Are Sildenafil And Tadalafil The Same? - Guide | Cured Pharmacy

Are Sildenafil And Tadalafil The Same?

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Tarun Kumar, Prescribing Pharmacist at Cured Pharmacy

Medically reviewed by

Tarun Kumar, Prescribing Pharmacist (GPhC 2233073)

Reviewed on: 17 June 2026

Last Updated: 12 August 2026

If you have been looking into treatments for erectile dysfunction, you have almost certainly come across two names: sildenafil and tadalafil. Both are widely prescribed across the UK and both belong to the same class of medication, but they are not the same drug. Understanding how they differ — from how long they last to how you take them, and what side effects each may bring — can make a real difference to which one works best for your lifestyle and needs.

Quick Summary

Sildenafil and tadalafil are both PDE5 inhibitors used to treat erectile dysfunction, but they differ in duration of action, dosing flexibility, and how they fit into daily life. Tadalafil lasts significantly longer, while sildenafil acts more quickly and is better suited to planned, spontaneous encounters within a set window.

  • Sildenafil (the active ingredient in Viagra) typically lasts 4 to 6 hours; tadalafil (Cialis) can last up to 36 hours.
  • Both work by increasing blood flow to the penis, but they have slightly different chemical structures.
  • Sildenafil should be taken 30 to 60 minutes before sexual activity; tadalafil offers more flexibility.
  • Tadalafil is available as a daily low-dose tablet, removing the need to plan around sex entirely.
  • Both medications share similar side effects and interact with nitrate medicines — you must not take either if you use nitrates.

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Table of Contents

  1. How Sildenafil and Tadalafil Work
  2. Are Sildenafil and Tadalafil the Same? Key Differences Explained
  3. Side Effects and Safety Considerations
  4. Dosing Guide: Sildenafil vs Tadalafil
  5. Side-by-Side Comparison Table
  6. Which Medication Is Right for You?
  7. Key Takeaways
  8. When to Seek Professional Advice
  9. Scientific References
  10. Frequently Asked Questions

How Sildenafil and Tadalafil Work

Both sildenafil and tadalafil belong to a group of medicines known as phosphodiesterase type 5 (PDE5) inhibitors. This is the mechanism that links them most closely — they both work by blocking the PDE5 enzyme, which in turn allows the smooth muscle tissue in the walls of the blood vessels supplying the penis to relax. When those vessels relax, blood flow increases significantly during sexual stimulation, making it easier to achieve and sustain an erection.

It is worth being clear here: neither sildenafil nor tadalafil causes an erection on its own. Sexual arousal is still required. The medication simply makes it physiologically easier for the erection to occur by removing the biochemical barrier that PDE5 creates. This is an important point that many men are not told when they first receive a prescription.

Despite sharing this core mechanism, the two drugs have distinctly different chemical structures, different half-lives, and different interactions with food and alcohol. These structural differences are what create the practical distinctions you will feel when using them day to day. If you are exploring erectile dysfunction treatments for the first time, understanding these differences will help you make a far more informed choice with your prescriber.

  • Both are PDE5 inhibitors that improve blood flow to the penis during arousal.
  • Neither produces an erection without sexual stimulation.
  • Sildenafil was developed first, entering the market in the late 1990s as Viagra.
  • Tadalafil followed as Cialis, noted primarily for its significantly longer duration of action.
  • Both are now widely available as generic medicines across the UK following patent expiry.

Are Sildenafil and Tadalafil the Same? Key Differences Explained

Are sildenafil and tadalafil the same is one of the most frequently searched questions by men beginning their journey with ED treatment — and it is an entirely reasonable one to ask. The short answer is no, they are not the same, even though they serve the same clinical purpose. The differences between them are clinically significant and worth knowing before you commit to one option.

