Apo-Erythro Base , A/T/S, E-Mycin, Eryc, EryDerm, EryTab, Erythrocin, Erythromid , Erythromycin Base, Novorythro , PCE, Ro-Mycin 
Apo-Erythro-S , Erythrocin Stearate, SK-Erythromycin
Classifications: macrolide antibiotic;
Therapeutic: antibiotic

Pregnancy Category: B


Erythromycin: 250 mg, 333 mg, 500 mg tablets, capsules; 2% topical solution; 2% gel; 2% ointment; 2% pledgets; 5% ophthalmic ointment;

Erythromycin Estolate: 125 mg, 250 mg capsules; 125 mg/mL, 250 mg/mL suspension;

Erythromycin Stearate: 250 mg, 500 mg tablets


Macrolide antibiotic that binds to the 50S ribosomal subunit, thus inhibiting bacterial protein synthesis.

Therapeutic Effect

More active against gram-positive organisms than against gram-negative organisms due to its superior penetration into gram-positive organisms.


Pneumococcal pneumonia, Mycoplasma pneumoniae (primary atypical pneumonia), acute pelvic inflammatory disease caused by Neisseria gonorrhoeae in females sensitive to penicillin, infections caused by susceptible strains of staphylococci, streptococci, and certain strains of Haemophilus influenzae. Also used in intestinal amebiasis, Legionnaires' disease, uncomplicated urethral, endocervical, and rectal infections caused by Chlamydia trachomatis, for prophylaxis of ophthalmia neonatorum caused by N. gonorrhoeae, C. trachomatis, and for chlamydial conjunctivitis in neonates. Considered an acceptable alternative to penicillin for treatment of streptococcal pharyngitis, for prophylaxis of rheumatic fever and bacterial endocarditis, for treatment of diphtheria as adjunct to antitoxin and for carrier state, and as alternate choice in treatment of primary syphilis in patients allergic to penicillins. Topical applications: Pyodermas, acne vulgaris, and external ocular infections, including neonatal chlamydial conjunctivitis and gonococcal ophthalmia.


Hypersensitivity to erythromycins or other macrolide antibiotics; congenital QT prolongation; electrolyte imbalances. Estolate: History of hepatotoxicity in patients with hepatic disease.

Cautious Use

Impaired liver function; seizure disorders; history of GI disorders; pregnancy (category B).

Route & Dosage

Moderate to Severe Infections
Adult: PO 250–500 mg q6h; 333 mg q8h
Child: PO 30–50 mg/kg/d divided q6h Topical Apply ointment to infected eye 1 or more times/d
Neonate: PO ≤7 d, 10 mg/kg q12h; >7 d, 10 mg/kg q8–12h Topical 0.5–1 cm in conjunctival sac once

Chlamydia trachomatis Infections
Adult: PO 500 mg q.i.d. or 666 mg q8h
Child: Topical Apply 0.5–1 cm ribbon in lower conjunctival sacs shortly after birth


  • Give on an empty stomach 1 h before or 3 h after meals. Do not give with, or immediately before or after, fruit juices, and advise patient not to crush or chew tablets.
  • Give enteric-coated tablets without regard to meals.
  • Ensure that enteric-coated tablets are not chewed or crushed. They must be swallowed whole.
  • Note: When switching from tablet to a PO liquid preparation, dosing may require adjustment.
  • Prophylaxis for neonatal eye infection: Ribbon of ointment approximately 0.5–1 cm long is placed into lower conjunctival sac of neonate shortly after birth. Use a new tube of erythromycin for each neonate.
  • Use only preparations labeled for ophthalmic use for treatment of eye infections.
  • Store all forms at 15°–30° C (59°–86° F) in tightly capped containers unless otherwise directed by manufacturer.

Adverse Effects (≥1%)

GI: Nausea, vomiting, abdominal cramping, diarrhea, heartburn, anorexia. Body as a Whole: Fever, eosinophilia, urticaria, skin eruptions, fixed drug eruption, anaphylaxis. Superinfections by nonsusceptible bacteria, yeasts, or fungi. Special Senses: Ototoxicity: reversible bilateral hearing loss, tinnitus, vertigo. Digestive: (Estolate) Cholestatic hepatitis syndrome. Skin: (topical use) Erythema, desquamation, burning, tenderness, dryness or oiliness, pruritus.

Diagnostic Test Interference

False elevations of urinary catecholamines, urinary steroids, and AST, ALT (by colorimetric methods).


Drug: Serum levels and toxicities of alfentanil, bexarotene, carbamazepine, cevimeline, cilostazol, clozapine, cyclosporine, disopyramide, estazolam, fentanyl, midazolam, methadone, modafinil, quinidine, sirolimus, digoxin, theophylline, triazolam, warfarin are increased. Ergotamine, dihydroergotamine may increase peripheral vasospasm.


Absorption: Erythromycin base is acid labile; most erythromycins are absorbed in small intestine. Peak: 1–4 h PO. Distribution: Widely distributed to most body tissues; low concentrations in CSF; concentrates in liver and bile; crosses placenta. Metabolism: Partially metabolized in liver. Elimination: Primarily in bile; excreted in breast milk. Half-Life: 1.5–2 h.

Nursing Implications

Assessment & Drug Effects

  • Report onset of GI symptoms after PO administration to physician. These are dose related; if symptoms persist after dosage reduction, physician may prescribe drug to be given with meals in spite of impaired absorption.
  • Monitor for adverse GI effects. Pseudomembranous enterocolitis (see Appendix F), a potentially life-threatening condition, may occur during or after antibiotic therapy.
  • Observe for S&S of superinfection by overgrowth of nonsusceptible bacteria or fungi. Emergence of resistant staphylococcal strains is highly predictable during prolonged therapy.
  • Lab tests: Periodic liver function tests during prolonged therapy.
  • Monitor for S&S of hepatotoxicity. Premonitory S&S include: Abdominal pain, nausea, vomiting, fever, leukocytosis, and eosinophilia; jaundice may or may not be present. Symptoms may appear a few days after initiation of drug but usually occur after 1–2 wk of continuous therapy. Symptoms are reversible with prompt discontinuation of erythromycin.
  • Monitor for ototoxicity that appears to develop most frequently in patients receiving 4 g/d or more, older adults, female patients, and patients with kidney or liver dysfunction. It is reversible with prompt discontinuation of drug.

Patient & Family Education

  • Notify physician for S&S of superinfection (see Appendix F).
  • Notify physician immediately for S&S of pseudomembranous enterocolitis (see Appendix F), which may occur even after the drug is discontinued.
  • Report any ototoxic effects including dizziness, vertigo, nausea, tinnitus, roaring noises, hearing impairment (see Appendix F).

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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