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Viagra vs Cialis: Speed and Duration Compared

Published on: June 03, 2026

When comparing viagra vs cialis which works faster, the answer depends on what matters most to you: immediate onset or extended duration. At Cured Pharmacy, our UK prescribers help thousands of patients choose between sildenafil (Viagra) and tadalafil (Cialis) based on their lifestyle, with prices from £0.45 and discreet next-day delivery across the UK.

How Quickly Does Viagra vs Cialis Work?

Sildenafil (Viagra) typically begins working within 30 to 60 minutes after administration on an empty stomach, with peak plasma concentrations reached around 60 minutes post-dose [1]. High-fat meals can delay absorption by up to 60 minutes, so many clinicians advise taking sildenafil at least one hour before anticipated sexual activity.

Tadalafil (Cialis) also reaches therapeutic levels within 30 minutes in many patients, though the manufacturer's guidance suggests allowing up to two hours for optimal effect [2]. Unlike sildenafil, tadalafil absorption is minimally affected by food, making it more flexible for patients who prefer not to plan around meals.

In clinical practice, both medications demonstrate similar onset times when taken under comparable conditions, but individual response varies. Some patients report faster subjective effects with sildenafil, while others find tadalafil equally rapid [1][2].

Duration of Action: Why Cialis Lasts Up to 36 Hours

The most significant difference between these two PDE5 inhibitors lies in their half-life and duration of therapeutic effect. Sildenafil has a plasma half-life of approximately 3 to 5 hours, with clinical effects lasting around 4 to 6 hours in most patients [1]. This shorter duration suits men who prefer treatment only when needed and want the medication to clear their system relatively quickly.

Tadalafil, by contrast, has an elimination half-life of 17.5 hours, allowing therapeutic plasma levels to persist for up to 36 hours after a single dose [2]. This extended window earned tadalafil the nickname 'the weekend pill' among UK patients, as a Friday evening dose may remain effective through Sunday morning.

For patients seeking spontaneity without timing sexual activity precisely, tadalafil's longer duration often proves more convenient. However, this extended presence also means side effects, if they occur, may persist longer compared to sildenafil [2].

Daily vs On-Demand Dosing

Tadalafil is unique among UK-licensed PDE5 inhibitors in offering both on-demand dosing (10mg or 20mg taken before activity) and daily low-dose regimens (2.5mg or 5mg taken once daily). Daily tadalafil maintains steady plasma levels, allowing sexual activity at any time without planning [2]. Sildenafil is prescribed exclusively as an on-demand treatment, typically at 25mg, 50mg, or 100mg doses taken approximately one hour before intercourse.

Efficacy Rates: Clinical Trial Data Compared

Head-to-head trials demonstrate comparable efficacy between sildenafil and tadalafil when used as directed. In pivotal studies, sildenafil 50-100mg improved erectile function in approximately 74-82% of men with erectile dysfunction across various aetiologies [1]. Success rates were similar across vascular, diabetic, and psychogenic causes.

Tadalafil 10-20mg showed efficacy rates of 75-81% in similar patient populations, with the added benefit of maintained effectiveness throughout the 36-hour dosing window [2]. A 2013 meta-analysis published in the European Urology journal found no statistically significant difference in overall treatment success between the two agents when comparing equivalent doses [3].

Patient preference studies reveal that many men favour tadalafil for its longer duration and reduced need to time doses precisely, while others prefer sildenafil's shorter action window and lower cost [3]. Both medications require sexual stimulation to produce an erection—they do not cause spontaneous erections.

Side Effect Profiles: What to Expect

Both sildenafil and tadalafil share a similar side effect profile as PDE5 inhibitors, though the frequency and duration of adverse effects differ slightly. Common side effects include headache (11-16% of patients), facial flushing (10-13%), nasal congestion (4-10%), and dyspepsia (4-12%) [1][2].

Because tadalafil remains in the system longer, patients who experience side effects may notice them persisting for up to 24-36 hours, whereas sildenafil-related adverse effects typically resolve within 6-8 hours. However, the overall incidence of side effects is comparable between the two medications at therapeutic doses [2].

Visual disturbances, particularly a blue-tinged vision or increased light sensitivity, occur more frequently with sildenafil due to its slight cross-reactivity with PDE6 enzymes in the retina [1]. Tadalafil shows greater selectivity for PDE5 and has minimal PDE6 inhibition, making visual side effects less common. Back pain and myalgia appear more frequently with tadalafil (affecting 6-12% of patients) due to mild PDE11 inhibition in skeletal muscle [2].