The most notable difference is duration. Sildenafil is active in the body for around 4 to 6 hours, which means you need to take it with reasonable timing before sexual activity. Tadalafil, by contrast, has a half-life of approximately 17.5 hours, meaning it remains effective for up to 36 hours after a single dose. This is why tadalafil earned the popular nickname "the weekend pill" — one dose on a Friday evening could still be effective on Sunday morning.

Timing relative to food is another meaningful distinction. Sildenafil is significantly affected by food, particularly high-fat meals, which can delay absorption by up to an hour and reduce its peak concentration in the blood. Tadalafil is largely unaffected by food, making it a more flexible option if you do not want to think about what or when you eat before taking your medication.

  • Sildenafil lasts 4–6 hours; tadalafil can last up to 36 hours.
  • Sildenafil's effectiveness is reduced by food; tadalafil's is not.
  • Tadalafil is available as a once-daily low dose (2.5mg or 5mg); sildenafil is not.
  • Both begin working within 30 to 60 minutes of taking a dose.
  • Tadalafil also has a licensed indication for benign prostatic hyperplasia (BPH), which sildenafil does not.

Side Effects and Safety Considerations

One of the most pressing concerns men have when choosing between these two medicines is the side effect profile. Because they share a mechanism of action, it should come as no surprise that sildenafil and tadalafil share many of the same common side effects. These include headache, facial flushing, nasal congestion, indigestion, and dizziness. Most of these are mild and resolve on their own within a few hours of taking the dose.

However, there are some differences worth highlighting. Sildenafil is more likely to cause a temporary blue-tinted vision disturbance, known as cyanopsia, because it has a mild crossover effect on PDE6, an enzyme found in the retina. This is generally not harmful, but it can be unsettling. Tadalafil, on the other hand, is more likely to cause back pain or muscle aches, which are thought to occur because it also inhibits PDE11, an enzyme found in skeletal muscle. In 2026, prescribers continue to advise patients that these differences are well-established and should be factored into the choice of treatment.

The most critical safety consideration that applies to both medications equally is their interaction with nitrate medicines. Nitrates are used to treat angina and certain heart conditions, and combining them with any PDE5 inhibitor can cause a sudden and dangerous drop in blood pressure. This interaction is an absolute contraindication — meaning you must not take sildenafil or tadalafil if you are currently using nitrates in any form, including GTN sprays, nitrate patches, or isosorbide tablets.

  • Common side effects for both: headache, flushing, stuffy nose, and indigestion.
  • Sildenafil is more associated with visual disturbances; tadalafil with back or muscle pain.
  • Both are contraindicated with nitrate medicines — this is a serious, potentially life-threatening interaction.
  • Both should be used with caution in men with cardiovascular disease — always inform your prescriber of your full health history.
  • Alcohol can reduce effectiveness and increase the risk of low blood pressure with both medications.

Dosing Guide: Sildenafil vs Tadalafil

Understanding the correct dosing for each medication helps set realistic expectations and reduces the risk of side effects. Sildenafil is available in three standard doses: 25mg, 50mg, and 100mg. The 50mg dose is typically where most men begin. It should be taken approximately 30 to 60 minutes before sexual activity, and not more than once in a 24-hour period. Taking it on an empty stomach or after a light meal will usually produce the best results.

Tadalafil comes in a slightly different dosing structure. For on-demand use, it is available in 10mg and 20mg tablets. The 10mg dose is the standard starting point, taken at least 30 minutes before sexual activity. If 10mg is not sufficient, the dose can be increased to 20mg. Because tadalafil lasts so much longer, it must only be taken once in a 36-hour period, not once every 24 hours like sildenafil.

The daily dose option is unique to tadalafil. At doses of 2.5mg or 5mg taken once daily, tadalafil maintains a consistent concentration in the bloodstream, removing the need to time your dose around sex. This approach is particularly popular with men in long-term relationships who find the on-demand timing of sildenafil intrusive or stressful. It is also the preferred prescribing approach when tadalafil is used for BPH symptoms alongside erectile dysfunction.

