Vardenafil and Efavirenz: Can They Be Taken Together?
Learn how these medicines interact and what safer ED treatment options are available through our UK pharmacist-led service.
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Vardenafil and Efavirenz: Understanding the Interaction
Published: 30 October 2026
Vardenafil and efavirenz can interact because efavirenz affects how your body processes vardenafil, potentially reducing its effectiveness. Efavirenz is an antiretroviral medicine used to treat HIV, while vardenafil (generic Levitra) is a PDE5 inhibitor used for erectile dysfunction. This page explains how the interaction works, what your prescriber will check, and what alternatives may be safer for you.
At a glance
What Are Vardenafil and Efavirenz?
Vardenafil is a prescription medicine for erectile dysfunction (ED), sold under the brand name Levitra and as a generic. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis to help achieve and maintain an erection when sexually aroused [5]. Vardenafil is usually taken 25 to 60 minutes before sexual activity, at doses of 5mg, 10mg or 20mg, and its effects can last for several hours.
Efavirenz is an antiretroviral medicine used to treat HIV infection. It belongs to a class called non-nucleoside reverse transcriptase inhibitors (NNRTIs) and is often part of combination therapy to control the virus [12]. Efavirenz is taken once daily, usually at bedtime, and works by blocking an enzyme the virus needs to replicate. It is a long-term treatment that must be taken consistently to keep HIV under control.
Both medicines are metabolised (broken down) in the liver by enzymes, which is where the potential for interaction arises. Understanding how each medicine works helps explain why your prescriber needs to review them together during your consultation.
How Do Vardenafil and Efavirenz Interact?
Efavirenz is a CYP3A4 inducer, meaning it speeds up the activity of liver enzymes that break down many medicines, including vardenafil [5][12]. When efavirenz increases the activity of these enzymes, vardenafil is metabolised more quickly than usual. This can lower the amount of vardenafil in your bloodstream, potentially making it less effective at treating erectile dysfunction.
In plain English, efavirenz may reduce how well vardenafil works. The interaction is not dangerous in the way that combining vardenafil with nitrates would be—it will not cause a sudden drop in blood pressure—but it may mean that vardenafil does not help your erections as much as expected. The degree of this effect can vary from person to person, depending on your dose of efavirenz, your liver function, and other individual factors.
Because of this interaction, vardenafil is not usually the first-choice PDE5 inhibitor for men taking efavirenz. Your prescriber will consider whether a different ED treatment might work better for you, or whether adjustments to your vardenafil dose could be made. It is important never to increase your dose of vardenafil on your own; always discuss any concerns with your prescriber or pharmacist.
Why CYP3A4 Induction Matters
CYP3A4 is one of the main enzymes in your liver responsible for breaking down medicines. When a medicine like efavirenz induces (speeds up) this enzyme, it affects not just vardenafil but many other medicines you might take. This is why your prescriber will ask about all your current medicines during your consultation, including over-the-counter products and supplements such as St John's wort, which is also a CYP3A4 inducer. Understanding this mechanism helps you see why some medicine combinations require careful monitoring or dose adjustments.
What Your Prescriber Will Check
When you request vardenafil through Cured Pharmacy's online consultation, a UK-registered prescriber will review your full medical history and all current medicines, including efavirenz. They will assess whether vardenafil is suitable for you or whether a different PDE5 inhibitor—such as sildenafil or tadalafil—might be a better choice given the interaction with efavirenz [3][4][5].
Your prescriber will also check for other medicines or health conditions that could affect your treatment. For example, if you are taking other antiretrovirals alongside efavirenz, some of these (such as ritonavir or cobicistat) are potent CYP3A4 inhibitors that have the opposite effect, raising PDE5 inhibitor levels and requiring dose reductions. Your prescriber will also ask about blood pressure, heart conditions, and any history of sudden vision or hearing loss, as these can affect whether PDE5 inhibitors are safe for you.
