Sildenafil (Viagra) Urine Detection Window: What the Science Says
Sildenafil citrate (Viagra, generic) detection in urine depends on pharmacokinetics — not a fixed clock.
Pharmacokinetics Recap
- Absorption: Tmax 30–120 min (food delays).
- Half-life: 3–5 hours (healthy adults).
- Metabolism: CYP3A4 (major), CYP2C9 → N-desmethyl metabolite (active, ~50% potency).
- Excretion: 80% feces (biliary), 13% urine (mostly metabolites).
Detection Windows (Urine, Immunoassay/LC-MS)
| Dosing | Detectable Window | Peak Concentration |
|---|
| Single dose (25–100 mg) | 12–36 hours post-dose; up to 48 hrs in some | 2–4 hrs |
| Multiple doses (steady state) | 24–72 hours post-last-dose | Accumulation factor ~1.5 |
Variables That Shift the Window
- Renal function: Impaired → longer.
- Age: >65 → 40% higher AUC.
- CYP3A4 inhibitors: Ketoconazole, ritonavir, grapefruit → 2–4× AUC.
- CYP3A4 inducers: Rifampin, carbamazepine → shorter.
- Hydration: Dilute urine → lower concentration, longer detectability (more volume).
- Urine pH: Acidic → faster excretion of weak base.
Testing Context
- Sports (WADA): Sildenafil not prohibited (since 2009). No routine screening.
- Workplace: Rarely tested; not on standard 5/10-panel.
- Forensic/Postmortem: LC-MS/MS confirms exposure.
Bottom Line
Expect 1–2 days after single use, 2–3 days after repeated use. But "negative" doesn't prove non-use; "positive" doesn't prove impairment. Clinical context rules.
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