescriber, distinct from combining them |
What Affects Timing Between Them
| Factor | What it means |
|---|---|
| Sildenafil's half-life, around 4 hours | Most of the medicine is eliminated over several half-lives, with the exact clearance time varying between individuals |
| Vardenafil's half-life, around 4 to 5 hours | A broadly similar picture, following the same principle |
| Neither has a daily-dose version | No ongoing background level to account for, unlike combinations involving a continuous daily dose |
| The core combining risk | Two active PDE5 inhibitors at once adds side effect risk with no established benefit, regardless of clearance speed |
| Other medicines | Alpha blockers, taken for blood pressure or an enlarged prostate, can contribute to low blood pressure. CYP3A4 inhibitors can raise exposure to either medicine, so all current medicines need reviewing |
| Nitrates and nitrites | Neither medicine may be taken with nitrates, nitric oxide donors or amyl nitrite, sometimes sold as poppers, because of the risk of a dangerous fall in blood pressure |
| Alcohol, food and supplements | Excessive alcohol can worsen blood pressure drops, high-fat meals can delay absorption, and grapefruit juice, herbal remedies and St John's wort can all affect risk |
Getting Advice That Fits You
General clearance principles explain why sildenafil and vardenafil should not be treated as interchangeable within the same day or so, but they cannot tell you the exact position for your own situation.
An online consultation with UK registered prescribers is built around a genuine clinical assessment, reviewing your medical history, health conditions and other medicines, rather than leaving you to estimate a gap from general principles alone.
Medical Disclaimer
This page is for general information only and is not a substitute for individual clinical advice. Sildenafil and vardenafil are prescription-only medicines, and the position for your specific circumstances can only be confirmed following an individual clinical assessment.
Do not combine sildenafil or vardenafil with another PDE5 inhibitor unless a qualified prescriber has specifically advised it.
Rare cases of non-arteritic anterior ischaemic optic neuropathy, a condition affecting the optic nerve, have been reported with PDE5 inhibitors, although a direct causal relationship has not been established.
If you experience an erection lasting longer than four hours, or symptoms such as chest pain, severe dizziness, fainting, difficulty breathing, signs of an allergic reaction, or sudden loss of vision or hearing, seek urgent medical attention by calling 999 or attending A&E.
For any other concerns about your medicine, speak to your prescriber or pharmacist.
