Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
AFINITOR vs AFATINIB
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Inhibitor of mammalian target of rapamycin (m TOR), specifically the m TORC1 complex, by binding to the FKBP-12 protein, reducing cell proliferation, angiogenesis, and glucose uptake.
Afatinib is an irreversible, covalent-binding inhibitor of the Erb B family of tyrosine kinases, including EGFR (Erb B1), HER2 (Erb B2), Erb B3, and Erb B4. It blocks downstream signaling pathways such as PI3K/AKT and MAPK, leading to inhibition of tumor cell proliferation and survival.
Advanced hormone receptor-positive, HER2-negative breast cancer in postmenopausal women in combination with exemestane after failure of letrozole or anastrozole,Progressive neuroendocrine tumors of pancreatic origin (PNET) in unresectable, locally advanced or metastatic disease,Advanced renal cell carcinoma (RCC) after failure of sunitinib or sorafenib,Subependymal giant cell astrocytoma (SEGA) associated with tuberous sclerosis complex (TSC) in patients requiring therapeutic intervention but not amenable to curative resection
First-line treatment of metastatic non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) exon 19 deletions or exon 21 (L858R) substitution mutations,Treatment of metastatic squamous NSCLC progressing after platinum-based chemotherapy,Off-label: Use in other EGFR-mutant cancers (e.g., head and neck cancer, colorectal cancer) with specific mutations
10 mg orally once daily for advanced breast cancer, neuroendocrine tumors, and renal cell carcinoma; 10 mg orally once daily for subependymal giant cell astrocytoma (SEGA) in adults; 5 mg/m^2 orally once daily for SEGA in pediatric patients (titrated to trough levels 5-15 ng/m L).
40 mg orally once daily, continuously.
Terminal elimination half-life: 30 hours (range 15–40 hours) in healthy subjects; increases to 40–70 hours in moderate hepatic impairment.
Terminal half-life is approximately 37 hours; supports once-daily dosing with steady-state achieved within 8 days.
Substrate of CYP3A4; metabolized primarily by CYP3A4; also a substrate of P-glycoprotein (P-gp).
Primarily metabolized by CYP3A4 and to a lesser extent by CYP3A4-independent pathways including flavin-containing monooxygenase (FMO). Excretion mainly via feces (85%) and urine (4%) as unchanged drug and metabolites.
Primarily fecal (80%) and renal (5%) as unchanged drug and metabolites. Biliary excretion is significant.
Primarily fecal (85%) as unchanged drug and metabolites; renal excretion accounts for <4% of the dose.
74% bound to plasma proteins (primarily albumin and α1-acid glycoprotein).
Approximately 95% bound to plasma proteins, primarily to albumin.
Mean steady-state Vd: 342 L (approx. 4.9 L/kg in a 70 kg adult), indicating extensive tissue distribution.
Volume of distribution is approximately 2300 L (about 33 L/kg for a 70 kg individual), indicating extensive tissue distribution.
Oral bioavailability: approximately 16% (low due to P-glycoprotein efflux and first-pass metabolism); food reduces variability but does not alter AUC significantly.
Oral bioavailability is approximately 92% relative to an oral solution; food reduces exposure, so take on an empty stomach.
No dose adjustment for mild to moderate renal impairment (Cr Cl >=30 m L/min). For severe renal impairment (Cr Cl <30 m L/min): reduce dose to 5 mg once daily. End-stage renal disease (Cr Cl <15 m L/min): use with caution, no specific recommendation.
No starting dose adjustment required for mild to moderate renal impairment (Cr Cl ≥30 m L/min). Not recommended for severe renal impairment (Cr Cl <30 m L/min) due to safety concerns.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose to 5 mg daily; Child-Pugh C: reduce dose to 2.5 mg daily, or consider alternate therapy.
Child-Pugh A: 40 mg once daily. Child-Pugh B: Reduce dose to 30 mg once daily. Child-Pugh C: Not recommended due to lack of data.
For SEGA: 5 mg/m^2 orally once daily, adjusted to achieve everolimus trough concentrations of 5-15 ng/m L. Dose adjustments per AUC or tolerability. Not approved for other indications in children.
Safety and efficacy not established in pediatric patients; no specific dosing recommendations.
