Lekap (Sildenafil)

Sildenafil is a phosphodiesterase type 5 inhibitor used to manage conditions involving impaired vascular smooth‑muscle relaxation.

• Erectile dysfunction: improves the ability to achieve and maintain an erection when sexual stimulation occurs.
• Pulmonary arterial hypertension: reduces pulmonary arterial pressure and enhances exercise capacity.
• Erectile dysfunction associated with diabetes: helps restore erectile function in men whose condition is linked to diabetic vascular changes.

• Sildenafil selectively inhibits the enzyme phosphodiesterase type 5, preventing the breakdown of cyclic guanosine monophosphate (cGMP) in smooth‑muscle cells. Elevated cGMP levels lead to relaxation of vascular smooth muscle, increased blood flow to the corpus cavernosum and pulmonary arteries, and consequently facilitates erection and reduces pulmonary vascular resistance.

Sildenafil may cause a range of adverse reactions, most of which are mild and transient.

Common Side Effects

• Headache
• Flushing
• Dyspepsia or indigestion
• Nasal congestion
• Visual disturbances (e.g., blue‑tinted vision)
• Back pain or muscle aches

Serious or Rare Side Effects

• Priapism (prolonged erection lasting >4 hours)
• Sudden loss of vision (non‑arteritic anterior ischemic optic neuropathy)
• Sudden hearing loss or tinnitus
• Myocardial infarction or unstable angina
• Stroke or transient ischemic attack
• Severe hypotension, especially when combined with nitrates

Before initiating therapy, consider the following safety measures.

• Cardiovascular assessment: evaluate for recent myocardial infarction, unstable angina, or severe heart failure.
• Nitrate use: avoid concurrent use with any nitrate medication due to risk of profound hypotension.
• Visual disorders: contraindicated in patients with hereditary retinal diseases such as retinitis pigmentosa.
• Renal or hepatic impairment: dose adjustment may be required; monitor organ function.
• Hypotension: caution in patients with low baseline blood pressure.
• Store at below 25°C: keep in the original packaging, protect from moisture and direct sunlight.

Sildenafil can interact with several drug classes; awareness of the interaction level guides clinical decisions.

Major Interactions (Avoid)

• Nitrates (e.g., nitroglycerin, isosorbide dinitrate)
• Nitric oxide donors (e.g., amyl nitrite)
• Guanylate cyclase stimulators (e.g., riociguat)
• Certain potent alpha‑blockers (e.g., prazosin) when combined may cause severe hypotension

Moderate Interactions (Monitor Closely)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole) – may increase sildenafil exposure.
• CYP3A4 inducers (e.g., rifampin, carbamazepine) – may reduce efficacy.
• Antihypertensive agents (e.g., beta‑blockers, ACE inhibitors) – monitor blood pressure.
• Protease inhibitors used in HIV therapy – may elevate plasma levels.
• Alcohol – can enhance hypotensive effects.