Vardenafil and Tizanidine: Can They Be Taken Together?

Takes less than 2 minutes to complete 100% online

What Is Vardenafil and How Does It Work?

Vardenafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction (ED) [5]. It works by relaxing the blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Vardenafil is available in 5 mg, 10 mg, and 20 mg tablets and is usually taken about 25 to 60 minutes before sexual activity [5].

Like all PDE5 inhibitors, vardenafil requires sexual stimulation to work—it will not cause an erection on its own [5]. The medicine is effective for many men with ED, but it must be prescribed after a clinical assessment because it is not suitable for everyone. For example, it should never be taken with nitrates, nicorandil, riociguat, or recreational drugs known as 'poppers', as this combination can cause a dangerous drop in blood pressure [5].

Common side effects of vardenafil include headache, flushing, nasal congestion, and indigestion [5]. Most side effects are mild and short-lived. However, if you experience chest pain during sex, sudden vision or hearing loss, or an erection lasting more than four hours, you should seek urgent medical help [5].

What Is Tizanidine and Why Is It Prescribed?

Tizanidine is a muscle relaxant used to treat muscle spasms and spasticity, often associated with conditions such as multiple sclerosis or spinal cord injury. It works by acting on the central nervous system to reduce muscle tone and relieve painful spasms. Tizanidine is usually taken as tablets, with the dose adjusted according to individual response and tolerability.

One of the key effects of tizanidine is that it can lower blood pressure, particularly when you first start taking it or when the dose is increased. This is because tizanidine acts on receptors in the brain that also influence blood pressure regulation. As a result, common side effects include drowsiness, dizziness, dry mouth, and fatigue. These effects are usually most noticeable shortly after taking a dose.

Because tizanidine can cause low blood pressure and dizziness, it is important to be cautious when combining it with other medicines that have similar effects. Your prescriber will need to consider your overall medication list and health status before approving any new treatment, including medicines for erectile dysfunction.

How Tizanidine Affects Blood Pressure

Tizanidine lowers blood pressure by reducing the activity of certain nerve signals that keep blood vessels constricted. This can be helpful for muscle relaxation but means that standing up quickly or combining tizanidine with other blood-pressure-lowering medicines may increase the risk of dizziness or fainting. Your prescriber will monitor your blood pressure and adjust doses carefully to minimise these risks.

How Do Vardenafil and Tizanidine Interact?

Vardenafil and tizanidine can both lower blood pressure, so taking them together may increase the risk of dizziness, light-headedness, or fainting. Vardenafil works by relaxing blood vessels in the penis, but it also has a mild blood-pressure-lowering effect throughout the body [5]. Tizanidine, as a muscle relaxant, reduces blood pressure by acting on the central nervous system. When these effects combine, the overall drop in blood pressure can be more pronounced.

This interaction is not an absolute contraindication—meaning the medicines are not strictly forbidden together—but it does require careful prescriber assessment. Your doctor or pharmacist will review your current blood pressure, how well controlled your muscle spasms are on tizanidine, and whether you have experienced dizziness or fainting in the past. They may recommend starting vardenafil at the lowest dose (5 mg) and monitoring how you respond.

It is important to declare all your current medicines, including tizanidine, during your online consultation at Cured Pharmacy. The prescriber will check for interactions and ensure that vardenafil is safe and appropriate for you. Never stop or change your prescribed tizanidine without medical advice, as this could worsen your muscle spasms or cause withdrawal symptoms.

The Mechanism Behind the Interaction

Both vardenafil and tizanidine cause blood vessels to relax, though through different pathways. Vardenafil inhibits an enzyme (PDE5) that breaks down a chemical messenger involved in blood vessel relaxation [5]. Tizanidine acts on alpha-2 receptors in the brain to reduce nerve signals that keep blood vessels tight. When these two mechanisms occur together, the combined effect on blood pressure can be greater than either medicine alone, which is why prescribers take extra care when approving this combination.

What you need to know

• Vardenafil and tizanidine can both lower blood pressure, so combining them requires careful prescriber assessment.
• Your prescriber will usually start vardenafil at the lowest dose (5 mg) if you take tizanidine.
• Monitor for dizziness or fainting and avoid standing up quickly after taking either medicine.
• Declare all your current medicines during your online consultation to ensure vardenafil is safe for you.
• Seek urgent help if you experience chest pain, severe dizziness, or an erection lasting over four hours.

