Natamycin

What Is Natamycin?

Natamycin is a prescription antifungal medicine. It belongs to a group called polyene antifungals. It is sold under the brand name Natacyn in the United States. In the U.S., it is used as an eye medicine to treat fungal infections of the eye. The same substance is also used as a food preservative, which is a separate use and is not the medicine described here.

FDA-Approved Uses

Natamycin ophthalmic (eye) suspension is approved to treat fungal infections of the eye and eyelid, including:

• Fungal keratitis, an infection of the cornea (the clear front surface of the eye), including infections caused by Fusarium and other molds and yeasts
• Fungal blepharitis, an infection of the eyelid
• Fungal conjunctivitis, an infection of the membrane covering the white of the eye

Other Prescribed Uses

In some countries, natamycin is also available as a cream, lotion, or vaginal product for certain skin or yeast infections. These forms are not FDA-approved in the U.S. Eye specialists may also use it in ways that go beyond the label, based on individual circumstances. These decisions belong to the treating specialist.

Available Forms and Strengths

• Ophthalmic suspension (eye drops): 5% (50 mg/mL), a thick, white liquid that must be shaken well before use

Available forms and strengths can vary by manufacturer and country.

What Is the Recommended Dosage of Natamycin?

There is no single dose that fits everyone. The prescribed schedule and length of treatment depend on several factors:

• The type and location of the infection. Corneal infections are usually treated more often and for longer than eyelid or conjunctival infections.
• How severe the infection is and how the eye responds to treatment.
• Other eye conditions or eye medicines being used.
• Age and overall health.

Treatment for fungal keratitis often starts with frequent drops (sometimes every hour or two while awake) and is then reduced as the eye improves. Treatment can last several weeks. The eye specialist usually checks the eye often during this time.

General tips for using the eye drops:

• Wash your hands before and after use.
• Shake the bottle well before each use.
• Do not let the tip of the bottle touch your eye, fingers, or any surface.
• Do not wear contact lenses while you have an eye infection unless your eye specialist says otherwise.

Use natamycin exactly as your licensed medical specialist or pharmacist instructs. Do not change the schedule, stop early, or extend treatment on your own, even if the eye looks better. Stopping too soon can allow the infection to return.

How Natamycin Works

Fungal cells have a protective outer membrane, and a substance called ergosterol is an important part of it. Natamycin attaches directly to ergosterol in the fungal membrane. This disrupts how the membrane works and stops the fungus from growing and multiplying normally. Human cells contain very little ergosterol, which is why the medicine targets fungi.

Natamycin treats and controls fungal infections of the eye. It works mainly by stopping the fungus from growing, which helps the body clear the infection. How well it works depends on the type of fungus, how deep the infection is, and the person’s overall eye health. Deep corneal infections can be hard to treat because the medicine may not reach the deeper layers well. Natamycin does not work against bacterial or viral eye infections.

Is a Prescription Required to Buy Natamycin Online?

In the United States, natamycin eye drops are prescription-only. A licensed healthcare professional must examine your eye before it is prescribed. Eye infections can damage vision quickly, so a prompt, in-person exam is important.

Depending on the infection, the specialist may be:

• An ophthalmologist (eye doctor), especially one who treats corneal and external eye disease
• An optometrist, who may refer you to an ophthalmologist for serious infections
• An infectious disease specialist, if the infection is severe or has spread

Only buy natamycin from a licensed pharmacy that requires a valid prescription. Be careful with websites that sell it without one. Counterfeit, expired, contaminated, or improperly stored eye products can be unsafe and may harm the eye. Products labeled for animals or for use as food additives are not approved for use in human eyes and should never be used.

Side Effects of Natamycin

Natamycin is applied to the eye, so little of it enters the bloodstream. Most side effects affect the eye itself.

Common Side Effects

• Eye discomfort or a feeling that something is in the eye
• Eye irritation or mild stinging or burning
• Eye redness
• Increased tearing
• Mild swelling of the eye or eyelid
• Temporary blurred vision right after putting in the drops (the medicine is a thick white suspension)

Talk to your eye specialist or pharmacist if these bother you or do not go away.

Serious Side Effects

Serious reactions are uncommon but possible. Get medical help right away if you notice:

• Swelling of the face, lips, tongue, or throat, or trouble breathing (allergic reaction)
• Chest pain
• Worsening eye pain, redness, or swelling
• A sudden change or loss of vision
• Increased sensitivity to light that becomes severe
• A rash, hives, or itching around the eyes or over the body
• Any sign that the infection is getting worse, such as more discharge, a growing white spot on the eye, or worsening symptoms after several days of treatment

Call emergency services if you have trouble breathing or think you are having a life-threatening reaction.

