Generate a custom probiotic schedule for your antibiotic course. Most people take probiotic the wrong way — bacteria-based probiotics taken with antibiotics get killed instantly. S. boulardii (yeast) survives. Calculator shows your optimal day-by-day timing. Math, not medical advice.
Your antibiotic course
Your optimal daily schedule
Strain reference: which probiotics survive antibiotics
| Strain | Type | Survives antibiotics? | Best for |
|---|---|---|---|
| Saccharomyces boulardii CNCM I-745 (Florastor) | Yeast | YES — take with antibiotic | AAD prevention, C. diff (Cochrane 2017) |
| Lactobacillus rhamnosus GG (Culturelle) | Bacterium | NO — needs 2hr gap | AAD prevention (Hempel 2012 meta-analysis) |
| Bifidobacterium infantis 35624 (Align) | Bacterium | NO — needs 2hr gap | Post-course gut restoration; IBS |
| Multi-strain blends (Lactobacillus + Bifidobacterium) | Bacterial mix | NO — needs 2hr gap | General gut restoration; broad-spectrum |
| Visbiome / VSL#3 (8 strains, 112B-900B CFU) | Bacterial mix | NO — needs 2hr gap; refrigerated | IBS, UC adjunct, pouchitis |
| Lactobacillus reuteri DSM 17938 (BioGaia) | Bacterium | NO — needs 2hr gap | Infant colic, H. pylori adjunct |
| Lactobacillus acidophilus + Bifidobacterium lactis | Bacterial | NO — needs 2hr gap | Generic gut health; widely available |
Antibiotic-specific notes
| Antibiotic | AAD risk | C. diff risk | Notes |
|---|---|---|---|
| Amoxicillin (penicillins) | Moderate | Low-moderate | Common in kids; probiotic well-studied (Hempel 2012) |
| Augmentin (+ clavulanate) | HIGH | Moderate | Clavulanate is the main GI offender; strong probiotic case |
| Azithromycin (Z-pack) | Low-moderate | Low | Shorter course; probiotic less critical but still helpful |
| Ciprofloxacin (FQ) | Moderate | Moderate-high | FQ class destroys gut flora broadly; long recovery needed |
| Doxycycline | Low-moderate | Low | Often used long-term (acne); 1-2 week probiotic course |
| Clindamycin | HIGH | VERY HIGH (4-8× baseline) | Highest C. diff risk; S. boulardii strongly recommended |
| Metronidazole (Flagyl) | Moderate | Treats C. diff, but can recur | Avoid alcohol; probiotic during + 2 weeks after |
| Cephalexin (cephalosporins) | Moderate-high | Moderate | Common surgical prophylaxis; probiotic useful |
| Bactrim (TMP-SMX) | Low-moderate | Low | Watch for hyperkalemia + skin reactions; probiotic helpful |
Why timing matters (and why most people get it wrong)
- Antibiotics are non-selective: they kill bacteria pathogenic AND commensal. Lactobacillus + Bifidobacterium probiotics ARE the commensal bacteria — they get killed too if taken at the same time.
- 2-hour separation is the consensus: ACG, BSG, and Cochrane recommendations all use 2+ hour spacing between bacterial probiotic and antibiotic doses.
- S. boulardii is the exception: as a yeast, it’s resistant to bacterial antibiotics. Taken simultaneously with the antibiotic, full dose survives gut transit.
- Continue probiotic 1-2 weeks AFTER antibiotic ends — gut flora takes weeks to recover. Stopping probiotic at antibiotic end is a common mistake.
- Higher CFU during antibiotic course: Lactobacillus + Bifidobacterium losses are higher, so 10-25 billion CFU/day is typical. Maintenance after course can drop to 5-10 billion.
C. difficile prevention (high-risk situation)
If you’re on a high-C. diff-risk antibiotic (clindamycin, FQ, broad-spectrum cephalosporin) OR have prior C. diff history, evidence supports more aggressive probiotic strategy:
- S. boulardii 1g/day (1 Florastor packet × 2) from day 1 of antibiotic. Continue 2 weeks post-course. Goldenberg 2017 Cochrane review showed ~60% reduction in CDAD with probiotics in adults.
- Avoid in immunocompromised, central-line patients, pre-term infants — probiotic bacteremia/fungemia risk.
- Hand hygiene + bathroom cleaning matter as much as probiotics for household C. diff prevention.
- If diarrhea persists past antibiotic course — get tested for C. diff, do NOT self-treat with anti-diarrheals (can worsen toxic megacolon).
Side effects and contraindications
- Generally well-tolerated. Mild gas, bloating in first few days is common — settles as gut adapts.
- DO NOT take probiotics if: immunocompromised (chemo, transplant, AIDS), central venous catheter, pre-term infant, severely critically ill — case reports of probiotic bacteremia/fungemia exist.
- Probiotic safety in severe acute pancreatitis showed increased mortality in PROPATRIA trial — context-specific contraindication.
- S. boulardii cautions: avoid with antifungal medications (defeats the purpose); avoid in patients with yeast sensitivities or central lines (fungemia risk).
- Refrigeration: Visbiome, certain Lactobacillus products require cold chain. Florastor (S. boulardii) is shelf-stable.