Gosuran (Letrozole)

Gosuran (letrozole) is indicated for endocrine therapy in postmenopausal women whose breast tumors express hormone receptors, and it is commonly prescribed as part of adjuvant or neoadjuvant treatment protocols.

• Treatment of hormone receptor‑positive breast cancer in postmenopausal patients.
• Adjuvant therapy following surgery to reduce recurrence risk.
• Neoadjuvant therapy to shrink tumors before surgery.
• Management of advanced or metastatic hormone‑sensitive breast cancer.
• Part of combination regimens with other endocrine agents when clinically appropriate.
• Use in clinical trials evaluating novel endocrine strategies.

The safety profile of Gosuran reflects the pharmacologic activity of letrozole, with most patients experiencing mild to moderate events while rare but serious reactions may also occur. These effects are generally reversible after discontinuation, but monitoring is recommended throughout therapy.

Common

• Hot flashes, night sweats, or feeling of warmth.
• Joint or muscle aches, especially in the hips and knees.
• Fatigue or general tiredness.
• Nausea, mild stomach discomfort, or loss of appetite.
• Headache or mild dizziness.
• Dry mouth or changes in taste perception.

Serious

• Severe bone loss leading to fractures.
• Elevated liver enzymes indicating potential hepatic injury.
• Allergic reactions such as rash, itching, or swelling.
• Blood clotting abnormalities including deep vein thrombosis.

When prescribing Gosuran, clinicians should evaluate patient history and risk factors, and patients should be informed of necessary monitoring to minimize potential complications associated with estrogen suppression.

• Assess bone mineral density before starting therapy and consider calcium/vitamin D supplementation.
• Monitor liver function tests periodically during treatment.
• Evaluate cardiovascular risk, especially in patients with hypertension or hyperlipidemia.
• Avoid use in pregnant or breastfeeding women; letrozole is contraindicated in these populations.
• Review concomitant medications that may affect QT interval or hepatic metabolism.

Gosuran may interact with other drugs that influence its metabolism or amplify hormonal effects, so careful review of a patient’s medication list is essential before initiating therapy.

Avoid

• Strong CYP3A4 inducers such as rifampin, carbamazepine, or phenytoin.
• Concurrent use of estrogen‑containing hormone replacement therapy.
• Medications known to cause prolonged QT interval (e.g., certain antiarrhythmics).
• Selective serotonin reuptake inhibitors (SSRIs) that may interfere with letrozole metabolism.

Use with caution

• Drugs metabolized by CYP2A6 that may have altered plasma levels.
• Anticoagulants, as estrogen suppression can affect clotting parameters.
• Herbal supplements such as St. John’s wort, which can induce hepatic enzymes.