It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.

Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away.

Leflunomide may also cause birth defects if the father is using it when his sexual partner becomes pregnant. Men taking leflunomide should use condoms as a form of birth control during sexual intercourse. A man intending to father a child should stop taking this medicine and check with his doctor right away.

Serious skin reactions can occur with this medicine. Stop using this medicine and check with your doctor right away if you have any of the following symptoms while taking this medicine: blistering, peeling, or loosening of the skin; chills; itching; joint or muscle pain; red skin lesions, often with a purple center; sores, ulcers, or white spots in the mouth or on the lips; or unusual tiredness or weakness.

Liver problems may occur while you are using this medicine. Stop using this medicine and check with your doctor right away if you are having more than one of these symptoms: abdominal or stomach pain or tenderness; clay-colored stools; dark urine; decreased appetite; fever; headache; loss of appetite; nausea or vomiting; skin rash; swelling of the feet or lower legs; unusual tiredness or weakness; or yellow eyes or skin.

Leflunomide can temporarily lower the number of white blood cells in your blood, increasing the chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this occurs, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:

• If you can, avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination
• Check with your doctor immediately if you notice any unusual bleeding or bruising; black, tarry stools; blood in the urine or stools; or pinpoint red spots on your skin.
• Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
• Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.
• Be careful not to cut yourself when you are using sharp objects such as a safety razor or fingernail or toenail cutters.
• Avoid contact sports or other situations where bruising or injury could occur.

Check with your doctor right away if you have a cough with or without a fever, shortness of breath, or any difficulty with breathing.

You will need to have a skin test for tuberculosis before you start using this medicine. Tell your doctor if you or anyone in your home has ever had a positive reaction to a tuberculosis test.

Using this medicine may increase your risk of getting serious infections or cancer. Talk to your doctor if you have concerns about this risk.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Adverse reactions associated with the use of leflunomide in RA include diarrhea, elevated liver enzymes (ALT and AST), alopecia and rash.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:
More common
Bloody or cloudy urine
cough
difficult or painful breathing
difficult, burning, or painful urination
dizziness
fever
frequent urge to urinate
headache
loss of appetite
nausea or vomiting
sneezing
sore throat
tightness in the chest
yellow eyes or skin
Less common
Burning feeling in the chest or stomach
burning, prickling, or tingling sensation in the fingers or toes
chest pain
diarrhea
fast heartbeat
indigestion
joint or muscle pain or stiffness
pounding heartbeat
severe stomach pain
shortness of breath
tenderness in the stomach area
unusual tiredness or weakness
Incidence not known
Area rash
black or tarry stools
bleeding gums
blistering, peeling, or loosening of the skin
bloating
blood in the stools
burning, numbness, tingling, or painful sensations
chills
clay-colored stools
confusion
constipation
continuing vomiting
cough or hoarseness
dark urine
fainting
fever with or without chills
general feeling of tiredness or weakness
high fever
large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
light-colored stools
lightheadedness
lower back or side pain
pains in the stomach, side, or abdomen, possibly radiating to the back
pale skin
pinpoint red spots on the skin
rapid, shallow breathing
red skin lesions, often with a purple center
red, irritated eyes
sores, ulcers, or white spots in the mouth or on the lips
swollen glands
unexplained bleeding or bruising
unpleasant breath odor
unsteadiness or awkwardness
unusual bleeding or bruising
upper right abdominal or stomach pain
vomiting of blood
weakness in the arms, hands, legs, or feet

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
More common
Back pain
hair loss
heartburn
skin rash
stomach pain
weight loss (unexplained)
Less common
Acne
anxiety
decreased appetite
dry mouth
gas
irritation or soreness of the mouth
itching of the skin
pain or burning in the throat
runny nose

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.