Azathioprine, leflunomide, mercatopurine, and methotrexate, drug monitoring in primary care during COVID-19

The following advice is for the management of patients taking DMARDs for rheumatology related conditions. 

General guidance on management of rheumatology patients during COVID-19 is available from the British Society for Rheumatology.

This page gives advice on drug monitoring in primary care during COVID-19 for the following drugs when used as DMARDs in stable patients (stable patients are defined as those who have been on current treatment for >12 months and at a stable dose for >6 weeks):

  • Azathioprine
  • Leflunomide
  • Mercaptopurine
  • Methotrexate

Advice on drug monitoring for other medicines during COVID-19 is here

For this group of drugs, usual monitoring recommendations are: 

  • Patients on any one these medicines usually require FBC, CrCl or calculated GFR, ALT and/or AST, and albumin monitored every 3 months
  • Additionally, blood pressure and weight to be checked at each monitoring visit for leflunomide
  • More frequent monitoring is appropriate in patients at higher risk of toxicity

During the COVID-19 pandemic, recommendations to reduce attendances are:

  • Where DMARD use has been successful and stable (see definition of stable above) consider extending the monitoring interval to up to every 6 months
  • However, extending blood monitoring is not suitable if the patient has:
    • poor renal function with CKD ≥ 3
    • severe liver disturbance or abnormal liver results due to DMARDs within previous 3 months
    • severe abnormal WBC results due to DMARDs within previous 3 months

For patients with symptoms of COVID-19, recommendations are:

  • Consider stopping medication (see “Should patients cease their medication as a precaution?” advice from BSR) and seek specialist advice on when to re-start
  • Undertake additional blood tests after self-isolation and within two weeks of re-starting medication
  • If results okay—revert to monitoring every 6 months; if abnormal—seek specialist advice
  • Refer patients to advice from Versus Arthritis

This page was developed in conjunction with Kalveer Flora, Chair, Rheumatology Pharmacists UK (RPUK); Lead Pharmacist, Specialised Rheumatology CRG for NHS England.  We are hugely grateful for her input.

This advice has been developed quickly in response to the COVID-19 pandemic; if you spot anything that’s wrong report a concern to us.