Maxon (Sildenafil Citrate)

Sildenafil citrate is employed in vascular‑related disorders where inhibition of phosphodiesterase‑5 leads to increased cyclic GMP and smooth‑muscle relaxation, thereby improving blood flow.

• Erectile dysfunction: enhances penile blood flow, facilitating the achievement and maintenance of an erection sufficient for sexual intercourse in men with this condition.
• Pulmonary arterial hypertension: reduces pulmonary vascular resistance, lowering arterial pressure and improving exercise tolerance in patients with this chronic lung vascular disease.

• Sildenafil citrate selectively inhibits the enzyme phosphodiesterase type 5 (PDE5) in smooth‑muscle cells. By blocking PDE5, it prevents the breakdown of cyclic guanosine monophosphate (cGMP), allowing cGMP to accumulate. Elevated cGMP leads to relaxation of smooth muscle in the corpus cavernosum and pulmonary vasculature, increasing blood flow to these regions and producing the therapeutic effect.

Common Side Effects

• Headache: mild to moderate pain often described as tension‑type.
• Flushing: warmth and reddening of the face or upper chest.
• Dyspepsia: indigestion or upset stomach.
• Nasal congestion: stuffy or runny nose.
• Visual disturbances: blurred vision or a blue‑tinted visual field.
• Dizziness: light‑headed sensation, especially on standing.

Serious or Rare Side Effects

• Priapism: prolonged erection lasting more than four hours, requiring urgent medical attention.
• Sudden vision loss: non‑arteritic anterior ischemic optic neuropathy.
• Sudden hearing loss: unexplained decrease or loss of hearing.
• Cardiovascular events: myocardial infarction or stroke, particularly in high‑risk patients.
• Severe hypotension: marked drop in blood pressure causing faintness.

Before initiating therapy, evaluate cardiovascular status and contraindications.

• Assess cardiovascular health: ensure the patient can tolerate sexual activity.
• Avoid concurrent nitrates: co‑administration can cause severe hypotension.
• Use caution with hepatic impairment: dose adjustments may be needed.
• Do not exceed prescribed dose: higher doses increase risk of adverse events.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Sildenafil citrate may interact with several medication classes.

Major Interactions (Avoid)

• Nitrates (e.g., nitroglycerin): risk of profound hypotension.
• Nitric‑oxide donors (e.g., riociguat): additive blood‑pressure lowering effect.
• Guanylate cyclase stimulators: may amplify vasodilatory response.

Moderate Interactions (Monitor Closely)

• Antihypertensives: may enhance blood‑pressure reduction.
• CYP3A4 inhibitors (e.g., ketoconazole): increase sildenafil plasma levels.
• CYP3A4 inducers (e.g., rifampin): decrease sildenafil effectiveness.
• Alpha‑blockers: may cause additive hypotensive effects.
• Protease inhibitors (e.g., ritonavir): raise sildenafil concentrations.