A long-acting oral medication that improves body-wide blood flow. Strong evidence supports treating erectile problems and enlarged-prostate urinary symptoms at a low daily dose. Weaker evidence suggests it improves blood-vessel health and modestly lowers blood pressure and blood sugar. Reports of longer life and fewer heart problems come from studies that cannot prove cause. (Full Review)

Protocol

Dose

2.5–5 mg daily

Continuous low dose mirroring the FDA-approved BPH regimen, not higher on-demand doses.

Timing

Same time each day

Steady-state dosing decouples effect from timing; many take it in the morning. Consistency matters more than the chosen hour.

Regimen

Single once-daily dose

The ~17.5-hour half-life gives near-continuous coverage; splitting the dose offers no advantage and is not used.

Time to effect

Erectile Function

Within hours

Vasodilatory effects begin within hours of the first dose; erectile benefit is often apparent quickly.

Urinary Symptoms

Days to a few weeks

Steady-state benefit of the daily regimen and BPH symptom improvement builds over days to a few weeks.

Vascular Changes

Over weeks

Urinary and vascular changes accrue over weeks rather than appearing immediately.

Benefits

High: Improved erectile function; relief of lower urinary tract symptoms from prostate enlargement

Medium: Improved vascular function and endothelial health; lower cardiovascular events and mortality; improved blood-sugar control

Low: Reduced vascular inflammation

Speculative: Reduced dementia and Alzheimer's risk; enhanced skeletal muscle perfusion and exercise capacity

Contraindications

Nitrates (nitroglycerin, isosorbide mononitrate, isosorbide dinitrate) and recreational nitrites ("poppers")

Guanylate cyclase stimulators (riociguat)

Recent heart attack (<90 days), unstable angina, or stroke

Severe or uncontrolled hypertension or hypotension (resting BP <90/50 mmHg)

Severe heart failure (NYHA Class III–IV)

Severe liver impairment (Child-Pugh Class C)

End-stage kidney disease on dialysis without dose adjustment

Hereditary degenerative retinal disorders

Prior non-arteritic anterior ischemic optic neuropathy

Key Interactions

Alpha-blockers (doxazosin, terazosin, tamsulosin, silodosin)

Other antihypertensives (ACE inhibitors, ARBs, calcium channel blockers, diuretics, beta-blockers)

Strong CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir, clarithromycin, grapefruit juice)

Strong CYP3A4 inducers (rifampin, carbamazepine, phenytoin)

Blood-pressure-lowering supplements (L-arginine, L-citrulline, beetroot/dietary nitrate, garlic extract, potassium)

Alcohol (substantial intake)

Risk & Side Effects

High: Severe hypotension with nitrates; headache, flushing, and common vasodilatory effects

Medium: Back pain and muscle aches; symptomatic hypotension with alpha-blockers and antihypertensives

Low: Visual and hearing disturbances; priapism

Speculative: Melanoma risk signal; long-term effects of continuous PDE5 inhibition

Monitoring

Marker	Target	Why
Blood pressure	~110–125 / 70–80 mmHg	Detects hypotension risk and tracks vascular effect
HbA1c	<5.4% (functional); <5.7% conventional non-diabetic cutoff	Tracks the metabolic/blood-sugar benefit in at-risk users
eGFR (kidney function)	>90 mL/min/1.73m²	Guides dosing; reduced clearance raises drug levels
ALT/AST (liver enzymes)	ALT <25 (men), AST <26 U/L functional; higher conventional cutoffs	Liver metabolizes the drug (CYP3A4); impairment alters clearance
IPSS (urinary symptom score)	0–7 (mild)	Quantifies prostate/urinary benefit over time

Cadence: Reassess blood pressure and tolerability at ~2–4 weeks after starting or any dose change, then periodically every 6–12 months; liver/kidney function as clinically indicated, and HbA1c or urinary scores repeated at 3–6 months if those were baseline targets.

Qualitative Assessment

Erectile function and spontaneity
Urinary flow, urgency, and frequency of nighttime urination
Energy and exercise tolerance
Presence or absence of side effects such as headache, flushing, back pain, or dizziness
Overall well-being and, where relevant, sexual confidence and relationship satisfaction

Tadalafil for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment