Tadalafil and Aciclovir: Can You Take Them Together?

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What is tadalafil and aciclovir used for?

Tadalafil is a prescription medicine used 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 the branded medicine Cialis or as a generic version, and it can be taken on-demand (10mg or 20mg at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low dose (2.5mg or 5mg) [4].

Aciclovir is an antiviral medicine commonly prescribed to treat infections caused by herpes viruses, including genital herpes, cold sores, shingles, and chickenpox [12]. It works by stopping the virus from multiplying in your body. Aciclovir is available as tablets, cream, or occasionally as an intravenous infusion for severe infections. Many people take aciclovir either as a short course during an outbreak or as a longer-term suppressive treatment to reduce the frequency of recurrent herpes episodes.

Both medicines serve very different purposes and work through completely different mechanisms in the body, which is why they do not typically interfere with each other's action.

Is there an interaction between tadalafil and aciclovir?

Based on current clinical evidence and prescribing guidance, there is no significant known interaction between tadalafil and aciclovir [3][4][12]. These two medicines are processed differently by your body and do not share the same metabolic pathways that would cause them to interfere with each other. Aciclovir is primarily eliminated unchanged by the kidneys, whereas tadalafil is broken down mainly by liver enzymes (specifically CYP3A4) [4].

This means that taking aciclovir is unlikely to raise or lower the levels of tadalafil in your bloodstream, and tadalafil should not affect how well aciclovir works against viral infections. Many men safely use both medicines together without experiencing problems. However, it is essential to remember that individual responses can vary, and other factors in your medical history—such as kidney function, other medicines you take, or underlying health conditions—may still need careful consideration.

During your online consultation at Cured Pharmacy, the prescriber will review your complete medication list, including aciclovir and any other treatments, to ensure tadalafil is safe and appropriate for you. This personalised assessment is a vital safeguard, even when no major interaction is expected.

When to get urgent help

• Erection lasting longer than 4 hours (priapism)—attend A&E or call 999 immediately
• Sudden loss of vision in one or both eyes—seek urgent medical assessment
• Sudden decrease or loss of hearing, possibly with ringing in the ears or dizziness
• Chest pain during or after sexual activity—stop activity and seek help; do not take nitrates if you have used tadalafil in the past 48 hours
• Severe allergic reaction (swelling of face, lips, throat, or difficulty breathing)—call 999

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

What does your prescriber check before approving tadalafil?

When you request tadalafil through an online consultation, a UK-registered prescriber reviews several important factors to ensure the treatment is safe for you [2]. They will ask about your cardiovascular health, including any history of heart attack, stroke, angina, heart failure, or abnormal blood pressure, because sexual activity itself places demands on your heart and tadalafil can lower blood pressure slightly [4].

The prescriber will also check all your current medicines to identify any that must never be taken with tadalafil. These include nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, and recreational drugs known as 'poppers' (amyl or alkyl nitrites)—combining tadalafil with any of these can cause a dangerous drop in blood pressure [4]. If you take alpha-blockers for prostate symptoms or high blood pressure (such as doxazosin or tamsulosin), you may still be able to use tadalafil, but you must be stable on the alpha-blocker and start on the lowest dose of tadalafil to minimise the risk of dizziness [4].

Certain other medicines can affect tadalafil levels in your body. Potent CYP3A4 inhibitors—including some HIV medicines (ritonavir, cobicistat), antifungals (ketoconazole, itraconazole), and antibiotics (clarithromycin)—can increase tadalafil levels, so your dose may need to be reduced [4]. Conversely, CYP3A4 inducers like rifampicin, carbamazepine, phenytoin, or St John's wort can make tadalafil less effective. The prescriber will also consider your kidney and liver function, any history of priapism (prolonged erection), and whether you have ever experienced sudden vision or hearing loss.

Declaring aciclovir and all other medicines

Even though aciclovir does not interact significantly with tadalafil, you must still list it—and every other medicine, supplement, or herbal remedy you take—in your consultation. This complete picture allows the prescriber to spot any less common interactions, assess your overall health, and tailor advice to your situation. Never assume a medicine is too minor to mention; over-the-counter products, vitamins, and herbal supplements can sometimes interact with prescription treatments in unexpected ways.

Practical advice when taking tadalafil and aciclovir together

If your prescriber approves tadalafil and you are already taking aciclovir, you can usually take both medicines as directed without needing to adjust the timing or dose of either [4][12]. Tadalafil on-demand tablets (10mg or 20mg) should be taken at least 30 minutes before you plan to have sex, and you should not take more than one dose in 24 hours. Daily tadalafil (2.5mg or 5mg) is taken once a day at roughly the same time, regardless of when you plan sexual activity. Aciclovir is typically taken two to five times a day for treatment of an outbreak, or twice daily for suppressive therapy, depending on your prescription.

