UK Clinical Pharmacy Association


Issues for surgery

For suppression of transplant rejection – risk of rejection if omitted

For rheumatology and inflammatory bowel disease (IBD) conditions – risk of perioperative flare in disease activity if omitted (see Further information).

Risk of post-operative infection if continued (see Further information).

Advice in the perioperative period

Elective surgery 

Suppression of transplant rejection indication

Continue – the patient’s relevant specialist should be involved in the planning for surgery.

Rheumatology indications 


Individualised decisions should be made for procedures considered to have a high risk of infection and should be balanced against the risk of disease flare (see Further information). The surgical team and the patient’s rheumatologist should be involved in the planning for elective surgery.

Steroid exposure should be minimised prior to surgical procedures, and increases in steroid dose to prevent adrenal insufficiency are not routinely required.

Other indications (e.g. dermatology indications, IBD indications)


The decision to continue should be made on an individual patient basis in conjunction with the surgical team and the patient’s specialist.

If the decision is made to stop azathioprine prior to surgery, it should be stopped 2 weeks pre-operatively. Withdrawal should be a gradual process performed under close monitoring owing to the risk of severe worsening of the condition if stopped suddenly.

Emergency surgery 


The patient should be closely monitored for signs of infection following emergency surgery.

Suppression of transplant rejection indication

Inform the patient’s relevant specialist at the earliest opportunity.

Post-operative advice

Suppression of transplant rejection indication

Restart treatment in the immediate post-operative period when next dose due. If the patient cannot take their usual oral azathioprine post-operatively, their relevant specialist must be consulted for advice.

Close monitoring of renal function is important so that inadvertent drug accumulation does not occur.

Other indications

For high-risk surgical procedures or where there are patient factors that may increase surgical infection risk, i.e. age and / or co-morbidity, consider withholding azathioprine in the immediate post-operative period.

If discontinued, restart once wound healing is satisfactory.

Where azathioprine is continued, close monitoring of renal function is important so that inadvertent drug accumulation does not occur.

Interactions with common anaesthetic agents

Non-depolarising neuromuscular blocking drugs (NMBDs)

Antagonism of the neuromuscular blocking effects of non-depolarising NMBDs has been reported with azathioprine, but other evidence suggests there is no clinically relevant interaction. Azathioprine probably inhibits phosphodiesterase activity at the motor nerve terminal resulting in release of acetylcholine. Any effects occurring seem likely to be managed by routine dose titration of the NMBDs and standard post-operative care.

Interactions with other common medicines used in the perioperative period

Non-steroidal anti-inflammatory drugs (NSAIDs)

NSAIDs should be avoided due to the risk of adverse interactions (including nephrotoxicity).

Further information

Rheumatoid arthritis (RA) flare

RA flares develop in 10-20% of patients undergoing surgery and have a potential to impact adversely on post-operative recovery. In addition, active RA increases infection risk, further complicating decisions regarding DMARD interruption.

Infection risk

Patients treated with immunosuppressants may be at increased risk of opportunistic infections, fatal infections and sepsis. Patients should be monitored for neutropenia. Patients may not present with the typical signs and symptoms of infections (i.e. fever, leucocytosis). Microbiology advice may need to be sought when infections develop.

Some data suggests that not all DMARDs carry the same infection risk. There are limited data available regarding use of azathioprine and perioperative infection. A retrospective study of joint surgeries in rheumatoid arthritis patients found that two-thirds of patients receiving DMARDs, including azathioprine, demonstrated no association with perioperative infection.


Azathioprine. In: Brayfield A (Ed), Martindale: The Complete Drug Reference. London: The Royal Pharmaceutical Society of Great Britain. [Accessed 2nd June 2019]

Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. [Accessed on 2nd June 2019]

Brusich KT, Acan I. Anesthetic Considerations in Transplant Recipients for Nontransplant Surgery. Organ Donation and Transplantation - Current Status and Future Challenges. 2018. Accessed via 08/08/19

Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press [Accessed on 2nd June 2019]

Ledingham J, Gullick N, Irving K et al. Rheumatology Guidelines. The British Society of Rheumatology and British Health Professionals in Rheumatology. BSR and BHPR guideline for the prescription and monitoring of non-biologic disease-modifying anti-rheumatic drugs. Rheumatology. 2017; 56(6):865-68 and online supplementary information [Accessed on 2nd June 2019]

Summary of Product Characteristics – Azathioprine 50mg Tablets. Accord-UK Ltd. Accessed via 2/06/2019 [date of revision of the text October 2017]