Alemtuzumab: what it treats, how you receive it, side effects
Last updated September 7, 2026.
**Alemtuzumab is an infused monoclonal antibody medicine used for certain forms of multiple sclerosis and leukemia.** It targets CD52, a protein on certain immune cells, helping remove those cells. Serious immune complications can occur long after treatment, so you must keep all scheduled monitoring appointments even when you feel well.
What does it treat?
Lemtrada treats relapsing forms of multiple sclerosis (MS) in adults, including relapsing-remitting MS and active secondary progressive MS, generally after an inadequate response to at least two MS medicines. MS can cause episodes of weakness, numbness, or vision changes. Campath treats B-cell chronic lymphocytic leukemia, a cancer involving abnormal white blood cells.
How do you take it?
You receive diluted liquid through an IV from a healthcare professional. Lemtrada is 12 mg daily over 4 hours for 5 consecutive days, then 3 consecutive days 12 months later; additional 3-day courses must be at least 12 months apart. Campath starts at 3 mg daily, then 10 mg daily as tolerated, then 30 mg on alternate days three times weekly, over 2 hours, for 12 weeks total. Its limits are 30 mg per dose and 90 mg weekly. Meals do not determine infusion timing; follow the food precautions below. Call your infusion team for a missed appointment; never double doses. Campath interruptions of at least 7 days require restarting dose escalation. Report fever, bleeding, or infusion symptoms immediately before receiving more.
Side effects to know
- Common: You may have rash, headache, fever, chills, nausea, diarrhea, fatigue, or trouble sleeping; report symptoms during an infusion immediately.
- Serious: Alert your infusion team immediately so they can stop treatment for a serious reaction; get urgent help for throat swelling, chest pain, unusual bleeding, bloody urine, or fever. Serious risks include infections and low blood counts; Lemtrada also carries warnings for autoimmune disease, stroke, and certain cancers.
Who should not take it?
You must not receive Lemtrada with HIV, an active infection, or a known allergy to its ingredients. Discuss kidney, thyroid, liver, bleeding, or heart problems and previous alemtuzumab exposure. Review immune-suppressing medicines and vaccines with your specialist. Discuss pregnancy or breastfeeding before treatment because alemtuzumab can harm a fetus; breastfeeding instructions differ by product. Ask your team about alcohol, especially with sedating premedicines.
When is it an emergency?
Call 911 for collapse, breathing trouble, throat swelling, sudden weakness on one side, trouble speaking, or a sudden severe headache or neck pain. Stroke and artery tears have occurred shortly after Lemtrada. Uncontrolled bleeding or fever with confusion needs emergency care. For a suspected overdose, call Poison Control at 1-800-222-1222 and your infusion team immediately; severe headache, dizziness, or fainting can occur.
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Common questions
What is the maximum dose?
Lemtrada's recommended daily dose is 12 mg on scheduled infusion days. Campath's maximum single dose is 30 mg, with no more than 90 mg weekly. These schedules are not interchangeable.
Can I drink alcohol?
The labels do not specify an alcohol allowance. Ask your infusion team before drinking. Avoid alcohol with premedicines that make you sleepy.
What about pregnancy and breastfeeding?
Use effective contraception during treatment and for 4 months after Lemtrada or at least 3 months after Campath. Contact your specialist immediately if you become pregnant. Do not breastfeed during Campath or for at least 3 months afterward. With Lemtrada, discuss breastfeeding benefits and potential infant risks with your specialist.
Do I need to avoid certain foods?
You do not take this infusion with a meal. With Lemtrada, avoid unpasteurized dairy and undercooked meat or seafood. Avoid deli meats unless adequately heated to reduce Listeria exposure. Begin these precautions before treatment and discuss how long to continue.
What happens after an overdose?
An overdose can cause severe infusion reactions or dangerously low blood counts. Symptoms can include headache, dizziness, or fainting. Contact your infusion team and Poison Control immediately, even without symptoms.
Which medicines or vaccines need review?
Tell your specialist about chemotherapy and other medicines that suppress immunity. Review vaccines before treatment and avoid live vaccines after treatment until your specialist advises otherwise. Take prescribed infection prevention medicines as directed. With Lemtrada, continue monthly blood and urine checks and thyroid testing every 3 months until 48 months after your last infusion.