Author: Sylvia (Xi) He – Medical / Scientific Editor & Writer
Introduction
Cialis (tadalafil) is a phosphodiesterase-5 (PDE5) inhibitor with two practical dosing styles that fit different needs: on-demand dosing for situational erectile dysfunction (ED) and once-daily dosing for men who prefer spontaneity or who also need relief from lower urinary tract symptoms due to benign prostatic hyperplasia (BPH). While both approaches use the same medicine, they differ in dose, timing, and expectations: on-demand aims for a single window of responsiveness (up to ~36 hours), whereas daily low-dose treatment builds a steady baseline effect.
This guide explains the standard ED doses, who benefits from 2.5–5 mg once daily, how meals, alcohol, and missed doses matter, and how to switch safely between regimens. Recommendations are grounded in authoritative sources (FDA label, UK SmPC, and AUA BPH guideline) to keep advice practical and evidence-based.
Standard Doses for ED (On-Demand)
For erectile dysfunction, the usual starting dose is 10 mg taken at least 30 minutes before sexual activity, with or without food. Depending on efficacy and tolerability, the dose may be increased to 20 mg or reduced to 5 mg. Do not take more than one dose in 24 hours. Clinical effect can persist for up to 36 hours, so timing can be flexible within that window. These directions are consistent across the FDA label and UK product information.
On-demand dosing is best suited to men with intermittent sexual activity who prefer to take tadalafil only when needed. It offers the longest window of responsiveness among PDE5 inhibitors while avoiding daily exposure. Counsel patients that sexual stimulation is required for tadalafil to work and that heavy alcohol intake may increase dizziness or hypotension.
As for special populations, in severe renal impairment or hepatic impairment, consider lower doses and more conservative titration; avoid use where the label advises. Absolute contraindications (e.g., concurrent nitrates or riociguat) still apply regardless of regimen and should be reviewed before prescribing.
If a patient finds they need medication frequently or also has LUTS/BPH, discuss switching to once-daily 2.5–5 mg (covered later) to reduce planning burden and address urinary symptoms when appropriate.
Once-Daily 2.5–5 mg: Who Benefits and Why
For some men, a low-dose daily regimen offers advantages that on-demand use cannot match. The approved doses for daily tadalafil are 2.5 mg or 5 mg once every day, taken at approximately the same time each day regardless of planned sexual activity. The 5 mg daily dose is also the standard for treating lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH), either alone or in combination with ED.
Once-daily dosing creates a steady plasma concentration of tadalafil, eliminating the need to coordinate intake with sexual activity. This approach is particularly suited for:
- Men with frequent sexual activity (e.g., ≥2–3 times per week)
- Those with both ED and BPH, as recommended in the American Urological Association (AUA) BPH guideline
- Individuals who prefer not to plan intimacy around medication timing
Clinical studies have shown that once-daily tadalafil maintains erectile function and improves urinary symptoms over months of treatment, with a side effect profile comparable to on-demand dosing. The gradual, continuous exposure may also reduce the psychological performance pressure associated with taking a tablet immediately before intercourse.
However, daily use means continuous drug exposure and associated cost, so it is less suitable for men with infrequent sexual activity or those sensitive to tadalafil-related side effects. Dose selection between 2.5 mg and 5 mg depends on symptom severity, tolerability, and treatment goals.
Timing, Meals, Alcohol, Missed Dose
One of tadalafil’s advantages over some other PDE5 inhibitors is that food does not significantly affect its absorption. This means patients can take it with or without meals without worrying about a delay in onset or a reduction in effectiveness. This applies equally to the on-demand and once-daily regimens. For men who prefer to take medication at the same time as breakfast or dinner, this flexibility can make adherence easier and reduce the chance of forgetting a dose.
Alcohol, however, is a more nuanced issue. While moderate intake (e.g., one or two standard drinks) is unlikely to cause significant problems in most healthy men, excessive drinking — about five or more units at once — can amplify tadalafil’s vasodilatory effects. This combination increases the risk of dizziness, orthostatic hypotension, rapid heartbeat, and fainting. For men with cardiovascular risk factors or those on antihypertensive medication, even moderate drinking may lead to unpleasant side effects. Patient counseling should highlight the importance of limiting alcohol, especially when initiating tadalafil or adjusting the dose.
With once-daily dosing, taking the tablet at the same time every day is important to maintain steady blood levels. A consistent schedule helps ensure stable therapeutic effects for erectile function or LUTS/BPH control. If a dose is missed, the guidance is straightforward: take it as soon as you remember, unless it’s close to the next scheduled time — in which case, skip the missed dose entirely. Patients should be reminded never to double the dose to compensate, as this increases the likelihood of side effects such as headache, flushing, nasal congestion, or muscle aches.
For on-demand dosing, the timing is different: the tablet should be taken at least 30 minutes before anticipated sexual activity. Since tadalafil remains effective for up to 36 hours, there is no need to take it repeatedly over that period. More than one dose in 24 hours is not recommended. This long duration allows for flexibility and can reduce anxiety about “perfect” timing, which is one reason many men favor tadalafil over shorter-acting PDE5 inhibitors.
Patients switching between regimens should be counseled on these differences. Moving from daily to on-demand use requires leaving a gap of at least 24 hours after the last daily dose before taking an on-demand tablet. Conversely, starting daily dosing after on-demand use should avoid overlapping doses to minimize the risk of hypotension or other adverse effects. Careful education during this transition helps ensure safety and maintains confidence in therapy.
Switching Between Regimens
Switching between on-demand and once-daily tadalafil is common and should avoid overlapping doses.
On-demand → daily:
Often chosen for frequent sexual activity or coexisting BPH/LUTS. Start the daily regimen at least 24 hours after the last on-demand dose, usually with 2.5 mg once daily, increasing to 5 mg if needed. Review tolerability after 1–2 weeks and efficacy after 4–6 weeks.
Daily → on-demand:
Preferred for reduced sexual frequency, cost savings, or limiting continuous drug exposure. Stop daily dosing and wait 24 hours before taking 10 mg on demand (adjustable to 5 mg or 20 mg).
In either case, reassess comorbidities, medications, and cardiovascular status before switching. Remind patients that tadalafil should not be taken more than once in 24 hours for on-demand use or above the prescribed daily dose. Choosing the right regimen depends on symptom control, safety, and lifestyle preferences, with regular follow-up to ensure optimal outcomes.
Monitoring Response & Side Effects
Ongoing assessment is essential to ensure that tadalafil provides meaningful improvement in erectile function and, where applicable, urinary symptoms from BPH/LUTS. For ED, response can be tracked using the International Index of Erectile Function (IIEF) or through direct patient-reported outcomes. In BPH, the International Prostate Symptom Score (IPSS) offers a structured measure of urinary symptom change. Review efficacy after 4–6 weeks, and again at three months, to decide whether dose adjustments or regimen changes are needed.
Common side effects include headache, dyspepsia, flushing, nasal congestion, and muscle or back pain. These are usually mild and transient but may persist with daily dosing. Advise patients that side effects often diminish over time, and simple measures, such as hydration or taking the tablet with food, may improve tolerability.
Serious adverse effects are rare but require immediate attention: prolonged erections (priapism), sudden vision or hearing loss, and signs of severe hypotension. Patients taking nitrates or guanylate cyclase stimulators should be reminded of the absolute contraindication.
In men with cardiovascular disease, monitor for changes in blood pressure and overall exercise tolerance. For those on interacting drugs, especially potent CYP3A4 inhibitors or inducers, consider dose adjustments or more frequent review.
Documenting both clinical benefits and adverse effects at each visit supports shared decision-making, ensures adherence, and allows early intervention if problems arise. This structured monitoring can help maintain both safety and patient satisfaction over the long term.
References
- European Medicines Agency. (2023). Cialis: EPAR – product information. https://www.ema.europa.eu/en/documents/product-information/cialis-epar-product-information_en.pdf
- Food and Drug Administration. (2018). Cialis (tadalafil) [Prescribing information]. https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/021368s030lbl.pdf
- Medicines.org.uk. (2024). Cialis 2.5 mg, 5 mg, 10 mg, 20 mg film-coated tablets – Summary of product characteristics (SmPC). https://www.medicines.org.uk/emc/product/3516/smpc
- American Urological Association. (2023). Benign prostatic hyperplasia (BPH) guideline. https://www.auanet.org/guidelines-and-quality/guidelines/benign-prostatic-hyperplasia-(bph)-guideline
- Porst, H., Kim, E. D., Casabé, A. R., Mirone, V., Secrest, R. J., Xu, L., & Sundin, D. P. (2011). Efficacy and safety of tadalafil once daily: Considerations for the practical application of a daily dosing option. Current Medical Research and Opinion, 27(8), 1581–1592. https://doi.org/10.1185/03007995.2011.589830
