Tadalafil and Voriconazole: Can They Be Taken Together?

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Tadalafil and Voriconazole: Understanding the Interaction

Published: 27 October 2026

Tadalafil and voriconazole can interact because voriconazole is a potent inhibitor of the liver enzyme CYP3A4, which breaks down tadalafil. This means taking them together can significantly raise tadalafil levels in your bloodstream, increasing the risk of side effects such as headache, flushing, dizziness, and low blood pressure. However, this interaction is manageable with careful dose adjustment by your prescriber, and many men take both medicines safely when the tadalafil dose is reduced and monitored appropriately.

What is tadalafil and voriconazole?

Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction (ED) and, in some cases, benign prostatic hyperplasia [4]. It works by relaxing blood vessels in the penis, allowing increased blood flow during sexual stimulation. Tadalafil is available as on-demand tablets (10 mg or 20 mg taken at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low-dose option (2.5 mg or 5 mg) [4]. Brand names include Cialis, and generic versions are widely available.

Voriconazole is a prescription-only antifungal medicine used to treat serious fungal infections, including invasive aspergillosis and candida infections [12]. It belongs to the triazole class of antifungals and is usually given as tablets or intravenous infusion. Voriconazole works by disrupting the fungal cell membrane, but it also strongly inhibits the CYP3A4 enzyme in the liver—the same enzyme responsible for breaking down tadalafil and many other medicines.

Because both medicines are processed by the same liver pathway, taking them together means tadalafil stays in your body longer and reaches higher concentrations than usual. This is why dose adjustments and careful monitoring are essential when tadalafil and voriconazole are prescribed together.

How do tadalafil and voriconazole interact?

The interaction between tadalafil and voriconazole occurs through a mechanism called enzyme inhibition [4]. Tadalafil is metabolised (broken down) primarily by an enzyme in the liver called CYP3A4. Voriconazole is a potent inhibitor of CYP3A4, meaning it slows down or blocks this enzyme's activity. When the enzyme is inhibited, tadalafil is cleared from your body much more slowly, leading to higher blood levels and a longer duration of action.

In practical terms, this means the effects of tadalafil—both the desired effect on erections and potential side effects such as headache, facial flushing, indigestion, nasal congestion, dizziness, and low blood pressure—can be stronger and last longer than expected [4]. The risk of side effects increases, particularly those related to blood pressure, because tadalafil causes blood vessels to widen. If you are also taking other medicines that lower blood pressure, the combined effect can be significant.

This interaction is well recognised and documented in the British National Formulary and the Summary of Product Characteristics for tadalafil [4][12]. It is not an absolute contraindication—meaning the two medicines are not forbidden to be used together—but the tadalafil dose must be reduced, and your prescriber will assess your overall medication list, medical history, and the severity of your fungal infection before deciding on the safest approach.

Why CYP3A4 matters

CYP3A4 is one of the most important enzymes in drug metabolism, responsible for processing roughly half of all medicines used today. Many common drugs—including some antibiotics, antifungals, antivirals, and heart medicines—either inhibit or induce this enzyme, leading to a wide range of potential drug interactions. Understanding whether a medicine affects CYP3A4 helps prescribers predict interactions and adjust doses safely. For tadalafil, potent CYP3A4 inhibitors like voriconazole, ketoconazole, itraconazole, ritonavir, and clarithromycin all require dose reductions to avoid excessive drug levels [4].

What does your prescriber check before prescribing tadalafil with voriconazole?

Before prescribing tadalafil to someone taking voriconazole, a UK prescriber will conduct a thorough medication review and health assessment [2][4]. They will confirm the dose and duration of your voriconazole treatment, as the interaction depends on how much voriconazole is in your system. They will also review your complete list of current medicines to identify any other drugs that might interact with tadalafil or further lower your blood pressure, such as alpha-blockers (e.g. tamsulosin, doxazosin), other antihypertensives, or additional CYP3A4 inhibitors.

Your prescriber will ask about your cardiovascular health, including any history of heart attack, stroke, angina, heart failure, or abnormal blood pressure [2][4]. Tadalafil is not suitable if sexual activity is inadvisable due to severe heart disease, or if you have very low blood pressure. They will also check for contraindications such as recent use of nitrates (GTN spray, isosorbide mononitrate), nicorandil, riociguat, or recreational drugs known as poppers, because combining tadalafil with any of these can cause a dangerous drop in blood pressure [4].

Based on this assessment, your prescriber will recommend a reduced starting dose of tadalafil—often the lowest available dose—and may advise taking it less frequently. They will explain the warning signs of excessive tadalafil levels (severe headache, dizziness, fainting, prolonged erection) and when to seek urgent help. At Cured Pharmacy, every prescription for tadalafil follows an online consultation reviewed by a UK-registered prescriber, ensuring your safety and suitability for treatment.

What tadalafil dose is safe with voriconazole?

When tadalafil and voriconazole are used together, the British National Formulary recommends a maximum tadalafil dose of 10 mg within a 72-hour period for on-demand use [4]. This is a significant reduction from the usual maximum of 20 mg per dose, taken no more than once daily. For men using daily tadalafil (2.5 mg or 5 mg), the prescriber may advise stopping tadalafil temporarily while on voriconazole, or continuing at the lowest dose with close monitoring, depending on individual circumstances and the duration of antifungal treatment.

