Maxon (Sildenafil)

Sildenafil acts on the nitric‑oxide/cGMP pathway to improve vascular smooth‑muscle relaxation in specific conditions.

• Erectile dysfunction: facilitates erection by increasing blood flow to the corpus cavernosum, helping men achieve and sustain sufficient rigidity for satisfactory sexual performance.
• Pulmonary arterial hypertension: causes pulmonary vasodilation, lowering arterial pressure and improving exercise tolerance in patients with this chronic lung vascular condition.
• Raynaud's phenomenon (off‑label): may reduce the frequency of vasospastic attacks by enhancing peripheral blood flow.

• Sildenafil selectively inhibits phosphodiesterase type 5 enzymes, preventing the breakdown of cyclic guanosine monophosphate (cGMP). Elevated cGMP levels lead to smooth‑muscle relaxation in the corpus cavernosum and pulmonary vasculature, thereby increasing blood flow to these tissues and producing the therapeutic effects.

Common Side Effects

• Headache
• Facial flushing
• Indigestion or dyspepsia
• Nasal congestion
• Visual disturbances (e.g., blurred vision, blue‑tinted vision)
• Back or muscle pain

Serious or Rare Side Effects

• Priapism (prolonged erection lasting more than 4 hours)
• Sudden loss of vision (non‑arteritic anterior ischemic optic neuropathy)
• Sudden hearing loss or tinnitus
• Cardiovascular events such as myocardial infarction or stroke
• Severe hypotension, especially when combined with nitrates

Before initiating therapy, patients should be evaluated for cardiovascular health and contraindications.

• Medical evaluation: assess cardiovascular status and underlying heart conditions.
• Nitrate use: avoid concurrent use with nitrates or nitric‑oxide donors due to risk of severe hypotension.
• Retinal disorders: use with caution in patients with retinitis pigmentosa or other retinal diseases.
• Alcohol consumption: limit excessive alcohol as it may increase the likelihood of side effects.
• Store at room temperature below 25°C: keep in the original packaging, protect from moisture and light.

Sildenafil may interact with several medication classes, requiring careful review.

Major Interactions (Avoid)

• Nitrates (e.g., nitroglycerin, isosorbide dinitrate): can cause dangerous drops in blood pressure.
• Potent CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, ritonavir): increase sildenafil plasma levels.
• Guanylate cyclase stimulators (e.g., riociguat): may lead to additive hypotensive effects.
• Alpha‑blockers (certain formulations): risk of marked hypotension.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce efficacy.
• Antihypertensive agents: monitor blood pressure for additive effects.
• Protease inhibitors (e.g., saquinavir): may modestly increase sildenafil exposure.
• Diuretics: watch for orthostatic hypotension.
• Other PDE5 inhibitors: avoid concurrent use to prevent overdose.