External links

Find more about Viagra on Wikipedia's sister projects:
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• Official Viagra Website
• Official Viagra UK Website
• Official Revatio Website
• prescribing information for Viagra and prescribing information for Revatio from Pfizer
• FDA Information
• MedlinePLUS information, including side effects
• U.S. National Library of Medicine: Drug Information Portal - Sildenafil
• Viagra bound to proteins in the PDB