Are tobramycin (an aminoglycoside antibiotic) eye drops safe to use during pregnancy?

Tobramycin Eye Drops in Pregnancy

Tobramycin eye drops are safe to use during pregnancy when clinically indicated, as the minimal systemic absorption from topical ophthalmic administration poses negligible risk to the developing fetus. 1, 2

Safety Classification and Evidence

The European Respiratory Society/TSANZ guidelines explicitly classify inhaled tobramycin as "compatible" during pregnancy, noting that while systemic tobramycin is FDA Category D, the inhaled/topical route has minimal absorption and is considered to have minimal risk. 1 This same principle applies to ophthalmic formulations, which have even lower systemic absorption than inhaled preparations.

The FDA drug label for tobramycin ophthalmic solution states that reproduction studies in three types of animals at doses up to 33 times the normal human systemic dose revealed no evidence of impaired fertility or harm to the fetus. 2 However, the label appropriately notes that animal studies are not always predictive of human response and recommends use during pregnancy only if clearly needed. 2

Key Distinction: Systemic vs. Topical Administration

This is a critical point that requires emphasis:

• Systemic (IV) tobramycin is Category D and should be avoided if possible during pregnancy due to documented risks of eighth cranial nerve damage (ototoxicity) and potential nephrotoxicity to the fetus, as seen with other aminoglycosides like streptomycin and kanamycin. 1

• Topical ophthalmic tobramycin has minimal systemic absorption, making the risk profile fundamentally different from parenteral administration. 1

The ERS/TSANZ guidelines specifically state: "Tobramycin (systemically) is category 'D'...but as the inhaled route has minimal absorption, it is considered to have minimal risk. If required for clinical stability, may continue during pregnancy." 1 This reasoning applies even more strongly to ophthalmic preparations.

Clinical Recommendations

For bacterial conjunctivitis or other ocular infections during pregnancy, tobramycin eye drops may be used when clinically indicated, particularly when the benefit of treating the infection outweighs the theoretical minimal risk. 1, 2, 3

The risk assessment should consider:

• Topical ophthalmic medications have very low systemic absorption compared to oral or IV routes 3
• Untreated bacterial eye infections can lead to complications that may pose greater risks than the medication itself 3
• The extensive animal safety data showing no teratogenic effects at doses far exceeding human exposure 2

Breastfeeding Considerations

During breastfeeding, tobramycin eye drops are considered "possibly safe" with appropriate precautions. 1 The ERS/TSANZ guidelines recommend minimizing breast skin exposure during inhalation of tobramycin, 1 though this is less relevant for eye drops.

For IV tobramycin during breastfeeding, guidelines suggest avoiding breastfeeding for 2 hours following injection when tobramycin is at maximal concentration, and note that low oral bioavailability limits infant exposure, though this is unknown in premature infants and neonates in the first weeks of life. 1

Important Clinical Pitfalls to Avoid

• Do not confuse systemic aminoglycoside risks with topical ophthalmic risks. The Category D designation applies to IV/IM administration, not eye drops. 1

• Advise patients not to wear contact lenses if they have signs and symptoms of bacterial ocular infection. 2

• Instruct patients not to touch the dropper tip to any surface to prevent contamination. 2

• Consider alternative antibiotics if systemic aminoglycoside therapy is being contemplated during pregnancy - penicillins and cephalosporins are safer first-line options for systemic infections. 1, 4

Algorithm for Decision-Making

1. Confirm diagnosis requires antibiotic eye drops (bacterial conjunctivitis, corneal ulcer, etc.)
2. Assess severity: Is treatment necessary or can infection be monitored?
3. If treatment needed: Tobramycin eye drops are acceptable throughout pregnancy 1, 2
4. Counsel patient: Explain minimal systemic absorption and favorable safety profile
5. Monitor: Standard follow-up for infection resolution; no special fetal monitoring required for topical use