Uses and Administration of Letrozole in Kenya
Letrozole is a selective nonsteroidal inhibitor of the aromatase (oestrogen synthetase) system, similar to anastrozole. It is used in the treatment of advanced or locally advanced breast cancer in postmenopausal women. It may be given as neoadjuvant (pre-operative) therapy to those with localised hormone-receptor positive disease, to allow subsequent breast-conserving surgery. Letrozole is also used for the adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer; treatment is generally given for 5 years or until tumour relapse occurs, although optimal duration of therapy is unknown. In postmenopausal women given 5 years of adjuvant tamoxifen for early breast cancer, letrozole may be used as extended adjuvant therapy; treatment should continue for 4 years or until tumour relapse occurs, although optimal duration of therapy is unknown. The usual dose is 2.5 mg daily by mouth.
Administration in hepatic impairment. Licensed product information in the Kenya and USA states that no dosage adjustment of letrozole is required for patients with mild to moderate hepatic impairment (Child-Pugh category A and B). While letrozole is contraindicated in the UK in severe hepatic impairment (Child-Pugh category C), in the USA, it is recommended that the dose of letrozole be reduced by 50% in those patients with cirrhosis and severe hepatic impairment; the recommended dose for these patients is 2.5 mg given every other day.
Infertility and Letrozole. Letrozole has been investigated as an adjunct to assisted reproduction technologies in the management of infertility. However, concerns about this unlicensed use have been raised by the Canadian manufacturer of Femara 2.5mg (Original Letrozole) (Novartis, Canad.) because of the potential for maternal and fetal toxicity, and fetal malformations: 5 licensed product information contraindicates the use of letrozole in premenopausal women, and there have been reports of congenital anomalies in the infants of women treated with letrozole for infertility. Never the less, Letrozole has been used extensively in Kenya to stimulation conception in infertile women in Kenya.
- Healey S, et al.Effects of letrozole on superovulation with gonadotropins in women undergoing intrauterine insemination. Fertil
- Al-Fozan H, et al.A randomized trial of letrozole versus clomiphene citrate in women undergoing superovulation. Fertil Steril
- Garcia-Velasco JA, et al.The aromatase inhibitor letrozole increases the concentration of intraovarian androgens and improves in vitro fertilization outcome in low responder patients: a
pilot study. Fertil Steril2005; 84:82–7.
- Al-Fadhli R, et al.A randomized trial of superovulation with two
different doses of letrozole. Fertil Steril2006; 85:161–4.
- Novartis, Canada. Health Canada endorsed important safety information: contraindication of Femara (letrozole) in premenopausal women (issued 17th November, 2005). Available at:
http://healthycanadians.gc.ca/recall-alert-rappel-avis/hc-sc/2005/14326a-eng.php (accessed 21/2/2016)
Adverse Effects and Precautions of Letrozole
The most common adverse effects of Letrozole are gastrointestinal disturbances including anorexia, nausea and vomiting, and diarrhoea; asthenia; hot flushes; dizziness; drowsiness; headache; and rash. Other reported effects in Kenya include hair thinning, vaginal dryness or bleeding, oedema, dyspnoea, myalgia and arthralgia, fever, weight gain, leucopenia, and a flu-like syndrome. There is concern that long term use may lead to osteoporosis and bone fractures. Abnormalities in liver enzyme values, thromboembolism, and increases in total cholesterol, have occurred in some patients receiving Letrozole. Very rare cases of erythema multiforme and Stevens-Johnson syndrome have occurred.
Mechanism of action of Letrozole/Femara
Letrozole prevents the aromatase from producing estrogens by competitive, reversible binding to the heme of its cytochrome P450 unit. The action is specific, and letrozole does not reduce production of mineralo- or corticosteroids.
Contraindications and warning of Letrozole Use
Letrozole is contraindicated in women having a pre-menopausal hormonal status, during pregnancy and lactation.