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Viagra
Aka: Viagra, Sildenafil
- Indications
- Psychogenic Impotence
- Neurogenic Impotence
- Vasculogenic Impotence
- Pharmacokinetics
- Onset 30-60 minutes
- Duration: 4-5 hours
- Peak: 1 hour if taken while Fasting
- Peak delayed by 1 hour if taken with fatty meal
- Half Life: 4 hours
- Metabolized by Liver and excreted mostly in stool
- Clearance delayed in age over 65 years
- Clearance delayed in Liver disease
- Dosing
- Start 50 mg PO 1 hour before intercourse
- Do not take more than once per day
- Most insurance limits to 6 per month
- Indications to start with half dosing (25 mg)
- Age over 65 years
- Hepatic Impairment
- Renal Impairment
- Consider crushing tablet and placing under Tongue
- May increase onset of action to 15 minutes
- May also increase absorption
- Consider lowering dose
- Cost
- Wholesale: $7 per pill
- Contraindications
- See Phosphodiesterase Inhibitors (PDE5 Inhibitors)
- Men using nitrates (causes profound Hypotension)
- Men using alpha blockers (e.g. Hytrin for BPH)
- Mechanism
- See Phosphodiesterase Inhibitors (PDE5 Inhibitors)
-
Drug Interactions
- See Phosphodiesterase Inhibitors (PDE5 Inhibitors)
- Profound Vasodilitation and Hypotension with Nitroglycerin and alpha blockers such as Prazosin (Avoid)
- Cytochrome P3A4 related interactions (Cimetidine, systemic Antifungals, Protease Inhibitors and Macrolides
- Adverse Effects: Viagra (but most apply to the PDE5 Class as a whole)
- See Phosphodiesterase Inhibitors (PDE5 Inhibitors)
- Hypotensive effect for men on Nitrates (Avoid)
- Vision effects (color vision, Vision Loss)
- Sensorineural Hearing Loss
- Mild Headache
- Reference
- Boolell (1996) Br J Urol 78:257-61 [PubMed]
- Cheitlin (1999) J Am Coll Cardiol 33:273-82 [PubMed]
- (1998) Med Lett Drugs Ther 40(1026):51-2 [PubMed]
- Rendell (1999) JAMA 281(5): 421-26 [PubMed]