What is IIEF-EF and why do reviews keep citing it?
A review that ranks pills is not a trial read
Claim: daily tadalafil 'works better' than the blue diamond. Label: unmeasurable as stated. Strike rank-talk. File questionnaires.
Erectile-dysfunction trials do not ask a man if the weekend felt magical. They score the International Index of Erectile Function, then isolate the erectile-function domain - IIEF-EF. A clinically meaningful rise against placebo is the bar. Beside that sit two Sexual Encounter Profile diary items: SEP2, could he penetrate; SEP3, could he keep the erection through intercourse. SEP3 is the number that maps to the evening people actually care about.
The Global Assessment Question is cruder - did erections improve, yes or no - and still useful as the patient's own verdict. A program that moves IIEF-EF, SEP2, SEP3 and GAQ against placebo is doing real work. A blog that says 'stronger than Viagra' without those instruments is reviewing marketing. Tadalafil's daily 2.5 or 5 mg carton cleared the instruments. It did not win a head-to-head potency cup the FDA never ran.
Brock's five-trial stack sold the PRN tablet, not breakfast
Claim: the famous early tadalafil papers already proved 2.5 or 5 mg daily. Label: date error. Strike: Brock's 2002 integrative analysis of five randomised trials, and Porst's 36-hour timing work, supported as-needed 10 mg and 20 mg. File those papers under the 2003 carton.
That stack mattered. It is why Europe signed in late 2002 and the FDA signed on 21 November 2003. Efficacy held across mixed causes, including diabetes, where every PDE5 inhibitor works less well and still beats placebo. Food did not erase absorption. The 20 mg tablet posted the highest raw scores and the most adverse events, which is why 10 mg became the sensible as-needed start.
None of that is a daily-dose review. If you paste Brock's SEP3 percentages onto a 2.5 mg breakfast chip, you are reading the wrong protocol. The daily file starts later, with lower milligrams and a swallow that ignores the clock.
Rajfer: 24 weeks of 2.5 or 5 mg, no timing of sex
Claim: 2.5 mg and 5 mg daily are interchangeable. Label: incomplete. Strike the tie. File Rajfer's dose split.
Rajfer and colleagues ran a US randomised, double-blind, placebo-controlled study in 287 men with at least three months of erectile dysfunction. They took tadalafil 2.5 mg or 5 mg once daily for 24 weeks, without tying the tablet to sexual activity. Primary endpoints were change in IIEF-EF, SEP2 and SEP3.
At 24 weeks the IIEF-EF rise was 6.1 points on 2.5 mg and 7.0 points on 5 mg, against 1.2 points on placebo. SEP2 improved 24.3% and 26.2% versus 5.2% on placebo. SEP3 improved 31.2% and 35.1% versus 9.5%. The 5 mg arm sat higher on every primary line. The gap is not theatrical. It is consistent. That is why clinicians who want the daily habit usually aim at 5 mg unless a limiter - a strong CYP3A4 inhibitor, a frail start - argues for 2.5 mg.
PAIRS sexual self-confidence moved with both daily doses. Spontaneity scores did not separate cleanly from placebo, which is a useful strike against the slogan that a breakfast tablet automatically restores romance. It restores readiness. Couples still have to show up.
Porst's 12 weeks, then the diabetes cohort
| Study file | Dose and span | What moved versus placebo |
|---|---|---|
| Brock 2002 (5 RCTs) | PRN 10-20 mg | IIEF-EF and SEP3; 2003 carton, not daily |
| Porst 2006 | 5 or 10 mg daily, 12 weeks | Both beat placebo; 10 mg daily not the US habit |
| Rajfer 2007 | 2.5 or 5 mg daily, 24 weeks | IIEF-EF +6.1 / +7.0; SEP3 +31.2 / +35.1 points |
| Hatzichristou | 2.5 or 5 mg daily, diabetes, 12 weeks | Signal holds, smaller, as in the whole class |
| Integrated daily ED | 2.5 or 5 mg | IIEF-EF to 19.2 / 21.9; SEP3 ~50% / 62% |
Porst had already tested a higher daily pair - 5 mg or 10 mg for 12 weeks in 293 men. Both doses beat placebo on IIEF-EF, SEP2 and SEP3. The 10 mg daily arm did not earn a US breakfast carton. Adverse events climb as you park a larger daily load, and the later 2.5 or 5 mg program was the one regulators filed for once-daily ED. Remember that when a forum swears 10 mg daily is 'the real dose.' It was a trial arm, not the labelled habit.
Hatzichristou enrolled 298 men with type 1 or type 2 diabetes and erectile dysfunction for 12 weeks of 2.5 mg or 5 mg daily. The signal survived. It was smaller, as every PDE5 program is smaller in diabetes, because vessels and nerves the drug relies on are already damaged. That is not a reason to skip a trial of the tablet. It is a reason not to judge it on one Saturday after a year of untreated glucose.
