The drug is generally safe for most men, but it is not devoid of side effects. Individuals with cardiovascular conditions, particularly those taking nitrate drugs for chest pain, are advised against using Viagra due to the risk of severe blood pressure drops. More serious but rare side effects can include priapism (a painful erection lasting longer than four hours), sudden hearing loss, or vision loss. Common adverse reactions include headaches, facial flushing, indigestion, nasal congestion, and, less commonly, lisinopril 15 mg tablets changes in vision such as increased sensitivity to light or blurred vision.
It has also spurred the development of other similar medications, such as tadalafil (Cialis) and vardenafil (Levitra), expanding the options available for erectile dysfunction treatment. Viagra’s introduction has also had significant social and cultural impacts. It has helped break the stigma associated with erectile dysfunction, bringing more openness to discussions about sexual health among men. The mechanism by which Viagra operates is through the inhibition of phosphodiesterase-5 (PDE5), an enzyme that promotes the breakdown of cyclic guanosine monophosphate (cGMP).
In the presence of sexual stimulation, nitric oxide is released in the corpus cavernosum, part of the penis, which activates the enzyme guanylate cyclase. By inhibiting PDE5, Viagra enhances the effect of nitric oxide and cGMP, leading to improved erectile function. This enzyme increases levels of cGMP, leading to smooth muscle relaxation and inflow of blood to the penile tissues, thereby producing an erection.
The mechanism of action of Viagra centers on its effects on the nitric oxide (NO) pathway. This compound relaxes smooth muscle tissue, allowing increased blood flow into the penis, leading to an erection. NO activates an enzyme called guanylate cyclase, which increases levels of cyclic guanosine monophosphate (cGMP). Nitric oxide is a naturally occurring compound in the body that plays a key role in the initiation and maintenance of an erection. During sexual stimulation, NO is released in the corpus cavernosum, a cylindrical tissue in the penis.
However, the effectiveness of Viagra can be influenced by certain factors such as the presence of food in the stomach, particularly high-fat meals, which can delay the onset of action. The clinical efficacy of Viagra has been demonstrated in numerous studies. It is effective in various populations of men with ED, including those with diabetes mellitus, spinal cord injury, and other conditions. Typically, Viagra is taken about one hour before sexual activity, and its effects can last for up to four hours.
Viagra is also used to treat other medical conditions. Notably, it is prescribed for pulmonary arterial hypertension (PAH) under the brand name Revatio. In this context, Viagra helps relax blood vessels in the lungs, improving blood flow and reducing the workload on the heart. However, it is important to note that an erection will not occur just by taking the pill; sexual stimulation is required for Viagra to work. It should be taken approximately one hour before sexual activity, and its effects can last up to four hours.
Viagra is administered orally and is available in 25 mg, 50 mg, and 100 mg doses. The recommended starting dose is typically 50 mg, adjusted based on effectiveness and toleration.