01 Which clock this 2.5-10 mg leaf actually keeps
Two labelled clocks share one generic name. Cialis tablets exist as 2.5, 5, 10, and 20 mg. This leaf locks the pair that matters for most first visits: 2.5 mg once daily for erectile dysfunction, or 10 mg taken before anticipated sexual activity.
Daily 2.5 mg sits at the same hour each day and ignores the calendar of sex. The as-needed 10 mg tablet is swallowed when an evening is likely, not more than once in twenty-four hours. The label lets a clinician raise daily use to 5 mg, or move the PRN tablet to 20 mg or down to 5 mg. Those steps stay on the prescription. They are not a self-edit.
Readers who want the weekend spread of one 10 mg tablet should open the two-evening Cialis margin. The daily-versus-weekend split lives on the 2.5 mg versus 10 mg ink note. The three-way clock against sildenafil sits on the Cialis versus Viagra binding sheet.
Virena does not dispense and does not write the order. Mail about the page, not about a personal plan, goes to [email protected].
02 When CYP3A4 inhibitors or a low creatinine rewrite the clock
Ketoconazole and ritonavir shrink the allowed tablet. For as-needed Cialis with a potent CYP3A4 inhibitor, the maximum is 10 mg, not more than once every 72 hours. For once-daily use with the same inhibitors, do not exceed 2.5 mg. Those are label limits, not polite suggestions.
Rifampin 600 mg daily cut a 10 mg tadalafil AUC by 88% and Cmax by 46%. Other inducers (carbamazepine, phenytoin, phenobarbital) are expected to do the same. Daily 2.5 mg can look like a ghost dose on rifampin. The insert does not invent a compensating milligram.
Creatinine clearance under 50 mL/min changes PRN math. Moderate impairment (31 to 50 mL/min): start 5 mg once daily at most, and do not exceed 10 mg once every 48 hours. Severe impairment or hemodialysis: 5 mg not more than once every 72 hours. Mild impairment needs no automatic cut. Daily-use Cialis is not recommended in severe renal disease on some label rows; the clinician reads that line, not a blog.
Age alone does not force a cut. Men 65 and over had about 25% higher AUC with no Cmax change. Diabetes after 10 mg showed a 19% lower AUC. Neither fact replaces a nitrate history.
Label cuts that change the 2.5-10 mg plan
- Potent CYP3A4 inhibitor + PRN: 10 mg every 72 hours at most
- Potent CYP3A4 inhibitor + daily: 2.5 mg ceiling
- Rifampin-level inducer: expect a much smaller exposure; no homemade extra tablet
- CrCl 31-50 mL/min (PRN): 5 mg start, 10 mg every 48 hours max
- Severe renal / hemodialysis (PRN): 5 mg every 72 hours max
03 Where a 2.5 mg thirty-count is actually written
Cash figures on this leaf come from a dated GoodRx row, not from a Virena till. The 2.5 mg daily lock is the thirty-tablet board. A 10 mg PRN pack is a different row on the same public table.
Kroger, Safeway, Harris Teeter, and Albertsons are listed because those are the official pharmacy pages this almanac points at. Virena does not fill a bag and does not invent a euro or a dollar.
Generic tadalafil 2.5 mg x 30, GoodRx Cialis daily table.
Generic tadalafil 2.5 mg, thirty tablets, the Virena daily leaf lock, August 2026. GoodRx lists 2.5 mg x 30 at $313.08 average retail and $16.93 with a coupon. Ten-milligram PRN packs are a separate row on the same table. Virena does not dispense.
04 Seventeen and a half hours, then a 48-hour nitrate hold
Seventeen and a half hours is the mean terminal half-life in healthy subjects. Mean oral clearance is 2.5 L/hr. Most of a dose leaves as metabolites in feces (about 61%) and the rest in urine (about 36%). Absolute oral bioavailability was not determined on the US label.
That long half-life is why the nitrate hold is 48 hours, not overnight. Organic nitrates in any form are contraindicated with Cialis. If nitroglycerin becomes medically necessary after a dose, at least 48 hours should elapse, and even then the nitrate is given only with close hemodynamic monitoring.
Lilly's crossover work in 150 men (daily tadalafil 20 mg or placebo for 7 days, then 0.4 mg sublingual nitroglycerin at set times) still showed a significant interaction at every point through 24 hours. At 48 hours, most hemodynamic measures no longer showed the interaction, which is why the hold is written at two days. It is not a casual 'wait until morning.'
