methotrexate

Question 1

what is methotrexate used for (indications)

Answer 1

Crohn’s disease, rheumatoid arthritis, neoplastic

disease (both malignant and benign tumour growths), psoriasis

Question 2

how often is a dose of methotrexate taken for all indications

Answer 2

once a week

Question 3

what are the contraindications for methotrexate

Answer 3

active infection, immunodeficiency

Question 4

what is the usual strength of methotrexate prescribed

Answer 4

usually 2.5mg tablets prescribed

to avoid any errors, only one strength of methotrexate tablet (usually 2.5 mg) is prescribed and dispensed

Question 5

what are the cautions for the use of methotrexate

Answer 5

• blood disorders (sore throat, bruising, mouth ulcers), -
• liver toxicity (nausea, vomiting, abdominal discomfort, dark urine)
• respiratory effects (pulmonary toxicity, shortness of breath)
• photosensitivity
• stomatitis (for an inflamed and sore mouth)

Question 6

when would you withdraw treatment of methotrexate from a patient

Answer 6

• clinically significant drop in white cell count or platelet count (sign of bone marrow suppression)
• if stomatitis (inflamed/sore mouth) or diarrhoea develops. (sign of GI toxicity)
• any abnormality of liver function or liver biopsy occurs
• if pneumonitis (inflamed lung tissue) suspected. (Pulmonary toxicity may be a special problem in rheumatoid arthritis)

Question 7

can methotrexate be used whilst pregnant or breastfeeding

Answer 7

avoid in pregnancy as it is teratogenic and present in breastmilk

Question 8

what monitoring needs to occur whilst on methotrexate

Answer 8

Monitoring – FBC, renal and liver function tests before and during treatment

Question 9

why is folic acid given if a patient is taking methotrexate

Answer 9

to reduce side-effects. Folic acid decreases mucosal and gastrointestinal side-effects of methotrexate and may prevent hepatotoxicity

Question 10

how long should men and women taking methotrexate use contraception for

Answer 10

need effective contraception during and for at least 6 months after treatment

Question 11

what OTC meds should patients taking methotrexate avoid

Answer 11

NSAIDS (aspirin + ibuprofen)

Question 12

why might you give FOLINIC acid to a patient taking methotrexate

Answer 12

treatment with folinic acid (as calcium folinate) may be required in acute toxicity

• folinic acid helps to prevent methotrexate-induced mucositis (sore/inflamed mouth/gut) and myelosuppression (decreased bone marrow activity)

Question 13

which antibiotic interacts with methotrexate and how

Answer 13

Trimethoprim

Both methotrexate and trimethoprim can increase the risk of nephrotoxicity. Also Trimethoprim increases the risk of adverse effects when given with methotrexate so should avoid giving both

Question 14

why must you NOT take methotrexate and folic acid on the same day

Answer 14

although folic acid is used to help reduce the side effects of methotrexate. methotrexate is an antifolate agent, so using folic acid the same day the once weekly dose of methotrexate is given, may reduce the efficacy of methotrexate

*note: it is ok to take folic acid on other days after dose of methotrexate because the half-life of methotrexate means most of the methotrexate will have left the body by the time the next dose of folic acid is given *

Question 15

what are the symptoms of methotrexate toxicity

Answer 15

• bone marrow suppression: sore throat, bruising, mouth ulcers
• GI toxicity
• liver toxicity : jaundice, N+V, dark stools, abdominal pain