An integrated look across the approved once-daily ED studies put mean IIEF-EF at 19.2 after 2.5 mg (up 6.2) and 21.9 after 5 mg (up 8.6), versus 14.9 after placebo (up 1.3). Mean SEP3 success sat near 50% and 62% versus 33% on placebo. Open-label extensions out to one and two years on 5 mg kept the effect without a new safety surprise. Daily 2.5 or 5 mg is not a stunt dose. It is a measured one.
Roehrborn's IPSS ladder is why 5 mg, not 20 mg, treats the stream
Claim: any daily Cialis dose treats an enlarged prostate. Label: sloppy. Strike the 20 mg fantasy. File Roehrborn 2008.
After a four-week placebo run-in, 1,058 men with lower-urinary-tract symptoms from benign prostatic hyperplasia were randomised to 12 weeks of placebo or tadalafil 2.5, 5, 10 or 20 mg once daily. IPSS least-squares mean change was -3.9, -4.9, -5.2 and -5.2 against -2.3 on placebo. The 5 mg step captured most of the symptom gain. The 10 and 20 mg steps added little IPSS and more backache, myalgia and dropout.
Peak flow did not move versus placebo at any dose. That is the honest limit. Tadalafil eases the symptom score. It is not a saw for obstruction. Alpha-blockers and 5-alpha-reductase inhibitors still own flow and volume when those are the real problem. The niche that 5 mg daily won in 2011 is the overlap: men who have both urinary symptoms and erectile dysfunction, one tablet, two scores. On-demand 20 mg cannot hold a chronic stream. The schedule split exists because of that job, not because 5 mg is 'stronger' than 20 mg.
PHIRST walked 33 metres at 40 mg. That is not Cialis daily.
Claim: more milligrams of daily tadalafil must mean a better erection. Label: indication smash. Strike. File PHIRST under Adcirca.
| Indication file | Dose the trial actually used | Primary yardstick | What to file |
|---|---|---|---|
| ED, as needed | 10-20 mg PRN | IIEF-EF, SEP2, SEP3 | 2003 carton; Brock / Porst window |
| ED, once daily | 2.5 or 5 mg | IIEF-EF, SEP3 | 2008 carton; Rajfer / integrated |
| BPH LUTS | 5 mg daily (dose-finding 2.5-20) | IPSS | 5 mg wins risk-benefit; Qmax flat |
| ED plus BPH | 5 mg daily | IIEF-EF and IPSS | One tablet, two scores |
| PAH (Adcirca) | 40 mg daily | 6-minute walk | PHIRST +33 m; not a Cialis review |
Galiè's PHIRST trial randomised 405 people with pulmonary arterial hypertension to placebo or tadalafil 2.5, 10, 20 or 40 mg once daily for 16 weeks. The primary endpoint was change in six-minute walk distance. Only 40 mg met the prespecified significance bar. The mean placebo-corrected gain was 33 metres (95% CI 15 to 50). Treatment-naive patients gained more than those already on bosentan. Time to clinical worsening improved on 40 mg. WHO functional class did not.
That 40 mg walk is why Adcirca exists. It is not a review of Cialis 2.5 or 5 mg. Mixing the two files is how people invent a 'strong daily Cialis' and wander toward a pulmonary dose without a pulmonary diagnosis. The nitrate and riociguat holds are stricter in this sicker group, not looser. The FDA interaction language is on the label at the FDA.
What the daily numbers refuse to say
They refuse a class ranking. Peak response for tadalafil, sildenafil and vardenafil sits in the same band. The daily 2.5 or 5 mg option is a tadalafil-only habit because the half-life allows it. That is a schedule fact, not an efficacy trophy. Food-independence and a thin PDE6 signal are real differences. They are not IIEF points.
They refuse the idea that 2.5 mg equals 5 mg. Rajfer and the integrated ED file both tilt toward 5 mg. 2.5 mg is the labelled start when you need a quieter exposure, not a matching twin. They also refuse the idea that IPSS relief equals a better stream on the flow meter. Roehrborn already struck that.
They never soften nitrates. No IIEF rise, no SEP3 percentage, no 24-week extension buys a combination with a nitrate. The long half-life stretches the danger past a single evening. Match the person to the schedule in the calendar split, and keep the hold. The origin of the linger is in the Bothell file.
File: 5 mg daily is the better-measured breakfast dose
Read across the ED daily program and the claim that survives is modest and solid. Tadalafil 2.5 or 5 mg once daily moves IIEF-EF and SEP3 versus placebo. Five milligrams posts the cleaner dose-response. Diabetes shrinks the effect but does not erase it. Extensions hold. The BPH file then picks 5 mg again on IPSS, with a flat Qmax. PHIRST is a different disease at 40 mg.
That is a Cialis daily review. It is not a monograph and not a shopping rank. If the numbers fit your life, the next argument is frequency and planning, not a larger milligram from a different carton.