Contraindications and Drug Interactions

Both medications are absolutely contraindicated with nitrate medications (such as GTN spray or isosorbide mononitrate) due to the risk of severe hypotension [1][2]. Patients taking alpha-blockers for benign prostatic hyperplasia require dose adjustments and careful monitoring. Concurrent use with certain antifungals, HIV protease inhibitors, or macrolide antibiotics may increase PDE5 inhibitor plasma levels, necessitating dose reduction. Your UK prescriber will review your complete medication list during the online consultation to ensure safe prescribing.

Cost Comparison: Sildenafil vs Tadalafil UK Pricing

Generic sildenafil represents the most cost-effective option for erectile dysfunction treatment in the UK, with prices at Cured Pharmacy starting from £0.45 per tablet. This significant price reduction compared to branded Viagra makes regular use affordable for most patients, particularly those requiring higher doses or frequent treatment.

Generic tadalafil pricing has also decreased substantially since patent expiry, though it typically costs more per tablet than sildenafil due to its longer duration of action and the complexity of its synthesis. At Cured Pharmacy, generic tadalafil starts from 20% offering exceptional value for patients who prefer the extended 36-hour window.

When comparing cost-effectiveness, consider frequency of use. Patients requiring treatment multiple times weekly may find daily low-dose tadalafil more economical than repeated on-demand sildenafil doses, while those needing treatment occasionally often prefer sildenafil's lower per-dose cost. All prices are shown upfront before your free consultation, with no hidden fees.

Which Treatment Is Right for You?

Choosing between sildenafil and tadalafil depends on your lifestyle, frequency of sexual activity, and personal preferences. Sildenafil suits patients who prefer a shorter duration of action, want the medication to clear quickly, or engage in sexual activity less than twice weekly. Its rapid onset and lower cost make it an excellent first-line option for many UK men.

Tadalafil is often preferred by patients seeking spontaneity, those in relationships with frequent sexual activity, or men who find planning around medication timing inconvenient. The option for daily low-dose tadalafil particularly appeals to patients who want to separate treatment from individual sexual encounters entirely [2].

At Cured Pharmacy, our UK-registered prescribers assess your medical history, current medications, and treatment goals during a free online consultation lasting under three minutes. Many patients try both medications at different times to determine which suits them best. All erectile dysfunction treatments require clinical assessment by a UK prescriber and are subject to medical suitability.

Starting Your Treatment at Cured Pharmacy

Begin by completing our confidential online assessment, which covers your medical history, current medications, and cardiovascular health. A UK prescriber reviews your information, typically within hours, and approves the most suitable treatment based on clinical guidelines. Once approved, your medication is dispensed by our GPhC-registered pharmacy (9012511) and delivered in 100% discreet packaging with next-day delivery available across the UK. Our superintendent pharmacist, Tarun Kumar (GPhC 2233073), oversees all clinical services to ensure the highest standards of patient care.

Scientific References

1. Goldstein, I., Lue, T. F., Padma-Nathan, H., Rosen, R. C., Steers, W. D., & Wicker, P. A. (1998). Oral sildenafil in the treatment of erectile dysfunction. New England Journal of Medicine, 338(20), 1397–1404. https://doi.org/10.1056/NEJM199805143382001 [accessed 13 August 2026]
2. Carson, C. C., & Lue, T. F. (2005). Phosphodiesterase type 5 inhibitors for erectile dysfunction. BJU International, 96(3), 257–280. https://doi.org/10.1111/j.1464-410X.2005.05614.x [accessed 13 August 2026]
3. Yuan, J., Zhang, R., Yang, Z., Lee, J., Liu, Y., Tian, J., Qin, X., Ren, Z., Ding, H., Chen, Q., Mao, C., & Tang, J. (2013). Comparative effectiveness and safety of oral phosphodiesterase type 5 inhibitors for erectile dysfunction: a systematic review and network meta-analysis. European Urology, 63(5), 902–912. https://doi.org/10.1016/j.eururo.2013.01.012 [accessed 13 August 2026]
4. NHS. (2026). Erectile dysfunction (impotence). https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ Accessed 13 August 2026.

Information on this page is for educational purposes only and is not medical advice. All prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting any new medication.