Pulmonary hypertension (PH) is a serious, progressive condition characterized by abnormally high blood pressure in the lung arteries, straining the right side of the heart. This elevated pressure makes it harder for the heart to pump blood through the lungs, leading to symptoms like shortness of breath, fatigue, and chest pain. Sildenafil is used to manage PH symptoms, aiming to improve exercise capacity and overall quality of life.
How Sildenafil Works in Pulmonary Hypertension
Sildenafil works by inhibiting phosphodiesterase-5 (PDE5), an enzyme found in the smooth muscle cells of the pulmonary arteries. Normally, nitric oxide (NO) stimulates cyclic guanosine monophosphate (cGMP), which promotes blood vessel relaxation and widening. PDE5 breaks down cGMP, limiting this effect.
By inhibiting PDE5, sildenafil prevents cGMP breakdown, increasing its levels in the pulmonary arteries. This causes the blood vessels to relax and widen, a process known as vasodilation. As a result, blood pressure in the lungs decreases, reducing the heart’s workload and allowing for easier blood flow.
Who Sildenafil is Prescribed For and How to Take It
Sildenafil is primarily prescribed for adults with pulmonary arterial hypertension (PAH), particularly those classified under World Health Organization (WHO) Group 1. This includes idiopathic PAH, PAH associated with connective tissue diseases, or PAH following repair of a congenital heart shunt. The medication aims to enhance exercise tolerance and delay the worsening of the condition.
It is available as 20 mg tablets, an oral suspension (10 mg/mL), and an injectable solution for hospital use. For adults, a typical starting dose is 20 mg taken three times daily, spaced approximately four to six hours apart. A healthcare provider may adjust the dose based on individual response and tolerability, potentially increasing it up to 80 mg three times a day. Always adhere strictly to the prescribed dosage and frequency.
Important Safety Information and Precautions
Patients taking sildenafil may experience side effects. Common ones include headaches, facial flushing, indigestion, nosebleeds, stuffy nose, difficulty sleeping, or upset stomach. These are generally mild and often resolve, but consult a healthcare professional if they persist or become bothersome.
More serious, though rare, side effects require immediate medical attention. These include sudden loss of vision (e.g., non-arteritic anterior ischemic optic neuropathy, NAION) or hearing (sometimes with ringing in ears and dizziness). Male patients should seek urgent care for an erection lasting longer than four hours (priapism), as it can lead to permanent damage. Severe allergic reactions, such as skin rash, hives, or swelling of the face, lips, tongue, or throat, also require immediate medical intervention.
Sildenafil must never be taken with nitrate medications, like nitroglycerin, often prescribed for chest pain. This combination can cause a dangerous and potentially fatal drop in blood pressure. Always inform your doctor about all medications, including over-the-counter drugs, supplements, and herbal remedies, before starting sildenafil.
Other drug interactions can occur. For example, certain alpha-blockers (for high blood pressure or prostate issues) can also lead to a significant drop in blood pressure. Protease inhibitors (for HIV) can increase sildenafil levels, potentially enhancing effects and side effects. Strong inhibitors of the CYP3A4 liver enzyme, like certain antifungal medications (e.g., ketoconazole, itraconazole) and some antibiotics (e.g., erythromycin), can affect how the body processes sildenafil, requiring careful dosage adjustments. Patients with low blood pressure, severe liver impairment, or pulmonary veno-occlusive disease should use sildenafil with caution.