Tadalafil and Truvada: Can They Be Taken Together?

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What is tadalafil and how does it work?

Tadalafil is the generic name for Cialis, a medicine licensed in the UK to treat erectile dysfunction (ED) [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 does not cause an erection on its own—sexual stimulation is still needed.

Tadalafil is available in two dosing options: on-demand tablets (10mg or 20mg) taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours, and daily low-dose tablets (2.5mg or 5mg) taken once a day at the same time [4]. The long duration of action is why tadalafil is sometimes called the 'weekend pill'. It is broken down in the body mainly by an enzyme system called CYP3A4, which is important when considering drug interactions.

At Cured Pharmacy, tadalafil is available on prescription after an online consultation with a UK-registered prescriber. Common side effects include headache, indigestion, back pain, muscle aches, flushing, and nasal congestion [4]. Tadalafil is not suitable for everyone, particularly those taking nitrates, nicorandil, riociguat, or poppers, or when sexual activity is inadvisable due to heart conditions.

What is Truvada and why is it prescribed?

Truvada is a brand name for a fixed-dose combination tablet containing two antiretroviral medicines: emtricitabine (200mg) and tenofovir disoproxil (245mg, equivalent to 300mg tenofovir disoproxil fumarate) [12]. It is used in two main ways: as part of combination antiretroviral therapy (ART) to treat people living with HIV, and as pre-exposure prophylaxis (PrEP) to reduce the risk of HIV infection in people who are HIV-negative but at high risk of exposure.

When used for PrEP, Truvada is taken once daily alongside safer sex practices. When used as part of HIV treatment, it is combined with other antiretroviral medicines as prescribed by an HIV specialist. Truvada works by blocking an enzyme (reverse transcriptase) that HIV needs to replicate inside human cells. Common side effects can include nausea, diarrhoea, headache, dizziness, and fatigue. Long-term use requires monitoring of kidney function and bone health.

Truvada does not interact with the enzyme system (CYP3A4) that breaks down tadalafil, which is why no major direct pharmacokinetic interaction is expected between the two medicines. However, your prescriber will always review your full medical history and all current medicines to ensure any ED treatment is safe and appropriate for you.

Is there an interaction between tadalafil and Truvada?

No major direct interaction between tadalafil and Truvada is commonly reported in clinical practice or drug interaction databases. Truvada (emtricitabine/tenofovir) does not significantly affect the CYP3A4 enzyme system that metabolises tadalafil, and tadalafil does not interfere with the way Truvada works against HIV [4][12]. This means that, from a pharmacological standpoint, the two medicines can generally be taken together without one affecting the blood levels or effectiveness of the other.

However, it is important to understand that 'no major interaction' does not mean 'no checks required'. Your prescriber will still need to review your overall health, blood pressure, kidney function, and any other medicines you take. Some people on antiretroviral therapy may also take other medicines—such as ritonavir or cobicistat, which are potent CYP3A4 inhibitors—and these can significantly raise tadalafil levels, requiring dose adjustments [4]. Always declare every medicine, supplement, and recreational substance during your consultation.

If you are taking Truvada for PrEP or HIV treatment and are experiencing erectile dysfunction, it is worth discussing this with your HIV clinic or GP. ED can have many causes, including psychological factors, cardiovascular health, or side effects from other medicines. Tadalafil may help, but a full assessment ensures the safest and most effective treatment plan for you.

What your prescriber will check

During your online consultation at Cured Pharmacy, the prescriber will ask about your current medicines, including Truvada and any other antiretrovirals, to check for interactions. They will review your cardiovascular health, blood pressure, kidney function, and any history of heart disease, stroke, or eye problems. They will also ask about recreational drug use, particularly poppers (amyl or alkyl nitrites), which must never be used with tadalafil due to the risk of a dangerous drop in blood pressure [4]. If you take other medicines that lower blood pressure or affect the CYP3A4 system, the prescriber may adjust the tadalafil dose or recommend an alternative. This thorough review ensures that tadalafil is safe and appropriate for you.

What you need to know

• No major direct interaction is commonly reported between tadalafil and Truvada.
• Ritonavir or cobicistat can raise tadalafil levels and require dose adjustments.
• Never use poppers with tadalafil—this can cause dangerous low blood pressure.
• Always declare all medicines during your consultation for a full safety review.
• Tadalafil is available on prescription after an online consultation at Cured Pharmacy.

Practical advice for taking tadalafil and Truvada together

If your prescriber approves tadalafil for you while you are taking Truvada, take each medicine exactly as directed. Continue taking Truvada at the same time every day as prescribed by your HIV specialist—do not skip doses, as this can affect HIV suppression or PrEP effectiveness. For on-demand tadalafil (10mg or 20mg), take it at least 30 minutes before you plan to have sex; for daily tadalafil (2.5mg or 5mg), take it at the same time each day, regardless of when you have sex [4].

