Sexual Health & Vascular

Sildenafil Citrate

A potent, selective inhibitor of cGMP-specific phosphodiesterase type 5 (PDE5). While standardly prescribed for ED, functional applications extend to endothelial rehabilitation, pulmonary arterial modulation, and systemic nitric oxide optimization.

HALF-LIFE
3-4 HOURS
BIOAVAILABILITY
41% (AVG)
METABOLISM
CYP3A4
ONSET
30-60 MIN

Primary Targets

  • Corpus Cavernosum Smooth muscle relaxation via NO/cGMP pathway.
  • Pulmonary Vasculature Reduction of pulmonary vascular resistance.
  • Endothelium (Systemic) Improvement of flow-mediated dilation.
> SELECT A TARGET SYSTEM ABOVE FOR FUNCTIONAL CONTEXT

Pharmacokinetics & Timing

Understanding the absorption window is critical for therapeutic efficacy. High-fat meals drastically alter the Tmax and Cmax, a common cause of "treatment failure" in functional protocols.

ABSORPTION LAG

In a fasted state, Tmax is reached within 30-120 minutes (median 60).

PEAK CONCENTRATION

Cmax reduced by ~29% when taken with a high-fat meal.

DURATION WINDOW

Therapeutic window persists for approximately 4 hours. Terminal half-life is 4 hours.

Clinical Nuance & Quirks

01
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Cyanopsia

"Blue Vision". Sildenafil has 10% affinity for PDE6 (retina) vs PDE5. High doses may cause transient blue tinge to vision.

02
🧠

Auditory Shift

Rare sudden decrease or loss of hearing, sometimes accompanied by tinnitus and dizziness.

03
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NO Boosters

Synergistic hypotension risk. Patients supplementing heavily with L-Citrulline or Nitrates may experience exaggerated BP drops.

04
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Reflux/GERD

Lower Esophageal Sphincter (LES) is smooth muscle. PDE5i causes relaxation of the LES, exacerbating GERD.

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Dosing & Cycles

THE "WASHOUT" PERIOD

Tachyphylaxis (tolerance) to PDE5i is debated but observed in clinical practice. Functional dosing often utilizes "Holidays" to reset NO sensitivity.

ON CYCLE OFF CYCLE
6-8 WEEKS 1-2 WEEKS