Capecitabine

Introduction Overview

Generic Name

capecitabine

Brand Name

Xeloda

Dosage Form

Oral tablet

Drug Class

Antimetabolites

Pharmacokinetics

Absorption:
Capecitabine is rapidly and almost completely absorbed after oral administration. It is designed as an oral prodrug that undergoes enzymatic conversion to 5-fluorouracil (5-FU) preferentially in tumor tissues. Peak plasma concentrations of capecitabine occur approximately 1.5 hours after administration with a high bioavailability of around 70-80%. Food has minimal impact on the extent of absorption but can slightly delay the time to peak concentration, hence the recommendation to take capecitabine within 30 minutes after a meal to minimize gastrointestinal toxicity.

Distribution:
Capecitabine exhibits moderate plasma protein binding (~54%) primarily to albumin. After absorption, it is widely distributed throughout the body with a mean apparent volume of distribution around 30-40 liters, indicating distribution into tissues beyond the vascular compartment. Its active metabolite, 5-FU, is also widely distributed with tissue-specific activation in tumor cells facilitated by high thymidine phosphorylase activity.

Metabolism:
Capecitabine undergoes extensive three-step enzymatic conversion to 5-FU. Initially, it is metabolized in the liver by carboxylesterase to 5'-deoxy-5-fluorocytidine (5'-DFCR), then by cytidine deaminase to 5'-deoxy-5-fluorouridine (5'-DFUR). Finally, 5'-DFUR is converted to the active drug 5-FU by thymidine phosphorylase, which is preferentially expressed in tumor tissues, allowing selective activation. This targeted activation contributes to an improved therapeutic index. Metabolism is primarily hepatic, but also intratumoral, with minimal involvement of cytochrome P450 enzymes.

Elimination:
Capecitabine and its metabolites are eliminated primarily via renal excretion. Approximately 95% of the administered dose is recovered in urine within 7 days, mainly as metabolites. The elimination half-life of capecitabine is approximately 45 to 60 minutes, while its active metabolites, including 5-FU, have shorter half-lives. Renal impairment significantly affects the clearance of some metabolites, necessitating dose adjustments in patients with moderate to severe renal dysfunction. There is minimal fecal excretion. Clearance variability correlates with renal function and patient-specific enzymatic activity, such as DPD status.

Dosage Forms

Available Dosage Forms:
Xeloda is available as oral tablets with specific strengths to facilitate dosing according to body surface area. The available tablet strengths include:
- 150 mg tablets
- 500 mg tablets

Dosages for Adults and Adolescents:
Adult dosing is weight- and body surface area-based, usually calculated per square meter (mg/m2). The common regimen for Xeloda is 1250 mg/m2 orally twice daily (total daily dose 2500 mg/m2) administered for 14 consecutive days followed by a 7-day rest period, constituting a 3-week cycle. This dosing applies for monotherapy in metastatic colorectal and breast cancer settings as well as adjuvant treatment in Dukes' C colon cancer.

For colorectal cancer:
- First-line monotherapy for metastatic disease or adjuvant treatment is 1250 mg/m2 twice daily for 14 days followed by 7 days off, repeated in 3-week cycles.

For breast cancer:
- Xeloda is used in combination with docetaxel at 1250 mg/m2 twice daily for 14 days with a 7-day rest in 3-week cycles.
- As monotherapy for metastatic breast cancer resistant or intolerant to other chemotherapies, the same dosing schedule applies.

Specific Patient Populations:
- Renal impairment: Xeloda is contraindicated in patients with severe renal impairment (creatinine clearance <30 mL/min). For moderate impairment (30–50 mL/min), dosage adjustments or avoidance is recommended due to increased toxicity risk.
- Hepatic impairment: No specific dosage adjustments are established, but caution is advised.
- Elderly: Increased monitoring is recommended due to higher risk of adverse reactions.
- Pediatric: Safety and efficacy not established; use not recommended.