Avoid drinking large amounts of alcohol when taking tadalafil, as this can increase the risk of dizziness, headache, and low blood pressure, and may make it harder to get an erection. Grapefruit juice can raise tadalafil levels and should be avoided. Never use poppers (amyl or alkyl nitrites) with tadalafil, as the combination can cause a life-threatening drop in blood pressure [4]. If you develop side effects such as severe headache, dizziness, chest pain during sex, or an erection lasting more than four hours, seek medical help immediately.

Stay in regular contact with your HIV clinic or GP, especially if you start any new medicines or notice changes in your health. If you experience new or worsening erectile dysfunction, discuss it with your healthcare team—it may be a sign of an underlying health issue that needs attention. Remember, tadalafil treats the symptoms of ED but does not address the underlying cause, so a holistic approach to your health is important [1][2].

Other medicines that can interact with tadalafil

While Truvada itself does not interact with tadalafil, other medicines you may be taking can. Never take tadalafil with nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or poppers, as the combination can cause a dangerous fall in blood pressure [4]. Do not take tadalafil with another PDE5 inhibitor (such as sildenafil, vardenafil, or avanafil) at the same time.

If you take alpha-blockers for an enlarged prostate (such as tamsulosin, doxazosin, or alfuzosin), there is a risk of low blood pressure and dizziness. Your prescriber will ensure you are stable on the alpha-blocker and will start you on the lowest dose of tadalafil [4]. Potent CYP3A4 inhibitors—including ritonavir, cobicistat (often used in HIV treatment), ketoconazole, itraconazole, and clarithromycin—can significantly raise tadalafil levels, so your dose may need to be reduced [4]. Conversely, CYP3A4 inducers such as rifampicin, carbamazepine, phenytoin, and St John's wort can lower tadalafil levels and make it less effective.

Other blood-pressure medicines (such as ACE inhibitors, beta-blockers, or calcium-channel blockers) can add to the blood-pressure-lowering effect of tadalafil, but this is usually manageable. Always declare every medicine, supplement, and recreational substance during your consultation. Your prescriber will review the full list and advise whether tadalafil is safe, or whether a dose adjustment or alternative treatment is needed [2][4].

Ritonavir, cobicistat, and tadalafil dosing

Ritonavir and cobicistat are medicines often used to 'boost' other antiretrovirals in HIV treatment. They are potent inhibitors of CYP3A4, the enzyme that breaks down tadalafil, and can significantly increase tadalafil levels in the blood [4]. If you are taking ritonavir or cobicistat, your prescriber will reduce the maximum dose of tadalafil. For on-demand use, the maximum dose is usually 10mg in 72 hours; for daily use, tadalafil may not be recommended or the dose will be carefully adjusted [4]. Never adjust your tadalafil dose yourself—always follow your prescriber's instructions and report any side effects promptly.

When to get urgent help

• Erection lasting more than 4 hours (priapism)—call 999 or go to A&E immediately
• Sudden loss of vision or hearing—seek urgent medical help
• Severe chest pain during sex—stop activity and call 999; do not take nitrates if you have used tadalafil recently
• Signs of severe allergic reaction (swelling of face, lips, throat, difficulty breathing)—call 999
• Severe dizziness, fainting, or very low blood pressure—seek same-day medical advice

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

When to seek medical help and ongoing support

Seek urgent medical help (call 999 or go to A&E) if you experience an erection lasting more than four hours (priapism), sudden loss of vision or hearing, severe chest pain during sex, or signs of a severe allergic reaction such as swelling of the face, lips, or throat [4]. Priapism is a medical emergency that requires immediate treatment to prevent permanent damage. If you develop chest pain during sex, stop and seek help—do not take nitrates to relieve the pain if you have used tadalafil within the last 48 hours, as this can be dangerous.

If you experience milder side effects such as headache, indigestion, back pain, or flushing, these are common and often settle with continued use. However, if side effects are severe or persistent, contact your prescriber or GP for advice. If tadalafil is not effective for you, do not increase the dose yourself—speak to your prescriber, as there may be other treatment options or underlying causes that need addressing [2].

Continue to attend regular appointments with your HIV clinic or GP, especially if you are on Truvada for PrEP or HIV treatment. Erectile dysfunction can sometimes be an early sign of cardiovascular disease or diabetes, so it is important to have a full health check if ED is new or worsening [1][2]. At Cured Pharmacy, our team is here to support you with discreet, professional advice and access to licensed ED treatments after a thorough online consultation with a UK-registered prescriber.

How Cured Pharmacy can help

Cured Pharmacy is a GPhC-registered online pharmacy (GPhC 9012511) offering discreet access to licensed ED treatments, including tadalafil, after an online consultation reviewed by a UK-registered prescriber. We understand that discussing ED can feel difficult, and our service is designed to be confidential, convenient, and non-judgemental. If you are taking Truvada or other HIV medicines and are experiencing erectile dysfunction, our prescribers will review your full medication list and health history to ensure tadalafil or another ED treatment is safe and appropriate for you. Use code Ednew on your first order for a discount. If you have any questions, our pharmacy team is here to help.