Tadalafil and sildenafil are both phosphodiesterase type 5 (PDE5) inhibitors used to treat erectile dysfunction, but taking them together is not recommended. Both medications work through the same mechanism—inhibiting the PDE5 enzyme to increase blood flow to the penis during sexual stimulation. Combining these drugs has not been studied for safety or additional benefit and may increase the risk of adverse effects, particularly hypotension (low blood pressure). The Medicines and Healthcare products Regulatory Agency (MHRA) approved product information advises against co-administration. If your current treatment is not working effectively, consult your GP to discuss alternative strategies rather than combining medications.

Can You Take Tadalafil and Sildenafil Together?

Co-administration of tadalafil and sildenafil is not recommended. Both medications belong to the same class of drugs called phosphodiesterase type 5 (PDE5) inhibitors, which are used to treat erectile dysfunction (ED). Taking them simultaneously or within a short timeframe is not recommended according to the Medicines and Healthcare products Regulatory Agency (MHRA) approved product information.

Tadalafil (commonly known by the brand name Cialis) and sildenafil (Viagra) work through the same mechanism of action in the body. They both inhibit the PDE5 enzyme, which leads to increased blood flow to the penis during sexual stimulation. Whilst they differ in duration of action—tadalafil can last up to 36 hours whilst sildenafil typically works for 4–6 hours—combining them does not have established additional benefits and may increase the risk of adverse effects.

Key points to remember:

• Both medications target the same biological pathway

• Combining them has not been studied for additional therapeutic benefit

• The risks of side effects are likely increased when taken together

• No clinical evidence supports the safety or efficacy of concurrent use

If you are considering switching from one PDE5 inhibitor to another, you should consult your GP or prescribing clinician for guidance on the appropriate timing between medications. Always seek medical advice before making any changes to your erectile dysfunction treatment regimen.

Why Combining Tadalafil with Sildenafil Is Not Recommended

The primary reason for avoiding the combination of tadalafil and sildenafil lies in their shared pharmacological mechanism. Both drugs work by inhibiting the PDE5 enzyme, which normally breaks down cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of blood vessels. By blocking this enzyme, both medications allow cGMP levels to remain elevated, promoting vasodilation and increased blood flow to the corpus cavernosum of the penis.

When you take both medications together, you are essentially doubling up on the same mechanism, which could lead to additive vasodilatory effects throughout your body. This may affect not only penile blood vessels but also blood vessels in other organs, particularly the cardiovascular system. The result could be an increased risk of side effects without any established increase in therapeutic benefit.

Clinical guidance supports using one PDE5 inhibitor at a time and switching if needed. The Summary of Product Characteristics (SmPC) for both tadalafil and sildenafil, as approved by the MHRA, states that combinations with other PDE5 inhibitors have not been studied and are not recommended.

Additional considerations include:

• Potential for additive effects on blood pressure

• Unpredictable effects on blood pressure regulation

• Potential for medication errors and confusion about dosing schedules

• Absolute contraindication with riociguat (a medication for pulmonary hypertension)

• Contraindication with nitrate medications (such as glyceryl trinitrate)

If you feel that your current ED medication is not working effectively, this indicates a need to discuss alternative treatment strategies with your GP rather than adding a second PDE5 inhibitor.

Risks and Side Effects of Taking Both Medications

Taking tadalafil and sildenafil together may increase the risk and severity of adverse effects associated with PDE5 inhibitors. A significant concern is hypotension (low blood pressure), which can lead to dizziness, fainting, and falls. This occurs because both medications cause vasodilation throughout the body, and their combined effect on blood pressure could be more pronounced than when taking either medication alone.

Common side effects that may become more likely when combining these medications include:

• Headaches – often due to cerebral vasodilation

• Flushing – redness and warmth of the skin

• Nasal congestion – blocked or runny nose from nasal blood vessel dilation

• Dyspepsia – indigestion, heartburn, and gastrointestinal discomfort

• Visual disturbances – blurred vision, changes in colour perception (particularly blue-tinted vision), or increased light sensitivity

• Dizziness and light-headedness – particularly when standing up quickly (postural hypotension)

More serious but rare adverse events include:

• Priapism – a prolonged, painful erection lasting more than four hours, which constitutes a medical emergency requiring immediate treatment to prevent permanent erectile tissue damage

• Non-arteritic anterior ischaemic optic neuropathy (NAION) – sudden visual loss that has been reported rarely in users of PDE5 inhibitors

• Sudden hearing loss or tinnitus – rare reports of sudden decrease or loss of hearing

• Cardiovascular events – rare reports in men with pre-existing risk factors

The risk is particularly elevated in individuals taking nitrate medications (such as glyceryl trinitrate for angina) or riociguat, which are absolutely contraindicated. Caution is also needed with alpha-blockers for prostate problems or hypertension; if you are stable on alpha-blocker therapy, PDE5 inhibitors should be started at the lowest dose with monitoring for symptoms of hypotension.

