Onset: 30 minutes to 2 hours for first noticeable effect. Slower than sildenafil (which kicks in at ~30-60 min) — tadalafil is meant to be taken with the long arc in mind.

Peak: 2-4 hours post-dose at PRN doses (10-20 mg). At daily 2.5-5 mg, there is no real "peak" — it's a steady mild background.

Plateau: 24-36 hours of clinically meaningful PDE5 inhibition from a single PRN dose ("the weekend pill" nickname comes from this). At daily steady-state, there's no plateau, just a smooth baseline.

Taper: Gradual; ~17.5 hr half-life means ~50% gone at 17.5 hr, ~25% at 35 hr, traces out to ~72-96 hr.

Characteristic effects (most users at 2.5-5 mg daily):

• Slightly warmer hands and feet, mild facial flush sometimes
• Easier to get and maintain erections (whether or not ED is present)
• Marginal improvement in resting blood pressure
• Possible mild headache for the first few days, usually resolves
• Possible mild lower back / glute ache (PDE11 cross-reactivity) — often mistaken for training soreness
• No cognitive jolt, no euphoria, no felt CNS effect — this is a peripheral/vascular drug, not a stimulant

Characteristic effects at PRN higher doses (10-20 mg):

• Above effects amplified
• Headache more common (15-20% of users)
• Dyspepsia / reflux common (10-15%)
• Nasal congestion (~5%)

• Tolerance buildup: Minimal. Long-term studies in PAH, ED, and BPH show sustained efficacy across years of daily dosing without dose escalation. Receptor downregulation does not appear to be a clinical issue.
• Recommended cycle: None required. Daily indefinite use is FDA-approved.
• Reset protocol if needed: Not applicable.
• Dependence: None. Stopping is uncomplicated; no withdrawal syndrome.

Synergistic with

• citicoline: Theoretical complement — citicoline supports endothelial function and ACh-driven NO release; tadalafil amplifies the resulting vasodilation. No RCT but mechanism aligns.
• methylene-blue: Both touch NO/cGMP signaling but at different nodes — MB at low dose is a soluble guanylate cyclase modulator with mitochondrial effects; tadalafil downstream at PDE5. Combined use is biohacker-popular for cognitive blood flow but lacks RCT data. Watch BP if both used.
• l-citrulline / l-arginine: Direct NO precursors. Stack adds substrate to the NO arm of the same pathway tadalafil amplifies. Generally safe, mild additive BP effect.
• agmatine: NO modulator + nNOS inhibitor balance — theoretical complement for vascular cognitive flow.
• beta-alanine, taurine, creatine: Neutral; tadalafil doesn't interfere with any of these.

Avoid stacking with

• Nitrates (any form — nitroglycerin, isosorbide, "poppers"/amyl nitrite): ABSOLUTE CONTRAINDICATION. Severe, potentially fatal hypotension. No exceptions. Includes recreational poppers.
• Alpha-blockers (tamsulosin, doxazosin, terazosin): Caution — additive hypotension. Spaced dosing and lower starting dose required if combined. Not relevant for Dylan.
• Riociguat (Adempas) and other sGC stimulators: Contraindicated; redundant pathway hit.
• Strong CYP3A4 inhibitors (ketoconazole, ritonavir, clarithromycin): Reduce tadalafil dose by 50-75% or avoid; AUC can rise 3-5×.
• Strong CYP3A4 inducers (rifampin, carbamazepine, St. John's Wort): Significantly reduce exposure; clinical efficacy compromised.
• Heavy alcohol (>5 drinks): Additive vasodilation/orthostasis; mild-moderate intake is fine.

Neutral / safe co-administration

• Modafinil — no known interaction; unrelated metabolic and pharmacodynamic profiles.
• Caffeine, l-theanine, omega-3, magnesium, vitamin D, NAC, citicoline, beta-alanine, creatine, rhodiola — all neutral.
• Bromantane, semax, selank — neutral.
• Cerebrolysin — neutral.

• CYP3A4 substrate — tadalafil is metabolized primarily by CYP3A4. Strong inhibitors (azole antifungals, macrolides, protease inhibitors, grapefruit juice in heavy quantities) raise exposure 2-5×. Strong inducers (rifampin, phenytoin, carbamazepine, St. John's Wort) drop exposure significantly.
• No effect on warfarin INR.
• No effect on glucose / insulin — safe in diabetes.
• No HPG-axis effect — does not affect testosterone, LH, FSH meaningfully.
• Does not interact with WADA-monitored compounds in a way that's flagged — but check current WADA list before any tested competition (currently not banned).

• CYP3A4 polymorphisms: Slow-metabolizers may experience higher AUC and longer effect duration, faster metabolizers the opposite. 23andMe + interpretation tools (Promethease, GeneticGenie) cover key CYP3A4/5 SNPs — relevant for Dylan once results land in June.
• CYP3A5*3 (loss-of-function, very common in Whites): typical Northern European phenotype — minimal clinical impact for tadalafil at low dose.
• NOS3 (eNOS) polymorphisms (rs1799983 G894T): may modulate baseline NO production and therefore the magnitude of tadalafil's amplification effect, though this is not clinically actionable yet.
• No black-box pharmacogenomic warnings.

For Dylan: cleanest paths are (1) telehealth Rx + GoodRx for ~$15-20/mo legitimate, or (2) the Indian pharmacy he already uses for modafinil — split 20 mg pills with the pill cutter already in V4. Either works.

• Baseline (before starting):
  • Resting BP (3-day average, supine and standing)
  • HR
  • Lipid panel (HDL, LDL, ApoB)
  • hsCRP
  • Liver panel (ALT, AST)
  • Visual acuity / any baseline eye complaints noted
  • Subjective: erectile quality VAS, exercise tolerance VAS, headache frequency
• During use (every 4-8 weeks):
  • Resting BP and orthostatic BP
  • Headache frequency and severity
  • Any back/glute/myalgia tracking (separate from training soreness if possible)
  • Eye symptoms (any change → stop and consult)
  • Subjective: erectile quality, perceived exercise tolerance, perceived cognitive flow
• Post-cycle (if cycled): Not generally cycled, but if discontinuing: BP and erectile quality should return to baseline within 1-2 weeks.