Two schedules, one molecule
The tablet people call the weekend pill and the tablet people call the daily almond are the same PDE5 inhibitor on two calendars. Mean terminal half-life is 17.5 hours in healthy subjects. That clock is why a single as-needed dose can still be in the comparison more than a day later. The erection still depends on stimulation, and the as-needed cap is still one dose that day.
After one oral dose, the maximum plasma concentration arrives between 30 minutes and 6 hours, with a median of 2 hours. Food does not change the rate or extent of absorption, so either schedule may be taken with or without food. The label also says not to split Cialis tablets. The whole dose is the dose.
The dosage-forms section of this Lilly label lists three almond-shaped strengths: 5 mg debossed C 5, 10 mg debossed C 10, and 20 mg debossed C 20. The once-daily starting instruction is still 2.5 mg. If the prescription says 2.5 mg, the pharmacy's dispensed tablet has to match that order. Breaking a 5 mg almond fights the split instruction.
Adcirca is also tadalafil, and it sits on a different ladder. The label tells prescribers that combinations of Cialis with other PDE5 inhibitors, including Adcirca, have not been studied, and patients should not take Cialis with those products.
The as-needed tablet and the 36-hour window
For most men the as-needed start is 10 mg, taken prior to anticipated sexual activity. If that dose is not enough, the label allows 20 mg. If it is more than the person tolerates, the dose can come down to 5 mg. The maximum recommended dosing frequency is once per day in most patients.
The effect claim is specific. As-needed Cialis improved erectile function compared with placebo for up to 36 hours after the dose. In the integrated as-needed studies, the share of attempts that resulted in successful intercourse was 33% on placebo, 56% on 10 mg, and 62% on 20 mg. Those three numbers are a comparison with placebo inside the as-needed program. The daily trials used their own placebo groups.
Arousal still has to happen. The patient information says some form of sexual stimulation is needed for an erection with Cialis. A tablet at noon does not book the evening. The wide window lets the couple drop the stopwatch. Desire and stimulation still have to show up.
Men who use this lane rarely are the ones the 10 mg start was written for. A month with a handful of nights stays an as-needed month. The unused mornings are the cost of the other schedule.
The daily tablet is a morning habit
Once-daily Cialis for erectile dysfunction starts at 2.5 mg, taken at approximately the same time every day, without regard to timing of sexual activity. The dose may be increased to 5 mg based on efficacy and tolerability. The point of that regimen is continuous plasma tadalafil. The label tells prescribers to keep that steady exposure in mind when they think about nitrates, alpha-blockers, blood-pressure medicines, strong CYP3A4 inhibitors, and a lot of alcohol.
Daily use was studied on its own. The label describes two trials of 12 weeks and one trial of 24 weeks, 853 patients in all, and says once-daily Cialis improved erectile function in men with erectile dysfunction. That sentence supports the daily regimen in its own placebo-controlled trials. A ranking against 10 mg or 20 mg as needed is a different study, and this label does not supply one.
Benign prostatic hyperplasia uses a different daily number. The recommended once-daily dose for BPH is 5 mg, at about the same time every day. The same 5 mg daily dose is the labeled dose when erectile dysfunction and BPH are being treated together. Urinary symptoms follow the BPH instruction: 5 mg daily. When Cialis and finasteride are started together for BPH, the Cialis dose in that combination is also 5 mg once daily, and the label limits that combined start to a defined course a prescriber reads on the indication line.
Cialis for BPH is not recommended together with an alpha-blocker. Efficacy of that pair was not adequately studied, and both drugs can lower blood pressure. That is a different sentence from erectile dysfunction. For ED, a man who is already stable on an alpha-blocker can be started on Cialis at the lowest recommended dose. Solo 5 mg for prostate symptoms remains an allowed use. The combination is the caution.
Which month belongs on which schedule
| As needed | Once daily | |
|---|---|---|
| Usual ED start | 10 mg before anticipated sex | 2.5 mg at about the same time every day |
| Dose may move to | 20 mg, or down to 5 mg | 5 mg |
| What was measured | Erectile function versus placebo out to 36 hours | Erectile function on a daily schedule, in separate trials |
| How often | Not more than once a day in most patients | Once a day |
| BPH | Not the BPH regimen | 5 mg daily for BPH, including ED with BPH |
| Food | With or without food | With or without food |
Count nights, not slogans. Sex less often than a couple of times in a week usually fits the as-needed column: one 10 mg tablet before the occasion, a window measured out to 36 hours, and no tablet on the quiet days. Sex often enough that a pre-sex ritual is the thing the couple wants to drop fits the daily column: 2.5 mg every day, possibly 5 mg, already in the blood when the evening changes plan.
