Xeloda (Capecitabine) - Drug Interactions, Contraindications, Overdosage, etc

DRUG INTERACTIONS

Antacid

The effect of an aluminum hydroxide- and magnesium hydroxide-containing antacid (Maalox) on the pharmacokinetics of XELODA was investigated in 12 cancer patients. There was a small increase in plasma concentrations of XELODA and one metabolite (5'-DFCR); there was no effect on the 3 major metabolites (5'-DFUR, 5-FU and FBAL).

Anticoagulants

Patients receiving concomitant capecitabine and oral coumarin-derivative anticoagulant therapy should have their anticoagulant response (INR or prothrombin time) monitored closely with great frequency and the anticoagulant dose should be adjusted accordingly (see Boxed WARNING and CLINICAL PHARMACOLOGY). Altered coagulation parameters and/or bleeding have been reported in patients taking XELODA concomitantly with coumarin-derivative anticoagulants such as warfarin and phenprocoumon. These events occurred within several days and up to several months after initiating XELODA therapy and, in a few cases, within 1 month after stopping XELODA. These events occurred in patients with and without liver metastases. In a drug interaction study with single-dose warfarin administration, there was a significant increase in the mean AUC of S-warfarin. The maximum observed INR value increased by 91%. This interaction is probably due to an inhibition of cytochrome P450 2C9 by capecitabine and/or its metabolites (see CLINICAL PHARMACOLOGY).

CYP2C9 substrates

Other than warfarin, no formal drug-drug interaction studies between XELODA and other CYP2C9 substrates have been conducted. Care should be exercised when XELODA is coadministered with CYP2C9 substrates.

Phenytoin

The level of phenytoin should be carefully monitored in patients taking XELODA and phenytoin dose may need to be reduced (see DOSAGE AND ADMINISTRATION: Dose Management Guidelines). Postmarketing reports indicate that some patients receiving XELODA and phenytoin had toxicity associated with elevated phenytoin levels. Formal drug-drug interaction studies with phenytoin have not been conducted, but the mechanism of interaction is presumed to be inhibition of the CYP2C9 isoenzyme by capecitabine and/or its metabolites (see PRECAUTIONS: Drug-Drug Interactions: Anticoagulants).

Leucovorin

The concentration of 5-fluorouracil is increased and its toxicity may be enhanced by leucovorin. Deaths from severe enterocolitis, diarrhea, and dehydration have been reported in elderly patients receiving weekly leucovorin and fluorouracil.

OVERDOSAGE

The manifestations of acute overdose would include nausea, vomiting, diarrhea, gastrointestinal irritation and bleeding, and bone marrow depression. Medical management of overdose should include customary supportive medical interventions aimed at correcting the presenting clinical manifestations. Although no clinical experience using dialysis as a treatment for XELODA overdose has been reported, dialysis may be of benefit in reducing circulating concentrations of 5'-DFUR, a low–molecular-weight metabolite of the parent compound.

Single doses of XELODA were not lethal to mice, rats, and monkeys at doses up to 2000 mg/kg (2.4, 4.8, and 9.6 times the recommended human daily dose on a mg/m² basis).

CONTRAINDICATIONS

XELODA is contraindicated in patients with known hypersensitivity to capecitabine or to any of its components. XELODA is contraindicated in patients who have a known hypersensitivity to 5-fluorouracil. XELODA is contraindicated in patients with known dihydropyrimidine dehydrogenase (DPD) deficiency. XELODA is also contraindicated in patients with severe renal impairment (creatinine clearance below 30 mL/min [Cockroft and Gault]) (see CLINICAL PHARMACOLOGY: Special Populations).