Sildenafil
Sildenafil Citrate
Overview
Sildenafil (Viagra/Revatio) is a phosphodiesterase type 5 (PDE5) inhibitor FDA-approved for erectile dysfunction and pulmonary arterial hypertension. It is one of the best-selling pharmaceuticals in history with one of the largest clinical evidence bases of any drug — thousands of controlled trials across ED pulmonary hypertension altitude sickness and various investigational applications. While technically a small molecule rather than a peptide sildenafil is fundamental to the sexual health pharmacology landscape and serves as the benchmark against which newer sexual health peptides are compared.
Mechanism of Action
Sildenafil inhibits PDE5 — the enzyme that breaks down cyclic GMP (cGMP) in vascular smooth muscle. In the penis sexual stimulation triggers nitric oxide release from cavernous nerves which activates guanylate cyclase producing cGMP. cGMP causes smooth muscle relaxation in the corpora cavernosa increasing blood flow and producing erection. By inhibiting PDE5 sildenafil prevents cGMP breakdown prolonging and enhancing the natural erectile response to sexual stimulation. The critical distinction from bremelanotide is mechanism dependency — sildenafil requires sexual stimulation to work because it amplifies the natural NO/cGMP pathway rather than generating desire de novo. In pulmonary hypertension the same mechanism reduces pulmonary vascular resistance through PDE5 inhibition in pulmonary arterial smooth muscle.
Dosage Information
Typical Dose
25-100 mg as needed for ED. 20 mg three times daily for pulmonary hypertension.
Frequency
As needed for ED (30-60 minutes before sexual activity). TID dosing for PAH.
Administration
Oral tablet
Notes
Requires sexual stimulation to produce erection — does not cause spontaneous erections. Avoid with nitrates (absolute contraindication — dangerous hypotension). Food slows absorption. Grapefruit juice increases drug levels.
Where does Sildenafil sit?
See how this peptide compares across all 111 peptides in our database.
Evidence Score
0.73
Compound Data
Molecular Formula
C22H30N6O4S
Molecular Weight
474.60 g/mol
IUPAC Name
5-[2-ethoxy-5-(4-methylpiperazin-1-yl)sulfonylphenyl]-1-methyl-3-propyl-6H-pyrazolo[4,5-d]pyrimidin-7-one
PubChem CID
135398744Potential Side Effects
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Quick Facts
- Administration
- Oral tablet
- Typical Dose
- 25-100 mg as needed for ED. 20 mg three times daily for pulmonary hypertension.
- Frequency
- As needed for ED (30-60 minutes before sexual activity). TID dosing for PAH.
- References
- 0 curated + 47 from PubMed
- Clinical Trials
- 50 registered
- Evidence Score
- 0.7 / 100