  • Sildenafil: start at 50mg, taken 30–60 minutes before sex, maximum once daily.
  • Tadalafil (on-demand): start at 10mg, taken at least 30 minutes before sex, maximum once in 36 hours.
  • Tadalafil (daily): 5mg once per day at a consistent time, with no need to plan around sexual activity.
  • Neither medication should exceed the maximum recommended dose — doing so increases side effect risk without improving effectiveness.
  • Always take your first dose when you are not under time pressure so you can monitor your response safely.

Side-by-Side Comparison Table

Feature Sildenafil Tadalafil
Drug class PDE5 inhibitor PDE5 inhibitor
Brand name Viagra (also available generic) Cialis (also available generic)
Onset of action 30–60 minutes 30 minutes (sometimes sooner)
Duration of action 4–6 hours Up to 36 hours
Available doses (on-demand) 25mg, 50mg, 100mg 10mg, 20mg
Daily dose option Not available 2.5mg, 5mg once daily
Food interaction Significantly affected by high-fat food Minimal food interaction
Dosing frequency Maximum once in 24 hours Maximum once in 36 hours (on-demand)
Unique side effect risk Visual disturbances (blue tint) Back pain, muscle aches
Nitrate interaction Contraindicated — absolute Contraindicated — absolute
Licensed for BPH No Yes (5mg daily)
Availability in UK Prescription; some available OTC (50mg) Prescription required

Which Medication Is Right for You?

The choice between sildenafil and tadalafil often comes down to personal preference, lifestyle, and how spontaneous you would like your sex life to be. Neither medication is universally better — they are different tools for the same problem, and the right one is whichever fits your life most naturally.

If you prefer to plan ahead, do not mind timing your medication, and want a shorter acting option with a more predictable window, sildenafil is likely to suit you well. It is also typically slightly less expensive than tadalafil as a generic, which may be a consideration if cost is a factor. Sildenafil has been around longer and has an extremely well-established safety record built up over more than two decades of use across the UK.

If you find the need to plan around sex stressful, or if spontaneity is important to you, tadalafil's longer duration — particularly the once-daily formulation — removes that pressure entirely. It is also a good option if you tend to eat fatty meals in the evenings, as it will not be affected by what is on your plate. Men who also have symptoms of BPH such as difficulty urinating or frequent trips to the bathroom at night may find that daily tadalafil addresses both conditions simultaneously, which makes it a particularly practical choice in 2026 when combination prescribing for both conditions is increasingly recognised in UK clinical guidelines.

  • Choose sildenafil if you prefer a shorter acting option with a predictable 4–6 hour window.
  • Choose tadalafil if you want the flexibility of a 36-hour window or prefer a daily tablet.
  • Discuss your full medical history with a prescriber before deciding — both have contraindications.
  • Your preference may change over time; switching between the two is clinically feasible with professional guidance.
  • Cost, convenience, and lifestyle fit are all valid factors to raise during your consultation.

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Key Takeaways

  • Sildenafil and tadalafil are both PDE5 inhibitors used to treat erectile dysfunction, but they are not the same medication — they differ significantly in duration, dosing, food interactions, and available formulations.
  • Tadalafil lasts up to 36 hours and is available as a once-daily tablet; sildenafil lasts 4–6 hours and must be timed around sexual activity.
  • Both medications are contraindicated with nitrates — this is a potentially life-threatening interaction that must be declared to any prescriber.
  • Sildenafil may cause vision disturbances; tadalafil is more associated with back and muscle pain — knowing these differences helps you report and manage side effects appropriately.
  • The best choice depends on your lifestyle, relationship dynamic, health history, and personal preference — discuss all options with a qualified prescriber or pharmacist before deciding.

When to Seek Professional Advice

While both sildenafil and tadalafil are widely available and generally safe when used correctly, there are circumstances where you must speak to a prescriber or pharmacist before starting, continuing, or switching your treatment. Do not attempt to self-medicate or adjust your dose without guidance.