No specific dose adjustment; start at recommended adult dose. Monitor for increased risk of infections, stomatitis, and metabolic effects due to age-related decline in organ function.
No specific dose adjustment recommended based on age alone; monitor renal function and tolerability, as elderly patients may have decreased renal function or comorbidities.
No black box warnings.
None.
Non-infectious pneumonitis,Infections (including opportunistic infections),Hypersensitivity reactions including anaphylaxis,Angioedema,Renal failure,Impaired wound healing,Metabolic effects (hyperglycemia, dyslipidemia),Myelosuppression,Immunosuppression leading to increased risk of infections,Cases of fatal hemorrhage in patients with history of bleeding,Radiation sensitization and recall reactions, especially in patients with previous radiation therapy,Increased risk of pneumocystis jirovecii pneumonia (PJP) and other opportunistic infections; consider prophylaxis,Avoid live vaccines
Severe diarrhea (including dehydration and acute kidney injury),Interstitial lung disease (ILD)/pneumonitis,Severe hepatotoxicity (elevated liver enzymes, hepatitis),Left ventricular dysfunction (assess LVEF at baseline and during treatment),Severe bullous, blistering, and exfoliative skin reactions (e.g., Stevens-Johnson syndrome),Gastrointestinal perforation,Ocular toxicities (keratitis, conjunctivitis),Renal toxicity (proteinuria, nephrotic syndrome),Fetal harm (embryo-fetal toxicity),Drug interactions with CYP3A4 inducers or inhibitors
Hypersensitivity to everolimus, sirolimus, or any component of the formulation
None reported,Relative contraindications: pre-existing severe hepatic impairment, severe renal impairment, pregnancy, and breastfeeding
Avoid grapefruit, grapefruit juice, and Seville oranges (including marmalade) due to CYP3A4 inhibition increasing everolimus levels. Take consistently with or without food, but high-fat meals reduce absorption. Avoid St. John's wort.
Take on an empty stomach (at least 1 hour before or 2 hours after food). Avoid grapefruit, grapefruit juice, and Seville oranges as they may alter drug metabolism. High-fat meals reduce absorption.
Pregnancy Category D. Positive evidence of human fetal risk. Based on its mechanism of action (m TOR inhibitor) and animal studies, AFINITOR (everolimus) is embryotoxic and fetotoxic. First trimester exposure carries risk of structural anomalies; second and third trimester exposure may cause fetal growth restriction, oligohydramnios, and renal impairment. Use only if benefit outweighs risk.
Afatinib is classified as Pregnancy Category D. First trimester exposure is associated with increased risk of major congenital malformations, including cardiac, skeletal, and neural tube defects based on animal studies showing embryotoxicity and teratogenicity at doses below human exposure. Second and third trimester exposure may cause fetal growth restriction, oligohydramnios, and impaired renal function due to inhibition of EGFR signaling critical for fetal development.
No data on presence in human milk, effects on breastfed infant, or milk production. M/P ratio unknown. Breastfeeding is not recommended due to potential adverse effects on the developing immune system and growth.
No human data on afatinib excretion in breast milk; however, animal studies indicate drug presence in milk. M/P ratio is unknown. Due to potential for serious adverse effects in breastfed infants, breastfeeding is contraindicated during therapy and for at least 2 weeks after the last dose.
No specific dose adjustments established for pregnancy. Pharmacokinetic changes in pregnancy (increased volume of distribution, altered hepatic metabolism) may reduce drug exposure; however, given the teratogenic risk, use during pregnancy should be avoided. If unavoidable, consider therapeutic drug monitoring if available and adjust dose to achieve target trough concentrations (typically 3-8 ng/m L for transplant indications; for oncology, refer to specific protocol).
No specific dosing guidelines for pregnancy. Pharmacokinetic changes (increased volume of distribution, altered metabolism) may occur but studies have not established dose adjustments. The drug should be avoided in pregnancy unless benefit outweighs risk; if used, consider therapeutic drug monitoring if available.
Monitor renal function and blood glucose regularly; Afinitor (everolimus) can cause non-infectious pneumonitis, so obtain baseline chest imaging and assess for new or worsening respiratory symptoms. Adjust dose for moderate hepatic impairment (Child-Pugh B). Avoid live vaccines during treatment.