The exact dose will depend on your overall health, other medicines, and how well you tolerate tadalafil. Some prescribers may start with an even lower dose—such as 5 mg on-demand—to minimise the risk of side effects. It is essential never to adjust your tadalafil dose yourself or take it more frequently than advised, even if you feel the effect is weaker than before. The interaction with voriconazole means the medicine stays in your system longer, so taking extra doses can lead to a dangerous accumulation.

If you have been prescribed tadalafil before starting voriconazole, inform your doctor or pharmacist immediately so they can review your dose. Similarly, if you are already taking voriconazole and wish to start treatment for ED, make sure your prescriber knows about the antifungal during your consultation. At Cured Pharmacy, our online consultation form asks about all your current medicines, and our prescribers will only approve a tadalafil prescription if it is safe and appropriate for you.

What if I need a higher dose?

If the reduced tadalafil dose does not provide sufficient benefit, your prescriber may consider alternative ED treatments that are less affected by CYP3A4 inhibition, or they may wait until your voriconazole course is finished before increasing the tadalafil dose. Never take more tadalafil than prescribed, as this significantly raises the risk of serious side effects, including dangerously low blood pressure, prolonged erection (priapism), and cardiovascular events. Always discuss your treatment goals and any concerns with your prescriber, who can tailor a safe and effective plan for you.

Practical advice for taking tadalafil and voriconazole together

If your prescriber has approved the combination of tadalafil and voriconazole, follow their dosing instructions exactly. Take tadalafil at the prescribed dose and frequency—do not take extra tablets or take them more often, even if you feel the effect is less than expected. On-demand tadalafil (10 mg or 20 mg) should be taken at least 30 minutes before sexual activity, but remember that the maximum dose while on voriconazole is 10 mg within 72 hours [4]. Daily tadalafil (2.5 mg or 5 mg) should be taken at the same time each day if your prescriber has advised continuing it.

Avoid drinking grapefruit juice while taking either medicine, as it can further inhibit CYP3A4 and raise tadalafil levels even more. Limit alcohol intake, as heavy drinking can worsen erectile dysfunction and add to the blood-pressure-lowering effects of tadalafil, increasing the risk of dizziness and fainting [1][4]. If you are taking other medicines that lower blood pressure—such as alpha-blockers for prostate symptoms, or medicines for high blood pressure—be especially cautious when standing up quickly, as the combination can cause postural hypotension (a sudden drop in blood pressure on standing).

Monitor yourself for side effects such as severe headache, dizziness, visual disturbances, chest pain, or an erection lasting more than four hours. If any of these occur, stop taking tadalafil and seek medical advice immediately. Keep all your medicines in their original packaging, store them as directed, and never share your tadalafil with anyone else. If you have any questions or concerns about your treatment, contact your prescriber or pharmacist—Cured Pharmacy's team is available to support you throughout your treatment journey.

Other antifungal medicines and tadalafil interactions

Voriconazole is not the only antifungal that interacts with tadalafil. Other azole antifungals, particularly ketoconazole and itraconazole, are also potent CYP3A4 inhibitors and require similar dose reductions when used with tadalafil [4]. Ketoconazole, for example, can more than double tadalafil blood levels, and the British National Formulary advises a maximum tadalafil dose of 10 mg in 72 hours when these medicines are used together [4]. Itraconazole has a comparable effect and requires the same precautions.

Fluconazole, another commonly prescribed antifungal, is a moderate CYP3A4 inhibitor. While the interaction is less pronounced than with voriconazole or ketoconazole, it can still raise tadalafil levels, and your prescriber may recommend a lower starting dose or closer monitoring. Topical antifungals (creams, pessaries, or sprays applied to the skin or mucous membranes) are generally absorbed in very small amounts and are unlikely to interact significantly with tadalafil, but you should still mention them during your consultation.

If you are prescribed a new antifungal medicine while taking tadalafil, or if you are starting tadalafil while on an antifungal, always inform your prescriber or pharmacist. They will check the specific interaction and adjust your treatment plan accordingly. At Cured Pharmacy, our online consultation captures your full medication history, and our prescribers review every potential interaction before approving your prescription, ensuring your safety and the effectiveness of your treatment.

What about other ED medicines?

Other PDE5 inhibitors—sildenafil (Viagra), vardenafil (Levitra), and avanafil (Spedra)—are also metabolised by CYP3A4 and interact with voriconazole and other potent inhibitors [3][5][6]. Sildenafil requires a lower starting dose (25 mg) when used with potent CYP3A4 inhibitors [3]. Vardenafil and avanafil are contraindicated or not recommended with potent CYP3A4 inhibitors due to the risk of excessive drug levels [5][6]. Your prescriber will choose the safest option based on your antifungal treatment, other medicines, and individual health factors. Never switch between ED medicines or adjust doses without professional advice.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 27 October 2026]
2. National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 27 October 2026]
3. Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 27 October 2026]
4. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 27 October 2026]
5. Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 27 October 2026]
6. Joint Formulary Committee. (n.d.). Avanafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/avanafil/ [accessed 27 October 2026]
7. Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 27 October 2026]

Information on this page is for educational purposes only and is not medical advice. Prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting or changing any medication.

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