Capecitabine is the name given to a cancer drug. It belongs to the group of cytostatic drugs.
What is capecitabine?
Capecitabine is a cytostatic drug used to treat cancer. The drug is a prodrug (precursor) of 5-fluorouracil (5-FU). Within the tumor, its conversion into an active substance occurs. Capecitabine is administered orally and is suitable for the treatment of metastatic or advanced breast cancer, metastatic colorectal cancer and the palliative treatment of gastric cancer. Capecitabine has been approved in the United States and Switzerland since 1998. In 2001, the drug was also approved in Germany. The cytostatic drug is marketed under the trade name Xeloda. Since 2013, the drug has also been available in generic form.
Pharmacological effect
Capecitabine is classified as belonging to the group of antagonists of pyrimidine and purine bases. As a precursor of 5-fluorouracil, it assumes great importance in the treatment of tumor cells. Thus, the effect of the cytostatic drug can be compared with that of 5-FU. The enzyme thymidine phosphorylase ensures the conversion of capecitabine into 5-fluorouracil. This occurs in strong concentrations within tumor tissue. By directing its action to the tumor cells, capecitabine can be better tolerated by cancer patients. This in turn results in fewer side effects requiring treatment. Capecitabine has the effect of inhibiting the division of the degenerated cancer cells. Optimally, the inability of the cells to divide stops the growth of the tumor. The active substance is rapidly absorbed in the gastrointestinal tract. It reaches its maximum plasma concentration after about 90 minutes. The plasma half-life of capecitabine is approximately 40 minutes. In the liver, capecitabine hydrolyzes to 5-deoxy-5-fluorouridine. As it progresses, conversion to 5-fluorouracil eventually occurs. Later, about 95 percent of the 5-FU is excreted from the body by the kidneys. The remaining excretion occurs in the stool.
Medical use and application
Capecitabine is administered as a single agent against colon cancer. However, combination therapy with other cytostatic agents can also be used. Capecitabine treatment is also considered useful if the colorectal cancer has already led to the formation of metastases (daughter tumors). Capecitabine is also used in the initial treatment of advanced gastric cancer. As part of the treatment, it is combined with active ingredients containing platinum, such as cisplatin. The indications for the cytostatic drug also include locally advanced breast cancer or metastatic breast carcinoma, in which case capecitabine is usually combined with the taxane docetaxel. However, such treatment only takes place if other chemotherapeutic measures have been unsuccessful in advance. Capecitabine can be used as a single agent if taxane therapy has been ineffective or if treatment with anthracycline appears unsuitable. Capecitabine is taken in the form of film-coated tablets. The patient takes these in the morning and in the evening half an hour after a meal. Depending on how high the doctor sets the dose, it may be necessary to swallow 3 to 7 tablets. If pronounced side effects occur, a reduction of the dose or an interruption of the treatment is necessary.
Risks and side effects
Compared with 5-FU, the side effects of capecitabine are less severe. This applies primarily to inflammation of the oral mucosa (stomatitis), nausea, vomiting, and hair loss. Nevertheless, various undesirable side effects are also possible with this cytostatic drug. These include abdominal pain, diarrhea, a decrease in lymphocytes, inflammation of the skin, an increase in the bile pigment bilirubin, and fatigue. It is not uncommon for hand-foot syndrome to manifest itself in the form of discomfort, such as insensations, tingling, numbness and severe pain in the hands and feet. Sometimes blisters or ulcers also form on them. Helpful antidotes include cold hand and foot baths and the application of creams containing uridine.Other possible side effects include indigestion, flatulence, dry mouth, itching, dry skin, headache and pain in the limbs, weakness, taste disorders, dizziness and the formation of edema (water retention). Likewise, breathing difficulties, depression, hyperglycemia, fever, back pain, nosebleeds or weight loss may occur. In the worst case, even a heart attack is possible. If severe skin reactions occur during capecitabine therapy, it must be discontinued immediately, in consultation with the physician. If the patient suffers from hypersensitivity to capecitabine or 5-FU, treatment with the anticancer agent must not be given. This is also the case if there is a deficiency of the enzyme dihydropyrimidine dehydrogenase. Other contraindications include pronounced kidney and liver dysfunction and a reduced number of blood cells such as platelets and leukocytes. In cases of severe heart disease such as cardiac insufficiency or cardiac arrhythmia, diabetes mellitus or diseases of the nervous system, the physician must carefully weigh up the risks and benefits. Capecitabine should never be used during pregnancy or breastfeeding. There is a risk of serious damage to the child. In principle, the active substance is not suitable for the treatment of children and adolescents under 18 years of age. Interactions with other drugs must also be taken into account. For example, simultaneous treatment with capecitabine and brivudine-type herpes medications must be avoided. This also applies to treatment with phenytoin, a drug for epilepsy. The use of phenytoin may lead to poisoning. If anticoagulants such as phenprocoumon or warfarin are taken at the same time, this results in a change in blood properties. This in turn may cause complications such as nosebleeds, blood in the urine or stool, and vomiting of blood.
