Sildenafil is an inexpensive prescription oral medication, approved for erectile problems in men, that strengthens the body's own blood vessel–relaxing signal. Its best-established benefit is reliably improved erectile and sexual function; it also helps certain circulation problems and modestly improves measures of blood vessel health. Links to longer survival come from prescription records, not controlled trials, and remain unproven. With nitrate heart medications, it can dangerously drop blood pressure. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Blood pressure (seated and standing) | Seated <120/80 mm Hg; standing drop <20/10 mm Hg | Detects hypotension risk |
| ApoB | <80 mg/dL (<60 mg/dL for higher-risk individuals) | Cardiovascular risk baseline |
| HbA1c | <5.4% | Glucose control affects response |
| Fasting insulin | <6 µIU/mL | Tracks insulin sensitivity |
| eGFR | >90 mL/min/1.73 m² | Sets starting dose |
| ALT | <25 U/L | Liver clearance of the drug |
| Total testosterone (men) | 500–900 ng/dL | Low levels blunt response |
| IIEF-5 score (men) | 22–25 | Tracks erectile function |
| hs-CRP | <1.0 mg/L | Vascular inflammation baseline |
Cadence: Baseline before starting; blood pressure rechecked 1–2 hours after the first doses and at 4 weeks; for daily users, labs at 3 months, then every 6–12 months; erectile function questionnaires at 4–8 weeks