Ligion (Tadalafil)

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

• Erectile dysfunction: improves the ability to achieve and maintain an erection sufficient for sexual activity.
• Benign prostatic hyperplasia: reduces urinary symptoms such as urgency, frequency and weak stream.
• Pulmonary arterial hypertension: enhances exercise capacity by lowering pulmonary vascular resistance.

• Tadalafil selectively inhibits the phosphodiesterase type 5 enzyme, preventing the breakdown of cyclic guanosine monophosphate (cGMP) in smooth‑muscle cells. Elevated cGMP levels lead to relaxation of vascular smooth muscle in the corpus cavernosum and pulmonary arteries, facilitating increased blood flow. The inhibition is long‑lasting, providing therapeutic effects for up to 36 hours after a single oral dose. This mechanism underlies its use in both erectile dysfunction and pulmonary hypertension.

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

Common Side Effects

• Headache: mild to moderate throbbing pain.
• Flushing: warmth and redness of the face or upper chest.
• Dyspepsia: indigestion or upset stomach.
• Nasal congestion: blocked or runny nose.
• Back pain: muscle aches, typically in the lower back.
• Vision changes: blurred or blue‑tinted vision.

Serious or Rare Side Effects

• Priapism: prolonged erection lasting more than four hours.
• Sudden vision loss: abrupt loss of vision in one or both eyes.
• Sudden hearing loss: rapid decrease or loss of hearing.
• Cardiovascular events: chest pain, arrhythmia, or stroke.
• Severe hypotension: marked drop in blood pressure causing dizziness.

When prescribing tadalafil, clinicians should consider several precautionary measures to minimize risk.

• Cardiovascular assessment: evaluate for recent heart attack, unstable angina, or severe heart failure before use.
• Concomitant nitrates: avoid co‑administration as it may cause dangerous hypotension.
• Blood pressure monitoring: check baseline and periodic readings, especially in patients with hypertension.
• Visual disorders: caution in patients with retinal disease or a history of non‑arteritic anterior ischemic optic neuropathy.
• Hepatic or renal impairment: adjust therapy and monitor closely in moderate to severe dysfunction.
• Store at ambient temperature: keep below 25 °C in the original container, protect from moisture and direct sunlight.

Tadalafil interacts with several medicines; awareness of the interaction level guides clinical decisions.

Major Interactions (Avoid)

• Nitrates (e.g., nitroglycerin): combined use can cause severe hypotension.
• Alpha‑blockers (e.g., doxazosin) in high doses: may lead to dangerous blood pressure drops.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin): increase tadalafil plasma levels, may require dose adjustment.
• CYP3A4 inducers (e.g., rifampicin, carbamazepine): reduce effectiveness of tadalafil.
• Antihypertensives: may enhance blood‑pressure‑lowering effect, monitor BP.
• Protease inhibitors (e.g., ritonavir): can elevate tadalafil concentrations.