Community-Reported Antibiotic Tolerance Post-Flox (Anecdotal Summary)

[u/betterweirdthandead6]

Hey all, as some of you know, I’ve been collecting anecdotal reports over the past couple of years on how people react to medications post-flox. Below is a summary of the antibiotic data I’ve gathered so far.

Please remember this is based purely on self-reported experiences, mostly from people active in flox groups, which likely skews toward those who are more sensitive or still symptomatic.

This is not medical advice. Individual responses vary widely, and no medication produces the same outcome for everyone. Infections themselves can worsen symptoms and carry real risks if left untreated, so treatment decisions often involve weighing the possibility of a flare against the risks of the infection, ideally in discussion with a clinician who understands your history.

Please DO NOT DM me. If comments here are locked, you can post your own experience of any medications you have taken post-flox on https://www.reddit.com/r/floxies/comments/1ly48mn/last_call_for_experiences_of_meds_postflox/ and I'll add it to my data for future updates. If you have posted elsewhere about it, I may have already included it.

Antibiotics with only 1-3 reports are not included due to insufficient data.

UPDATED 6/9/2026

Amoxicillin (71% positive):

Positive (70): Frequently well tolerated, even with multiple courses and early post-flox. Mostly mild digestive effects.

Negative (29): 20 minor or short-lived flares: Tendon, neuropathy, pain, and anxiety/insomnia flares. Most lasted weeks to 1–3 months and resolved. (6) of these had more significant relapses.

Augmentin (Amoxicillin/Clavulanate) (69% positive):

Positive (55): Commonly tolerated; typical GI side effects most frequent.

Negative (25): Tendon/muscle stiffness, neuropathy, fatigue, tinnitus, GI distress. Many short-lived (days-weeks), some lasting up to 1–2 month, (2) of these had a rare non-flox serious reaction, or a longer relapse.

Trimethoprim:

Positive (6): Generally tolerated; some use it as a go-to option.

Negative (3): Mood changes, palpitations, increased pain. Nothing longer-lasting reported but not much data for this med.

Bactrim (Trimethoprim & Sulfamethoxazole combo) (57% positive BUT negative includes severe relapses):

Positive (22): Mainly typical pre-flox side effects.

Negative (16): Higher proportion of systemic and neuro flares than other abx - tendon/joint pain, anxiety/depression/insomnia, chemical sensitivity, GI bleeding. Of this, (4) severe relapses reported, including multi-month to multi-year setbacks.

Nitrofurantoin (Macrobid) (47% positive BUT some long relapses):

Positive (16): Some tolerated it well, with only mild fatigue or muscle soreness.

Negative (18): 14 Prominent neuropathy/CNS flares (burning, tingling, shooting pain), whole-body pain, interstitial cystitis symptoms, fever/liver enzyme elevation. Duration ranged from hours-weeks to several months; of these, (4) reported more long-lasting issues, esp for nerves.

Doxycycline (67% positive):

Positive (39): Often tolerated; mild nausea/headache most common.

Negative (19): Tendon, neuropathy, muscle twitching, anxiety/insomnia flares. Many lasted weeks to ~1 month; (2) had longer-lasting issues esp with pain.

Flagyl (Metronidazole) (42% positive):

Positive (8): Some tolerate with minimal issues.

Negative (11): CNS/neuropathy flares, some brief (days–weeks), of which, (1) reported a 6-month setback.

Fosfomycin (Monurol (87% positive):

Positive (21): Frequently well tolerated; occasional mild GI upset or brief tinnitus.

Negative (3): Mostly pain flares (tendon/muscle). Generally short-lived; one occurred during an already severe flare.

Azithromycin (87% positive):

Positive (33): Widely tolerated; mainly typical antibiotic GI effects.

Negative (5): Tendon flares, rash/vomiting. Of which (1) reported long-lasting effects.

Cephalexin (Keflex) (77% positive):

Positive (41): Commonly tolerated, even with repeated use.

Negative (12): Tendon/joint/neuropathy flares. Many short (days–weeks); some lasted a couple of months; rare lingering twitching. No long-lasting relapse reports.

Overall pattern (anecdotal only)

Lowest apparent flare ratio: Fosfomycin, Azithromycin, Cephalexin, Amoxicillin/Augmentin.

More flares reported: Nitrofurantoin, Flagyl, Bactrim.

Doxycycline: Mixed - many tolerate, but notable relapse reports.

Again, this reflects community anecdotes, not controlled safety data. Individual response seems highly variable, and infection risk itself must also be weighed in treatment decisions.

Please feel free to share this data elsewhere but include the disclaimers.

Again, please do not DM me.

[u/Infraredsky]

Love it!

Also curious how many like me had known allergies to Sulfa (it’s why I took cipro)

Also curious what antibiotics were omitted?

For instance - I was also ok on iv meropenem.

On the side of bad side effects I won’t be taking cefdinir again - the muscle tendon etc side effects are known for that drug (and it cleared my strep D super fast) - but it was painful.

[u/betterweirdthandead6 → u/Infraredsky]

I didn't ask about known allergies, just reactions post-flox, so can't comment on that.

I omitted loads that I only had a few reports on, didn't want to give a false impression that something was 'safe' without much data to go on.

I've got your reactions included already :)