Ciprofloxacin Concentration in Breast Milk at 4 Hours Post-Dose
At 4 hours after taking ciprofloxacin, breast milk concentrations are at their lowest point (approximately 2.26-3.79 mcg/mL), making this the optimal time for breastfeeding to minimize infant exposure. 1, 2
Specific Concentration Data
The most direct evidence comes from a pharmacokinetic study in lactating women who received 750 mg oral ciprofloxacin:
- At 4 hours post-dose: mean breast milk level was 2.26 mcg/mL 2
- At 2 hours: 3.79 mcg/mL (peak concentration) 2
- At 6 hours: 0.86 mcg/mL 2
- At 9 hours: 0.51 mcg/mL 2
A separate case report of a single 500 mg oral dose found:
- At 4 hours: 9.1 mcmol/L (approximately 3.0 mcg/mL) 3
- Concentrations remained stable at 9.1 mcmol/L through 8 and 12 hours 3
Clinical Significance of These Levels
These breast milk concentrations are two orders of magnitude (100-fold) lower than typical therapeutic infant doses, making the exposure clinically insignificant 1, 4, 5:
- The infant receives far less drug through breast milk than would be given for direct treatment 1
- Calcium in breast milk further reduces absorption of ciprofloxacin in the infant's gastrointestinal tract 1, 4, 5
Practical Timing Recommendation
To minimize infant exposure further, breastfeeding should be timed to occur 3-4 hours after each maternal ciprofloxacin dose, when drug concentrations in breast milk reach their nadir 1, 4, 5. This timing strategy reduces theoretical risks while allowing continued breastfeeding 1.
Important Caveats
While these concentrations are measurable, the actual risk to breastfed infants remains theoretical:
- Despite animal studies showing cartilage concerns, human data during breastfeeding show low risk 4, 5
- No cases of arthropathy have been documented in breastfed infants exposed to ciprofloxacin 4
- Potential minor effects include altered intestinal flora or false-negative cultures if the infant becomes febrile 4, 5
If ciprofloxacin is medically necessary for the mother, breastfeeding can continue with strategic timing around the 3-4 hour mark post-dose 1, 4, 5.