Dosing administration guidance:
- Tablets should be swallowed whole with water within 30 minutes after a meal to reduce gastrointestinal side effects.
- Dosing schedules are cyclical with 14 days on treatment followed by 7 days rest, thereby mitigating cumulative toxicity.

Mechanism Of Action

Capecitabine (Xeloda) is a fluoropyrimidine carbamate prodrug that undergoes preferential enzymatic conversion in tumor tissue to 5-fluorouracil (5-FU), an active cytotoxic agent. This metabolic activation step allows for targeted delivery of 5-FU, enhancing antitumor efficacy while reducing systemic toxicity compared to intravenous 5-FU administration. The initial metabolism involves hepatic conversion to intermediates followed by tumor-selective conversion through increased thymidine phosphorylase activity in cancer cells.

Once converted to 5-FU intracellularly, it exerts its antineoplastic effect by inhibiting thymidylate synthase (TS), a key enzyme involved in DNA synthesis through synthesis of thymidine nucleotides. Inhibition of TS results in thymidine depletion, DNA synthesis disruption, and subsequent apoptosis of rapidly proliferating tumor cells. By impairing DNA replication, capecitabine selectively targets rapidly dividing cancer cells.

Additionally, 5-FU metabolites get incorporated into RNA and DNA as fraudulent bases, further disrupting nucleic acid function. This incorporation interferes with RNA processing and function, leading to defective protein synthesis and enhanced cytotoxicity. The combination of TS inhibition and nucleic acid misincorporation contributes to the broad cytotoxic profile of capecitabine.

Clinical studies have confirmed that capecitabine's mechanism provides efficacy comparable to intravenous 5-FU regimens, with improved convenience and tolerability. The tumor-selective activation mechanism reduces systemic exposure to 5-FU, potentially leading to a more favorable side effect profile. Additionally, it can be combined safely with other chemotherapeutic agents such as docetaxel, enhancing therapeutic benefit in metastatic breast and colorectal cancers.

Pharmacological Actions

Antimetabolite agent that interferes with DNA and RNA synthesis in rapidly dividing cancer cells.
Prodrug converted enzymatically to 5-fluorouracil preferentially within tumor tissues.
Inhibits thymidylate synthase, causing depletion of thymidine and disruption of DNA replication.
Incorporates into RNA and DNA, interfering with nucleic acid function and protein synthesis.
Exerts selective cytotoxicity against tumor cells through targeted activation.
Oral fluoropyrimidine chemotherapy providing systemic antineoplastic effect.
Used as monotherapy or in combination regimens, e.g., with docetaxel in breast cancer.
Demonstrates antiproliferative and pro-apoptotic effects in colorectal, breast, and other cancers.
Effective for metastatic and adjuvant treatment settings in colorectal and breast cancers.
Bypasses first-pass metabolism through sequential enzymatic activation leading to tumor specificity.
Offers improved patient convenience and compliance due to oral dosing schedule.
Capable of inducing cell cycle arrest during S-phase in sensitive tumor cells.
Modulates expression of enzymes involved in fluoropyrimidine metabolism enhancing cytotoxic effects.
Contributes to antiangiogenic effects by impacting tumor microenvironment.

Therapeutic Or Clinical Uses

First-line treatment of metastatic colorectal carcinoma as monotherapy when fluoropyrimidine therapy alone is preferred.
Adjuvant treatment of Dukes' C colon cancer post complete surgical resection using monotherapy.
Treatment of metastatic breast cancer resistant to paclitaxel and anthracycline containing chemotherapy.
Combination therapy with docetaxel for metastatic breast cancer after failure of prior anthracycline chemotherapy.
Used in colorectal cancer treatment protocols requiring oral fluoropyrimidine chemotherapy.
Applicable for treatment of advanced and metastatic colorectal and breast cancers.
Component of chemotherapy regimens such as CAPOX (capecitabine plus oxaliplatin) for colorectal cancer.
Used in patients preferring oral chemotherapy or unable to tolerate intravenous 5-FU.
Treatment alternative aiming for improved quality of life via oral administration.
Indicated for patients with disease progression following prior chemotherapy regimens.
Utilized in oncology protocols requiring thymidylate synthase inhibition to attenuate tumor growth.
Treatment for patients with contraindications or intolerance to intravenous fluoropyrimidines.
Part of multi-agent chemotherapy regimens to improve disease-free and overall survival rates.
May be employed in certain gastrointestinal cancers beyond colorectal, off-label with clinical discretion.
Provides an option in palliative and curative oncology treatment plans depending on disease stage.