What Your Prescriber Checks Before Approving Vardenafil and Tizanidine

During your online consultation, the prescriber will ask detailed questions about your medical history, current medicines, and any symptoms you have experienced. For vardenafil and tizanidine specifically, they will want to know your current tizanidine dose, how long you have been taking it, and whether you have had any episodes of low blood pressure, dizziness, or fainting.

The prescriber will also check your cardiovascular health. Vardenafil is not suitable if you have had a recent heart attack or stroke, unstable angina, severe heart failure, or very low blood pressure [5]. They will review any other blood-pressure medicines you take, such as antihypertensives, because these can add to the blood-pressure-lowering effect. If you are on multiple medicines that lower blood pressure, the prescriber may decide that vardenafil is not the safest option, or they may recommend a lower starting dose and close monitoring.

You will be asked about other medicines that can interact with vardenafil, including nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, and recreational drugs like 'poppers' [5]. These combinations are dangerous and strictly contraindicated. The prescriber will also check for potent CYP3A4 inhibitors (such as ritonavir, ketoconazole, or clarithromycin), which can raise vardenafil levels and require dose adjustments or avoidance [5]. Declaring all your medicines, including over-the-counter products and supplements, is essential for your safety.

Practical Advice for Taking Vardenafil and Tizanidine Safely

If your prescriber approves vardenafil while you are taking tizanidine, there are several practical steps you can take to minimise the risk of side effects. First, start with the lowest effective dose of vardenafil (usually 5 mg) and see how your body responds before considering a higher dose. Take vardenafil about 25 to 60 minutes before planned sexual activity, and avoid taking it at the same time as your tizanidine dose if possible, to reduce the peak blood-pressure-lowering effect.

Be cautious when standing up, especially after sitting or lying down for a while, as this is when dizziness is most likely to occur. Avoid heavy alcohol, as it can worsen erectile dysfunction, increase the risk of low blood pressure, and add to the drowsiness caused by tizanidine. Grapefruit juice can raise vardenafil levels and should be avoided [5].

Monitor yourself for warning signs such as severe dizziness, fainting, chest pain during sex, or an erection lasting more than four hours (priapism). If any of these occur, stop taking vardenafil and seek urgent medical help. Keep your GP informed about all your medicines, and attend regular reviews so that your prescriber can adjust doses if needed. Never share your vardenafil with others, and store it safely out of reach of children.

When to Seek Medical Advice

Contact your GP or pharmacist if you experience persistent dizziness, fainting, or any new symptoms after starting vardenafil. If you develop chest pain during sexual activity, call 999 immediately and do not take another dose of vardenafil. Sudden loss of vision or hearing, or an erection lasting more than four hours, also requires emergency medical attention [5]. Always inform healthcare professionals that you are taking both vardenafil and tizanidine so they can provide appropriate advice.

When to get urgent help

• Chest pain during or after sexual activity—call 999 immediately
• Erection lasting more than 4 hours (priapism)—go to A&E
• Sudden loss of vision or hearing—seek emergency medical help
• Severe dizziness, fainting, or collapse—call 999 or go to A&E
• Allergic reaction (swelling of face, lips, or throat, difficulty breathing)—call 999

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

Alternative ED Treatments and When to See Your GP

If the combination of vardenafil and tizanidine is not suitable for you, or if you experience troublesome side effects, there are other licensed ED treatments available in the UK. These include sildenafil (generic Viagra), tadalafil (generic Cialis), and avanafil (Spedra) [3][4][6]. All are PDE5 inhibitors and work in a similar way to vardenafil, but they differ in how quickly they start to work and how long their effects last. For example, tadalafil can remain effective for up to 36 hours, while avanafil may work in as little as 15 to 30 minutes [4][6].

Each PDE5 inhibitor has its own interaction profile, so your prescriber will assess which is safest for you based on your current medicines and health conditions. In some cases, a different class of treatment may be more appropriate. For example, alprostadil (available as Vitaros cream or Caverject injection) works locally and does not have the same blood-pressure effects as PDE5 inhibitors [7]. Eroxon is a topical gel medical device available without prescription that may be suitable for some men.

It is important to see your GP if you have new or worsening erectile dysfunction, as ED can be an early warning sign of underlying health conditions such as heart disease, diabetes, or high blood pressure [1][2]. Your GP can investigate the cause, optimise treatment for any chronic conditions, and refer you to a specialist if needed. Cured Pharmacy offers a convenient online consultation service led by UK prescribers, but we always encourage you to keep your GP informed and attend regular health checks.