Your child is receiving high dose IV methotrexate. Side effects of methotrexate include kidney damage and mouth sores. It is important to know what to watch for, and when and who to call for medical help.
What care does my child need?
After an infusion of methotrexate:
- Your child will need continuous IV methotrexate for 24 hours. This will keep the medicine at a blood level that will kill cancer cells.
- Your child will need continuous IV fluids.
Urine pH and methotrexate
Methotrexate is removed from the body by the kidneys. This works best when the urine’s pH (acid-base balance) is higher than 7. A urine pH less than 7 means the urine is too acidic. This may slow excretion or cause methotrexate crystals to form in the kidneys. This can cause damage to the kidneys or increase the side effects. To prevent kidney damage and increased side effects, IV fluids that have sodium bicarbonate in them are given. These fluids are started hours before the methotrexate is given.
-
- Testing the urine pH
It is important to keep the pH of the urine between 7 and 8. We will need to test the urine every 6 hours. If the urine pH is below 7, your child will receive an additional dose of sodium bicarbonate.
Leucovorin rescue and methotrexate
Leucovorin is a medicine that rescues healthy cells from the effects of methotrexate. It will be started 42 hours after methotrexate starts to help neutralize the side effects of methotrexate on healthy cells.
The leucovorin is given every 6 hours. It is continued until the methotrexate levels are low enough in the body that the leucovorin isn’t needed and your child can be discharged. (See the education sheet “Leucovorin.”)
Methotrexate levels
After the infusion of methotrexate is completed, blood tests may be done to measure the level of methotrexate in the blood.
Are there any precautions about other medicines?
Some medicines can interfere with how the body processes the high dose methotrexate. Those medicines should not be given for 24 hours before starting chemotherapy until the IV fluids are stopped after the methotrexate infusion. The medicines to avoid are:
- trimethoprim/sulfamethoxazole antibiotic (Bactrim®, Septran®, Co- trimoxazole®, SMX-TMP®)
- non-steroidal medications: ibuprofen (Advil®), naproxen (Naprosyn®), aspirin
- COX-2 inhibitors: rofecoxib (Vioxx®), celecoxib (Celebryx®)
- fluroquinolone antibiotics: ciprofloxacin (Cipro®), gatifloxacin (Tequin®), levofloxacin (Levaquin®)
- Proton pump inhibitors: Pantoprazole®