Katora (Sildenafil Citrate)

Sildenafil citrate is indicated for conditions involving the nitric oxide–cGMP pathway where enhanced vasodilation is therapeutic.

• Erectile dysfunction: improves ability to achieve and maintain an erection sufficient for sexual activity.
• Pulmonary arterial hypertension: lowers pulmonary arterial pressure and enhances exercise capacity.
• Pulmonary hypertension‑related symptoms: reduces shortness of breath and improves functional class in affected patients.

• Sildenafil citrate selectively inhibits phosphodiesterase type 5 enzymes, preventing the breakdown of cyclic guanosine monophosphate (cGMP). Elevated cGMP levels cause relaxation of smooth muscle in the corpus cavernosum and pulmonary vasculature, resulting in increased blood flow to these tissues and facilitating erection or reducing pulmonary arterial pressure.

Sildenafil citrate may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Headache
• Facial flushing
• Dyspepsia or indigestion
• Nasal congestion
• Visual disturbances (e.g., blurred vision, color tinge)
• Back pain or muscle aches

Serious or Rare Side Effects

• Priapism (prolonged erection)
• Sudden loss of vision (non‑arteritic anterior ischemic optic neuropathy)
• Sudden hearing loss
• Severe hypotension or cardiovascular events
• Allergic reactions such as rash, swelling, or anaphylaxis

Before initiating therapy, clinicians should consider several safety measures.

• Assess cardiovascular status: evaluate for underlying heart disease before prescribing.
• Avoid use with nitrates: concurrent use can cause severe hypotension.
• Caution in severe hepatic impairment: dose adjustment may be needed.
• Monitor visual changes: report sudden loss of vision promptly.
• Limit excessive alcohol consumption: may increase side effects.
• Store at ambient temperature: keep below 25 °C, in original packaging, protected from moisture.

Sildenafil citrate can interact with several drug classes, requiring careful management.

Major Interactions (Avoid)

• Nitrates (e.g., nitroglycerin): risk of profound hypotension.
• Guanylate cyclase stimulators (e.g., riociguat): additive vasodilatory effect.
• Potent CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): increase sildenafil exposure.
• Alpha‑blockers (e.g., doxazosin): may cause marked blood pressure drops.
• Concomitant PDE5 inhibitors: risk of severe 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., ritonavir): may increase plasma levels.
• Diuretics: watch for orthostatic hypotension.
• SSRIs or other serotonergic drugs: observe for rare serotonin syndrome signs.