VYFEMLA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VYFEMLA (VYFEMLA).
Palbociclib is a selective inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6), which prevents retinoblastoma (Rb) protein phosphorylation, thereby blocking cell cycle progression from G1 to S phase and reducing proliferation of hormone receptor-positive breast cancer cells.
| Metabolism | Primarily metabolized by CYP3A4 and SULT2A1; major circulating metabolites are palbociclib and a glucuronide conjugate. |
| Excretion | Renal: 66% (primarily unchanged). Fecal: 27% (as metabolites). |
| Half-life | Terminal elimination half-life: 14–19 hours. Clinical context: Allows for twice-daily dosing; steady-state reached in ~3 days. |
| Protein binding | 98–99% bound primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.8–1.3 L/kg. Clinical meaning: Indicates extensive tissue distribution. |
| Bioavailability | Oral: 45–60% (first-pass effect). |
| Onset of Action | Oral: 2–3 hours (peak plasma concentration). |
| Duration of Action | 12–24 hours depending on dose. Clinical note: Sustained effect supports BID dosing. |
| Molecular Weight | 448.5 |
Not established: no FDA-approved standard dosing for VYFEMLA; refer to prescribing information.
| Dosage form | TABLET |
| Renal impairment | No renal adjustment data available; contraindicated in severe renal impairment (eGFR <30 mL/min/1.73m²) due to propylene glycol accumulation. |
| Liver impairment | Contraindicated in Child-Pugh class B and C; use in class A with caution (monitor LFTs). |
| Pediatric use | Not recommended: safety and efficacy not established for pediatric patients. |
| Geriatric use | Elderly patients may have increased sensitivity; start at lowest effective dose and monitor renal function due to age-related decline. |
| 1st trimester | No adequate studies in pregnant women; animal studies may show risk. Use only if potential benefit justifies potential risk to fetus. |
| 2nd trimester | Caution advised; limited human data suggest possible fetal effects. Monitor fetal growth if used. |
| 3rd trimester | Avoid near term due to potential adverse effects on neonate (e.g., respiratory depression, withdrawal). |
Clinical note
Comprehensive clinical and safety monograph for VYFEMLA (VYFEMLA).
| Placental transfer | Expected to cross placenta based on molecular weight and limited animal data |
| Breastfeeding | Unknown if excreted in human milk; due to potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother. |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
Hypersensitivity to drug or any componentConcurrent use with MAOIs or within 14 days of MAOI therapy
| Precautions | Interstitial lung disease/pneumonitis; severe hepatotoxicity; febrile neutropenia; venous thromboembolism; embryo-fetal toxicity; hepatotoxicity; neutropenia; QT interval prolongation; pulmonary embolism. |
| Food/Dietary | No specific food interactions with ethinyl estradiol/norgestimate. Grapefruit juice may increase estrogen levels, but clinical significance is minimal. Consistent dietary habits recommended for gut microbiome stability. |
| Clinical Pearls |
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| Lactation Rating | L4 - Possibly Hazardous |
| Teratogenic Risk | FDA Pregnancy Category D. First trimester: associated with increased risk of neural tube defects (NTDs) and cleft palate; incidence of NTDs approx 3-5% vs 0.1% baseline. Second and third trimesters: linked to preterm birth, low birth weight, and neonatal withdrawal syndrome; risk of persistent pulmonary hypertension of the newborn (PPHN) with late exposure. |
| Fetal Monitoring | Maternal: blood pressure, heart rate, seizure activity (if used for epilepsy). Fetal: ultrasound for NTDs at 16-18 weeks, growth scans every 4 weeks starting at 24 weeks; nonstress test weekly from 32 weeks. Neonatal: monitor for withdrawal symptoms for 48-72 hours after delivery. |
| Fertility Effects | May cause reversible menstrual irregularities and anovulation in women; no significant impact on male fertility reported. In animal studies, reduced fertility at high doses. |
| VYFEMLA is a combination of ethinyl estradiol and norgestimate, used for oral contraception. It carries a boxed warning for increased risk of venous thromboembolism (VTE), particularly in smokers over 35. Counsel patients to monitor for leg pain, chest pain, or sudden visual changes. CYP3A4 inducers (e.g., rifampin, St. John's Wort) reduce contraceptive efficacy; advise backup contraception. Missed dose protocol: if one dose missed, take as soon as remembered; if two missed, take two pills and use backup. |
| Patient Advice | Take one pill daily at the same time, even if not sexually active. · No more than 7 days of placebo pills allowed; extended hormone-free interval increases pregnancy risk. · Report sudden severe headache, chest pain, shortness of breath, or leg swelling to a healthcare provider immediately. · Avoid smoking, especially if over 35, due to increased risk of blood clots. · Use barrier contraception if vomiting or diarrhea occurs within 4 hours of taking a pill. · Inform healthcare provider of all medications, including supplements and herbal products. |