PDE5 inhibitors should be avoided when sexual activity is inadvisable due to underlying cardiovascular status. If you experience chest pain, severe dizziness, fainting, sudden visual or hearing changes, or an erection lasting more than four hours after taking any ED medication, seek immediate medical attention by calling 999 or attending A&E.

You can report any suspected side effects to the MHRA through the Yellow Card Scheme at yellowcard.mhra.gov.uk.

Safe Alternatives to Combining ED Medications

If you find that your current erectile dysfunction treatment is not providing satisfactory results, there are several evidence-based alternatives to consider rather than combining PDE5 inhibitors. The first step is to optimise your current medication by ensuring you are taking it correctly—for example, sildenafil should be taken on an empty stomach approximately one hour before sexual activity, whilst tadalafil can be taken with or without food.

It's worth trying a PDE5 inhibitor on 6–8 occasions under optimal conditions before judging its efficacy. Avoid taking alcohol or a heavy meal before use, as these can reduce effectiveness.

Dose adjustment may be appropriate. Both tadalafil and sildenafil are available in different strengths, and your GP may recommend increasing the dose within the licensed range if the lower dose is ineffective and well-tolerated. For sildenafil, doses range from 25mg to 100mg, whilst tadalafil is available in 10mg and 20mg doses for on-demand use, or 2.5mg and 5mg for daily use.

Switching between PDE5 inhibitors is a valid strategy, as individual response can vary. Some men respond better to tadalafil's longer duration of action, which can reduce performance anxiety and allow for more spontaneous sexual activity. Others prefer sildenafil's shorter action profile. Additional options include vardenafil (Levitra) and avanafil (Spedra), which offer different onset and duration profiles. Discuss with your GP which might be most suitable for you.

Non-pharmacological approaches should also be considered:

• Lifestyle modifications – addressing obesity, increasing physical activity, reducing alcohol consumption, and stopping smoking can significantly improve erectile function

• Psychological support – cognitive behavioural therapy (CBT) or psychosexual counselling, particularly if anxiety or relationship issues contribute to ED

• Vacuum erection devices – mechanical devices that draw blood into the penis, which NICE guidance indicates can be offered as an alternative treatment

• Intracavernosal injections – alprostadil injections directly into the penis for men who do not respond to oral medications

• Penile implants – surgical options for refractory cases

Your GP can also review any underlying health conditions (such as diabetes, hypertension, or hormonal imbalances) and other medications that might be contributing to erectile dysfunction. Addressing these root causes often improves treatment outcomes more effectively than increasing medication.

When to Speak to Your GP About Erectile Dysfunction Treatment

You should arrange an appointment with your GP if you are experiencing erectile dysfunction, particularly if it is persistent, worsening, or affecting your quality of life and relationships. ED can be an early warning sign of cardiovascular disease, as the blood vessels supplying the penis are smaller than coronary arteries and may show signs of atherosclerosis earlier. NICE guidance recommends that all men presenting with ED should undergo cardiovascular risk assessment.

You should contact your GP if:

• Your current ED medication is not working effectively despite taking it correctly

• You are experiencing troublesome side effects from your current treatment

• You have been considering combining medications or increasing doses without medical supervision

• Your erectile dysfunction has developed suddenly or is accompanied by other symptoms

• You have underlying health conditions such as diabetes, heart disease, or high blood pressure

• You are taking other medications that might interact with ED treatments

Seek urgent medical attention (call 999 or go to A&E) if you experience:

• An erection lasting more than four hours (priapism)

• Chest pain or severe dizziness after taking ED medication

• Sudden loss of vision or hearing

• Signs of an allergic reaction (difficulty breathing, swelling of face or throat)

During your consultation, your GP will take a comprehensive medical history, including details about your erectile function, cardiovascular risk factors, mental health, and current medications. They may perform a physical examination and order blood tests to check for diabetes (HbA1c), cholesterol levels, morning total testosterone (which may need to be repeated if low), and thyroid function if indicated. This holistic approach ensures that any underlying causes are identified and treated appropriately.

Your GP may consider referral to a specialist if:

• ED persists despite optimised treatment

• You have suspected endocrine disorders (e.g., hypogonadism)

• There is penile deformity or Peyronie's disease

• You have complex cardiovascular status requiring specialist input

• Psychosexual issues need specialist counselling

Your GP can help by:

• Reviewing and optimising your current ED treatment regimen

• Discussing alternative PDE5 inhibitors or different treatment modalities

• Addressing modifiable risk factors through lifestyle advice

• Referring you to specialist services if needed, such as urology or psychosexual medicine

• Ensuring your treatment is safe given your overall health status and other medications

ED is a common condition that increases with age and affects many men. It is a legitimate medical concern, and your GP is well-equipped to discuss treatment options in a confidential, non-judgemental manner. Never attempt to self-medicate by combining prescription medications or purchasing ED drugs from unregulated online sources, as this poses significant health risks.

Frequently Asked Questions