Tadalafil and Doravirine: Can They Be Taken Together?

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At a glance

What is tadalafil and how does it work?

Tadalafil is a prescription medicine licensed in the UK to treat erectile dysfunction [4]. It belongs to a group of medicines called phosphodiesterase type 5 (PDE5) inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Tadalafil is the active ingredient in branded Cialis and is also available as a generic medicine.

Tadalafil can be taken in two ways: on-demand (10 mg or 20 mg taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours) or daily (2.5 mg or 5 mg taken once a day, allowing for spontaneity) [4]. It requires sexual stimulation to work and does not increase sexual desire on its own. Common side effects include headache, indigestion, back pain, and flushing.

At Cured Pharmacy, tadalafil is available after an online consultation reviewed by a UK-registered prescriber. The prescriber will check your medical history, current medicines, and overall health to ensure tadalafil is suitable and safe for you.

What is doravirine and why is it prescribed?

Doravirine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) used to treat HIV-1 infection in adults [12]. It is available as Pifeltro (doravirine alone) or as part of the fixed-dose combination tablet Delstrigo (doravirine, lamivudine, and tenofovir disoproxil). Doravirine works by blocking an enzyme that HIV needs to multiply, helping to control the virus and maintain immune function.

Unlike some older HIV medicines, doravirine is generally well tolerated and has fewer effects on cholesterol and mood. However, like all antiretroviral medicines, it can interact with other drugs by affecting liver enzymes that break down medicines in the body. Doravirine is a mild inducer of certain enzymes (CYP3A) and can also be affected by strong enzyme inducers or inhibitors [12].

If you are taking doravirine or any other HIV medication, it is essential to tell your prescriber during your ED consultation. They will check whether tadalafil is safe to use alongside your HIV treatment and whether any dose adjustments are needed.

How do tadalafil and doravirine interact?

Tadalafil is broken down in the body mainly by an enzyme called CYP3A4 [4]. Doravirine is a weak inducer of CYP3A, which means it can slightly speed up the breakdown of tadalafil, potentially reducing its levels in the blood [12]. However, this effect is generally mild, and no major interaction between tadalafil and doravirine is commonly reported in clinical practice.

In most cases, tadalafil can be used safely alongside doravirine without the need for dose adjustment. The prescriber will review your full medication list, including all HIV medicines, to check for any additional interactions. For example, if you are taking doravirine as part of Delstrigo (which also contains lamivudine and tenofovir), the prescriber will consider all components of your treatment.

It is important not to take tadalafil with certain other medicines that are absolutely contraindicated, such as nitrates (GTN spray, isosorbide mononitrate), nicorandil, riociguat, or recreational drugs known as 'poppers' (amyl or alkyl nitrites), as these combinations can cause a dangerous drop in blood pressure [4]. Always declare every medicine, supplement, and recreational substance you use during your consultation.

What your prescriber will check

During your online consultation at Cured Pharmacy, the prescriber will ask about all your current medicines, including your HIV treatment. They will check for any interactions, review your cardiovascular health (as sexual activity places demands on the heart), and ensure tadalafil is safe for you [2]. If you are on other medicines that affect blood pressure or are broken down by the same liver enzymes, the prescriber may adjust the dose or recommend a different ED treatment.

You should also tell the prescriber if you have any history of heart problems, stroke, low blood pressure, liver or kidney disease, or eye conditions such as non-arteritic anterior ischaemic optic neuropathy (NAION) [4]. These factors will help the prescriber make an informed decision about your treatment.

What you need to know

• Tadalafil and doravirine can usually be taken together safely with no major interaction reported.
• Doravirine may slightly reduce tadalafil levels, but dose adjustment is rarely needed.
• Your prescriber will check your full HIV medication list for any additional interactions.
• Never take tadalafil with nitrates, nicorandil, riociguat, or poppers.
• Seek urgent help for erections lasting over four hours or sudden vision or hearing loss.

Can I take tadalafil and doravirine together safely?

In most cases, yes—tadalafil and doravirine can be taken together safely. No major interaction is commonly reported, and the mild enzyme-inducing effect of doravirine is not usually significant enough to prevent tadalafil from working effectively [12]. However, every person's situation is different, and your prescriber will assess your individual circumstances during the consultation.

