Cladribine belongs to the class of medications called selective immunosuppressants.

This medication is used to treat adults with relapsing remitting multiple sclerosis (RRMS) who have not responded well to, or cannot tolerate, other treatments for multiple sclerosis.

Multiple sclerosis (MS) is a disease that affects the nervous system. It is believed that MS is an autoimmune disease, a condition in which an individual's immune system starts reacting against his or her own tissues. For unknown reasons, the immune system sees the myelin sheath (a protective layer covering the nerves) as foreign and attacks it.

Cladribine appears to affect the immune system to reduce the activity of the immune system attacking the myelin sheath, slowing down damage to the nerves and the frequency of MS flare-ups.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

Treatment with cladribine consists of two treatment courses over 2 years. The dose of cladribine is 10 mg or 20 mg taken by mouth once daily, for 4 or 5 days at the beginning of the first and second months of year 1. This is then repeated at the beginning of the first and second months of year 2. The dose of cladribine, when used to treat MS, is based on weight. Your doctor will calculate the total dose and the correct number of tablets you are to take.

Cladribine may be taken with food or on an empty stomach. Other medications that you take by mouth should be separated from cladribine by at least 3 hours on the days that you take cladribine.

Because these tablets do not have a coating, it is important that your hands are dry before you remove the medication from the packaging. The tablets must be taken immediately with a glass of water. Do not crush or chew the tablets. Wash your hands immediately after taking cladribine, to remove any residue that may be left after handling the medication.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor.

If you miss a dose, and you remember on the same day you were supposed to take it, take it as soon as possible and continue with your regular schedule. If you miss a dose and do not remember until the following day, do not take a double dose to make up for the missed one. You will need to extend the number of treatment days by one extra day. You must take the total number of doses in each treatment cycle for cladribine to have the best effect for you. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature in its original packaging until you are ready to take a dose. This will protect it from light and moisture. Keep this and all medications out of the sight and reach of children.

Each round, white, biconvex tablet, engraved with "C" on one side and "10" on the other side contains 10 mg of cladribine. Nonmedicinal ingredients: hydroxypropyl betadex, sorbitol, and magnesium stearate.

Do not take this medication if you:

• are allergic to cladribine or any ingredients of the medication
• are at an increased risk of developing infections
• have a disease that reduces the effectiveness of the immune system
• are taking other medications that suppress the immune system
• are breast-feeding
• are pregnant
• have a history of progressive multifocal leukoencephalopathy (PML)
• have active cancer
• have moderate to severely decreased kidney function
• have severe active or long-term infections caused by bacteria, viruses, or fungi (e.g., hepatitis, tuberculosis)
• men who could father children or women who could become pregnant and do not plan to use effective birth control while taking this medication and for 6 months after taking the last dose of cladribine

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• back pain
• cold sores
• cold symptoms (e.g., fatigue, nasal congestion, cough, sore throat)
• diarrhea
• hair loss or thinning
• headache
• nausea
• rash
• toothache
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• abdominal pain
• anxiety
• fever
• flu and flu-like symptoms (e.g., fatigue, sore throat, headache, fever, chills)
• symptoms of a chest or lung infection (bronchitis, pneumonia; e.g., shortness of breath, cough, chest pain)
• symptoms of infection (e.g., unusual fatigue, fever, aches, pain, flu-like symptoms)
• symptoms of shingles (e.g., "band" of severe pain, blistering rash, headache, burning, tingling, numbness or itchiness of the skin, general feeling of being unwell)
• symptoms of tuberculosis (e.g., persistent cough, fever, weight loss)
• vaginal yeast infection (e.g., itching, white, curd-like discharge)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• symptoms of progressive multifocal leukoencephalopathy (PML) (e.g., worsening weakness on one side of the body, clumsiness, vision changes, confusion, personality changes)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Birth control: This medication should not be used during pregnancy. Women who could become pregnant who are taking cladribine and female partners of men who are taking cladribine should use an effective method of birth control during treatment and for at least 6 months after the last dose of the medication. It is not known if cladribine will make birth control pills less effective. If you are using birth control pills, a barrier method of contraception (e.g., condoms) should be added during treatment and for at least 4 weeks after the last dose in each treatment year. If you become pregnant while taking this medication, contact your doctor immediately.

