Tadalafil and Abacavir: Can They Be Taken Together?

Takes less than 2 minutes to complete 100% online

At a glance

What is tadalafil and abacavir used for?

Tadalafil is a prescription medicine licensed in the UK to treat erectile dysfunction (ED) in men [4]. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Tadalafil is available as on-demand tablets (10mg or 20mg taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours) or as a daily low-dose tablet (2.5mg or 5mg) for men who prefer spontaneity [4]. It requires sexual stimulation to work and does not increase sexual desire.

Abacavir is an antiretroviral medicine used to treat HIV infection [12]. It is a nucleoside reverse transcriptase inhibitor (NRTI) that works by blocking an enzyme the virus needs to multiply, helping to control the viral load and protect the immune system. Abacavir is usually taken as part of combination antiretroviral therapy (cART), often alongside other HIV medicines such as lamivudine or dolutegravir. It does not cure HIV but is an essential part of long-term treatment to keep the virus under control and maintain health.

Both medicines serve very different purposes, and many men living with HIV may wish to use tadalafil for erectile dysfunction. Understanding how these medicines interact is important for safe and effective treatment.

Do tadalafil and abacavir interact with each other?

No major interaction between tadalafil and abacavir is commonly reported. Abacavir does not significantly inhibit or induce CYP3A4, the liver enzyme primarily responsible for breaking down tadalafil [4][12]. This means abacavir is unlikely to raise or lower tadalafil levels in your bloodstream, and the two medicines can usually be taken together without dose adjustment.

However, it is important to remember that abacavir is rarely used alone. It is typically prescribed as part of combination antiretroviral therapy, which may include other medicines that do interact with tadalafil. For example, some HIV medicines such as ritonavir or cobicistat are potent CYP3A4 inhibitors and can significantly increase tadalafil levels, requiring a lower dose of tadalafil to avoid side effects [4]. Your prescriber will review your complete list of HIV medicines during the consultation to check for any interactions and adjust your tadalafil dose if necessary.

Always declare every medicine you are taking, including over-the-counter products and supplements, when you complete your online consultation. This ensures your prescriber can make a safe, individualised decision about your treatment.

What about other medicines in your HIV treatment?

If you are taking a combination HIV treatment that includes a protease inhibitor (such as ritonavir, atazanavir, or darunavir) or an integrase inhibitor boosted with cobicistat, these medicines can raise tadalafil levels [4]. Your prescriber may recommend starting with a lower dose of tadalafil (for example, 10mg instead of 20mg for on-demand use, or avoiding daily tadalafil altogether) and monitoring for side effects such as headache, flushing, or dizziness. The maximum recommended dose of tadalafil is also reduced when taken with potent CYP3A4 inhibitors [4]. Your prescriber will check the specific medicines in your regimen and advise you accordingly.

What does your prescriber check before prescribing tadalafil?

When you request tadalafil through an online consultation at Cured Pharmacy, a UK-registered prescriber will review your medical history and current medicines to ensure it is safe for you [2]. They will check for conditions that make tadalafil unsuitable, such as recent heart attack or stroke, unstable angina, severe heart failure, very low blood pressure, or a history of sudden vision loss (non-arteritic anterior ischaemic optic neuropathy, or NAION) [4].

Your prescriber will also review all your current medicines, including your HIV treatment. They will look for interactions with medicines that are never safe to take with tadalafil, such as nitrates (GTN spray, isosorbide mononitrate), nicorandil, riociguat, or amyl/alkyl nitrites (poppers), because the combination can cause a dangerous drop in blood pressure [4]. If you are taking an alpha-blocker for prostate symptoms (such as tamsulosin or doxazosin), your prescriber will ensure you are stable on that medicine and start you on the lowest dose of tadalafil to reduce the risk of dizziness or fainting [4].

If your HIV treatment includes a potent CYP3A4 inhibitor, your prescriber will adjust your tadalafil dose accordingly. They may also ask about your cardiovascular health, as erectile dysfunction can be an early warning sign of heart disease or diabetes [1][2]. If you have not seen a GP about your ED before, it is a good idea to arrange a check-up to rule out underlying health conditions.

What you need to know

• Tadalafil and abacavir can usually be taken together without a significant interaction.
• Abacavir does not affect the liver enzyme that breaks down tadalafil.
• Your prescriber will review all HIV medicines to check for interactions with other drugs in your regimen.
• Ritonavir and cobicistat can raise tadalafil levels and require dose adjustment.
• Continue your HIV treatment as prescribed; tadalafil does not interfere with antiretrovirals.

How to take tadalafil safely with abacavir

If your prescriber approves tadalafil for you, follow the dosing instructions carefully. For on-demand tadalafil, take one 10mg or 20mg tablet at least 30 minutes before you plan to have sex [4]. The effect can last up to 36 hours, but you should not take more than one dose in 24 hours. Tadalafil requires sexual stimulation to work; it will not cause an erection on its own. You can take it with or without food, although a very heavy or high-fat meal may delay how quickly it works.

