Carboplatin and Pemetrexed: What to Expect

This page is for people about to start carboplatin and pemetrexed, and for the people helping them. It walks through what each drug does, the vitamins you start first, and what a cycle looks like. It ends with the signs that mean you should call for help.

Pemetrexed is an antifolate. That means it blocks enzymes that need folate, the B vitamin your cells use to build DNA. Cancer cells divide fast, so they feel the block first. Carboplatin is a platinum drug. It binds to DNA and creates cross-links that the cell cannot repair. The two drugs damage cancer cells in different ways, which is why they are paired.

The pairing is used most often in nonsquamous non-small cell lung cancer (NSCLC). Nonsquamous means the tumor cells are adenocarcinoma or large cell, not squamous. That distinction matters. Pemetrexed is not approved for squamous NSCLC. Its label says trials showed a lack of benefit there. Pemetrexed is also used with cisplatin for pleural mesothelioma.

This step surprises people. The pemetrexed label tells your team to start folic acid 400 to 1,000 micrograms by mouth once a day, beginning 7 days before the first dose. You keep taking it until 21 days after the last dose. You also get a vitamin B12 shot into a muscle 1 week before the first dose, then every 3 cycles.

These are not general health vitamins. The label says low blood counts are more likely without them. The label is blunt on one point: do not swap oral B12 for the shot. Later B12 shots can be given on the same day as treatment.

You also take dexamethasone, a steroid, 4 milligrams by mouth twice a day for 3 days in a row, starting the day before each infusion. That schedule is there to prevent a skin rash.

Those steroid tablets are yours to take at home. Starting them the day before is the part people most often miss. Follow the schedule and the amount on your own prescription rather than this page. Tell the unit if you have not been able to take them, because it changes what happens on the day.

One cycle is 21 days. Day 1 is infusion day. Days 2 through 21 are recovery. Blood work happens before each cycle.

On day 1, the order matters. Pemetrexed goes in first, over 10 minutes. Carboplatin follows. The adult dose of pemetrexed is worked out from your body surface area. Carboplatin is not dosed by body size. It is dosed to a target blood exposure called AUC, or area under the curve. The Calvert formula sets it:

Total dose in milligrams = target AUC x (GFR + 25)

GFR is your kidney filtration rate. Your team picks a target exposure, then the pharmacy converts it into milliliters in a bag. Note what this means in practice: two people of the same height and weight can get very different carboplatin doses, because their kidneys differ.

Ask how long day 1 will take. If pembrolizumab (Keytruda) is part of your plan, it goes in before the pemetrexed.

Pemetrexed leaves the body through the kidneys. The label sets a hard floor: do not give it when creatinine clearance is under 45 mL/min. Creatinine clearance is a kidney number your team estimates with the Cockcroft-Gault equation, using your creatinine level, age, weight, and sex. There is no recommended dose below 45 mL/min.

So expect a creatinine check before every cycle. If it drifts up, treatment gets held until clearance is back to 45 mL/min or higher.

One over-the-counter drug matters here. Ibuprofen raised pemetrexed toxicity in people with mild to moderate kidney impairment. If your clearance is between 45 and 79 mL/min, ask before taking ibuprofen (Advil, Motrin). Ask your team what to use for aches instead.

Blood counts drive dose changes, and the rules are written down. Treatment is not given when the absolute neutrophil count (ANC, the infection-fighting white cells) is under 1,500 per cubic millimeter or platelets are under 100,000.

After a cycle, the next dose drops based on the worst count reached:

• ANC under 500, or platelets under 50,000 without bleeding: next dose is 75 percent of the last one.
• Platelets under 50,000 with bleeding: next dose is 50 percent.
• Severe drop again after two reductions: the label says the drug is stopped.

These figures come from the FDA’s “Pemetrexed for Injection Prescribing Information.”

Non-blood problems have their own rules. Grade 3 or 4 mouth sores cut the dose to 50 percent. Diarrhea bad enough to need hospital care cuts it to 75 percent. Grade 3 or 4 nerve damage means stopping pemetrexed for good.

KEYNOTE-189 was the trial that paired this chemo with pembrolizumab. In that trial, the effects seen in at least 20 percent of people were fatigue, nausea, constipation, diarrhea, low appetite, rash, vomiting, cough, shortness of breath, and fever. Treatment was interrupted in 49 percent of people at some point. The most common reasons were low neutrophils (12 percent) and anemia (7 percent).

Carboplatin adds its own list. Its label reports hypersensitivity in about 2 percent of people, with rash, hives, itching, and rarely wheezing or low blood pressure. The label says the risk of an allergic reaction is higher in people who have had platinum drugs before. Anemia from carboplatin can build up over cycles and may need a transfusion.

Two rarer pemetrexed warnings are worth knowing by name. Bullous skin toxicity means blistering or peeling skin, and the label lists it as a reason to stop the drug for good. Report blistering or peeling skin to your team right away rather than deciding this yourself. Interstitial pneumonitis is inflammation in the lung tissue itself. New or worsening breathing problems mean treatment is held, and it is stopped for good if pneumonitis is confirmed.

Fever during chemotherapy is an emergency, not something to watch overnight. Call your oncology team at once, at any hour, or go to an emergency department if you cannot reach them.

Call 911 or go to an emergency department for bleeding that will not stop, black or tarry stools, or vomiting blood or material like coffee grounds (MedlinePlus). Blistering or peeling skin that is spreading, especially with fever, is also a 911 call. Do not drive yourself.

Call your oncology team right away, at any hour, for:

• Fever of 100.4 F (38 C) or higher. CDC's fever page for people in cancer treatment says to call your doctor immediately at that number (CDC). One reading is enough. NCI's patient page prints the 38 C threshold as 100.5 F, so call at 100.4 F and let them decide. If your team has given you a lower number, use theirs.
• Shaking chills, even with a normal temperature.
• New or worse shortness of breath.
• Blood in urine.
• A new or changed cough, a sore throat or new mouth sore, a stiff neck, burning or pain when you urinate, diarrhea, vomiting, or redness, soreness, or swelling at a port or wound. CDC lists these as signs of infection during chemotherapy (CDC).
• Skin blisters or peeling that is not spreading.

For emergencies, call 911 or go to the ER.

These signs should not wait for your next visit. The pemetrexed label says to tell your provider right away about blisters, skin sores or peeling, and about passing less urine.

• Sores in the nose or genital area.
• You are passing much less urine than usual.
• Numbness or tingling that is spreading in hands or feet.

• What carboplatin AUC target did you pick, and what was my GFR estimate?
• How many cycles of the platinum are planned?
• Will pemetrexed continue alone after the carboplatin stops?
• Who do I call at 2 a.m.? Get the number written down before you leave.

Chemotherapy, How Chemotherapy Is Given, Low White Blood Cells During Chemotherapy, Fever During Chemo, and Maintenance Immunotherapy After Lung Cancer Treatment.

• https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ae77f00f-d43b-4b75-afd5-a2a9cb7138da
• https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=48aa7ef3-9f44-2a08-e054-00144ff88e88
• https://medlineplus.gov/druginfo/meds/a607043.html
• https://www.cancer.gov/types/lung/hp/non-small-cell-lung-treatment-pdq
• https://www.cancer.gov/about-cancer/treatment/side-effects/infection
• https://www.cdc.gov/cancer-preventing-infections/patients/fever.html