Letrozole (brand name Femara) is an oral medication primarily used as hormonal therapy for postmenopausal women diagnosed with hormone-receptor-positive breast cancer. This cancer type grows in response to estrogen, making estrogen suppression a viable treatment. Letrozole is an aromatase inhibitor that blocks the aromatase enzyme, which converts other hormones (androgens) into estrogen in peripheral tissues. By inhibiting this enzyme, Letrozole significantly lowers circulating estrogen levels, starving estrogen-dependent cancer cells and preventing their growth.
Dizziness as a Known Side Effect
Dizziness is a documented side effect associated with taking Letrozole, often presenting as lightheadedness or general unsteadiness. Clinical data confirms this is a common occurrence, affecting approximately 1 to 10 out of every 100 people. Dizziness is among the frequently reported adverse effects, alongside hot flashes and joint pain. The experience is often mild and transient, particularly during the initial phase of treatment. Official warnings advise caution while engaged in activities that require mental alertness.
How Hormonal Shifts Relate to Dizziness
The mechanism underlying the dizziness is directly linked to Letrozole’s intended action: the rapid suppression of estrogen. Since the body produces estrogen mainly through the aromatase enzyme after menopause, Letrozole drastically reduces this production. This sudden, profound drop in estrogen levels mimics and intensifies natural hormonal fluctuations experienced during menopause. The body struggles to quickly adapt to this new, significantly lower baseline.
Estrogen receptors are present throughout the body, including areas that regulate the central nervous system and cardiovascular function. The hormonal deprivation caused by the drug can affect the body’s ability to regulate blood pressure and blood flow to the brain, manifesting as lightheadedness. Furthermore, the hormonal shift can trigger or worsen vasomotor symptoms, such as hot flashes. These symptoms involve sudden changes in blood vessel dilation that may also contribute to temporary feelings of dizziness or vertigo.
Monitoring Symptoms and Safety Precautions
Patients experiencing dizziness should prioritize safety to prevent accidental injury. It is advised to avoid driving or operating heavy machinery until you understand how Letrozole affects your alertness and coordination. Simple actions can manage mild lightheadedness, such as rising slowly from a seated or lying position to stabilize blood pressure. Maintaining adequate hydration may also help mitigate some symptoms.
Contact your healthcare provider if the dizziness becomes severe, persistent, or interferes significantly with daily activities. Immediate medical attention is necessary if the dizziness is accompanied by more severe symptoms, such as fainting, chest pain, a fast or irregular heartbeat, or sudden changes in vision. These symptoms could indicate a more serious underlying condition or a severe reaction to the medication, requiring prompt evaluation.