Tadalafil
Tadalafil is a long-acting PDE5 inhibitor known for its ~17.5-hour half-life, which allows once-daily low-dose use ('the weekender'). It is used for erectile dysfunction and benign prostatic hyperplasia, and among PED users it is popular for daily low-dose administration to support erectile function and blood pressure across a suppressive cycle without timing doses to activity.
01 Overview
Tadalafil inhibits PDE5 like sildenafil but has a much longer duration of action and, unlike sildenafil and vardenafil, does not meaningfully inhibit retinal PDE6, so visual side effects are uncommon. Its long half-life supports both on-demand dosing and a continuous daily 2.5-5 mg regimen that keeps steady-state PDE5 inhibition.
In the androgen-using population daily tadalafil is favoured for convenience and for its mild blood-pressure-lowering and lower-urinary-tract benefits. Some also use it speculatively for a sustained 'pump'. The same nitrate contraindication as all PDE5 inhibitors applies, and its long duration means an interacting hypotensive effect can persist for a day or more.
02 Mechanism
Long-acting selective inhibitor of PDE5, raising cGMP in cavernosal and vascular smooth muscle; minimal PDE6 cross-reactivity.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Daily low-dose | 2.5–5 mg/day | Oral | Continuous once-daily dosing for ED and/or BPH; steady erectile support without timing. |
| On-demand | 10–20 mg | Oral | Taken as needed; effect can last 24-36 hours. |
| Pulmonary hypertension (label) | 40 mg/day | Oral | Adcirca dosing; not for routine ED use. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Sustained erectile supportLong duration allows spontaneity; daily dosing gives continuous responsiveness. | up to 36 h window | Clinical | |
| Improved lower urinary tract symptomsApproved for BPH; relaxes prostatic and bladder-neck smooth muscle. | modest | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Back pain and myalgiaDelayed back and muscle pain, more characteristic of tadalafil than other PDE5 inhibitors. | Mild | Common | Clinical | |
| Headache and flushingVasodilatory headache, flushing and dyspepsia. | Mild | Very common | Clinical | |
| Nitrate interaction (severe hypotension)Additive hypotension with nitrates, prolonged by tadalafil's long half-life. | Life-threatening | Rare but potentially fatal | Clinical |