Ritlecitinib is used in adults and children at least 12 years old to treat a certain type of hair loss called severe alopecia areata.

Ritlecitinib is not for use in rheumatoid arthritis.

Ritlecitinib may also be used for purposes not listed in this medication guide.

You should not use ritlecitinib if you are allergic to it.

Tell your doctor if you have any signs of infection such as fever, chills, cough, body aches, tiredness, open sores or skin wounds, diarrhea, stomach pain, weight loss, painful urination, or coughing up blood.

Tell your doctor if you've had or been exposed to tuberculosis, or if you recently traveled. Some infections are more common in certain parts of the world, and you may have been exposed during travel.

Also tell your doctor if you have or have ever had:

• are being treated for an active or chronic infection;
• use any other medications;
• lung disease;
• a weak immune system (caused by disease such as HIV or by using certain medicine);
• herpes zoster (also called shingles);
• hepatitis B or hepatitis C;
• a heart attack, stroke, or other heart problems;
• any type of cancer;
• diabetes;
• if you smoke or have smoked in the past;
• low levels of platelets or low levels of white blood cell (WBC) counts in your blood; or
• severe liver disease.

Using ritlecitinib may increase your risk of developing certain cancers such as lymphoma, lung, and skin cancers. Ask your doctor about your individual risk and skin symptoms to watch for.

Tell your doctor if you recently received a vaccine or are scheduled to receive a vaccine. Make sure you are current on all vaccines before you start using ritlecitinib.

It is not known if ritlecitinib will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

If you are pregnant, your name may be listed on a pregnancy registry to track the effects of ritlecitinib on the baby.

Do not breastfeed while using this medicine, and for at least 14 hours after your last dose.

Use Ritlecitinib (Oral) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Get emergency medical help if you have signs of an allergic reaction: hives, difficult breathing, swelling of your face, lips, tongue, or throat.

Some people taking ritlecitinib have developed heart attacks, strokes, or blood clots. Stop taking ritlecitinib and seek emergency medical attention if you have:

• signs of a blood clot--numbness or weakness on one side of the body, chest pain, problems with vision or speech, pain or swelling in one leg, sudden cough or shortness of breath, wheezing, dizziness, rapid breathing, coughing up blood; or
• heart attack symptoms--chest pain or pressure, pain spreading to your jaw or shoulder, nausea, sweating.

Call your doctor at once if you have:

• signs of infection--fever, chills, sore throat, body aches, easy bruising or bleeding;
• signs of tuberculosis--cough, night sweats, loss of appetite, weight loss, and feeling very tired; or
• symptoms of herpes zoster (shingles)--skin sores or blisters, itching, tingling, burning pain, rash on your face or torso.

Your treatments may be delayed or permanently discontinued if you have certain side effects.

Common side effects may include:

• headache, dizziness, fever;
• acne, itching, hives, burning, rash, dryness, or inflammation of the skin;
• inflammation of the hair pores (folliculitis);
• low red blood cell counts (anemia);
• diarrhea;
• abnormal blood tests; or
• blisters or ulcers in your mouth, red or swollen gums, trouble swallowing.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Avoid receiving a "live" vaccine while you are being treated or right before starting treatment with ritlecitinib. Live vaccines include measles, mumps, rubella (MMR), rotavirus, typhoid, yellow fever, varicella (chickenpox), and zoster (shingles).