Sildenafil
/ Phosphodiesterase type 5 (PDE-5) inhibitor; pyrazolopyrimidinone classALIAS · Viagra (trade) · Revatio (trade) · Sildenafil citrate
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Tier 1. FDA-approved 1998 for erectile dysfunction (Viagra) and 2005 for pulmonary arterial hypertension (Revatio). Decades of post-marketing data; gold-standard reference for the PDE-5 inhibitor class.
Sildenafil selectively inhibits cGMP-degrading PDE-5, the predominant phosphodiesterase isoform in corpus cavernosum smooth muscle and pulmonary vasculature. Inhibition prolongs the action of nitric-oxide-mediated cGMP signalling, producing smooth-muscle relaxation, vasodilation, and (with sexual stimulation) penile erection. The pulmonary vasculature also expresses PDE-5, providing the mechanistic basis for the PAH indication.
Tier 1. Pivotal Goldstein 1998 NEJM trial in erectile dysfunction; pivotal SUPER-1 trial in pulmonary arterial hypertension supporting Revatio approval.
Well-characterised: headache, flushing, dyspepsia, transient blue-green color vision changes (PDE-6 cross-reactivity). Contraindicated with nitrate co-administration due to potentiated hypotension. Rare cases of non-arteritic anterior ischaemic optic neuropathy (NAION) and sudden sensorineural hearing loss have led to label warnings; causal relationship debated.
Regulatory status
- FDA status:
- FDA-approved
- Compounding:
- Not eligible for compounding (approved, not in shortage)
The 'research peptide' framing is misplaced — sildenafil is a small molecule (not a peptide) and an FDA-approved generic prescription drug since 2017. Pepticker tracks it because some of the same vendors selling research peptides also sell sildenafil; that does not put it in the peptide research category.