What Is Erythromycin Ethylsuccinate? Uses, Dosage, and What You Need to Know in 2026

Erythromycin Ethylsuccinate — sold under brand names including E.E.S. and EryPed — is a macrolide antibiotic that has been treating bacterial infections since the 1950s. It's one of the oldest antibiotics still in use today, and while newer alternatives have taken over many of its uses, E.E.S. remains an important option for specific patients and situations.

This guide covers everything patients and caregivers need to know about Erythromycin Ethylsuccinate in 2026 — what it treats, how to take it, what to watch out for, and where to find it.

What Is Erythromycin Ethylsuccinate?

Erythromycin Ethylsuccinate is an ester form of erythromycin — meaning it's erythromycin that has been chemically modified to improve oral absorption and tolerability. The "ethylsuccinate" part refers to the chemical group attached to the erythromycin molecule that makes it suitable for oral use.

Erythromycin itself is produced naturally by a strain of bacteria called Saccharopolyspora erythraea (formerly Streptomyces erythraeus). It belongs to the macrolide class of antibiotics, which also includes azithromycin and clarithromycin.

What Conditions Does Erythromycin Ethylsuccinate Treat?

E.E.S. is FDA-approved to treat infections caused by susceptible bacteria, including:

Respiratory tract infections: Strep throat, pneumonia, bronchitis, and other upper and lower respiratory infections

Skin and soft-tissue infections: Impetigo, cellulitis, and other skin infections — particularly in patients allergic to penicillin

Chlamydial infections: Urethritis, cervicitis, and neonatal conjunctivitis or pneumonia caused by Chlamydia trachomatis

Pertussis (whooping cough): Used to treat and prevent the spread of pertussis, particularly in exposed household contacts

Legionnaire's disease: Caused by Legionella pneumophila

Rheumatic fever prophylaxis: Long-term prevention of recurrent streptococcal infections in patients with rheumatic heart disease who are allergic to penicillin

Intestinal amebiasis: Intestinal infections caused by Entamoeba histolytica

What Forms Does E.E.S. Come In?

Film-coated tablets (400mg): For adults and older children — the most commonly stocked form

Oral suspension (200mg/5mL): Intended primarily for infants and young children; comes in fruit/cherry flavor

Oral suspension (400mg/5mL): Higher-concentration suspension in banana flavor; can be used in adults or older children

How Is Erythromycin Ethylsuccinate Dosed?

Dosing depends on age, weight, and the infection being treated. Here are the general guidelines:

Adults: 400mg every 6 hours (1,600mg/day). For severe infections, up to 4g/day. Doses can also be given every 8 or 12 hours.

Children: 30–50mg/kg/day in divided doses every 6–12 hours. For severe infections, this can be doubled.

Strep throat: Must be treated for at least 10 days to prevent rheumatic fever.

Rheumatic fever prophylaxis: 400mg twice daily, ongoing long-term.

Note: 400mg of erythromycin ethylsuccinate provides activity equivalent to 250mg of erythromycin base. This is why the dose looks different from other erythromycin formulations.

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Is E.E.S. a Controlled Substance?

No. Erythromycin Ethylsuccinate is

not a controlled substance. It is a standard prescription antibiotic with no DEA scheduling. Any licensed prescriber can write a prescription, and telehealth is an option.

Key Things to Know Before Taking E.E.S.

Can be taken with or without food (taking with food reduces stomach upset)

Shake the liquid suspension well before each dose; use a calibrated measuring spoon

Complete the full course even if you feel better — stopping early promotes antibiotic resistance

Tell your doctor about all medications you take — erythromycin has many drug interactions (see our drug interactions guide)

Reconstituted suspension: refrigerate after mixing and use within 10 days (check your specific product label)

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Having Trouble Filling Your E.E.S. Prescription?

E.E.S. is available but isn't stocked at every pharmacy. If you're having trouble locating it, medfinder contacts pharmacies near you to find which ones have it in stock — so you don't have to call around yourself.

Also read: Erythromycin Ethylsuccinate side effects — what to expect and when to call your doctor.