Sulfamethoxazole and Trimethoprim vs Amoxicillin: side effects in FDA adverse event reports
At a glance
| Sulfamethoxazole and Trimethoprim | Amoxicillin | |
|---|---|---|
| Drug class | Sulfonamide Antimicrobial, Dihydrofolate Reductase Inhibitor Antibacterial | – |
| Brand names | – | – |
| FAERS reports | 83,846 | 75,882 |
| Serious | 83% | 80% |
| Death outcome | 10,343 | 5,023 |
| Boxed warning | No | No |
Signals both drugs share
| Reaction | Sulfamethoxazole and Trimethoprim | Amoxicillin | Label screen (A / B) |
|---|---|---|---|
| Neuritis | 106 · PRR 18.4 | 61 · PRR 11.4 | Labeled adverse reaction / Not in label — unassessed |
| Radiculopathy | 200 · PRR 20.4 | 198 · PRR 22.4 | Not in label — unassessed / Not in label — unassessed |
| Female genital tract fistula | 189 · PRR 30.8 | 174 · PRR 31.0 | Not in label — unassessed / Not in label — unassessed |
| Proctitis | 190 · PRR 18.1 | 163 · PRR 17.0 | Not in label — unassessed / Not in label — unassessed |
| Vaginal flatulence | 167 · PRR 303.9 | 146 · PRR 254.1 | Not in label — unassessed / Not in label — unassessed |
| Pulmonary vasculitis | 102 · PRR 59.7 | 57 · PRR 33.3 | Not in label — unassessed / Not in label — unassessed |
| Mycotic allergy | 86 · PRR 28.3 | 57 · PRR 20.0 | Not in label — unassessed / Likely indication confounding |
| Mite allergy | 77 · PRR 34.2 | 65 · PRR 31.2 | Not in label — unassessed / Likely indication confounding |
| Dust allergy | 68 · PRR 18.9 | 66 · PRR 20.2 | Not in label — unassessed / Likely indication confounding |
Labeled signals distinctive to Sulfamethoxazole and Trimethoprim
- Sleep disorder due to general medical condition, insomnia type — n=1,017, PRR 46.8 Labeled (related wording)
- Rheumatic fever — n=489, PRR 31.4 Labeled adverse reaction
Labeled signals distinctive to Amoxicillin
- Acute generalised exanthematous pustulosis — n=421, PRR 15.8 Labeled adverse reaction
- Lip oedema — n=251, PRR 17.3 Labeled (related wording)
- Meningitis aseptic — n=238, PRR 15.5 Labeled (related wording)
- Crystalluria — n=119, PRR 76.8 Labeled adverse reaction
- Enterocolitis haemorrhagic — n=103, PRR 20.5 Labeled (related wording)
- Serum sickness-like reaction — n=81, PRR 42.1 Labeled adverse reaction
Common questions
Which has more reported side effects, Sulfamethoxazole and Trimethoprim or Amoxicillin?
Sulfamethoxazole and Trimethoprim has 83,846 FAERS reports and Amoxicillin 75,882. 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 (83% vs 80%) is a better like-for-like signal of the kind of problems reported.
Which side effects do Sulfamethoxazole and Trimethoprim and Amoxicillin share?
Both drugs carry disproportionality signals for neuritis, radiculopathy, female genital tract fistula, proctitis, vaginal flatulence. Shared signals often reflect a shared drug class or the condition both are used for.
Is Sulfamethoxazole and Trimethoprim or Amoxicillin 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.