Cancer: As with other medications that reduce the effectiveness of the immune system, cladribine may increase the risk of developing certain types of cancer. Discuss any concerns you may have with your doctor. Report any unusual infections, swelling or persistent pain, or unintentional weight loss to your doctor as soon as possible.

Fructose intolerance: This medication contains sorbitol. If you have hereditary problems of fructose intolerance, you should not take this medication.

Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Progressive multifocal leukoencephalopathy (PML): There have been reports of PML after using cladribine. PML is a rare disorder that causes nerve damage in the brain. If you experience memory loss, vision loss, trouble thinking, or difficulty walking, contact your doctor immediately.

Serious infections: Cladribine affects the way your body's natural defences work to fight infection. This makes the body more likely to develop infections due to bacteria, viruses, and fungi. This effect is increased if you are taking cladribine with other medications that reduce the body's ability to fight infection. For some people, these infections have been fatal. If you have a history of chronic or frequent infections, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Contact your doctor right away if you notice symptoms of a serious infection, such as fever, chills, headache, flu-like symptoms, feeling tired, cough, blood in the sputum, shortness of breath, night sweats, weight loss, nausea, vomiting, diarrhea, frequency or burning while passing urine, redness or swelling of skin or joint, cold sores, tooth pain, or new or worsening pain in any part of the body.

Vaccinations: It is not known how effective vaccines may be after treatment with this medication. Certain immunizations may be dangerous if given while receiving or shortly after receiving a treatment course of cladribine. Before starting treatment with this medication, check with your doctor to ensure your immunizations are up to date. Vaccinations, including vaccination against chicken pox or shingles, should be completed at least 6 weeks before starting to take cladribine.

Pregnancy: There is very little information about the effects of cladribine on the mother or developing baby if this medication is taken during pregnancy. It must not be used if you are pregnant. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if cladribine passes into breast milk. If you are breast-feeding and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

Seniors: People 65 years of age and over were not included in studies for cladribine. Because seniors are more likely to have decreased kidney or liver function, they may be more likely to experience side effects of cladribine.

There may be an interaction between cladribine and any of the following:

• 5-ASA medications (e.g., mesalamine, olsalazine, sulfasalazine)
• aldesleukin
• antiviral medications (e.g., acyclovir, cidofovir, famciclovir, ganciclovir, valacyclovir, valganciclovir)
• apalutamide
• azathioprine
• baricitinib
• biologic disease-modifying anti-rheumatic medications (e.g., abatacept, etanercept, infliximab, tocilizumab)
• birth control pills
• carbamazepine
• BCG (bacillus Calmette-Guérin)
• cancer medications (e.g., capecitabine, carboplatin, clofarabine, cyclophosphamide, cytarabine, doxorubicin, fludarabine, fluorouracil, gemcitabine, ifosfamide, mercaptopurine, nelarabine, pimecrolimus pomalidomide, thioguanine, vincristine)
• carbamazepine
• clopidogrel
• clozapine
• cobicistat
• corticosteroids (e.g., budesonide, dexamethasone, hydrocortisone, fluticasone, prednisone)
• cyclosporine
• denosumab
• dexrazoxane
• dipyridamole
• echinacea
• eltrombopag
• eslicarbazepine
• everolimus
• fingolimod
• hydroxyurea
• hepatitis C antivirals (e.g., elbasvir, glecaprevir and pibrentasvir, grazoprevir, ledipasvir, velpatasvir, voxilaprevir)
• HIV nucleoside reverse transcriptase inhibitors (NRTIs; abacavir, didanosine, emtricitabine, lamivudine, tenofovir, zidovudine)
• HIV protease inhibitors (e.g., atazanavir, lopinavir, ritonavir)
• imiquimod
• interferon
• leflunomide
• linezolid
• methimazole
• mycophenolate
• nifedipine
• ozanimod
• phenytoin
• ribavirin
• rifampin
• roflumilast
• St. John's wort
• siponimod
• sirolimus
• tacrolimus
• teriflunomide
• tofacitinib
• tolvaptan
• upadacitinib
• vaccines

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.