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Capecitabine

Capecitabine: Generic Medication Overview

Capecitabine is an oral chemotherapy agent used to treat several types of cancer. In the United Kingdom it is available as a 500 mg pill and is prescribed by a specialist oncology team. The drug is classified under oncology support medications and is regulated by the Medicines and Healthcare products Regulatory Agency (MHRA). It is also listed in NICE technology appraisal guidance for certain cancer indications.

How Capecitabine Works in the Body

Capecitabine is a pro-drug that is converted in the body to 5-fluorouracil (5-FU), a drug that interferes with DNA synthesis. The conversion occurs in three steps:

• Absorption: After oral ingestion, capecitabine is absorbed from the gastrointestinal tract.
• First conversion: Liver enzymes (carboxylesterase) change capecitabine into 5′-deoxy-5-fluorocytidine (5′-dFC).
• Final activation: Tumour-associated enzymes, especially thymidine phosphorylase, transform 5′-dFC into 5-FU directly inside cancer cells.

Because thymidine phosphorylase is more abundant in many tumour tissues than in normal tissue, a higher concentration of 5-FU is produced where it is needed, which helps to limit systemic toxicity. Once formed, 5-FU inhibits thymidylate synthase, an enzyme required for DNA replication, leading to cell-cycle arrest and tumour cell death.

Conditions Treated by Capecitabine

Capecitabine is approved by the MHRA for the following adult indications:

• Metastatic colorectal cancer (often in combination with oxaliplatin)
• Early-stage colorectal cancer as adjuvant therapy after surgery
• Metastatic breast cancer (particularly in patients who have previously received anthracycline- and taxane-based regimens)
• Gastric cancer in combination with other chemotherapy agents

These approvals are based on multiple phase III clinical trials that demonstrated improved progression-free survival compared with older regimens. Capecitabine is not indicated for paediatric cancers.

Evidence-Based Off-Label Uses

Some peer-reviewed studies have explored capecitabine in other tumour types, such as pancreatic and oesophageal cancer. However, these uses remain off-label and are not endorsed by UK regulatory agencies. Off-label prescribing must be guided by an oncologist who evaluates the individual risk-benefit profile.

Who Should and Should Not Use Capecitabine?

Ideal Patient Profile

• Adults with one of the approved cancer indications
• Adequate organ function (renal, hepatic, bone-marrow) as determined by blood tests
• Ability to swallow pills and adhere to a twice-daily dosing schedule

Absolute Contraindications

• Known hypersensitivity to capecitabine or any component of the tablet
• Severe renal impairment (creatinine clearance <30 mL/min)
• Pregnancy (category D) - teratogenic risk; capecitabine is contraindicated
• Breast-feeding - the drug is excreted in milk

Relative Contraindications / Cautions

• Moderate hepatic impairment (bilirubin >1.5 × upper limit of normal)
• Existing cardiac disease (risk of coronary vasospasm)
• Diarrhoea or inflammatory bowel disease (higher risk of severe gastrointestinal toxicity)
• Concomitant use of drugs that affect the enzyme dihydropyrimidine dehydrogenase (DPD), such as certain antifolates

Special populations such as the elderly may need dose adjustments based on renal and hepatic function.

Safety Profile: Side Effects and Interactions

Common Side Effects

• Hand-foot syndrome (palmar-plantar erythrodysesthesia) - redness, swelling, tingling of palms and soles
• Diarrhoea - may be moderate to severe; hydration is important
• Nausea and vomiting - often manageable with anti-emetics
• Fatigue - general tiredness, may affect daily activities
• Mouth soreness (stomatitis) - painful ulcers in the oral cavity

These effects are usually reported in more than 1 % of patients and often improve with dose modification or supportive care.

Serious Adverse Events

• Severe neutropenia (low white-blood-cell count) - raises infection risk; requires prompt medical review
• Severe thrombocytopenia (low platelet count) - may lead to bleeding complications
• Cardiac events such as angina or myocardial infarction, though rare
• Severe hand-foot syndrome that limits mobility and may necessitate treatment interruption

Any sudden fever, persistent vomiting, or unexplained bleeding should be reported immediately.

