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Tadalafil (Cialis)

PDE5 Inhibitorprescriptionoral · predicted

Long-acting selective PDE5 inhibitor for erectile dysfunction and BPH/LUTS. Unique 36-hour therapeutic window due to 17.5h half-life. Also available as 5 mg daily dosing for continuous coverage. Metabolized by CYP3A4. Can be taken with or without food.

Projected serum levels — 10 mg, as needed (shown daily)

Tadalafil (Cialis)
Tadalafil (Cialis) modeled serum levels, 10 mg as needed (shown daily) over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 3 days. 0 5 10 15 20 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 3
Tadalafil (Cialis) modeled serum levels with a loading dose of 19.7 mg, then 10 mg as needed (shown daily) The first dose is larger so levels approach steady state faster. 0 5 10 15 20 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 10 mg as needed (shown daily) (oral).

Loading schedule: 19.7 mg on day 1, then 10 mg as needed (shown daily) — reaching therapeutic levels sooner.

Modeled steady state after ~3 days: peak ≈ 13.6 mg, trough ≈ 8.1 mg body load. Population-based estimate over 15 days for a 10 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
PDE5 Inhibitor
Route modeled
Oral
Model confidence
predicted
Half-life
18 h
Common dose
10 mg
Suggested maximum
40 mg/day
Reference dose range
2.5–40 mg (single dose)
Suggested cadence
as needed (shown daily)
Validated against
20 mg oral — Cmax 0.30 mg/L at 2 h

Documented interactions

  • contraindicated
    Carbamazepine (Tegretol) + Tadalafil (Cialis) CYP induction

    Carbamazepine (Tegretol) inducer of CYP3A4 predicted to change Tadalafil (Cialis) AUC by ~0.20x

  • contraindicated
    Clarithromycin (Biaxin) + Tadalafil (Cialis) CYP inhibition

    Clarithromycin (Biaxin) mechanism_based of CYP3A4 predicted to change Tadalafil (Cialis) AUC by ~10.00x

  • contraindicated
    Dasatinib (Sprycel) + Tadalafil (Cialis) CYP inhibition

    Dasatinib (Sprycel) time_dependent_inhibitor of CYP3A4 predicted to change Tadalafil (Cialis) AUC by ~5.00x

  • contraindicated
    Diltiazem + Tadalafil (Cialis) CYP inhibition

    Diltiazem mechanism_based of CYP3A4 predicted to change Tadalafil (Cialis) AUC by ~10.00x

  • contraindicated
    Efavirenz (Sustiva) + Tadalafil (Cialis) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Tadalafil (Cialis) AUC by ~0.12x

  • contraindicated
    Grapefruit (whole fruit) + Tadalafil (Cialis) CYP inhibition

    Grapefruit (whole fruit) mechanism_based of CYP3A4 predicted to change Tadalafil (Cialis) AUC by ~10.00x

Serum checks 63 modeled interaction pairings for tadalafil (cialis) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Tadalafil pharmacokinetics in healthy subjects Forgue ST et al. · British Journal of Clinical Pharmacology, 2006 DOI

    Definitive PK study establishing tadalafil mean half-life of 17.5 hours, linear pharmacokinetics, 94% protein binding, and no clinically significant food effect on absorption.

  2. Efficacy and safety of tadalafil once daily in the treatment of men with lower urinary tract symptoms suggestive of BPH Oelke M et al. · European Urology, 2012 DOI

    International phase III RCT demonstrating tadalafil 5 mg daily significantly improved IPSS by -6.1 points versus -3.8 for placebo in men with BPH-related LUTS.

  3. Tadalafil in the treatment of erectile dysfunction Brock GB et al. · International Journal of Impotence Research, 2002 DOI

    Multicenter dose-response study of 1,112 men with ED showing tadalafil 10 and 20 mg significantly improved erectile function, with a 36-hour window of responsiveness supporting flexible timing.

3 published studies referenced in the app, each with a plain-language summary.