Drug Interactions

Because natamycin is used in the eye and very little is absorbed, significant interactions with other medicines taken by mouth are not expected. Interactions with other eye products are more relevant. Major categories include:

• Corticosteroid eye drops or ointments (such as prednisolone or dexamethasone). These can allow fungal infections to worsen and are generally used with great caution, and only under specialist supervision, when a fungal eye infection is present.
• Other eye drops or ointments, including antibiotics, lubricating drops, and glaucoma medicines. If you use more than one, your specialist or pharmacist may advise waiting several minutes between products and may recommend an order to use them in.
• Other antifungal medicines, which specialists sometimes combine with natamycin for severe infections.
• Contact lens solutions and products. Contact lenses should generally not be worn during treatment.

Tell your provider about all prescription and over-the-counter medicines (including eye drops and ointments), vitamins, supplements, and herbal products.

Give your licensed medical specialist and pharmacist a complete, up-to-date list of everything you use. This list is not complete, so always check before starting or stopping any medicine.

Safety & Important Considerations

• Use only as directed in the eye. Natamycin eye suspension is not for injection or for swallowing.
• Follow-up exams: Fungal eye infections can progress or resist treatment. Your eye specialist will usually examine the eye regularly, and may take samples (scrapings) to confirm the type of fungus and check that treatment is working.
• When to reassess treatment: If the eye does not improve within about a week or two, the specialist may change the treatment plan.
• Contact lenses: Contact lens use is a common risk factor for fungal eye infections. Ask your provider when it is safe to wear lenses again, and follow proper lens hygiene.
• Contamination: Do not share eye drops, and do not let the bottle tip touch anything, to avoid contaminating the medicine or spreading infection.
• Pregnancy: Very little medicine is absorbed into the body from eye use, but limited information is available for pregnant patients. Tell your provider if you are pregnant, may become pregnant, or are trying to conceive.
• Breastfeeding: It is not well established whether natamycin passes into breast milk after eye use. Discuss the risks and benefits with your provider.
• Children: Safety and effectiveness in children have not been well established. Any use in a child should be directed by an eye specialist.
• Older adults: No major differences in safety have been reported, but older adults often use several eye or other medicines, so a full medication review is helpful.
• Vision and driving: Blurred vision can occur right after applying the drops. Wait until your vision is clear before driving or using machinery.

Who This Medication Is For

Natamycin eye suspension is prescribed for adults (and, in some cases, children under specialist direction) who have a confirmed or strongly suspected fungal infection of the eyelid, conjunctiva, or cornea, within its approved indications. Whether it is appropriate depends on the type of infection, the severity, the person’s eye history, and test results such as eye scrapings or cultures.

Who Should Not Take Natamycin

Natamycin is not suitable for everyone. Do not use it if:

• You have had an allergic reaction to natamycin or to any ingredient in the product.

Use extra caution and discuss risks with your provider if you:

• Are using steroid eye drops or ointments
• Wear contact lenses
• Have other eye conditions or recent eye surgery
• Have a bacterial or viral eye infection, since natamycin will not treat these
• Are pregnant, planning pregnancy, or breastfeeding

What to Do If You Miss a Dose

• Apply the missed dose as soon as you remember.
• If it is almost time for your next dose, skip the missed one and go back to your regular schedule.
• Do not apply extra drops to make up for a missed dose.
• Because the early schedule can involve frequent dosing, missing several doses can affect treatment. If you are unsure what to do, or you miss more than one dose, contact your licensed medical specialist or pharmacist.

Related medications to Natamycin

Other antifungal medicines exist for eye infections, and the right one depends on the type of fungus and the depth of the infection. Only a licensed specialist can decide whether a different medicine is appropriate.

Other polyene antifungals (same class):

• Amphotericin B, sometimes prepared as eye drops or given by injection for severe infections
• Nystatin, used mainly for yeast infections of the mouth, skin, and gut

Antifungals from other classes:

• Voriconazole (an azole), which may be given as eye drops, by mouth, or by IV depending on the infection
• Fluconazole (an azole), used for some yeast-related eye infections
• Echinocandins (such as caspofungin and micafungin), sometimes used for specific infections
• Chlorhexidine, an antiseptic that some eye specialists use for certain corneal infections

Some of these options are prepared by special pharmacies rather than sold as ready-made eye products. Do not switch or stop natamycin without talking to your licensed medical specialist.

Storage Instructions

• Eye suspension: Store at a cool to room temperature, generally between 36°F and 75°F (2°C and 24°C), unless the label says otherwise. Keep the bottle tightly closed, upright, and protected from light and excessive heat.
• Freezing: Do not freeze the medicine.
• Shake well before each use, and follow the pharmacy label for how long an opened bottle can be kept.
• Contamination: Do not let the dropper tip touch your eye or any surface, and recap the bottle right after use.
• Child safety: Keep all medicines out of reach and sight of children and pets, preferably in a locked or high cabinet.
• Do not use medicine past its expiration date. Ask your pharmacist about safe disposal of unused or expired medicine.

Disclaimer:

This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Patients must consult a licensed medical specialist, such as an ophthalmologist, optometrist, or infectious disease specialist, depending on the type of infection, before starting, changing, or stopping treatment. Treatment decisions must be based on a full clinical evaluation by a qualified specialist. Information about dosing, strengths, and safety may change, so always follow the guidance of your prescriber and the current product labeling.