Tadalafil and Amantadine: Can You Take Them Together?

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What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medicine licensed in the UK to treat erectile dysfunction (ED). It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused [3][4]. Tadalafil is the active ingredient in branded Cialis and is also available as a generic medicine at a lower cost.

Tadalafil is available in two main dosing options: on-demand tablets (10 mg or 20 mg) taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours, and daily low-dose tablets (2.5 mg or 5 mg) taken once a day to allow spontaneity [4]. Both require sexual stimulation to work and are only supplied after an online consultation reviewed by a UK prescriber.

Common side effects include headache, indigestion, back pain, muscle aches, and flushing. Tadalafil must never be taken with nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, or recreational drugs known as 'poppers', as this combination can cause a dangerous drop in blood pressure [4]. Your prescriber will check for these contraindications during your consultation.

What Is Amantadine and What Is It Used For?

Amantadine is a prescription medicine primarily used to treat Parkinson's disease, particularly to reduce involuntary movements (dyskinesia) and improve motor symptoms. It is also occasionally prescribed for certain viral infections, although this use is less common in current UK practice. Amantadine works by affecting dopamine activity in the brain and has some antiviral properties.

The medicine is usually taken as capsules or tablets, typically once or twice daily. Common side effects of amantadine include dizziness, difficulty sleeping, dry mouth, constipation, and sometimes confusion or hallucinations, especially in older adults. Because amantadine can affect the nervous system, it is important that your doctor knows about all your other medicines.

If you are taking amantadine for Parkinson's disease, you may also be on other medications such as levodopa, dopamine agonists, or MAO-B inhibitors. Your prescriber will review your full medication list during your ED consultation to check for any potential interactions and ensure that tadalafil is safe and appropriate for you.

Does Amantadine Affect Erectile Function?

Parkinson's disease itself can contribute to erectile dysfunction, as can some of the medicines used to treat it. Amantadine is not typically associated with causing ED; in fact, some men with Parkinson's disease may experience improved sexual function when their motor symptoms are better controlled. However, the condition and its treatment are complex, and ED in Parkinson's disease often has multiple contributing factors, including psychological, neurological, and vascular elements [1][2].

When to get urgent help

• Erection lasting more than 4 hours (priapism) – go to A&E immediately
• Sudden loss of vision in one or both eyes – stop tadalafil and seek urgent medical advice
• Chest pain during or after sex – stop activity and call 999; do not take nitrates if you have used tadalafil in the past 48 hours
• Severe dizziness, fainting, or signs of allergic reaction (face/lip swelling, difficulty breathing) – call 999
• Sudden hearing loss or persistent ringing in the ears – seek prompt medical attention

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

Tadalafil and Amantadine: Is There an Interaction?

No major interaction between tadalafil and amantadine is commonly reported in clinical practice or in the British National Formulary [3][4]. The two medicines work through different mechanisms in the body: tadalafil acts on blood vessels in the penis, while amantadine affects dopamine pathways in the brain. They are not known to interfere with each other's effectiveness or significantly increase the risk of side effects when taken together.

However, both medicines can occasionally cause dizziness or light-headedness. If you experience these side effects from amantadine, adding tadalafil may potentially add to this effect, especially when you first start treatment or change doses. It is important to be cautious when standing up from sitting or lying down, particularly in the first few doses of tadalafil.

During your online consultation at Cured Pharmacy, the prescriber will review your full medical history and current medications, including amantadine, to ensure tadalafil is safe for you. You should never stop or change your amantadine dose without consulting your doctor, as this could worsen your Parkinson's symptoms. Always declare all your medicines, including over-the-counter products and supplements, during your consultation.

What Your Prescriber Checks Before Approving Tadalafil

When you request tadalafil through Cured Pharmacy, a UK-registered prescriber reviews your online consultation answers to ensure the treatment is safe and suitable for you. They will check your current medicines, including amantadine, to identify any contraindications or interactions. The prescriber will also review your cardiovascular health, as sexual activity places demands on the heart [2][4].

