NATACYN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NATACYN (NATACYN).
Natamycin is a polyene antifungal that binds to ergosterol in fungal cell membranes, increasing permeability and causing cell death.
| Metabolism | Not systemically absorbed; hepatic metabolism unlikely due to topical ophthalmic route. |
| Excretion | Primarily fecal via biliary elimination; less than 5% renal excretion of absorbed dose. |
| Half-life | Not well characterized due to minimal systemic absorption; estimated to be 2-3 hours in plasma if absorbed. |
| Protein binding | >90% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Very low, estimated <0.1 L/kg due to minimal systemic absorption; Vd not clinically relevant. |
| Bioavailability | Negligible (<0.5%) after ophthalmic or topical administration due to poor absorption; not administered orally or parenterally. |
| Onset of Action | Ophthalmic: clinical effect within 24-48 hours for Candida keratitis; topical administration. |
| Duration of Action | Ophthalmic: continued therapy for 14-21 days to prevent relapse; duration depends on infection severity. |
| Molecular Weight | 665.73 |
One drop of 5% ophthalmic suspension into the conjunctival sac every 1-2 hours for 48 hours, then taper to one drop 4-6 times daily.
| Dosage form | SUSPENSION |
| Renal impairment | No adjustment required. |
| Liver impairment | No adjustment required. |
| Pediatric use | Same as adult dosing: one drop of 5% ophthalmic suspension into the conjunctival sac every 1-2 hours, then taper. |
| Geriatric use | Same as adult dosing. |
| 1st trimester | Safety not established; avoid unless clearly needed. |
| 2nd trimester | Safety not established; avoid unless clearly needed. |
| 3rd trimester | Safety not established; avoid unless clearly needed. |
Clinical note
Comprehensive clinical and safety monograph for NATACYN (NATACYN).
| Placental transfer | Unknown; not studied due to topical administration. |
| Breastfeeding | Minimal systemic absorption after topical ocular use; unlikely to pose risk to infant. |
| Lactation Rating | L1 – Safe |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to natamycin or any component of the formulation
| Precautions | Not for injection, May cause corneal opacities with prolonged use, Discontinue if hypersensitivity occurs |
| Food/Dietary | None known. Natacyn is for topical ophthalmic use only and is not absorbed systemically; therefore, no dietary restrictions are needed. |
| Clinical Pearls | Natacyn (natamycin) is a polyene antifungal used topically for fungal keratitis. It is not systemically absorbed and has no activity against bacteria. Must be used every 1-2 hours initially for corneal ulcers. Monitor for corneal toxicity with prolonged use. |
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| Teratogenic Risk |
| Natacyn (natamycin) is a polyene antifungal ophthalmic suspension. Systemic absorption is negligible (<1%) after topical ocular administration. No adequate and well-controlled studies in pregnant women. Animal studies have not been conducted. Based on minimal systemic exposure, risk to fetus is considered low. However, use during pregnancy only if clearly needed. |
| Fetal Monitoring | No specific monitoring required beyond standard ophthalmologic follow-up for the maternal infection being treated. |
| Fertility Effects | No known effects on fertility. Systemic exposure is negligible, making reproductive impact unlikely. |
| Patient Advice | Shake the bottle well before each use. · Instill 1 drop into the affected eye every 1-2 hours for the first few days, then reduce frequency as directed. · Do not touch the dropper tip to any surface to avoid contamination. · Do not wear contact lenses during treatment. · Report any worsening symptoms or allergic reactions to your doctor. |