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ViagraAka: Sildenafil
- Indications
- Psychogenic Impotence
- Neurogenic Impotence
- Vasculogenic Impotence
- Contraindications
- Absolute Contraindications
- Men using nitrates (causes profound hypotension)
- Relative Contraindications
- Active coronary ischemia in men not on nitrates
- Congestive Heart Failure
- Borderline low Blood Pressure
- Bordrline low volume status
- Multidrug antihypertensive regimen
- Taking Cytochrome P450-3A4 (CYP3A4) inhibitor
- Areas where sildenafil may be used safely
- Safe in stable coronary disease (no nitrates)
- Debusk (2004) Am J Cardiol 93:147
- Mechanism
- Phosphodiesterase Type 5 causes Erection to subside
- Viagra blocks Phosphodiesterase Type 5
- Results in enhanced Erection if man is aroused
- Unlike Alprostadil, will not cause Erection
- Viagra enhances vasodilating effect of Nitrous Oxide
- Normally released during sexual stimulation
- Pharmacokinetics
- 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
- Efficacy
- Benefits those with organic and psychological Impotence
- Initial studies showed improved Erections in 70%
- Over Placebo, 3.6 times more likely to improve Erection
- Burls (2001) Br J Gen Pract 51:1004
- Drug Interactions
- Inhibit breakdown of Viagra via Cytochrome P3A4
- Cimetidine (Tagamet)
- Erythromycin
- Ketoconazole (Nizoral)
- Itraconazole (Sporonox)
- Mibefradil (Posicor)
- Profound Vasodilitation and Hypotension (Avoid)
- Nitrates
- Adverse Effects
- Hypotensive effect for men on Nitrates (Avoid)
- Vision effects
- Temporary color vision disturbance (6%)
- Blue colors may appear to be green
- Blurred vision or vision loss
- Higher risk if atherosclerosis
- Rare occurence, but can be permanent
- Appears to occur with Levitra and Cialis as well
- Mild Headache (21%)
- Facial Flushing (27%)
- Indigestion or Dyspepsia (11%)
- Does not cause Priapism
- Cost
- Wholesale: $7 per pill
- Reference
- Boolell (1996) Br J Urol 78:257
- Cheitlin (1999) J Am Coll Cardiol 33:273
- (1998) Med Lett Drugs Ther 40(1026):51
- Rendell (1999) JAMA 281(5):421
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| Definition (PDQ) | The citrate salt of a pyrazolopyrimidinone derivative structurally related to zaprinast. Sildenafil selectively inhibits cyclic guanosine monophosphate (cGMP)-specific type 5 phosphodiesterase, resulting in vasodilation in the corpus cavernosum of the penis and penile erection. Check for "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=269137&idtype=1" active clinical trials or "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=269137&idtype=1&closed=1" closed clinical trials using this agent. ("http://nciterms.nci.nih.gov:80/NCIBrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&code=C26670" NCI Thesaurus) |
| Concepts | Organic Chemical (T109)
, Pharmacologic Substance (T121)
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| English | sildenafil, SILDENAFIL PREPARATION |
| Spanish | sildenafil, sildenafilo |
| Credits | Derived from the NIH UMLS (Unified Medical Language System)
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| Concepts | Organic Chemical (T109)
, Pharmacologic Substance (T121)
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| English | Abbott brand of sildenafil citrate, Pfizer brand 1 of sildenafil citrate, Viagra |
| Credits | Derived from the NIH UMLS (Unified Medical Language System)
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