DMARDs Flashcards
Name the conventional synthetic DMARDs (csDMARDs)
Methotrexate
Hydrochloroquine
Sulfosalazine
Leflunomide
What are the indications for methotrexate?
Rheumatoid arthritis
Tx of psoriasis that has not responded to topical, steroids or phototherapy
Psoriatic arthritis
Crohn’s disease
Ectopic pregnancies
Neoplastic disease
What is the pharmacodynamic of methotrexate?
Inhibits dihydrofolate reductase, essential for the synthesis of purines and pyrimidines (i.e., nucleotides)
This prevents cell division and leads to anti-inflammatory action
What is the pharmacokinetic of methotrexate?
Bioavailability = 64-90%
Protein binding = 46.5-54% plasma proteins
Half-life = 3-10 hours (low dose), 8-15 hours (high dose)
Metabolism = hepatic (via folylpolyglutamate synthase)
Excretion = kidney (via urine), some in bile (8.7-26%) with IV administration
N.B: methotrexate has a narrow therapeutic index and should not be taken everyday
What are the contraindications for methotrexate?
Acute infection
Pregnancy and breastfeeding
Ascites
Immunodeficiency syndrome
Significant pleural effusion
Severe hepatic impairment
What are the side-effects of IV/Oral methotrexate?
Anaemia
Liver cirrhosis
Decreased appetite
Pulmonary fibrosis
GI symptoms (i.e., vomiting, diarrhoea)
Nausea
Leucopenia/bone marrow disorders/agranulocytosis
What are the side-effects specific to IV methotrexate?
Necrotising demyelinating leukoencephalopathy
Neurotoxicity
According to NICE guidelines what monitoring should be done for patients with blood dyscrasias (i.e., any disorder of the blood e.g., leukaemia etc) or liver cirrhosis on low-dose methotrexate?
FBCs + Us&Es every 1-2 week until therapy is stabilised then every 2-3 months thereafter
Also patients should be advised to report all symptoms and signs suggestive of infection, especially sore throat
How is methotrexate monitoring done at the Royal Sussex?
Once a week for 6 weeks
Then once a month for 3 months
Then 3 monthly thereafter
What are the significant drug interactions for methotrexate?
Methotrexate + trimethoprim = depletion of folic
Methotrexate + PPIs = increased clearance of Methotrexate
Methotrexate + NSAIDs = increased risk of toxicity
Methotrexate + Phenoxymethylpenicillin/Piperacillin/Piroxicam/Pivmecillinam = increased risk of toxicity
Methotrexate + live vaccines (e.g., infleunza, MMR) = increased risk of generalised infection (possibly life threatening)
Methotrexate + Levetiracetam = decreased clearance of Methotrexate (this can cause toxicity as Methotrexate has a narrow therapeutic window)
Methotrexate + Nitrous oxide = increased risk of toxicity
What other supplement should be prescribe in conjunction with methotrexate and why?
Folic acid
Decreases mucousal and GI side-effects (no evidence it reduced haematological side effects)
When should methotrexate be withdrawn?
If the patient has:
ulcerative stomatitis
diarrhoea
Suggests GI toxicity
What drug may be required in acute methotrexate toxicity?
Folinic acid (as calcium folinate)
A patient has moderate-severe active rheumatoid arthritis. What dose of methotrexate would they be given?
7.5g once weekly
(max dose = 20mg)
A patient has severe active rheumatoid arthritis. What dose of methotrexate would they be given?
Initially 7.5mg
Then increase in steps of 2.5mg once weekly
Max 25mg per week