emthotrexate

Question 1

Low-dose methotrexate is a very effective treatment for a number of autoimmune conditions, but is still a powerful cytotoxic and must be taken with care to avoid toxicity, patients should be well informed on how to take it, and side effects to look out for.

what dose regime is methotrexate given

Answer 1

once weekly dosing regimen

2.5mg

Question 2

side effects of methotrexate

Answer 2

Cytopenia - Monitor full blood count and advise patients to report suspected infections and bruising.
Hepatotoxicity - Monitor liver function tests. Mild elevation is normal, but discontinue if they rise to more than 3x normal.
Renal impairment - Monitor renal function.
Pulmonary fibrosis - Take a baseline CXR. Advise patients to report any respiratory symptoms eg. dyspnoea/dry cough.
Teratogenicity - Advise patients to use contraception while taking methotrexate, and for 3 months after use.

Question 3

Methotrexate’s mechanism of action is to impair folate metabolism. Any other anti-folate drug must be avoided, or it will potentiate toxicity. Examples of anti-folate agents include: Methotrexate, Trimethoprim, Permetrexed and Proguan (anti-malarial).

what should be given with

Answer 3

Folic Acid (5mg) has to be prescribed together with Methotrexate and has to be taken on a separate day to avoid interference with the therapeutic action of Methotrexate. Depending on the toxicity experienced, Folic Acid can be taken from once a week to six days a week. The standard dose is 5mg once per week, but an alternative is 1mg daily. In either case however, folic acid should not be taken on the same day as methotrexate.

“Methotrexate Monday” and “Folate Friday” may help you, and patients, remember the once weekly dosing regimen of these drugs.

Question 4

if you want to wash out methotraxta to start a fnma what should you do

Answer 4

Methotrexate is contraindicated during conception and pregnancy as it is teratogenic. The recommendation is a wash out of a few months (at least 3 months) before conception. In the event of a disease flare, low dose steroids are thought to be relatively safe. Note that high doses are associated with a small increased risk of the child having a cleft palate.

Question 5

antidote for methotrexate

Answer 5

folinic acid

Folinic acid is the reduced, and thus, active form of folic acid. The other two less common antidotes are thymidine and glucarpidase.