Azathioprine vs Mycophenolate Mofetil: side effects in FDA adverse event reports
At a glance
| Azathioprine | Mycophenolate Mofetil | |
|---|---|---|
| Drug class | Purine Antimetabolite | – |
| Brand names | – | – |
| FAERS reports | 87,582 | 32,904 |
| Serious | 87% | 84% |
| Death outcome | 8,696 | 4,489 |
| Boxed warning | Yes - MALIGNANCY Chronic immunosuppression with azathioprine, a purine antimetabolite increases risk of malignancy in humans. Reports of malignancy include post-tra | Yes EMBRYOFETAL TOXICITY, MALIGNANCIES and SERIOUS INFECTIONS Use during pregnancy is associated with increased risks of first trimester pregnancy loss and congenit |
Signals both drugs share
| Reaction | Azathioprine | Mycophenolate Mofetil | Label screen (A / B) |
|---|---|---|---|
| Lung transplant rejection | 93 · PRR 38.8 | 251 · PRR 94.0 | Labeled (related wording) / Labeled (related wording) |
| Deep vein thrombosis postoperative | 413 · PRR 63.8 | 952 · PRR 147.0 | Not in label — unassessed / Not in label — unassessed |
| Lupus vulgaris | 437 · PRR 139.3 | 530 · PRR 124.9 | Not in label — unassessed / Not in label — unassessed |
| Grip strength | 119 · PRR 254.5 | 134 · PRR 214.4 | Not in label — unassessed / Not in label — unassessed |
Labeled signals distinctive to Azathioprine
- Hepatosplenic t-cell lymphoma — n=155, PRR 171.2 Labeled — boxed warning
- Cholestasis of pregnancy — n=100, PRR 67.0 Labeled adverse reaction
Labeled signals distinctive to Mycophenolate Mofetil
- Post transplant lymphoproliferative disorder — n=2,254, PRR 126.8 Labeled (related wording)
- Polyomavirus-associated nephropathy — n=1,473, PRR 272.3 Labeled adverse reaction
- Bk virus infection — n=1,455, PRR 119.5 Labeled adverse reaction
- Chronic allograft nephropathy — n=435, PRR 192.7 Labeled (related wording)
- Renal transplant failure — n=425, PRR 117.2 Labeled (related wording)
- Graft loss — n=296, PRR 105.1 Labeled adverse reaction
- Human polyomavirus infection — n=227, PRR 120.6 Labeled (related wording)
- Renal graft infection — n=144, PRR 257.5 Labeled (related wording)
Common questions
Which has more reported side effects, Azathioprine or Mycophenolate Mofetil?
Azathioprine has 87,582 FAERS reports and Mycophenolate Mofetil 32,904. More reports does not mean more dangerous: volume follows how widely and how long a drug has been used, prescription vs over-the-counter status, and publicity. The seriousness share (87% vs 84%) is a better like-for-like signal of the kind of problems reported.
Which side effects do Azathioprine and Mycophenolate Mofetil share?
Both drugs carry disproportionality signals for lung transplant rejection, deep vein thrombosis postoperative, lupus vulgaris, grip strength. Shared signals often reflect a shared drug class or the condition both are used for.
Is Azathioprine or Mycophenolate Mofetil safer?
FAERS cannot answer that: it has no denominator and no comparator. Use this page to see which risks are already on each label and which signals are unlabeled, then check the prescribing information and your clinician for your situation.
Sources: openFDA FAERS pair statistics (OpenPV build 2026-09-14), FDA labels via openFDA, openFDA count queries for seriousness and deaths. Pair chosen because it is a commonly searched comparison. Generated 2026-10-08.