Methotrexate Flashcards
Methotrexate - MoA
Anti-folate
Inhibits conversion of dihydrofolate (folic acid) to tetrahydrofolate.
Tetrohydrofolate is needed to make purines/pyrimidines and therefore DNA
Anti-folate drugs
Teratogenic
Blood dyscrasias
Methotrexate - use
RA
Cancer
Psoriasis
Crohns disease
Dose + prescription
Once WEEKLY
- same day each week
Prescription requirements:
- Dose and frequency (e.g. Xmg weekly)
- One strength tablet only
Methotrexate + folic acid
Helps reduce MTX side effects
Dose:
- 5 mg once weekly on diff day to MTX (BNF dose
- 5 mg OD except on MTX day
- 1 mg OD except on MTX day
Methotrexate - missed dose
< 3 days = take ASAP
> 3 days = take next scheduled dose on usual day
Methotrexate - patient counselling
- Take full dose once a week
- Avoid OTC NSAIDs (risk of toxicity)
- Annual flu vaccination (MTX causes immunosuppresion)
- MTX treatment book
Methotrexate - Side effects
Blood dyscrasias
- Low WBC
- Low RBC
- Low platelets
Hepatotoxicity
Nephrotoxicity
Pulmonary toxicity
GI toxicity
Blood dyscrasias - low WBC
- Susceptible to infection
- Report mouth ulcers, fever, malaise, sore throat
Blood dyscrasias - low RBC
- Anaemia
- Report extreme tiredness, pallor, dizziness
Blood dyscrasias - low platelets
- Thrombocytopoenia
- Report bruising/bleeding
Hepatotoxicity
Report:
- N + V
- Dark urine
- Jaundice
- Abdominal pain (upper right)
- Itching
- Malaise
- Pale coloured stools
Nephorotoxicity
MTX is renally excreted
Nephrotoxicity = risk of MTX toxicity
Pulmonary toxicity
Report:
- SoB
- Cough
- Fever
GI toxicity
Report:
- Stomatitis
- First sign of GI toxicity
