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Class: Antifungals
ATC Class: S01AA10
VA Class: OP210
CAS Number: 7681-93-8
Brands: Natacyn

Medically reviewed by on Jul 13, 2021. Written by ASHP.


Antifungal; tetraene polyene.

Uses for Natamycin

Fungal Ophthalmic Infections

Topical treatment of blepharitis, conjunctivitis, and keratitis caused by susceptible fungi, including keratitis caused by Fusarium solani.

Efficacy not established for use as a single agent for treatment of fungal endophthalmitis.

Use clinical diagnosis, laboratory diagnosis by smear and culture of corneal scrapings, and drug response to guide initial and continued therapy of fungal keratitis. Whenever possible, use in vitro susceptibility testing to confirm that causative organism is susceptible to natamycin.

Natamycin Dosage and Administration


Ophthalmic Administration

Apply 5% ophthalmic suspension topically to the eye.

For topical ophthalmic use only; do not inject directly into eye.

To avoid contaminating the ophthalmic suspension, do not allow tip of dispensing dropper to touch any surface.

Shake suspension well prior to each use.



Fungal Ophthalmic Infections
Fungal Blepharitis or Conjunctivitis

Instill 1 drop of 5% ophthalmic suspension into conjunctival sac of affected eye(s) 4–6 times daily.

Fungal Keratitis

Instill 1 drop of 5% ophthalmic suspension into conjunctival sac of affected eye(s) every 1–2 hours. After 3–4 days, may decrease frequency to 1 drop 6–8 times daily; in many cases, frequency may be gradually decreased every 4–7 days.

If no signs of improvement after 7–10 days of topical therapy, infection may be caused by pathogens not susceptible to natamycin; base continued therapy on clinical reevaluation and additional laboratory studies.

If evidence of improvement, continue topical therapy for 14–21 days or until there are no signs or symptoms of active fungal keratitis.

Special Populations

No special populations dosage recommendations.

Cautions for Natamycin


  • Known hypersensitivity to natamycin or any ingredient in the formulation.


Sensitivity Reactions


Allergic reactions reported.

Administration Precautions

For topical ophthalmic use only; not for injection into the eye.

Do not wear contact lenses if any signs or symptoms of fungal blepharitis, conjunctivitis, or keratitis are present.

Specific Populations


Animal reproduction studies not performed to evaluate whether natamycin can cause fetal harm or affect reproduction capacity.

Use during pregnancy only if clearly needed.


Not known whether distributed into milk.

Use with caution in nursing women.

Pediatric Use

Safety and efficacy not established in pediatric patients.

Geriatric Use

No overall differences in safety and efficacy relative to younger adults.

Common Adverse Effects

Allergic reaction, change in vision, chest pain, corneal opacity, dyspnea, eye discomfort, eye edema, eye hyperemia, eye irritation or pain, foreign body sensation, paresthesia, tearing.

Interactions for Natamycin

No formal drug interaction studies using natamycin 5% ophthalmic suspension.

Natamycin Pharmacokinetics



Systemic absorption not expected following topical application to the eye.

Following topical application of natamycin 5% ophthalmic suspension to the eye, the drug adheres to cornea in areas of epithelial ulceration and is retained in conjunctival fornices. Effective natamycin concentrations are attained within corneal stroma, but not in intraocular fluid.



Not known whether natamycin is distributed into milk.





2–24°C; do not freeze.

Protect from light and excessive heat.

Actions and Spectrum

  • Antifungal antibiotic derived from Streptomyces natalensis.

  • Predominantly fungicidal.

  • Binds to sterols in the fungal cell membrane. Affects permeability of the membrane barrier, depleting essential cellular constituents.

  • Mechanism of action appears similar to that of amphotericin B and nystatin.

  • Active in vitro against a variety of yeast and filamentous fungi, including Aspergillus, Candida, Cephalosporium, Fusarium, and Penicillium.

  • Inactive in vitro against gram-positive and gram-negative bacteria.

Advice to Patients

  • Advise patients to avoid contaminating tip of dispensing dropper.

  • Advise patients not to wear contact lenses if any signs or symptoms of fungal blepharitis, conjunctivitis, or keratitis are present.

  • Advise patients to inform clinician if condition worsens or does not improve after 7–10 days of therapy or if any adverse reactions occur.

  • Importance of informing clinician of existing or contemplated concomitant therapy, including prescription and OTC drugs and dietary or herbal supplements, as well as any concomitant illnesses.

  • Importance of women informing clinician if they are or plan to become pregnant or plan to breast-feed.

  • Importance of informing patients of other important precautionary information. (See Cautions.)


Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.



Dosage Forms


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AHFS DI Essentials™. © Copyright 2022, Selected Revisions July 23, 2018. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

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