If vardenafil is not the best option, your prescriber may recommend sildenafil (generic Viagra) or tadalafil (generic Cialis) instead. Sildenafil is also affected by CYP3A4 inducers but may still be effective at standard doses; tadalafil is less affected by efavirenz and is often a preferred choice for men on this antiretroviral [3][4]. Your prescriber will explain the options and help you choose the treatment most likely to work safely for you.
What you need to know
- Efavirenz may reduce vardenafil effectiveness by speeding up how your liver breaks it down.
- Tadalafil is often a better choice than vardenafil for men taking efavirenz.
- Never increase your vardenafil dose without medical advice if it is not working.
- All PDE5 inhibitors require a prescriber consultation and should not be taken with nitrates or poppers.
- Seek urgent help for erections lasting over four hours or sudden vision or hearing loss.
Safer Alternatives for Erectile Dysfunction
If you are taking efavirenz, tadalafil (generic Cialis) is often a more suitable choice than vardenafil for treating erectile dysfunction. Tadalafil is less affected by CYP3A4 inducers, so efavirenz is less likely to reduce its effectiveness [4]. Tadalafil is available as an on-demand tablet (10mg or 20mg taken at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low-dose tablet (2.5mg or 5mg) for men who prefer spontaneity.
Sildenafil (generic Viagra) is another option. While efavirenz can reduce sildenafil levels to some extent, many men still find it effective at standard doses of 50mg or 100mg [3]. Your prescriber may suggest starting with a higher dose if you are on efavirenz, or trying the medicine to see how well it works for you. Sildenafil is taken about one hour before sex and is effective for around four to six hours.
Avanafil (Spedra) is a newer PDE5 inhibitor that works quickly—often within 15 to 30 minutes—but it is also metabolised by CYP3A4 and may be less effective with efavirenz [6]. Your prescriber will discuss which medicine best fits your needs, lifestyle, and other health factors. All PDE5 inhibitors require sexual stimulation to work and are only supplied after a consultation with a UK prescriber.
Non-Tablet Options
If oral PDE5 inhibitors are not suitable or effective for you, other treatments are available. Vitaros is a prescription alprostadil cream applied to the tip of the penis a few minutes before sex [7]. Caverject is an alprostadil injection given into the side of the penis; it works independently of sexual stimulation and is not affected by efavirenz. Eroxon is a topical gel medical device available without prescription. Your GP or a specialist can discuss these options if tablets do not work for you.
Practical Advice When Taking Vardenafil and Efavirenz
If your prescriber decides that vardenafil is appropriate for you despite the interaction with efavirenz, take it exactly as directed. Do not increase your dose without medical advice, even if you feel it is not working as well as you hoped. Increasing the dose on your own can raise the risk of side effects such as headache, flushing, dizziness, or visual disturbances, without necessarily improving effectiveness.
Avoid drinking large amounts of alcohol when using vardenafil, as alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect of the medicine, increasing the risk of dizziness or fainting. Grapefruit juice can also affect how vardenafil is broken down in your body, so it is best to avoid it. If you experience side effects or feel the medicine is not working, contact your prescriber or pharmacist for advice rather than adjusting your dose yourself.
Never take vardenafil with nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, or recreational drugs known as poppers (amyl or alkyl nitrites). This combination can cause a dangerous drop in blood pressure. Do not take vardenafil with another PDE5 inhibitor such as sildenafil or tadalafil. Always tell your prescriber about every medicine you take, including those prescribed by your HIV clinic, your GP, and any over-the-counter products or supplements.
When to get urgent help
- Erection lasting longer than four hours (priapism) – go to A&E immediately
- Sudden loss of vision in one or both eyes – stop vardenafil and seek urgent medical help
- Sudden decrease or loss of hearing, possibly with ringing or dizziness – seek urgent medical attention
- Severe chest pain during or after sex that does not go away – call 999
- Severe dizziness or fainting – sit or lie down and seek medical advice if it does not improve
Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.
