In which situations is palbociclib strictly contraindicated?

In which situations is palbociclib strictly contraindicated?

Before starting palbociclib, you must inform your doctor if any of the following apply: First, if you are allergic to palbociclib or any of its excipients (such as microcrystalline cellulose, crospovidone, magnesium stearate, etc.), you must absolutely not use it. Second, while taking palbociclib, you must not use any herbal products containing St. John's wort, as this herb (commonly used for mild depression and anxiety) can significantly reduce palbociclib blood levels, potentially leading to treatment failure. Additionally, if you are already pregnant or planning to become pregnant, you should not use this medication.

Signs of serious adverse reactions to palbociclib

Palbociclib may cause several serious conditions that require immediate medical attention. First, it can significantly lower white blood cell counts, weakening the immune system and increasing the risk of infection. If you experience chills, fever, sore throat, or any other signs of infection, you must notify your doctor immediately. During treatment, your doctor will regularly order complete blood counts to monitor white blood cell, red blood cell, and platelet counts. Second, palbociclib may induce venous thromboembolism, presenting as pain, swelling, or redness in a leg or arm, as well as unexplained chest pain, shortness of breath, or dizziness. Finally, this drug can rarely cause life-threatening pneumonitis, with symptoms including new or worsening dry cough, shortness of breath, and chest pain. If any of these signs occur, contact your doctor right away.

Drug interactions with palbociclib

Palbociclib is metabolized by enzyme systems in the liver, so many drugs can affect its blood levels. The following medications, when used together, may increase the toxic effects of palbociclib: certain anti-HIV drugs (e.g., lopinavir, ritonavir), specific antibiotics (clarithromycin, telithromycin), antifungal agents (itraconazole, ketoconazole), and the antidepressant nefazodone. Conversely, drugs such as carbamazepine, phenytoin, rifampin, and enzalutamide can reduce the efficacy of palbociclib. Regarding diet, you must avoid eating grapefruit or drinking grapefruit juice while taking palbociclib, as grapefruit can increase drug levels and raise the risk of side effects. For women of childbearing potential and their male partners, reliable contraception (e.g., dual-barrier method with condom plus diaphragm) must be used during treatment and for at least 3 weeks (women) or 14 weeks (men) after the last dose. Male patients should be aware that this drug may reduce fertility; sperm cryopreservation should be considered before starting treatment.