What is Pembrolizumab: Uses, Dosage, Side Effects and More

Pembrolizumab is a targeted cancer treatment that helps your immune system fight cancer cells more effectively. It's given through an IV infusion and belongs to a class of medicines called immune checkpoint inhibitors, which work by removing the "brakes" that cancer cells put on your immune system.

This medication has revolutionized cancer treatment for many patients by harnessing the power of their own immune system. While it's a powerful tool in fighting various cancers, understanding how it works and what to expect can help you feel more prepared and confident about your treatment journey.

What is Pembrolizumab?

Pembrolizumab is a laboratory-made antibody that blocks a protein called PD-1 on your immune cells. Think of PD-1 as a "stop sign" that prevents your immune system from attacking cancer cells. By blocking this protein, pembrolizumab allows your immune system to recognize and fight cancer more effectively.

This medication is also known by its brand name Keytruda. It's classified as a monoclonal antibody, which means it's designed to target one specific protein in your body. Unlike traditional chemotherapy that directly attacks rapidly dividing cells, pembrolizumab works by enhancing your body's natural defense mechanisms.

What is Pembrolizumab Used For?

Pembrolizumab treats several types of cancer by helping your immune system work better against cancer cells. Your doctor has likely prescribed it because your specific type of cancer responds well to this immunotherapy approach.

The most common cancers treated with pembrolizumab include melanoma (skin cancer), lung cancer, head and neck cancers, and certain types of kidney cancer. It's also used for Hodgkin lymphoma, bladder cancer, and stomach cancer in specific situations. Your oncologist will determine if your cancer type and stage make you a good candidate for this treatment.

Some rarer conditions that may be treated with pembrolizumab include certain types of liver cancer, cervical cancer, and endometrial cancer. The decision to use pembrolizumab often depends on specific genetic markers in your tumor, such as PD-L1 expression levels or microsatellite instability status.

How Does Pembrolizumab Work?

Pembrolizumab works by blocking the PD-1 pathway, which cancer cells use to hide from your immune system. When this pathway is blocked, your T-cells (immune fighting cells) can better recognize and attack cancer cells throughout your body.

This is considered a moderately strong cancer medication, but it works differently than traditional chemotherapy. Instead of directly killing cancer cells, it empowers your immune system to do the work. The effects can be long-lasting because your immune system has a "memory" and may continue protecting you even after treatment ends.

The medication typically takes several weeks to months to show its full effect. This is because your immune system needs time to mount an effective response against the cancer. Some patients may see results within the first few treatment cycles, while others may need longer to experience benefits.

How Should I Take Pembrolizumab?

Pembrolizumab is given only through an IV infusion at a hospital or cancer treatment center. You cannot take this medication at home, and it's always administered by trained healthcare professionals who monitor you closely during the infusion.

The infusion typically takes about 30 minutes to complete. You'll sit in a comfortable chair during this time, and many patients bring books, tablets, or have family members stay with them. Before your infusion, you may receive pre-medications to help prevent allergic reactions or reduce side effects.

You don't need to make any special dietary changes before your infusion. You can eat normally and take your regular medications unless your doctor specifically tells you otherwise. Staying well-hydrated by drinking plenty of water before and after treatment can help your body process the medication more effectively.

How Long Should I Take Pembrolizumab For?

The duration of pembrolizumab treatment varies significantly based on your specific cancer type and how well you respond to the medication. Most patients receive treatment for anywhere from several months to two years, with infusions typically given every three to six weeks.

Your oncologist will regularly monitor your progress through scans, blood tests, and physical examinations. If your cancer responds well and you're tolerating the treatment, you may continue for the full recommended duration. However, if you experience significant side effects or your cancer progresses, your doctor may adjust or stop treatment.

Some patients may be able to take treatment breaks or "drug holidays" if their cancer shows excellent response. Your medical team will work with you to determine the optimal treatment schedule that balances effectiveness with your quality of life and overall health status.

What Are the Side Effects of Pembrolizumab?

