Methotrexate: Uses, Side Effects and Dosage

ABOUT THIS MEDICATION

What the medication is used for:

Methotrexate belongs to a group of medicines known as antimetabolites. It is used in high doses to treat certain types of cancers, including breast cancer, Non-Hodgkin's lymphoma and leukemia. At lower doses, it may also be used to treat severe psoriasis and severe rheumatoid arthritis. Methotrexate therapy is used to control psoriasis and rheumatoid arthritis but it will not cure them.

What it does:

Methotrexate works by blocking an enzyme needed by body cells to live. This interferes with the growth of some cells, such as skin cells in psoriasis that are growing rapidly. In rheumatoid arthritis, Methotrexate helps to reduce inflammation resulting in joint swelling. In cancer, Methotrexate works by blocking an enzyme process in cancer cells so that they cannot grow. Some normal cells in the body may be affected as well.

When it should not be used:

Do not take Methotrexate if you:

• Are allergic to any component of the drug.

• Are pregnant. Methotrexate can cause harm to your unborn

  baby. Women of childbearing potential should not be started on Methotrexate until pregnancy is excluded.

• Are breast feeding.

• Have psoriasis or rheumatoid arthritis and the following:

  • alcoholism (drink excessive alcohol)

  • chronic liver disease

  • immunodeficiency (resistance to infectious diseases is

    reduced)

  • blood disorders

Methotrexate formulations and diluents containing preservatives must not be used for intrathecal (injected into the spinal canal/fluid), intraventricular (injected into the ventricle) or high dose therapy.

What the medicinal ingredient is:

Methotrexate (meth-o-TREX-ate).

What the important nonmedicinal ingredients are:

• Tablets: Corn starch, lactose and magnesium stearate; dye free.
• Injection: Benzyl alcohol, hydrochloric acid, sodium chloride, sodium hydroxide and water for injection.

What dosage form it comes in:

• Tablet: 2.5 mg.
• Injection: 25 mg/mL.

WARNINGS AND PRECAUTIONS

Before Using This Medicine

Before you start taking Methotrexate, you should tell your doctor if you have any of the following conditions:

• have or have had any unusual or allergic reaction to

  Methotrexate

• are pregnant or planning to become pregnant. Methotrexate can cause birth defects (deformed babies) or death of an unborn baby. Both male and female patients must use effective birth control methods all the time while taking Methotrexate and a few months after the last dose of the drug Methotrexate may cause sterility (infertility), which could be permanent. Be sure to discuss this with your doctor before taking Methotrexate. Tell your doctor right away if you think you have become pregnant while taking Methotrexate.
• are breast-feeding or plan to breastfeed. Methotrexate may cause serious side effects. Do not breastfeed while you are taking the drug
• have kidney problems
• have or have had liver problems, including hepatitis B or hepatitis C infection
• have lung problems
• have problem with your immune system, or infections
• have gastrointestinal problems such as vomiting, diarrhea, mouth sores or inflammation, ulcer, or colitis (ulcer of intestines)
• have a skin disease
• have a neurologic disorder
• drink alcohol

Methotrexate increases sensitivity to sunlight. Avoid sun exposure and do not use a sunlamp while taking this drug.

Precautions While Using This Medicine

• Do not take Methotrexate daily or more than the dose

  prescribed. Methotrexate can cause serious toxic reactions which may result in death.

• Do not drink alcohol.

• Do not drive a car or operate machinery until you know how

  Methotrexate affects you since the drug may cause dizziness and fatigue.

• Drink extra fluid to prevent kidney problems.

• Have regular blood tests to reduce the risk of infection or

  bleeding. Methotrexate can lower the number of white blood cells and there is an increased risk of infection or bleeding.

• Talk to your doctor if you need a vaccination. Live vaccines

  may cause severe infections. Live vaccines or contact with any individual who has had a live vaccination should be avoided, since your ability to fight an infection (immune system) is decreased while taking Methotrexate.

INTERACTIONS WITH THIS MEDICATION

Tell your doctor and pharmacist what prescription and nonprescription medications, vitamins and herbal preparations you are taking or have recently taken. Methotrexate may interact with the following drugs:

• nonsteroidal anti-inflammatory drugs (NSAIDs) and

  salicylate (acetylsalicylic acid or ASA)

• drugs that may cause harm to the liver (leflunomide,

  azathioprine, sulfasalazine, retinoid)

• phenylbutazone
• phenytoin (to treat seizures)
• probenecid
• amphotericine B (may cause harm to kidneys)

• certain antibiotics such as penicillins, tetracycline,

  vancomycin, nystatin, neomycin, trimethoprim/ sulfamethoxazole, ciprofloxacin

• theophylline
• mercaptopurine
• folic acid or folinic acid
• cytarabine
• radiotherapy

The absorption of Methotrexate when taken orally is reduced by food, particularly milk.

PROPER USE OF THIS MEDICATION

Take Methotrexate only as directed by your doctor. Do not take more or less of it, and do not take it more often than your doctor ordered. The exact amount of medicine you need has been carefully worked out. Taking too much may increase the chance of side effects, while taking too little may not improve your condition. You should check with your doctor if you are not certain how to take the medication.

• In most cases, Methotrexate is taken once weekly; the prescribed dose is taken on a single day of the week.

• In some cases, your healthcare professional may instruct you to take Methotrexate every 12 hours for 3 doses; you

  should only do this once a week, and should not take more than 3 doses each week.