Urinary bother pulls toward 5 mg daily even when the erection question is quiet. Retention, infection, or a large amount of urine left in the bladder is a urology problem. A reading note does not sort that.
As-needed 10 mg and 20 mg are higher single doses. Daily 2.5 mg and 5 mg are lower doses kept present. A man who needs the higher single-night dose will feel under-dosed on 2.5 mg, because that tablet was written as a steady dose, not as a copy of a 20 mg peak.
Some search headlines say the daily dose causes fewer side effects, or that one published comparison found daily tadalafil more effective. Side effects on this label were counted inside each program, at that program's doses. A paper in a selected group stays in that group. The Lilly label never ranks one schedule above the other for every couple.
A prescriber picks one regimen. The as-needed instructions cap dosing at once a day. The daily instructions are already that day's tadalafil. Adding a 20 mg tablet on top of a morning 5 mg is a second exposure. The label has not studied Cialis together with other PDE5 inhibitors.
Kidneys, liver, and other medicines change the numbers
Organic nitrates stop both schedules. Regular or intermittent nitrate use is a contraindication, because Cialis potentiates the blood-pressure drop from nitrates. If a life-threatening angina forces the question of nitroglycerin, the label wants at least 48 hours after the last Cialis dose, then monitoring in a setting that can watch the blood pressure. The 48 hours belongs in a monitored setting. Chest pain after a tablet is emergency care, with the drug history included. Guanylate cyclase stimulators such as riociguat are in the same stop list.
Daily users are inside that nitrate problem the whole time they take the tablet, because the plasma level is continuous. Chest pain is emergency care. A morning tablet already swallowed still counts toward the 48-hour wait.
Kidneys split the two lanes further. For as-needed use, creatinine clearance 30 to 50 mL/min means a 5 mg start, not more than once a day, and a maximum of 10 mg not more than once every 48 hours. Clearance under 30 mL/min, or hemodialysis, caps as-needed treatment at 5 mg not more than once every 72 hours. Once-daily Cialis is not recommended at that low clearance.
For BPH, or for ED together with BPH, clearance 30 to 50 mL/min starts at 2.5 mg, with a possible increase to 5 mg. Once-daily use is not recommended when clearance is under 30 mL/min or the person is on hemodialysis.
The liver is stricter than a one-line chart. Mild or moderate hepatic impairment (Child-Pugh A or B) means as-needed Cialis should not exceed 10 mg once a day. Once-daily use has not been extensively evaluated in hepatic impairment, so the label advises caution. Severe impairment (Child-Pugh C): Cialis use is not recommended.
Strong CYP3A4 inhibitors such as ketoconazole or ritonavir change the ceiling again. As-needed Cialis is then limited to 10 mg, and not more often than once every 72 hours. Once-daily Cialis should not exceed 2.5 mg. Rifampin can lower tadalafil exposure. Those are prescriber adjustments, read from the label, not a home change.
An erection lasting more than 4 hours, painful or not, needs emergency care. Sudden loss of vision in one or both eyes, or a sudden change in hearing, means stop the tablet and get medical care. Those warnings sit on both schedules.
What the label's trials compared
The as-needed program and the daily program were each tested against placebo. Each one answers whether that schedule improved erectile function in its own trials. Frequency, urinary symptoms, other medicines, and the kidney number decide which schedule fits.
The trial rows, including how to read a nitrate study, are on the tadalafil trials and evidence note. How the 10 mg start arrived years after sildenafil is on how Cialis was developed. The milligram ladder for a fill, including the prescription and the pharmacy check, is on the tadalafil medicine page.
Asking the pharmacy without a made-up price
A single dollar figure in a library note would be stale the week the pharmacy changes the contract. The comparison that holds up is local. Ask for the price of a small count of 10 mg, a small count of 20 mg, and a 30-count of the daily strength that was actually prescribed. Multiply the as-needed price by the number of uses in a real month. Set that next to the 30-count. Insurance can flip the result. Tablets left in a drawer are part of the as-needed cost too.
Then match the imprint to the prescription. On this Lilly label the almonds are C 5, C 10, and C 20. A 2.5 mg order has to be the product the pharmacy dispenses for that strength. Confirm nitrates and riociguat are absent before anyone pays. Julian Frost signs this PDE5 note. The limit of a reading note is on the margin disclaimer. How the notes are filed is on How we review. The label text used here is the Lilly CIALIS entry on DailyMed.