Cytotoxic Drugs

Last updated: Thursday, December 30, 2004


What are they?

Cytotoxic drugs are very powerful medicines. They work by affecting the growth and action of some cells that cause the joint pain,  swelling,  warmth and damage of arthritis.

Cytotoxic drugs work over a long period of time. You may not notice much effect from the drugs for the first several weeks or months of treatment.

The three cytotoxic drugs usually used to treat arthritis and related conditions are:

Generic name Brand name
Azathioprine Imuran
Cyclophosphamide Cytoxan
Methotrexate Rheumatrex

These drugs are usually given in pill form but some may be given intravenously or by injection.

This information does not cover all generic and brand names possible uses actions precautions side effects or interactions of cytotoxic drugs. It should not replace the advice and guidance given by your doctor. If you have questions about these or other medications contact your doctor or pharmacist.

Uses of Cytotoxic Drugs

Conditions treated by cytotoxic drugs

Cytotoxic drugs can be used to treat many forms of arthritis including juvenile rheumatoid arthritis, psoriatic arthritis, rheumatoid arthritis and systemic lupus erythematosus as well as conditions such as steroid-resistant polymyositispolymyositisor dermatomyositis,  Wegener's granulomatosis polyarteritis or some forms of vasculitis.


If cytotoxic drugs are recommended for you be sure to consult a doctor who has experience using these drugs. When considering treatment with cytotoxic drugs you your doctor and your family will want to consider factors such as:

  • the severity of your disease
  • the potential benefits of the drug
  • the potential side effects

As with other drugs there are no guarantees that cytotoxic drugs will work for you. On the other hand it isn't certain that serious negative effects will occur if you try these drugs. For severe cases of arthritis many experts agree that when properly used the risk of side effects from the drugs may be less than the risk to your health from the disease itself. Talk to your doctor about the side effects and whether the benefits of the medicine outweigh the risks.

Tips for taking these drugs

Taking cytotoxic drugs incorrectly can result in serious side effects. Here are some tips for taking them:

  • Learn about the medicine: Find out all you can about the medicine you're taking its risks and its benefits. Talk to your doctor about the drug and read the package insert that comes with the drug.
  • Take the right amount: Take only the amount your doctor tells you to take and take it exactly as prescribed. If you accidentally take too much contact your doctor at once. If you vomit shortly after taking a dose or miss a dose for other reasons check with your doctor to find out when to take another dose.
  • Have regular checkups: Side effects can occur at any time during your treatment with cytotoxic drugs. To keep track of side effects your doctor will order regular checkups and blood and urine tests--usually before during and for a time after treatment with the drug. Side effects are often a sign that your doctor must change the amount of medicine you're taking. Since many side effects can be detected before they become serious be sure to keep your scheduled lab test and doctor appointments.
  • Do not take any prescription or over-the-counter medicines without first checking with your doctor. Other medicines may increase the side effects or decrease the benefits of the cytotoxic drugs.
  • Keep in close touch with your doctor and contact him or her at the first sign of any problem with the medicine.


The Arthritis Foundation and the University of Washington Department of Orthopedics do not endorse any brand name or generic name medication listed here. Portions of the information presented here are adapted from the USP DI copyright 1990 the United States Pharmacopeial Convention Inc. (USP). Permission granted.

Some of this material may also be available in an Arthritis Foundation brochure. Contact the Washington/Alaska Chapter Helpline: (800) 542-0295. If dialing from outside of WA and AK contact the National Helpline: (800) 283-7800.

Adapted from a pamphlet originally prepared for the Arthritis Foundation. This material is protected by copyright.

Dangers and Side Effects

Serious side effects

Cytotoxic drugs cause different side effects in different people.

One of the most serious side effects is the suppression of certain cells:

  • White blood cells which help your body fight infections. When these are suppressed you may get infections more easily.
  • Platelets which help your blood clot. When these are suppressed you may bruise and/or bleed more easily.
  • Red blood cells which carry oxygen to your tissues. When these are suppressed you may have anemia (extreme tiredness and fatigue).

