Imatinib — practical guide for patients

One drug changed many people’s lives: imatinib (often known by the brand Gleevec) turned some deadly cancers into manageable conditions. If you or someone you care about is starting imatinib, this page gives straight, useful facts—what it treats, how it works, common side effects, and the checks your doctor will do.

How imatinib works and when it’s used

Imatinib is a targeted cancer drug called a tyrosine kinase inhibitor (TKI). It blocks specific proteins that help cancer cells grow. The two most common uses are chronic myeloid leukemia (CML) and gastrointestinal stromal tumors (GIST). Doctors choose imatinib when tests show the tumors depend on those abnormal proteins.

It’s usually a daily pill. Doses vary—often 400 mg a day for many CML patients and sometimes higher for GIST—but your doctor will pick the right dose for you based on the disease, response, and side effects.

What to watch for: side effects, tests, and interactions

Most people tolerate imatinib, but expect some side effects. Common ones are swelling (especially around the ankles), nausea, muscle cramps, fatigue, rash, and mild low blood counts. Less common but serious issues include liver problems and fluid around the lungs or heart. If you get sudden breathlessness, jaundice (yellow skin/eyes), or severe belly pain, get medical attention fast.

Your doctor will monitor blood counts and liver tests regularly—often every few weeks at first, then less often when things are stable. Tell your team about new symptoms and bring a list of all medicines and supplements you take.

Imatinib interacts with other drugs. Strong CYP3A4 inhibitors (like some antifungals and certain antibiotics) can raise imatinib levels. CYP3A4 inducers (like rifampin or some seizure meds) can lower its effect. It can also affect blood thinners (warfarin) and certain heart medicines. Avoid grapefruit or grapefruit juice unless your doctor says it’s OK.

Resistance can happen: sometimes cancer cells change and imatinib stops working. If that occurs, doctors may switch to another TKI or try different treatments. Regular monitoring helps spot resistance early.

Pregnancy and breastfeeding: imatinib can harm an unborn baby. Use reliable contraception and talk with your oncologist if you’re planning pregnancy or become pregnant while on treatment.

Want a quick checklist? Keep a symptom log, attend scheduled blood tests, avoid grapefruit, share all medicines with your team, and never stop the drug suddenly without medical advice.

If you need more in-depth articles, look for posts on our site about dosing, managing side effects, and safe ways to buy medications online. Always follow your doctor’s plan—this guide helps you ask the right questions and stay safe while on imatinib.