Riociguat, a guanylate-cyclase stimulator, is also contraindicated. Street 'poppers' (amyl or butyl nitrite) count as nitrates. Anyone with chest pain after tadalafil needs emergency care, not a second tablet and not a home nitrate.
| Absorption | Cmax between 30 minutes and 6 hours; median about 2 hours. Food does not change rate or extent. |
|---|---|
| Distribution | Widely distributed. Protein binding is high; the insert treats tadalafil as a tissue-facing molecule. |
| Metabolism | Predominantly CYP3A4 in the liver. Ketoconazole 400 mg daily raised 20 mg AUC by 312%. |
| Excretion | Mean t½ 17.5 hours. Metabolites in feces ~61% and urine ~36%. Hemodialysis adds almost nothing. |
05 The 2.5 mg morning habit the label starts with
Morning 2.5 mg does not wait for a date. The US Cialis label for once-daily erectile dysfunction starts at 2.5 mg taken at approximately the same time every day, without regard to timing of sexual activity.
That sentence is the whole point of the daily clock. You swallow the tablet because it is Tuesday, not because someone texted. Steady plasma tadalafil is the design. After several days the trough is no longer a guess.
If 2.5 mg is tolerated and still thin on response, the same label allows 5 mg once daily. It does not allow a second 2.5 mg later the same day as a homemade booster. One tablet, one calendar day.
BPH-only dosing on Cialis is 5 mg daily, and the ED-plus-BPH pair is also 5 mg daily. Those indications are real. They are not this leaf's SERP lock. If both prostate symptoms and erections are on the same visit, the clinician picks 5 mg daily and says so. Do not stack a 10 mg PRN tablet on top of a running daily course unless that mix was written on purpose.
06 Thirty minutes out, then the 36-hour window
Labelled erectile function versus placebo holds out to 36 hours after an as-needed dose. That number is why people call Cialis a weekend tablet. It is also why a Saturday 10 mg still occupies Sunday's nitrate question.
Lilly ran timed-attempt studies at 24 and 36 hours. In one 348-patient trial of Cialis 20 mg versus placebo, at least one successful intercourse was reported by 61% on tadalafil versus 37% on placebo at the 24-hour window (22 to 26 hours), and by 64% versus 37% at the 36-hour window (33 to 39 hours). A second study that included 10 mg and 20 mg showed the same directional gap at both clocks.
Those percents are 20 mg and 10 mg PRN data, not a promise that every 2.5 mg morning will feel like hour two. Daily 2.5 mg is a different exposure pattern. It is meant to be there on a Wednesday with no planning, not to reprint the 36-hour weekend story.
If a first 10 mg feels late, check the clock you actually used. Swallowing at 22:30 and expecting a 22:40 peak fights the median Tmax of 2 hours. The leaf on sildenafil after food is the one that argues with dinner. Tadalafil usually does not.
| Clock | What the Cialis label and timed trials say |
|---|---|
| Earliest labelled cue | As soon as 30 minutes after a PRN tablet, with stimulation |
| Median Tmax | About 2 hours (range 30 minutes to 6 hours) |
| 24-hour attempt window | Cialis 20 mg 61% vs placebo 37% with at least one success |
| 36-hour attempt window | Cialis 20 mg 64% vs placebo 37% with at least one success |
| Daily 2.5 mg | Same hour each day; no link to the night's plan |
07 Ten milligrams before a planned evening
Ten milligrams before a planned evening is the as-needed start for most adults on the Cialis label. Take it prior to anticipated sexual activity. Some men notice a usable erection from about 30 minutes. The median time to peak plasma is about 2 hours, with a spread from 30 minutes to 6 hours.
Do not treat the 10 mg tablet as a 2.5 mg that failed this afternoon. Daily and PRN are different regimens. Switching from a morning habit to a night tablet, or the reverse, is a prescribing change.
The labelled ceiling on frequency is once per day in most patients. A second 10 mg at 02:00 because the first felt quiet is not on the insert. If 10 mg is weak after several attempts with stimulation, the label allows 20 mg. If flushing or headache dominate, 5 mg is the step down.
Stimulation is still required. Tadalafil does not create desire and does not raise an erection in sleep the way an injection might. Couples who hate a stopwatch often pick this PRN clock because the 36-hour window (below) is longer than a dinner reservation.
