Indication: Palbociclib (INN) is approved for treating advanced or metastatic hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) breast cancer. It’s used in combination with an aromatase inhibitor as initial endocrine-based therapy in postmenopausal women or with fulvestrant in women who have experienced disease progression following endocrine therapy.

Pharmacology: Palbociclib is a cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor. It acts by suppressing CDK4/6, essential regulators of the cell cycle. This inhibition halts cell cycle progression from the G1 phase to the S phase, thereby curtailing cancer cell proliferation.

Dosage and Administration: The usual dose of palbociclib is 125 mg orally once daily for 21 consecutive days, followed by 7 days off treatment, given in repeated 28-day cycles. It’s typically administered alongside an aromatase inhibitor or fulvestrant. Adjustments in dosage may be necessary depending on individual patient factors and tolerance.

Interactions: Palbociclib may interact with various medications, including potent CYP3A inhibitors and inducers. Patients should disclose all medications to their healthcare providers to avoid potential interactions.

Side Effects: Common side effects of palbociclib can include neutropenia, leukopenia, fatigue, nausea, alopecia, diarrhea, and infections. Serious adverse effects may encompass pulmonary embolism, interstitial lung disease, and hepatotoxicity.

Precautions and Warnings: Patients taking palbociclib should undergo monitoring for signs of myelosuppression, such as neutropenia, thrombocytopenia, and anemia. Regular liver function tests are advisable, along with vigilance for pulmonary embolism and interstitial lung disease. Due to potential fetal harm, women of reproductive potential should employ effective contraception during treatment and for at least three weeks after the final dose.

Overdose Effects: In instances of overdose, supportive measures are recommended. Specific effects of palbociclib overdose are not extensively documented, thus management should primarily focus on symptomatic and supportive care.