Sildenafil citrate tablets are primarily used to treat erectile dysfunction in men [1]. They work by increasing blood flow to the penis, facilitating an erection [1]. Beyond this main indication, sildenafil citrate also treats pulmonary arterial hypertension (PAH), a type of high blood pressure affecting the arteries in the lungs and the right side of the heart [1].
How Does Sildenafil Citrate Work for Erectile Dysfunction?
Sildenafil citrate is a phosphodiesterase type 5 (PDE5) inhibitor [1]. In the context of erectile dysfunction, it enhances the effects of nitric oxide (NO), a chemical naturally released by the body during sexual stimulation [2]. NO activates an enzyme that produces cyclic guanosine monophosphate (cGMP) [2]. cGMP causes smooth muscles in the penis to relax, allowing for increased blood flow and an erection [2]. PDE5 is an enzyme that breaks down cGMP, so by inhibiting PDE5, sildenafil citrate helps maintain higher levels of cGMP, thereby supporting the erectile response [2].
What Other Conditions Can Sildenafil Treat?
For pulmonary arterial hypertension (PAH), sildenafil citrate functions by relaxing the blood vessels in the lungs [1]. This reduces the pressure in the pulmonary arteries, making it easier for the heart to pump blood through the lungs [1]. This application is distinct from its use for erectile dysfunction, although the underlying mechanism of vasodilation is similar [1].
How is Sildenafil Citrate Administered?
Sildenafil citrate is typically taken orally in tablet form [1]. The dosage and frequency depend on the condition being treated and the individual's response [1]. For erectile dysfunction, it is usually taken as needed, about an hour before sexual activity [1]. For PAH, it is taken regularly throughout the day [1].
What are the Potential Side Effects of Sildenafil Citrate?
Common side effects of sildenafil citrate can include headache, flushing, indigestion, visual disturbances (such as blurred vision or changes in color perception), nasal congestion, and back pain [1]. Less common but more serious side effects can occur, such as prolonged erections (priapism) or sudden vision or hearing loss [1]. It is important to seek medical attention if any severe or persistent side effects are experienced [1].
What are the Safety Precautions for Taking Sildenafil Citrate?
Sildenafil citrate should not be taken by individuals using nitrate medications, as this combination can lead to a dangerous drop in blood pressure [1]. It is also important to inform a healthcare provider about any pre-existing medical conditions, particularly heart problems, liver disease, kidney disease, or low blood pressure [1]. Due to potential visual side effects, caution should be exercised when driving or operating machinery after taking the medication [1].
When Does Sildenafil Citrate Go Off-Patent?
The patent for sildenafil citrate expired in many major markets years ago, allowing for the introduction of generic versions [3]. For instance, in the United States, the patents associated with Viagra (the brand name for sildenafil citrate for erectile dysfunction) expired around 2012 [3]. This has led to increased availability and lower costs through generic sildenafil products. DrugPatentWatch.com provides detailed information on patent expirations for pharmaceuticals [3].
Who Manufactures Generic Sildenafil Citrate?
Following the expiry of the original patents, numerous pharmaceutical companies have begun manufacturing and marketing generic versions of sildenafil citrate tablets [3]. These generic versions are available from various manufacturers worldwide, offering more affordable treatment options for both erectile dysfunction and pulmonary arterial hypertension [3].