Side Or Adverse Effects

Hand-foot syndrome characterized by redness, pain, swelling, blistering, or peeling of skin on hands and feet.
Severe diarrhea which may require treatment interruption and supportive care.
Nausea and vomiting contributing to dehydration if prolonged.
Stomatitis or mouth ulcerations causing pain and difficulty swallowing.
Jaundice indicating potential hepatotoxicity or liver injury.
Myelosuppression leading to low blood cell counts: anemia, leukopenia, thrombocytopenia.
Increased risk of infections secondary to neutropenia.
Fatigue and generalized weakness common during chemotherapy cycles.
Rare but serious allergic reactions presenting with hives, facial swelling, and respiratory distress.
Cardiotoxicity manifestations including chest pain, arrhythmias, and heart failure symptoms.
Potential for severe skin reactions such as Stevens-Johnson syndrome in rare cases.
Abdominal pain with episodes of bloody diarrhea indicative of mucosal injury or colitis.
Elevated liver enzymes signaling hepatic dysfunction in some patients.
Dehydration symptoms due to gastrointestinal losses and systemic effects.
Delayed wound healing and increased bruising due to platelet reduction.

Precautions

Contraindicated in patients with confirmed dihydropyrimidine dehydrogenase (DPD) deficiency due to risk of severe toxicity.
Use cautiously in patients with moderate to severe renal impairment; dose adjustments may be necessary.
Monitor closely in patients with preexisting liver disease given potential hepatotoxicity.
Frequent blood counts are recommended to detect and manage myelosuppression promptly.
Advise patients to maintain hydration especially during periods of vomiting or diarrhea.
Use birth control in both men and women during treatment and for months following cessation due to teratogenicity.
Avoid breastfeeding during treatment and for at least 2 weeks after the last dose.
Patients on warfarin or other anticoagulants require close INR monitoring due to increased bleeding risk.
Assess for cardiac symptoms before and during treatment, especially in patients with cardiovascular conditions.
Patients should be educated to report signs of infection, bleeding, or severe gastrointestinal symptoms promptly.
Temporary interruption of therapy may be required to manage severe adverse events or toxicity.
Consider dose reduction or discontinuation if severe hand-foot syndrome develops.
Evaluate hydration status and counsel on nutritional support to prevent treatment delays.
Advise avoidance of medications and supplements that may interact or increase toxicity risk without physician consultation.
Regular monitoring for liver and renal function tests is necessary to detect early organ dysfunction.

Warnings

Do not use in patients with severe kidney disease due to increased risk of toxicity.
Avoid use in individuals with DPD enzyme deficiency, as this can cause life-threatening adverse effects.
Taking warfarin or other blood thinners concurrently increases risk of severe bleeding; monitor coagulation parameters closely.
Potential teratogenic effects mandate avoidance during pregnancy and effective contraception during and post-treatment.
Severe diarrhea and dehydration can be life-threatening and require immediate medical attention.
Risk of severe skin reactions and allergic hypersensitivity that may necessitate discontinuation.
Prolonged myelosuppression can increase susceptibility to fatal infections and bleeding.
Cardiac events including arrhythmia and myocardial ischemia reported; monitor patients with cardiac history carefully.
Dose adjustments or treatment discontinuation needed in cases of severe toxicity or intolerance.
Not recommended in pediatric patients due to lack of safety and efficacy data.
May cause hand-foot syndrome that can severely impair daily functioning if untreated.
Chemotherapy-induced immunosuppression increases risk of opportunistic infections.
Monitor liver function tests due to potential hepatotoxicity and jaundice development.
Risk of potentially fatal overdose if administered improperly; ensure dosing accuracy.
Patients should avoid activities requiring alertness until they know how drug affects them due to potential fatigue.