Reader mail
Reader questions on this article
Answered by Dr. Priya Anand, MD · Urology & men's health
Trial claims about 2.5 or 5 mg daily show up as rankings. I file them as endpoints.
It is the erectile-function domain of a validated questionnaire, not a vibe. A man scores recent erections; a higher total is better function. Trials need a number that behaves the same way in Boston and in a smaller site, then they test that number against placebo. SEP2 and SEP3 sit beside it as diary facts - penetration, then intercourse completed. GAQ is the blunt yes-or-no. Daily tadalafil 2.5 or 5 mg had to move this set, not win a forum poll. If a 'Cialis daily review' never names IIEF-EF, it is not reviewing the trials.
Is 5 mg daily actually better than 2.5 mg, or is that marketing?
Rajfer's 24-week file is the cleanest answer I have. IIEF-EF rose 7.0 points on 5 mg and 6.1 on 2.5 mg, against 1.2 on placebo. SEP3 followed the same tilt. The integrated daily-ED look put endpoint IIEF-EF at 21.9 versus 19.2. That is a real, modest dose-response, not a billboard. I still start some men at 2.5 mg when a CYP3A4 blocker or a cautious first month argues for less exposure. I do not tell them the two strengths are twins.
Do the daily numbers beat Viagra's numbers?
They were not run as a cup. Peak response across tadalafil, sildenafil and vardenafil lands in the same league. What daily 2.5 or 5 mg uniquely has is a labelled breakfast habit, because the 17.5-hour half-life can hold a low level. That is convenience evidence, not a higher IIEF ceiling than a 50 or 100 mg sildenafil night. If sildenafil already works and timing is fine, the trials do not give you an efficacy reason to switch. If timing is the complaint, they do give you a reason to try the daily carton.
I have diabetes. Are these daily studies even about me?
Hatzichristou's cohort was exactly about you: 298 men with type 1 or type 2 diabetes, 2.5 or 5 mg daily for 12 weeks. The drug beat placebo. The rise was smaller than in mixed-cause ED, which is true for the whole class because the vessels and nerves are already injured. So yes, try it - often the 5 mg daily arm, and not as a single Saturday experiment. Fix glucose, pressure, and any low testosterone in parallel or you will blame a tablet for a vascular year. MedlinePlus is a readable disease overview at MedlinePlus.
Why do prostate ads talk about 5 mg if 20 mg scored a similar IPSS?
Roehrborn's dose-finding study is the file. IPSS fell 4.9 points on 5 mg and 5.2 on both 10 and 20 mg, against 2.3 on placebo. The extra milligrams bought almost no extra symptom relief and more muscle ache and dropout. Peak flow stayed flat at every dose. So 5 mg is the risk-benefit pick, not the 'weak' pick. Twenty milligrams daily is not a better prostate drug in that program. It is a heavier load for a plateaued score.
What was PHIRST, and why do Cialis pages mention a walk test?
PHIRST is a pulmonary arterial hypertension trial, 405 people, 16 weeks, primary endpoint six-minute walk. Only tadalafil 40 mg once daily cleared the statistical bar, with a 33-metre placebo-corrected gain. That is the Adcirca file, not a Cialis 2.5 or 5 mg review. When a page pastes the walk into a breakfast-tablet story, label it an indication smash and strike it. Same enzyme, different disease, different dose. Do not self-invent a 40 mg 'strong daily Cialis.'
Did anyone study daily tadalafil past a few months?
Yes. Men who finished the 12-week and 24-week daily studies rolled into open-label extensions on 5 mg, some out to one and two years. Efficacy held. No new serious safety pattern showed up on ECG or labs in those extensions. That is not the same as a lifetime guarantee, and it is not a licence to ignore nitrates or a new heart symptom. It is enough to file daily 5 mg as a studied habit, not a three-week stunt.
Where do I put Brock 2002 if I am trying to review daily Cialis?
Under the PRN carton. Brock's five-trial analysis and the 36-hour timing work cleared as-needed 10 and 20 mg in 2003. They do not measure a 2.5 or 5 mg breakfast swallow. Mixing those SEP3 percentages into a daily review is how people over-promise a small tablet. Use Brock for the weekend window. Use Rajfer, Porst, Hatzichristou and the integrated daily file for the 2008 carton. The Bothell dates keep the cartons apart.
Can a good IIEF score cancel a nitrate if I only take 2.5 mg?
No. Endpoints do not punch a hole in a contraindication. Nitrates plus tadalafil - 2.5 mg daily, 5 mg daily, or 20 mg PRN - can drop blood pressure to a dangerous level. The half-life keeps that risk on the calendar for more than a day. If a nitrate is still required, the PDE5 class is closed. If a cardiologist can retire the nitrate, that is a different conversation. The FDA states the ban without a milligram exception at the FDA.
General education from a clinician, not personal medical advice. Bring your own history to your own prescriber.
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