  • It should never be taken every day of the week.
  • Taking Methotrexate daily, or in a dose larger than prescribed can result in serious complications, often requiring hospitalization, and sometimes resulting in death. Taking even small doses of Methotrexate daily for less than a week can result in serious consequences, including death.
  • Select a day of the week when you are most likely to remember to take Methotrexate, and take it on that same day each week.
  • Each time you refill your prescription, check to see whether the dose and/or the number of tablets you need to take have changed.

Methotrexate is often given together with certain other medicines. If you are using a combination of medicines, make sure that you take each one at the proper time and do not mix them. Ask your doctor or pharmacist to help you plan a way to remember to take your medicines at the right times.

While you are using Methotrexate, your doctor may want you to drink extra fluids so that you will pass more urine. This will help the drug to pass from the body, and will prevent kidney problems and keep your kidneys working well.

If you vomit shortly after taking a dose of Methotrexate, check with your doctor. You will be told whether to take the dose again or to wait until the next scheduled dose.

Usual dose:

The dose of Methotrexate will be different for different patients. The dose that is used may depend on a number of things, including what the medicine is being used for, the patient's size, whether the medicine is being given by mouth or by injection, and whether or not other medicines are also being taken. If you are taking or receiving Methotrexate at home, follow your doctor's orders or the directions on the label. If you have any questions about the proper dose of Methotrexate, ask your doctor.

Overdose:

• Immediately call your doctor or go to the nearest hospital emergency department or call your poison control centre.
• Do this even if you have no signs of discomfort.
• Always take the labelled medicine bottle with you, even if it is empty.

Missed Dose:

• If you missed a scheduled dose, contact your doctor for instruction.

SIDE EFFECTS AND WHAT TO DO ABOUT THEM

Along with their needed effects, medicines like Methotrexate can sometimes cause unwanted effects. Also, because of the way these medicines act on the body, there is a chance that they might cause other unwanted effects that may not occur until months or years after the medicine is used. These delayed effects may

include certain types of cancer, such as leukemia. Discuss these possible effects with your doctor.

Methotrexate commonly causes nausea and vomiting. Even if you begin to feel ill, do not stop using this medicine without first checking with your doctor. Ask your doctor for ways to lessen these effects.

The most common side effects include;

• Upset stomach, stomach pain, vomiting, nausea, loss of

  appetite, dizziness, chills and fever, diarrhea or sores on lips or mouth.

• A fall in the number of white blood cells. This may reduce

  your resistance to infection and increase your chances of cold sores, blood poisoning or swelling of blood vessels.

• Tiredness (fatigue).

Less common side effects are:

• Headaches, hair loss, mood changes, confusion, ringing in the

  ears, sore eyes, skin rashes, increased sensitivity to sunlight or unexplained weight loss.

• A fall in the number of other blood cells. This may increase

  your chances of bruising, bleeding or tiredness.

• Damage to the lungs.
• Harm to the unborn baby.
• Convulsions

Rarely, Methotrexate can cause other side effects including:

• Liver damage, kidney damage, pain or difficulty urinating,

  lower back or side pain, blood in urine or stools, dark urine

• Fits, blurred vision, short term blindness
• Drowsiness, weakness
• Hoarseness

• Bloody vomit, black, tarry stools or pin-point red spots on the

  skin

• Reddening or whitening of the skin, acne, boils, itching

  yellow skin or eyes

• Impotence or loss of interest in sex , decreased fertility,

  abortion

• Diabetes, thinning of the bones, painful muscles and joints
• Low blood pressure
• Gastrointestinal ulcers

More rarely, it can cause:

• Skin rash and other skin disorders.
• Cancer of lymph glands, sudden death
• Severe allergic reactions.
• Leukoencephalopathy
• Damage to heart

This is not a complete list of side effects. For any unexpected effects while taking Methotrexate contact your doctor or pharmacist.

HOW TO STORE IT

To store this medicine:

• Keep out of the reach and sight of children.
• Do not handle Methotrexate if you are pregnant or intend to become pregnant.
• Store it at room temperature and away from heat and direct light. Avoid freezing Methotrexate Injection.
• Do not store the Methotrexate Tablets in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.
• Ask your pharmacist how to dispose of medicines no longer required.

REPORTING SUSPECTED SIDE EFFECTS

To monitor drug safety, Health Canada through the Canada Vigilance Program collects information on serious and unexpected side effects of drugs. If you suspect you have had a serious or unexpected reaction to this drug you may notify Canada Vigilance:

You can report any suspected adverse reactions associated with the use of health products to the Canada Vigilance Program by one of the following 3 ways:

---------------------------------------------------------------------------- Report online at www.healthcanada.gc.ca/medeffect Call toll-free at 1-866-234-2345

Complete a Canada Vigilance Reporting Form and:

• Fax toll-free to 1-866-678-6789, or

• Mail to: Canada Vigilance Program Health Canada

  Postal Locator 0701D

  Ottawa, ON K1A 0K9

Postage paid labels, Canada Vigilance Reporting Form and the adverse reaction reporting guidelines are available on the MedEffect^™ Canada Web site at

www.healthcanada.gc.ca/medeffect.

NOTE: Should you require information related to the management of side effects, contact your health professional. The Canada Vigilance Program does not provide medical advice.

MORE INFORMATION

This document plus the full Product Monograph, prepared for health professionals can be found at:

www.Pfizer.ca

or by contacting the sponsor, Pfizer Canada Inc. at: 1 800-463-6001

Last revised: April 21, 2011