When to contact the doctor

Contact your doctor right away if you notice these side effects:

  • Signs of infection
    • fever chills or very sore throat
  • Signs of bleeding
    • any unusual bleeding or bruising
    • black tarry stools a sign of internal bleeding
    • pinhead-size red spots on lower legs
  • Signs of anemia
    • unusual tiredness or weakness
  • Lung problems caused by methotrexate
    • cough or severe shortness of breath with or without a fever
  • Bladder problems caused by Cytoxan
    • blood in the urine or painful urination

While these side effects don't happen very often you should still be aware of them. Some of them are signs of serious problems which should be treated right away.

Other side effects

Other side effects may occur with these drugs. If you have any of these side effects or other problems not listed here check with your doctor or pharmacist:

  • loss of appetite
  • nausea or stomach pain
  • diarrhea
  • sores or ulcers in the mouth
  • hair loss
  • missed menstrual periods
  • rash

What to do for side effects

The most important thing you can do to treat and help avoid some side effects is to have regular checkups. Here are some other things you can do to handle the following side effects:

Risk of infection Stay away from adults and children who have contagious illnesses such as colds the flu or chickenpox. Do NOT have any immunizations without checking with your doctor because they could lead to infection. Report any sign of an infection to your doctor right away.
Loss of appetite Plan meals when you're not feeling nauseous. Try eating small more frequent meals. Ask your doctor if you can take the medicine at bedtime to reduce this side effect.
Mouth sores Contact your doctor if these develop. Use a soft-bristled toothbrush. Use salt water or peroxide as a mouth wash. Eat soft non-spicy foods of medium to cold temperature. If the pain doesn't go away ask your doctor about using a topical pain reliever before meals.
Easy bruising or bleeding This could be a sign of serious problems so you should contact your doctor right away.

Talk to the doctor

Your doctor needs to know about the following conditions in order to decide whether to recommend cytotoxic drugs:

  • If you are pregnant or if you plan to have children: cytotoxic drugs may cause birth defects if either parent is taking them during the time of conception or if taken during pregnancy. These drugs may also cause short- or long-term sterility. After treatment is stopped women should wait at least one menstrual cycle before trying to get pregnant. Men should wait at least three months before trying to have children.
  • If you have allergies to any medications.
  • If you are breast-feeding: breast-feeding is generally not recommended while taking these medications.
  • If you are taking any other medications vitamins mineral supplements or over-the-counter drugs: don't take other medications without your doctor's approval.
  • If you have any other medical problems especially kidney or liver disease.
  • If you are often around people who have colds the flu or other infections: you may have a higher risk of catching their infection.
  • If you have ever been treated with X-rays or cancer medications.
  • If you drink alcohol.

Different types

Each cytotoxic drug is different and has its own special instructions.

Azathioprine (Imuran) is usually given in pill form (2-3 tablets daily) or by injection. The dose may be lowered after the desired response is obtained.

  • Do not take with allopurinol (Zyloprim) a drug used to treat gout. The combination of these two drugs may be toxic.
  • Take the drug with or after meals to reduce stomach upset.

Cyclophosphamide (Cytoxan) is usually given in pill form or intravenously according to a prescribed schedule. It is probably the strongest cytotoxic drug. It may cause additional side effects such as cystitis (inflammation of the bladder marked by blood in the urine and painful urination) as well as bladder cancer.

  • Drink extra fluids every day to help dilute toxic build-up in the bladder. Ask your doctor how much extra fluid to drink.
  • Do not take cyclophosphamide at bedtime. It will build up in your urine and will stay in your bladder too long. Some doctors recommend emptying your bladder in the middle of the night at least once even if it means setting an alarm clock to do so.

Methotrexate (Rheumatrex) is usually given in pill form and sometimes by weekly injections. This drug can cause additional side effects such as liver scarring (cirrhosis) and a lung problem similar to pneumonia which causes shortness of breath cough and a fever.

  • If you accidentally take too much contact your doctor right away to receive an antidote.
  • Do not drink alcohol while taking this drug because it can make any liver problems worse.
  • Contact your doctor before you take any other medicines especially antibiotics. Some antibiotics can make methotrexate much more toxic.