Viagra contraindications
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Contraindications of Viagra: A Comprehensive Overview
Cardiovascular Contraindications
Use with Nitrates
Viagra (sildenafil citrate) is absolutely contraindicated in patients who are taking any form of nitrate medication, such as glyceryl trinitrate or isosorbide dinitrate. The combination of Viagra with nitrates can lead to severe drops in blood pressure, which can be life-threatening 1345.
Cardiac Conditions
Patients with certain cardiac conditions should exercise caution when using Viagra. It is inadvisable for those with unstable angina pectoris, and it should be used cautiously in individuals with cardiac failure or those who have experienced an acute myocardial infarction or stroke within the past six months . Additionally, patients with uncontrolled hypertension and impaired cardiac reserve are advised against using Viagra .
Myocardial Infarction Risk
There have been reports of myocardial infarction following the use of Viagra, particularly when combined with other substances such as cannabis, which can inhibit the cytochrome P450 3A4 isoenzyme responsible for metabolizing Viagra . Therefore, patients with a history of heart disease or those at risk should consult their physician before using the medication .
Drug Interactions
Cytochrome P450 System
Viagra is metabolized predominantly by the cytochrome P450 3A4 hepatic microsomal isoenzyme. While medications that affect this system can influence the metabolism of Viagra, these interactions do not typically translate into significant clinical effects . However, caution is advised when Viagra is used in combination with other drugs that inhibit this enzyme .
Ophthalmologic Considerations
Visual Side Effects
Viagra has a mild inhibitory effect on PDE6, which controls the level of cyclic guanosine monophosphate in the retina. This can cause visual disturbances such as a perception of bluish haze or increased light sensitivity in some patients. Although long-term retinal damage has not been reported, patients should be aware of these potential side effects .
Online Prescribing Risks
Quality and Safety Concerns
The sale of Viagra over the Internet poses significant risks, especially when prescriptions are issued without proper medical oversight. Studies have shown that many online pharmacies dispense Viagra without taking a complete medical history or using appropriate medical terminology, which can lead to the drug being prescribed despite clear contraindications . This underscores the importance of obtaining Viagra through legitimate medical channels to ensure safety.
Conclusion
Viagra is a widely used and generally safe treatment for erectile dysfunction when taken under proper medical supervision. However, it is contraindicated in patients taking nitrates, those with certain cardiovascular conditions, and those at risk of myocardial infarction. Additionally, potential visual side effects and the risks associated with online prescribing highlight the need for caution and proper medical guidance when using this medication.
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