Monitor for diarrhea, which can be severe; consider loperamide and hydration. Assess for interstitial lung disease (ILD) and hepatotoxicity. Dose reduction required for severe renal impairment (Cr Cl 15–29 m L/min). For patients with EGFR exon 19 deletion or exon 21 L858R mutation, first-line use improves PFS. Avoid P-glycoprotein strong inducers (e.g., rifampin) during treatment.
Take Afinitor at the same time each day, consistently either with or without food.,Avoid grapefruit, grapefruit juice, and Seville oranges during treatment.,Report any new or worsening cough, chest pain, or difficulty breathing immediately.,Monitor for signs of infection such as fever, chills, or sore throat; avoid large crowds and sick individuals.,Use effective contraception during treatment and for 8 weeks after stopping.,Do not crush or chew tablets; swallow whole with a glass of water.
Take afatinib at least 1 hour before or 2 hours after a meal.,Do not crush, chew, or split tablets; swallow whole with water.,Seek medical help for severe or persistent diarrhea, cough, or difficulty breathing.,Avoid grapefruit and Seville oranges during treatment.,Report signs of liver problems (yellowing skin/eyes, dark urine).,Use effective contraception during and for 2 weeks after stopping therapy.,Avoid direct sunlight exposure; use sunscreen.
No interactions on record
"Afatinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, and fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), both undergo metabolism via CYP450 enzymes. Afatinib is a moderate inhibitor of CYP2D6 and may also inhibit CYP1A2 and CYP3A4, while fluvoxamine is a known inhibitor of CYP1A2 and CYP2C19. Coadministration can lead to increased fluvoxamine concentrations due to inhibition of its metabolism, potentially resulting in enhanced serotonergic effects such as serotonin syndrome, as well as increased adverse effects like nausea, dizziness, or QT prolongation."
"The combination of afatinib, a tyrosine kinase inhibitor, with pantoprazole, a proton pump inhibitor (PPI), can lead to reduced absorption of afatinib due to elevated gastric pH. Afatinib exhibits pH-dependent solubility, and higher gastric pH decreases its dissolution and bioavailability, potentially reducing its therapeutic efficacy. This interaction may result in suboptimal plasma concentrations of afatinib, increasing the risk of treatment failure in patients with non-small cell lung cancer."
"Estrone, an estrogen hormone, may induce the expression of UDP-glucuronosyltransferase (UGT) enzymes, which are involved in the glucuronidation and subsequent clearance of afatinib. This induction can lead to a decrease in afatinib serum concentrations, potentially reducing its efficacy in the treatment of non-small cell lung cancer. Clinically, this interaction may result in suboptimal therapeutic outcomes unless the afatinib dose is adjusted."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about AFINITOR vs AFATINIB, answered by our medical review team.
AFINITOR is a mTOR Inhibitor Antineoplastic that works by Inhibitor of mammalian target of rapamycin (m TOR), specifically the m TORC1 complex, by binding to the FKBP-12 protein, reducing cell proliferation, angiogenesis, and glucose uptake.. AFATINIB is a Tyrosine Kinase Inhibitor Antineoplastic that works by Afatinib is an irreversible, covalent-binding inhibitor of the Erb B family of tyrosine kinases, including EGFR (Erb B1), HER2 (Erb B2), Erb B3, and Erb B4. It blocks downstream signaling pathways such as PI3K/AKT and MAPK, leading to inhibition of tumor cell proliferation and survival.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between AFINITOR and AFATINIB depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of AFINITOR is: 10 mg orally once daily for advanced breast cancer, neuroendocrine tumors, and renal cell carcinoma; 10 mg orally once daily for subependymal giant cell astrocytoma (SEGA) in adults; 5 mg/m^2 orally once daily for SEGA in pediatric patients (titrated to trough levels 5-15 ng/m L).. The standard adult dose of AFATINIB is: 40 mg orally once daily, continuously.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between AFINITOR and AFATINIB in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. AFINITOR is classified as Category C. Pregnancy Category D. Positive evidence of human fetal risk. Based on its mechanism of action (mTOR inhibitor) and animal studies, AFINITOR (everolimus) is embryotoxic and fetotoxi. AFATINIB is classified as Category C. Afatinib is classified as Pregnancy Category D. First trimester exposure is associated with increased risk of major congenital malformations, including cardiac, skeletal, and neura. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.