Should I take a probiotic when on oral antibiotics?

Should You Take Probiotics with Oral Antibiotics?

Yes, you should consider taking specific probiotic strains when prescribed oral antibiotics, particularly if you are at higher risk for antibiotic-associated complications, are not immunocompromised, and select evidence-based strains at appropriate doses.

Key Recommendation

The evidence supports using Lactobacillus rhamnosus (5-10 billion CFU/day) or Saccharomyces boulardii (1g or 3×10¹⁰ CFU/day) starting with your antibiotic and continuing throughout the entire course plus 1-2 weeks after completion. 1

Who Benefits Most

Probiotics reduce antibiotic-associated diarrhea risk by approximately 37-64%, with the greatest benefit in high-risk populations: 2, 1, 3

• Elderly patients (>65 years) 1
• Hospitalized patients with prolonged stays 1
• Those with severe underlying illness 1
• Patients with previous C. difficile infection 1
• Populations with >15% baseline risk of complications 2

Studies with low baseline risk showed minimal benefit, while moderate-to-high risk populations demonstrated significant risk reduction. 3

Specific Strains That Work

Not all probiotics are equal—strain specificity is critical, and benefits from one strain cannot be extrapolated to others. 2, 1 The following have the strongest evidence:

Single-Strain Options:

• Lactobacillus rhamnosus: 5-10 billion CFU/day 2, 1
• Saccharomyces boulardii: 1g (3×10¹⁰ CFU/day) 2, 1

Multi-Strain Combinations with Evidence:

• Two-strain: L. acidophilus CL1285 + L. casei LBC80R 2
• Three-strain: L. acidophilus + L. delbrueckii subsp bulgaricus + Bifidobacterium bifidum 2
• Four-strain: L. acidophilus + L. delbrueckii subsp bulgaricus + B. bifidum + Streptococcus salivarius subsp thermophilus 2

Note that L. rhamnosus GG specifically was found ineffective for C. difficile prevention in meta-analysis. 2

Critical Contraindications

Do NOT use probiotics if you are immunocompromised—there is a rare but serious risk of bacteremia or fungemia. 2, 1 This includes:

• Neutropenic patients 1
• Severely debilitated patients 1
• Patients with central venous catheters 1
• Those on immunosuppressive therapy 2

There are case reports of Lactobacillus bacteremia in patients with acute severe colitis. 2

Dosing Matters

Higher doses are more effective than lower doses of the same probiotic strain. 3 Subgroup analysis demonstrated that high-dose probiotics showed significant protective effects (RR 0.54,95% CI 0.38-0.76) compared to low doses. 3

Timing and Duration

• Start probiotics at the same time as your antibiotic 1
• Continue throughout the entire antibiotic course 1, 4
• Extend for 1-2 weeks after antibiotic completion 1

Mechanism and Rationale

Antibiotics disrupt gut microbiota, creating open niches that opportunistic pathogens like C. difficile can exploit. 2 Probiotics work by:

• Re-colonizing and restoring microbiota diversity 2
• Producing antimicrobial compounds that inhibit pathogens 2
• Preventing bacterial translocation across gut barriers 2
• Promoting anti-inflammatory cytokine production 2

Saccharomyces boulardii (a yeast) is particularly logical since antibiotics don't kill yeast, allowing it to survive antibiotic exposure. 2

Evidence Quality

The overall certainty of evidence is Low to Moderate using GRADE criteria due to: 2, 1, 3

• Heterogeneity in study populations and probiotic strains 2, 1
• Risk of bias in outcome assessment 2
• Variations in recruitment criteria and outcome measures 2

However, the 2020 AGA Technical Review and multiple meta-analyses consistently show benefit for specific strains. 2

Common Pitfalls to Avoid

• Don't assume all probiotics are equivalent—only specific strains have demonstrated efficacy 2, 1
• Don't use probiotics if immunocompromised—risk outweighs benefit 2, 1
• Don't use inadequate doses—ensure you're taking evidence-based amounts 1, 3
• Don't stop probiotics when antibiotics end—continue 1-2 weeks beyond 1

Adverse Events

Probiotics are generally safe with rare adverse events, typically limited to mild gastrointestinal symptoms (abdominal cramping, flatulence, nausea). 1 Serious adverse events like bacteremia are exceedingly rare and primarily occur in immunocompromised patients. 2

Prebiotics

There is insufficient evidence to recommend prebiotics specifically for antibiotic use. The question focuses on probiotics, and prebiotics (carbohydrate compounds that promote bacterial growth) have not been adequately studied for this indication. 2