Warning Signs and When to Seek Help
Most men tolerate vardenafil well, but you should be aware of warning signs that need urgent attention. If you develop an erection that lasts longer than four hours (priapism), go to A&E immediately. Priapism is a medical emergency that can cause permanent damage to the penis if not treated quickly. It is rare but can occur with any PDE5 inhibitor.
Sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing (sometimes with ringing in the ears or dizziness), requires immediate medical attention. Stop taking vardenafil and seek urgent help if this happens. If you experience chest pain during or after sex, do not use more vardenafil; sit down, rest, and seek medical advice. If the chest pain is severe or does not go away, call 999.
Common side effects of vardenafil include headache, flushing, nasal congestion, and indigestion. These are usually mild and temporary. If you feel dizzy or light-headed, especially when standing up, sit or lie down until it passes; this can happen if vardenafil lowers your blood pressure. If side effects are troublesome or persistent, speak to your pharmacist or prescriber. Never stop taking efavirenz or any other prescribed medicine without advice from the doctor who prescribed it, as this could affect your HIV treatment.
Coordinating Your Care
If you are under the care of an HIV clinic or specialist, it is helpful to let them know you are using an ED treatment. Your HIV team can work with your GP or online prescriber to ensure all your medicines are coordinated safely. Cured Pharmacy's prescribers review your full medicine list during the consultation, but you should also keep your own healthcare providers informed. Good communication between your healthcare team helps ensure you receive safe, effective treatment for all your health needs.
Tadalafil May Work Better
If you are taking efavirenz, tadalafil (generic Cialis) is often more effective than vardenafil because it is less affected by the interaction. Speak to your prescriber about which ED treatment is best for you.
Scientific References
- Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 30 October 2026]
- Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 30 October 2026]
- Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 30 October 2026]
- Joint Formulary Committee. (n.d.). Avanafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/avanafil/ [accessed 30 October 2026]
- Joint Formulary Committee. (n.d.). Alprostadil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/alprostadil/ [accessed 30 October 2026]
- Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 30 October 2026]
- NHS. (n.d.). Erectile dysfunction (impotence). https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ Accessed 30 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.
Common Questions
Can I take vardenafil if I am on efavirenz?
Efavirenz may reduce how well vardenafil works, so it is not usually the first choice. Your prescriber will assess your individual situation and may recommend tadalafil or sildenafil instead, which are often more effective for men taking efavirenz.
Why does efavirenz affect vardenafil?
Efavirenz speeds up liver enzymes that break down vardenafil, lowering the amount in your bloodstream. This can make vardenafil less effective at treating erectile dysfunction, though the interaction is not dangerous.
Is tadalafil safer than vardenafil with efavirenz?
Tadalafil is less affected by efavirenz and is often a better choice for men on this antiretroviral. Your prescriber will discuss which PDE5 inhibitor is most suitable for you based on your full medical history and current medicines.
Can I increase my vardenafil dose if it is not working?
No, never increase your dose without medical advice. If vardenafil is not effective, speak to your prescriber, who may suggest a different medicine or adjust your treatment plan safely.
Will efavirenz stop vardenafil from working completely?
Not necessarily. The degree of interaction varies, and some men may still find vardenafil helpful. However, tadalafil or sildenafil are often more reliable choices for men taking efavirenz.
Do I need to tell my HIV clinic I am using ED treatment?
It is helpful to keep your HIV team informed, as they can coordinate your care with your GP or online prescriber. Good communication ensures all your medicines work together safely.
Are there any ED treatments not affected by efavirenz?
Alprostadil treatments (Vitaros cream or Caverject injection) work differently from PDE5 inhibitors and are not affected by efavirenz. Your GP or specialist can discuss these options if oral tablets are not suitable.
What should I do if I get side effects from vardenafil?
Common side effects like headache or flushing are usually mild. If you experience dizziness, chest pain, sudden vision or hearing loss, or an erection lasting over four hours, seek medical help immediately.
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Medically reviewed by
Tarun Kumar, Superintendent Pharmacist (GPhC 2233073)