Tadalafil
Cialis, Adcirca
Long-acting PDE5 inhibitor. The 17-hour half-life makes daily low-dose use practical, which is why it is the one people build into a stack rather than take situationally.
FDA-approved
FDA-approved for erectile dysfunction, benign prostatic hyperplasia, and - as Adcirca - pulmonary arterial hypertension. Available generically and inexpensively with a prescription.
What it is
Tadalafil inhibits phosphodiesterase type 5, the enzyme that degrades cGMP in vascular smooth muscle. Blocking it means cGMP persists, smooth muscle stays relaxed, and blood flow increases - in the penis, and to a lesser extent in the prostate, lungs and systemic vasculature.
It is one of only two compounds in this reference that is both approved and cheap, which is worth stating plainly given how much of this site documents unapproved material.
Why the half-life changes the strategy
Sildenafil lasts around 4 hours. Tadalafil lasts around 17.5 - roughly a day and a half of coverage from a single dose, which is where the "weekend pill" nickname came from.
That duration enables low-dose daily use, and daily use is a different intervention from as-needed use:
- Effect becomes continuous rather than scheduled, removing the timing problem entirely.
- It is the dosing pattern approved for BPH - daily tadalafil improves lower urinary tract symptoms.
- Sustained PDE5 inhibition is the basis of the endothelial-function arguments that make it a longevity-community staple. Those effects are real in mechanistic terms; the hard-outcome evidence is thinner than the enthusiasm.
Practical notes
- Nitrates are an absolute contraindication. Not a caution. The combination causes profound hypotension, and this includes recreational nitrite poppers, which is the version that actually sends people to emergency rooms.
- Alpha-blockers for blood pressure or prostate need dose separation and medical supervision.
- PDE5 inhibitors do not create desire. They address the vascular step. Low libido with normal erectile function is a different problem, usually hormonal - which is where enclomiphene enters the same conversation.
- Do not stack PDE5 inhibitors. Tadalafil plus vardenafil compounds hypotension without adding benefit.
- New erectile dysfunction is a cardiovascular signal. The penile arteries are small and narrow first. Treating the symptom without investigating the cause misses the more important finding.
Side effects and warning signs
Commonly reported
- Headache - the most common by a wide margin
- Flushing and nasal congestion
- Back and muscle aches, more characteristic of tadalafil than of other PDE5 inhibitors
- Indigestion and reflux
- Blood pressure reduction
Stop and get medical help
- Erection lasting over 4 hours - priapism is a medical emergency and delay costs tissue
- Sudden vision or hearing loss
- Chest pain during sexual activity
- Absolute contraindication with nitrates in any form - the combination can cause catastrophic hypotension. This includes recreational amyl nitrite poppers
Sources
From the community
Discussion for this compound concentrates in r/Biohackers.
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