You should seek professional advice immediately if you experience chest pain, sudden vision or hearing loss, an erection lasting more than four hours (priapism), severe dizziness, or any sign of an allergic reaction such as rash, swelling of the face or throat, or difficulty breathing. These are rare but serious events that require urgent medical attention.

You should also consult a prescriber before taking either medication if you have cardiovascular disease, uncontrolled high or low blood pressure, severe liver or kidney impairment, a history of stroke, or if you are taking any medicines that could interact — including alpha-blockers, certain antifungals, HIV medications, or recreational drugs containing nitrates such as poppers. The NHS and MHRA continue to advise that all ED medication should be obtained through a legitimate, regulated route in the UK to ensure your safety and that the product you receive is genuine.

  • Seek emergency help for chest pain, priapism (lasting erection over 4 hours), or sudden loss of vision or hearing.
  • Always disclose all current medications to your prescriber — drug interactions are common and can be serious.
  • Do not purchase ED medication from unregulated online sources — counterfeit pills are a real and well-documented risk in the UK.
  • If your ED is newly developed and unexplained, it can sometimes signal an underlying cardiovascular issue that warrants further investigation.

Scientific References

  1. NHS (2024). Sildenafil (Viagra) — NHS Medicines Information. National Health Service, UK. [Accessed 12 August 2026]
  2. NICE British National Formulary (2025). Tadalafil — BNF Drug Monograph. National Institute for Health and Care Excellence, UK. [Accessed 12 August 2026]
  3. Electronic Medicines Compendium (2024). Cialis 10mg and 20mg Film-Coated Tablets — Summary of Product Characteristics. Eli Lilly and Company Ltd, UK. [Accessed 12 August 2026]
  4. Viagra (sildenafil) 25mg, 50mg, 100mg film-coated tablets – Summary of Product Characteristics, Viatris UK Healthcare, EMC, 2023 [Accessed 12 August 2026]
  5. Cialis (tadalafil) 2.5mg, 5mg, 10mg, 20mg film-coated tablets – Summary of Product Characteristics, Eli Lilly and Company, EMC, 2023 [Accessed 12 August 2026]
  6. Sildenafil for the treatment of erectile dysfunction – Technology Appraisal TA98, NICE, 2004 [Accessed 12 August 2026]
  7. Tadalafil monograph, British National Formulary (BNF), NICE/BMJ Group, 2024 [Accessed 12 August 2026]
  8. Sildenafil (Viagra) and other PDE5 inhibitors: reminder of cardiovascular contraindications – Drug Safety Update, MHRA, 2014 [Accessed 12 August 2026]
  9. Erectile dysfunction and diabetes – patient guidance, Diabetes UK, 2023 [Accessed 12 August 2026]

Frequently Asked Questions

How long does sildenafil last compared to tadalafil?

Sildenafil typically lasts 4 to 6 hours after taking a dose, while tadalafil lasts significantly longer — up to 36 hours — earning it the nickname the weekend pill. This makes tadalafil a popular choice for men who prefer not to time their dose precisely before sexual activity.

Is it safe to switch from sildenafil to tadalafil?

Switching from sildenafil to tadalafil is generally considered safe, but it should always be done under the guidance of a prescriber or pharmacist. Both medications interact with nitrates and share some similar side effects, so a clinical review ensures the switch is appropriate for your individual health circumstances.

Can you take sildenafil and tadalafil together?

Taking sildenafil and tadalafil together is not recommended and should be avoided. Combining two PDE5 inhibitors at the same time significantly increases the risk of a dangerous drop in blood pressure, which can cause dizziness, fainting, or more serious cardiovascular complications. Always consult a prescriber before changing your ED treatment.

What is the standard dose of tadalafil for erectile dysfunction?

The standard dose of tadalafil for erectile dysfunction is 10mg taken at least 30 minutes before sexual activity, with the option to increase to 20mg if needed. A lower daily dose of 2.5mg or 5mg is also available for men who prefer a continuous, as-needed approach without planning ahead.

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