Background/Purpose: Disease activity in systemic lupus erythematosus is an important predictor of subsequent organ damage and mortality from lupus. However, the optimal agent for chronic immunosuppression of SLE is unknown. Our aim was to determine the reasons for changing treatment from MMF to AZA or vice versa in lupus patients and to evaluate the effect of the change.

Methods:

Medical records of 92 lupus patients in whom treatment were changed from MMF to AZA or vice versa were reviewed. Global disease activity in the 6 months prior to the change in therapy and 6 months after the change was calculated using the Adjusted Mean SLEDAI (AMS) a validated measure of disease activity over time. The AMS was then calculated for both its clinical and laboratory parameters individually. The reasons for changing therapy were identified. AMS was compared in the 6 months prior to and after the switch using GEE adjusting for repeated measures.

Results:

We identified 92 lupus patients in whom treatment was switched once in 80, twice in 8 and three times in 4 with total of 108 times between MMF and AZA.  There were 89 switches from AZA to MMF: 76 (85.4%) for drug failure; 11 (12.4%) for side effects; 2 (2.2%) for renal transplant.  There were 19 switches from MMF to AZA: 7 (36.8%) for pregnancy; 8 (42.1%) for side effects; 3 (15.8%) for drug failure and 1 (5.3%) for financial issues.   There was a statistically significant improvement in AMS in the 6 months after drug switching compared to the 6 months prior to the switch when the reason was a drug failure, (11.2 ± 6.1) vs. (9.1 ± 5.7 p<0.0001).The improvement in the laboratory component was most significant (p=0.0006) and clinical component showed only a trend (p=0.08).  There was no statistically significant deterioration in AMS or its clinical and laboratory components  in 6 months after drug switching  when the reason for the switch was a side effect, pregnancy, financial or other, AMS (6.7 ± 4.6)vs. (5.9 ± 4.6 p<0.33). Side effects occurred in 15 of 19 of the total group who switched (78.9%) and persisted in 4(21.1%) after drug switching. Modeling to adjust for repeated measures confirmed the results.

Conclusion:

Switching from azathioprine to MMF is most often due to azathioprine failure and in that case a statistically significant improvement in disease activity occurs. When AZA is used to replace MMF, often due to pregnancy, there is no statistically significant deterioration in AMS.                                                                                 Switching between MMF and AZA for side effects usually resulted in elimination of the side effect.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/switching-treatment-between-mycophenolate-mofetil-and-azathioprine-in-lupus-patients-the-reasons-and-the-effect/