There is no need to separate the doses of tadalafil and aciclovir by a specific time gap, as they do not interfere with each other's absorption or action. You can take them together or at different times of day, whichever fits your routine. Both medicines can be taken with or without food, although a very heavy, high-fat meal may slightly delay the absorption of tadalafil (this is more relevant for on-demand use).

Stay well hydrated, especially if you are taking aciclovir, as this helps protect your kidneys. Avoid drinking excessive alcohol when using tadalafil, because alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect, increasing the risk of dizziness or fainting [4]. Grapefruit juice can raise tadalafil levels and should be avoided. If you develop any new symptoms—such as dizziness, headache, or visual changes—contact your GP or pharmacist for advice. Do not stop or change the dose of any prescribed medicine, including aciclovir, without consulting a healthcare professional first.

At a glance

What are the warning signs to watch for with tadalafil?

Tadalafil is generally well tolerated, but like all medicines it can cause side effects in some people [4]. Common side effects include headache, indigestion, back pain, muscle aches, flushing, and a blocked or runny nose. These are usually mild and short-lived. However, there are a few serious warning signs that require urgent medical attention.

If you experience an erection that lasts longer than four hours (priapism), you must seek emergency help immediately by attending A&E or calling 999. Priapism can damage the tissues of the penis permanently if not treated promptly [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), are rare but serious side effects that also require urgent medical assessment [4].

Chest pain during or after sexual activity is another important warning sign. If this happens, do not continue sexual activity and seek medical help straight away—do not take nitrate medicines (such as GTN spray) for chest pain if you have used tadalafil within the past 48 hours, as the combination can be dangerous [4]. Severe allergic reactions (such as swelling of the face, lips, or throat, or difficulty breathing) are very rare but require emergency treatment. If you feel unwell in any way that concerns you, contact your GP, call NHS 111, or seek emergency help as appropriate.

When to see your GP about erectile dysfunction

If you are experiencing erectile dysfunction for the first time, it is important to see your GP for a face-to-face assessment [1][2]. ED can be an early warning sign of underlying health conditions such as heart disease, high blood pressure, diabetes, or hormonal imbalances. Your GP can arrange blood tests, check your cardiovascular health, review your medicines, and discuss lifestyle factors such as smoking, alcohol, exercise, and stress. Treating the underlying cause—or making lifestyle changes—can sometimes improve ED without the need for medication, or make ED treatments work better. An online consultation is a convenient option for ongoing treatment once ED has been assessed, but it should not replace an initial GP review.

How to access tadalafil and aciclovir through Cured Pharmacy

Cured Pharmacy is a GPhC-registered online pharmacy (GPhC 9012511) offering convenient access to prescription erectile dysfunction treatments after a clinical consultation with a UK-registered prescriber [4]. To request tadalafil, you complete a short online health questionnaire covering your medical history, current medicines (including aciclovir), and any relevant health conditions. A prescriber reviews your answers and, if appropriate, approves your treatment. Your medicine is then dispensed by our pharmacy team and delivered discreetly to your home.

We stock a range of tadalafil options to suit different needs and budgets. Generic tadalafil is available from £7.95 for on-demand tablets, or £6.36 for your first order using code Ednew. We also offer branded Cialis from £12.00 (£9.60 with code Ednew), Tadalafil 20mg (Teva) at £9.99 (£7.99 with code Ednew), and Avarante (tadalafil) 10mg at £11.49 (£9.19 with code Ednew). If tadalafil is not suitable for you, alternative PDE5 inhibitors are available, including sildenafil (generic Viagra) from £0.45 per tablet, vardenafil (generic Levitra) from £16.95, and Spedra (avanafil) from £20.95.

Aciclovir is also a prescription medicine, and if you need a new prescription or a repeat supply, you should consult your GP or use an appropriate online service. If you have any questions about taking tadalafil alongside aciclovir or any other medicine, our pharmacy team is here to help—you can contact us for advice at any stage of your treatment journey.

Why choose Cured Pharmacy for ED treatment?

Cured Pharmacy combines clinical expertise with convenience and discretion. Every prescription is reviewed by a UK-registered prescriber and dispensed by qualified pharmacists, ensuring you receive safe, effective treatment tailored to your needs. Our service is fully regulated by the General Pharmaceutical Council, giving you confidence in the quality and safety of your care. Delivery is fast and discreet, with plain packaging to protect your privacy. We are here to support you at every step, from your initial consultation through to ongoing treatment and advice.

In summary

• No major interaction is reported between tadalafil and aciclovir—they can usually be taken together safely.
• Always declare aciclovir and all other medicines in your online consultation for a full safety review.
• Tadalafil must never be taken with nitrates, nicorandil, riociguat, or poppers due to dangerous blood pressure drops.
• Seek urgent help for erections lasting over four hours, sudden vision or hearing loss, or chest pain during sex.
• See your GP if you have new erectile dysfunction, as it can signal underlying heart or metabolic conditions.

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