Continue taking your abacavir and other HIV medicines exactly as prescribed by your HIV specialist. Do not stop or change your antiretroviral therapy without medical advice, as this can lead to viral resistance and treatment failure. Tadalafil does not interfere with the effectiveness of abacavir or other antiretrovirals, so your HIV treatment will continue to work as expected.

Avoid drinking large amounts of alcohol when taking tadalafil, as alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect, increasing the risk of dizziness or fainting [4]. Grapefruit juice can also raise tadalafil levels and should be avoided. If you experience side effects such as headache, indigestion, back pain, or flushing, these are usually mild and temporary. If side effects are troublesome or persistent, speak to your prescriber about adjusting your dose.

What if you are taking other medicines?

If you take medicines for high blood pressure, heart conditions, or prostate symptoms, declare these during your consultation. Tadalafil can add to the blood-pressure-lowering effect of these medicines, which is usually manageable but must be checked by your prescriber [4]. If you are prescribed a new medicine by your GP or HIV specialist after starting tadalafil, let them know you are using ED treatment so they can check for interactions. Never take another PDE5 inhibitor (such as sildenafil or vardenafil) at the same time as tadalafil, as this can increase the risk of serious side effects [3][4][5].

Warning signs and when to seek help with tadalafil and abacavir

Most men tolerate tadalafil well, but you should be aware of warning signs that need urgent medical attention. If you develop an erection that lasts longer than four hours (priapism), go to A&E immediately, as this can cause permanent damage to the penis [4]. 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 urgent medical help, as these are rare but serious side effects [4].

If you experience chest pain during or after sexual activity, stop and seek medical help. Do not take nitrate medicines (such as GTN spray) if you have used tadalafil in the past 48 hours, as the combination can cause a dangerous drop in blood pressure [4]. If you feel dizzy, lightheaded, or faint after taking tadalafil, sit or lie down and avoid driving or operating machinery until you feel better. If symptoms are severe or do not improve, contact your GP or call NHS 111.

Abacavir can cause a serious allergic reaction (hypersensitivity reaction) in some people, usually within the first six weeks of treatment [12]. Symptoms include fever, rash, nausea, vomiting, diarrhoea, abdominal pain, extreme tiredness, or shortness of breath. If you develop these symptoms, stop taking abacavir and contact your HIV clinic or GP immediately. This is unrelated to tadalafil but is important to be aware of if you are starting abacavir for the first time.

When to get urgent help

• Erection lasting longer than 4 hours (priapism) – go to A&E immediately
• Sudden loss of vision in one or both eyes – seek urgent medical help
• Sudden decrease or loss of hearing, ringing in ears, or dizziness – contact a doctor immediately
• Chest pain during or after sexual activity – stop and seek medical help; do not use nitrates
• Severe dizziness or fainting after taking tadalafil – sit or lie down and call NHS 111 if symptoms persist

Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.

Getting tadalafil and abacavir: what you need to know

Abacavir is a prescription-only medicine supplied by your HIV clinic or GP as part of your antiretroviral therapy. You should continue to collect your HIV medicines from your usual source and attend regular monitoring appointments to check your viral load and overall health.

Tadalafil is also a prescription-only medicine in the UK. At Cured Pharmacy, you can request tadalafil through a confidential online consultation, which is reviewed by a UK-registered prescriber [2]. If approved, your medicine is dispensed by our GPhC-registered pharmacy (GPhC 9012511) and delivered discreetly to your door. The consultation will ask about your medical history, current medicines (including your HIV treatment), and any other health conditions to ensure tadalafil is safe and suitable for you.

Tadalafil is available in several forms, including generic tadalafil tablets and branded Cialis. Prices at Cured Pharmacy start from £7.95 for generic tadalafil, with a first-order discount available using code Ednew (£6.36). All prices include the prescriber consultation and delivery. You can choose on-demand tablets (10mg or 20mg) or, if suitable, daily low-dose tablets (2.5mg or 5mg) for more spontaneous use. Your prescriber will recommend the best option based on your needs and medical history.

Why see a GP about erectile dysfunction?

If you have not already discussed erectile dysfunction with a healthcare professional, it is a good idea to see your GP or HIV specialist. ED can be an early sign of cardiovascular disease, diabetes, or other health conditions that benefit from early treatment [1][2]. Your GP can arrange blood tests to check for underlying causes such as low testosterone, high cholesterol, or poorly controlled blood sugar. Addressing these conditions can improve your overall health and may also improve erectile function. Your HIV clinic can also provide support and advice, as some antiretroviral medicines can contribute to sexual health concerns.