Drug Interactions

• CYP2C9 inhibitors (e.g., fluconazole) - may increase capecitabine exposure
• Warfarin - capecitabine can enhance anticoagulant effect; INR monitoring is advised
• Antimetabolites (e.g., methotrexate) - combined toxicity may occur
• DPD inhibitors - drugs that reduce dihydropyrimidine dehydrogenase activity can markedly raise 5-FU levels, increasing toxicity

Patients should provide a complete medication list (including over-the-counter and herbal products) to the oncology team.

Food and Lifestyle Interactions

• Food: Capecitabine is taken on an empty stomach - preferably within 30 minutes after a light snack and before a larger meal, as high-fat meals can delay absorption.
• Alcohol: Moderate alcohol intake is permissible, but excessive consumption can worsen liver toxicity and dehydration.
• Sun exposure: Hand-foot syndrome may be aggravated by heat; patients are advised to avoid prolonged sun or heat exposure and to wear protective footwear.

How to Take Capecitabine

Standard Dosing Regimen

Capecitabine tablets (500 mg) are usually prescribed in a two-weeks-on, one-week-off cycle:

• Initial phase: 1250 mg/m² taken twice daily (approximately every 12 hours) for 14 days
• Rest period: No medication on days 15-21
• The exact number of tablets depends on the patient’s body surface area (BSA) and the prescriber’s calculation. A typical adult with a BSA of 1.8 m² would require about eight 500 mg tablets per dose (total 2 g per day).

Important: Dosing must be individualized by the treating oncologist. The above schedule illustrates a common protocol but should not replace professional guidance.

Adjustments for Special Populations

• Renal impairment: Dose reductions of 25-50 % are recommended for creatinine clearance 30-50 mL/min.
• Hepatic dysfunction: Reduce dose by 25 % if bilirubin is 1.5-3 × ULN.
• Elderly patients: Often start at a lower dose to assess tolerance.

Administration Tips

• Swallow tablets whole with a glass of water; do not crush or chew.
• Take the first dose after a light snack (e.g., toast) and the second dose at least 12 hours later, before a larger meal.
• Keep a dosing diary to track missed doses and side-effect patterns.

Missed Dose

If a dose is forgotten, take it as soon as remembered provided it is at least 6 hours before the next scheduled dose. Do not double up doses.

Overdose

Signs of overdose may include severe diarrhoea, vomiting, confusion, or low blood counts. Seek emergency medical care; supportive measures such as fluid replacement and monitoring of blood parameters are standard. There is no specific antidote.

Discontinuation

If treatment must be stopped because of toxicity, the oncologist may taper the dose or switch to an alternative chemotherapy regimen. Abrupt cessation without medical advice is discouraged.

Monitoring and Follow-Up

Regular monitoring is essential to maximise efficacy while minimising toxicity:

• Complete blood count (CBC): Weekly during the first two cycles, then at each clinic visit.
• Renal and liver function tests: At baseline and before each cycle.
• Electrolytes: Particularly if diarrhoea is severe.
• Physical examination: Assessment for hand-foot syndrome, mucositis, and skin changes.
• Imaging (CT/MRI): As directed by the oncology protocol to evaluate tumour response.

Patients should contact their oncology team promptly if they develop fever, persistent diarrhoea, severe hand-foot symptoms, or any new neurological signs.

Storage and Handling

• Store capecitabine tablets at room temperature (15-30 °C), protected from moisture and light.
• Keep the medication out of reach of children; use child-proof containers.
• Do not use tablets after the expiry date printed on the pack.
• Unused tablets should be returned to a pharmacy for safe disposal; do not flush them down the toilet.

Medication-Specific Glossary

Hand-Foot Syndrome

A skin reaction characterised by redness, swelling, and pain on the palms and soles, commonly associated with capecitabine therapy.

Thymidine Phosphorylase

An enzyme highly expressed in many tumours that converts capecitabine’s intermediate metabolite into the active drug 5-fluorouracil.

Dihydropyrimidine Dehydrogenase (DPD)

The primary enzyme responsible for breaking down 5-fluorouracil; deficiency can lead to severe toxicity when capecitabine is administered.

Medical Disclaimer

This article provides educational information about capecitabine and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.