Pembrolizumab can cause side effects because it activates your immune system, which may sometimes attack healthy tissues in addition to cancer cells. Most side effects are manageable, and your healthcare team has experience helping patients through any challenges that arise.

The most common side effects you might experience include fatigue, skin rash, diarrhea, nausea, and decreased appetite. These symptoms are usually mild to moderate and often improve as your body adjusts to the medication. Many patients find that these side effects are more manageable than those from traditional chemotherapy.

More serious but less common side effects can affect various organs when your immune system becomes overactive. These may include inflammation of the lungs (pneumonitis), liver problems, thyroid disorders, or kidney issues. Your medical team will monitor you closely with regular blood tests and imaging studies to catch any problems early.

Rare but serious side effects can include severe immune-related reactions affecting the heart, brain, or other organs. While these complications are uncommon, they require immediate medical attention. Your healthcare team will teach you warning signs to watch for and provide you with contact information for urgent concerns.

Who Should Not Take Pembrolizumab?

Pembrolizumab isn't suitable for everyone, and your doctor will carefully review your medical history before prescribing it. People with certain autoimmune conditions may not be good candidates because the medication could worsen their underlying condition.

If you have active autoimmune diseases like rheumatoid arthritis, lupus, or inflammatory bowel disease, your doctor will weigh the risks and benefits carefully. You may still be able to receive pembrolizumab, but you'll need extra monitoring and possibly additional medications to manage your autoimmune condition.

Pregnant women should not receive pembrolizumab as it can harm the developing baby. If you're of childbearing age, you'll need to use effective contraception during treatment and for several months after your last dose. Your doctor will discuss family planning options and timing if this is a concern for you.

People with severe kidney or liver disease may need dose adjustments or may not be suitable candidates for treatment. Your doctor will review your organ function through blood tests before starting treatment and continue monitoring throughout your care.

Pembrolizumab Brand Name

Pembrolizumab is marketed under the brand name Keytruda, manufactured by Merck & Co. You may hear your healthcare team use either name interchangeably, as they refer to the same medication.

When you receive your treatment, the medication vial will be labeled as Keytruda, and this is what you'll see on your medical records and insurance paperwork. Both names refer to the exact same active ingredient and formulation.

Pembrolizumab Alternatives

Several other immune checkpoint inhibitors work similarly to pembrolizumab, though the best choice depends on your specific cancer type and individual circumstances. Your oncologist will select the most appropriate option based on clinical evidence and your particular situation.

Nivolumab (Opdivo) is another PD-1 inhibitor that works very similarly to pembrolizumab. For some cancer types, these medications are equally effective, while for others, one may be preferred based on research studies. Your doctor will explain why they've chosen pembrolizumab specifically for your treatment.

Other immunotherapy options include ipilimumab (Yervoy), which targets a different immune checkpoint called CTLA-4, and various PD-L1 inhibitors like atezolizumab (Tecentriq). Sometimes these medications are used in combination with pembrolizumab for enhanced effectiveness.

Traditional treatments like chemotherapy, radiation therapy, or targeted therapy drugs may also be alternatives or used alongside pembrolizumab. Your treatment plan will be personalized based on your cancer's characteristics, your overall health, and your treatment goals.

Is Pembrolizumab Better Than Nivolumab?

Both pembrolizumab and nivolumab are excellent PD-1 inhibitors that work in very similar ways, and neither is universally "better" than the other. The choice between them often depends on your specific cancer type, the research evidence available, and sometimes practical considerations like dosing schedule.

For some cancers like melanoma, both medications have shown similar effectiveness in clinical trials. For lung cancer, pembrolizumab may be preferred as a first-line treatment in certain situations, while nivolumab might be chosen for others. Your oncologist will base their decision on the most current research for your specific situation.

The side effect profiles of both medications are quite similar, though some patients may tolerate one better than the other. If you experience significant side effects with one medication, your doctor might consider switching to the other if it's appropriate for your cancer type.