Virena 2.5-10 mg lock from the Cialis dosage sections
08 Food barely moves tadalafil; five units of alcohol can
Food leaves the AUC almost unchanged. The Lilly insert states that the rate and extent of absorption of tadalafil are not influenced by food, so Cialis may be taken with or without a meal. That is the clean difference from the sildenafil 50-100 mg leaf, where a high-fat dinner delays Tmax by a mean of 60 minutes and cuts Cmax by 29%.
Alcohol is a different sentence. Both alcohol and tadalafil are mild vasodilators. Substantial drinking (the label's example is 5 units or greater) with Cialis can raise the chance of a standing-pressure drop, a faster pulse, dizziness, and headache.
Two pharmacology studies used 0.7 g/kg of alcohol with 10 mg or 20 mg tadalafil. More subjects had clinically important blood-pressure drops on the combination than on alcohol alone, and some had postural dizziness or orthostatic hypotension. A lower alcohol load (0.6 g/kg, described as about 4 units) with 20 mg tadalafil did not show that extra hypotensive effect. Tadalafil did not change alcohol levels, and alcohol did not change tadalafil levels.
A heavy Bordeaux dinner is fine for the tablet's absorption. A heavy Bordeaux dinner plus five glasses plus a 10 mg tablet is the combination the insert actually warns about.
09 The delayed backache and the alpha-blocker overlap
Diffuse lumbar ache can arrive twelve to twenty-four hours after a dose and usually settles within 48 hours. The Cialis trials described bilateral lower lumbar, gluteal, or thigh discomfort that felt worse when lying still. Most reports were mild or moderate. About 0.5% of on-demand subjects stopped because of back pain or myalgia.
Acetaminophen or an NSAID was enough when treatment was wanted. A small group needed a mild opioid. This ache is not a kidney-stone clone and not a reason to take a second 10 mg 'to push through.'
Alpha-blockers add another pressure story. Tadalafil and doxazosin, tamsulosin, or alfuzosin are both vasodilators. The insert asks for caution, a stable alpha-blocker dose first, and a low PDE5 start. Cialis as a single daily tablet is approved for BPH symptoms. The caution is the two-hypotensive stack, not 'tadalafil is forbidden in prostate disease.'
Common listed reactions on Cialis also include headache, dyspepsia, flushing, nasal congestion, and myalgia. Sudden vision or hearing loss is a stop-and-call event. An erection past 4 hours is the same. None of those lines is a lifestyle tip.
Priapism risk is higher if there is sickle-cell disease, multiple myeloma, leukemia, or a penile anatomical deformity. Those backgrounds do not change the 2.5-10 mg SERP lock. They do change whether any PDE5 tablet belongs on the chart. Sudden decrease or loss of vision in one or both eyes, including NAION, is a stop. Sudden hearing loss, sometimes with tinnitus and dizziness, is the same stop. Call emergency services rather than waiting for a Monday clinic slot.
Cialis is not an on-demand nitrate buffer and not a substitute for treating diabetes, smoking, or an untreated blood-pressure list. If erections fail after a fair 10 mg clock and a fair 2.5 mg week, the next visit is about those causes, not a homemade 20 mg plus 10 mg stack. Adcirca (tadalafil for pulmonary arterial hypertension) is a different product. Do not add Cialis on top of it.
10 What to carry into the visit that sets the clock
Bring the last nitrate time and the name of every alpha-blocker, antifungal, and protease inhibitor. Those three facts rewrite 2.5 mg versus 10 mg faster than a preference for weekends.
If the goal is a tablet that ignores dinner, tadalafil is the cleaner clock. If the goal is a same-night peak after a light plate, the sildenafil after-food leaf is the better first read. Fast peak at 20 mg with a QT screen sits on the vardenafil 20 mg leaf.
Bring a written last-dose time if a nitrate emergency is even remotely possible. Change the regimen only with the clinician who knows the rest of the chart. Elise dated this tadalafil leaf on 21 August 2026.
| INN | tadalafil |
|---|---|
| Brand on this leaf | Cialis |
| US tablet strengths | 2.5, 5, 10, 20 mg |
| Virena SERP lock | 2.5 mg daily or 10 mg PRN |
| Mean t½ | 17.5 hours |
| Nitrate hold | 48 hours after the last dose |