Tadalafil is not suitable if you take nitrates for angina, nicorandil, riociguat for pulmonary hypertension, or another PDE5 inhibitor. If you take alpha-blockers such as tamsulosin or doxazosin for prostate symptoms or blood pressure, you must be stable on that medicine and start tadalafil at the lowest dose to avoid a sudden drop in blood pressure [4]. Your prescriber will also check for recent heart attack or stroke, severe heart failure, very low blood pressure, or previous sudden vision loss.

The prescriber may ask about other medicines you take for Parkinson's disease, as some can affect blood pressure. They will also consider whether sexual activity is safe for you given your overall health. If tadalafil is not suitable, the prescriber may suggest an alternative ED treatment or recommend you see your GP or specialist for further assessment.

Declaring All Your Medicines

It is essential to list every medicine you take during your consultation, including prescription medicines like amantadine, over-the-counter products, herbal supplements, and recreational drugs. Even medicines that seem unrelated to ED can interact with tadalafil or affect your suitability for treatment. Your prescriber relies on accurate information to make a safe decision, and incomplete answers may delay your treatment or lead to an unsafe prescription.

At a glance

Practical Advice for Taking Tadalafil with Amantadine

If your prescriber approves tadalafil, take it exactly as directed. For on-demand tadalafil (10 mg or 20 mg), take one tablet at least 30 minutes before sexual activity; the effect can last up to 36 hours, so you do not need to rush. For daily tadalafil (2.5 mg or 5 mg), take one tablet at the same time each day, whether or not you plan to have sex. Do not take more than one dose in 24 hours [4].

Continue taking your amantadine as prescribed by your doctor. Do not stop or change the dose because you are starting tadalafil, as this could worsen your Parkinson's symptoms. If you experience dizziness or light-headedness, especially when you first start tadalafil, stand up slowly from sitting or lying down and avoid driving or operating machinery until you know how the medicine affects you.

Avoid drinking large amounts of alcohol, as this can make erectile dysfunction worse and increase the risk of dizziness and low blood pressure. Grapefruit juice can raise tadalafil levels in the blood, so it is best to avoid it. If you develop a headache, you can take paracetamol or ibuprofen, but check with your pharmacist first if you are unsure. If side effects are troublesome or do not settle after a few doses, contact your prescriber.

When to Seek Urgent Medical Help

Most men tolerate tadalafil well, but you should seek urgent medical help if you experience certain warning signs. If you have an erection lasting more than four hours (priapism), go to A&E immediately, as this can cause permanent damage to the penis if not treated promptly [4]. If you experience sudden loss of vision in one or both eyes, stop taking tadalafil and seek urgent medical advice, as this may be a sign of a rare condition called non-arteritic anterior ischaemic optic neuropathy (NAION).

If you develop 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. Tell the healthcare professional that you have taken tadalafil. Sudden hearing loss or ringing in the ears is rare but requires prompt medical attention.

If you experience severe dizziness, fainting, or signs of an allergic reaction (such as swelling of the face, lips, or throat, or difficulty breathing), call 999 or go to A&E. For less urgent concerns, such as persistent side effects or questions about your treatment, contact your GP, pharmacist, or the Cured Pharmacy team for advice. Never ignore symptoms that worry you.

Talking to Your Parkinson's Specialist

If you have Parkinson's disease and are considering ED treatment, it can be helpful to discuss this with your neurologist or Parkinson's disease nurse. They can review your overall treatment plan and ensure that managing your ED fits well with your other care. Erectile dysfunction is common in Parkinson's disease and is a legitimate concern that healthcare professionals are used to discussing [1][2]. Your specialist may also check whether any adjustments to your Parkinson's medicines might help.

In summary

• No major interaction between tadalafil and amantadine is commonly reported in clinical practice.
• Your prescriber reviews all your medicines, including amantadine, during your online consultation.
• Both medicines can occasionally cause dizziness; stand up slowly when starting tadalafil.
• Never stop or change your amantadine dose without consulting your doctor.
• Seek urgent help if you have an erection lasting over four hours or sudden vision loss.

Frequently Asked Questions