Contraindication

Hypersensitivity or known allergy to capecitabine, fluorouracil, or any components of the formulation.
Severe renal impairment with creatinine clearance less than 30 mL/min.
Dihydropyrimidine dehydrogenase (DPD) deficiency confirmed by diagnostic testing.
Pregnancy due to high risk of teratogenicity and fetal harm.
Breastfeeding mothers during treatment and for at least two weeks post-therapy.
Concomitant use with certain live vaccines contraindicated due to immunosuppression.
Severe hepatic impairment as safety is not established and risk may outweigh benefit.
Concurrent use with other fluoropyrimidines or chemotherapeutic agents contraindicated without specialist oversight.
Patients with active severe infections or uncontrolled systemic illness.
Inability to take oral medications or severe gastrointestinal conditions impairing absorption.
Known hypersensitivity to other antimetabolites with potential for cross-reactivity.
Uncontrolled bleeding disorders or significant coagulopathies.
Severe cardiac dysfunction without appropriate monitoring and management.
Patients undergoing concurrent radiation therapy to the same region unless protocol permits.
History of severe dermatological reactions to fluoropyrimidines.

Drug Interactions

Concurrent use with warfarin, Coumadin, or Jantoven increases the risk of severe bleeding; requires frequent INR monitoring.
Allopurinol may increase toxicity of capecitabine by affecting its metabolism.
Co-administration with other chemotherapeutic agents requires careful monitoring for additive toxicity.
Anticoagulants may enhance bleeding risk when combined with capecitabine.
Use of phenytoin with capecitabine has been reported to alter phenytoin plasma levels, requiring monitoring.
Oral folate supplementation could potentially modify the efficacy and toxicity profile but clinical relevance remains unclear.
Agents that cause diarrhea may exacerbate capecitabine-induced gastrointestinal toxicity.
Live vaccines are contraindicated due to immunosuppressive effects of chemotherapy.
Herbal products and vitamins should be disclosed as they may interact or alter metabolism of capecitabine.
Combination with other fluoropyrimidine drugs increases risk of cumulative toxicity.
Drugs affecting renal function may alter clearance of metabolites, necessitating dosage adjustments.
Use with high-dose proton pump inhibitors or antacids has not shown significant interaction but clinical vigilance is advised.
Patients on multiple medications require comprehensive interaction assessment to avoid enhanced toxicities.
Drug metabolism may be slowed in presence of hepatic enzyme inhibitors, increasing adverse effect risk.
CYP450 enzymes are minimally involved; major drug-drug interactions through this pathway are unlikely but cannot be ruled out.

Preparations Of The Drug

Film-coated tablets available in 150 mg strength for precise dose titration.
Film-coated tablets available in 500 mg strength to facilitate higher dose administration according to body surface area.
Oral solid dosage form designed for convenient administration with food to minimize gastrointestinal adverse effects.
Packaged in bottles with desiccants to maintain tablet integrity and protect from moisture.
Supplied with patient medication guides describing dosing schedules, potential side effects, and safety precautions.
Manufactured under strict quality control ensuring consistent potency and bioavailability.
Available as branded compound Xeloda and generic capecitabine formulations with verified bioequivalence.
Accompanied by removable storage and handling instructions advising room temperature conditions away from heat and moisture.
Special pediatric formulations are not currently available; adult tablets adapted as per oral dosing requirements.
Prescribing information includes detailed instructions on dose calculation, administration, and cycle timing.
Prepared for oral use only, with no intravenous or injectable formulations of capecitabine authorized.
Dispensed with appropriate labeling to delineate warnings related to teratogenicity and drug interactions.
Available in standardized packaging to support oncology clinical protocols and combination chemotherapy regimens.
Long shelf life with stability data supporting storage up to labeled expiry when conditions are met.
Patient support programs often provided by manufacturers to assist with dosing adherence and adverse event management.