If you are taking other HIV medicines alongside doravirine, or if you are on additional treatments for other conditions, the prescriber will check each medicine carefully. Some HIV medicines (such as ritonavir or cobicistat, which are potent CYP3A4 inhibitors) can significantly raise tadalafil levels and require dose adjustments [4]. Doravirine itself does not have this effect, but it is important to declare your full regimen.

Never start, stop, or change the dose of any prescribed medicine without consulting your doctor or pharmacist. If you experience any unexpected side effects or if your ED treatment does not seem to be working as expected, contact your prescriber or GP for advice.

What are the warning signs to watch for with tadalafil and doravirine?

Most men taking tadalafil alongside doravirine will not experience any problems. However, you should be aware of the common side effects of tadalafil, which include headache, indigestion, back pain, muscle aches, flushing, and nasal congestion [4]. These are usually mild and temporary. If side effects are troublesome or persistent, speak to your prescriber—they may adjust your dose or suggest an alternative treatment.

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 in one or both eyes, sudden decrease or loss of hearing, or chest pain during sexual activity [4]. These are rare but serious side effects that require immediate attention.

If you develop dizziness, fainting, or a significant drop in blood pressure, stop taking tadalafil and contact your doctor. This is more likely if you are also taking medicines for high blood pressure or prostate problems (alpha-blockers), but it is important to report any unusual symptoms. Do not take tadalafil with nitrates, nicorandil, riociguat, or poppers, as this combination can cause a dangerous fall in blood pressure [4].

Practical tips for taking tadalafil safely

Take tadalafil exactly as prescribed. If you are using the on-demand dose (10 mg or 20 mg), take it at least 30 minutes before sexual activity; the effect can last up to 36 hours, so you do not need to take it more than once a day [4]. If you are on the daily dose (2.5 mg or 5 mg), take it at the same time each day, with or without food.

Avoid drinking large amounts of alcohol, as this can make erectile dysfunction worse and increase the risk of side effects such as dizziness and low blood pressure [4]. Grapefruit juice can also raise tadalafil levels in the blood, so it is best to avoid it. Store your medicine in a cool, dry place, out of reach of children, and check the expiry date before use.

When to get urgent help

• Erection lasting more than 4 hours (priapism) – call 999 or go to A&E immediately
• Sudden loss of vision in one or both eyes – seek urgent medical help
• Sudden decrease or loss of hearing – contact a doctor immediately
• Chest pain during sexual activity – stop and seek urgent medical attention
• Severe dizziness or fainting – stop tadalafil and contact your doctor

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

How to get tadalafil and doravirine prescriptions checked at Cured Pharmacy

If you are taking doravirine (or any other HIV medication) and would like to try tadalafil for erectile dysfunction, Cured Pharmacy offers a straightforward online consultation. You will complete a short medical questionnaire that asks about your current medicines, medical history, and overall health. A UK-registered prescriber will review your answers and check for any interactions or contraindications [2].

If tadalafil is suitable for you, your prescription will be dispensed by our GPhC-registered pharmacy (GPhC 9012511) and delivered discreetly to your door. If the prescriber has any concerns or needs more information, they will contact you before approving the prescription. You can also message the pharmacy team at any time if you have questions about your treatment.

Tadalafil is available in several forms at Cured Pharmacy, including generic tadalafil and branded Cialis, with on-demand and daily dosing options. First-time customers can use the code Ednew for a discount on their first order. Remember, erectile dysfunction can be an early sign of heart disease or diabetes, so if you have not already done so, it is a good idea to see your GP for a general health check [1].

Other ED treatments available

If tadalafil is not suitable or does not work well for you, there are other licensed ED treatments available at Cured Pharmacy. These include sildenafil (generic Viagra), vardenafil (generic Levitra), and avanafil (Spedra) [3][5][6]. Each medicine works in a similar way but has different timings and durations of action. Your prescriber can help you choose the most appropriate option based on your lifestyle, preferences, and medical history.

All PDE5 inhibitors require sexual stimulation to work and should not be taken with nitrates, nicorandil, riociguat, or poppers [3][4][5][6]. If you are taking an alpha-blocker for prostate problems or high blood pressure, you will need to start on the lowest dose of the ED medicine, and your prescriber will monitor you carefully.

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