erythromycin base
Apo-Erythro base ◆, E-Base, E-Mycin, Erybid ◆, Eryc, Ery-Tab, Erythromycin Base/Filmtabs, Ilotycin, PCE

erythromycin estolate
Ilosone, Novo-rythro ◆

erythromycin ethylsuccinate
E.E.S., E.E.S. Granules, EryPed, EryPed Drops, Pediazole

erythromycin gluceptate
Ilotycin Gluceptate

erythromycin lactobionate
Erythrocin Lactobionate

erythromycin stearate
Apo-Erythro-S ◆, Erythrocin Stearate Filmtab, Novo-rythro ◆

erythromycin (ophthalmic)
Ilotycin

erythromycin (topical)
Akne-Mycin, A/T/S, Del-Mycin, Erycette, EryDerm, Erygel, Erymax, Ery-Sol, Erythra-Derm, Staticin, Theramycin Z, T-Stat

Available forms
Available by prescription only
erythromycin base
Capsules (delayed-release): 250 mg
Tablets (enteric-coated): 250 mg, 333 mg, 500 mg
erythromycin estolate
Capsules: 250 mg
Suspension: 125 mg/5 ml, 250 mg/5 ml
Tablets: 500 mg
erythromycin ethylsuccinate
Granules for oral suspension: 200 mg/5 ml (after reconstitution)
Oral suspension: 200 mg/5 ml, 400 mg/5 ml
Powder for oral suspension: 100 mg/2.5 ml, 200 mg/ 5 ml, 400 mg/5 ml (after reconstitution)
Tablets: 400 mg
Tablets (chewable): 200 mg
erythromycin gluceptate
Injection: 500-mg, 1-g vials
erythromycin lactobionate
Injection: 500-mg, 1-g vials
erythromycin stearate
Tablets (film-coated): 250 mg, 500 mg
erythromycin (ophthalmic)
Ointment: 0.5%
erythromycin (topical)
Pledgets: 2%
Topical gel: 2%
Topical ointment: 2%
Topical solution: 1.5%, 2%

Indications and dosages
 Acute pelvic inflammatory disease caused by Neisseria gonorrhoeae. Adults: 500 mg I.V. (gluceptate, lactobionate) q 6 hours for 3 days; then 250 mg (base, estolate, stearate) or 400 mg (ethylsuccinate) P.O. q 6 hours for 7 days.
 Intestinal amebiasis in patients who can’t receive metronidazole. Adults: 250 mg (base, estolate, stearate) or 400 mg (ethylsuccinate) P.O. q 6 hours for 10 to 14 days.
Children: 30 to 50 mg/kg (base, estolate, ethylsuccinate, stearate) P.O. daily, divided q 6 hours for 10 to 14 days.
 Mild to moderately severe respiratory tract, skin, and soft-tissue infections caused by susceptible organisms. Adults: 250 to 500 mg (base, estolate, stearate) P.O. q 6 hours. Or, 333 mg (base) P.O. q 8 hours. Or, 400 to 800 mg (ethylsuccinate) P.O. q 6 hours. Or, 15 to 20 mg/kg (gluceptate, lactobionate) I.V. daily, in divided doses q 6 hours.
Children: 30 mg/kg to 50 mg/kg (oral erythromycin salts) P.O. daily, in divided doses q 6 hours. Or, 15 to 20 mg/kg I.V. daily in divided doses q 4 to 6 hours.
 Syphilis. Adults: 500 mg (base, estolate, stearate) P.O. q.i.d. for 14 days.
 Legionnaires’ disease. Adults: 500 mg to 1 g I.V. or P.O. (base, estolate, stearate) or 800 mg to 1,600 mg (ethylsuccinate) P.O. q 6 hours for 21 days.
 Uncomplicated urethral, endocervical, or rectal infections when tetracyclines are contraindicated. Adults: 500 mg (base, estolate, stearate) or 800 mg (ethylsuccinate) P.O. q.i.d. for at least 7 days.
 Urogenital Chlamydia trachomatis infections during pregnancy. Adults: 500 mg (base, estolate, stearate) P.O. q.i.d. for at least 7 days or 250 mg (base, estolate, stearate) or 400 mg (ethylsuccinate) P.O. q.i.d. for at least 14 days.
 Conjunctivitis caused by C. trachomatis in neonates. Neonates: 50 mg/kg P.O. daily in four divided doses for at least 2 weeks.
 Pneumonia of infancy caused by C. trachomatis. Infants: 50 mg/kg P.O. daily in four divided doses for at least 3 weeks.
 Topical treatment of acne vulgaris. Adults and children: Apply to the affected area b.i.d.
 Prophylaxis of ophthalmia neonatorum. Neonates: Apply 1-cm long ribbon ointment in the lower conjunctival sac of each eye no later than 1 hour after birth. Use new tube for each infant and don’t flush after instillation.
 Acute and chronic conjunctivitis, trachoma, other eye infections. Adults and children: Apply 1-cm long ribbon of ointment directly into infected eye up to six times daily, depending on severity of infection.

Pharmacodynamics
Antibacterial action: Erythromycin inhibits bacterial protein synthesis by binding to the ribosomal 50S subunit. It’s used in the treatment of infection with Haemophilus influenzae, Entamoeba histolytica, Mycoplasma pneumoniae, Corynebacterium diphtheriae, C. minutissimum, Legionella pneumophila, and Bordetella pertussis. It may be used as an alternative to penicillins or tetracycline in the treatment of infection with Streptococcus pneumoniae, Streptococcus viridans, Listeria monocytogenes, Staphylococcus aureus, C. trachomatis, N. gonorrhoeae, and Treponema pallidum.

Pharmacokinetics
Absorption: Because base salt is acid-sensitive, it must be buffered or have enteric coating to prevent destruction by gastric acids. Acid salts and esters (estolate, ethylsuccinate, and stearate) aren’t affected by gastric acidity and therefore are well absorbed. Give base and stearate preparations on an empty stomach. Absorption of estolate and ethylsuccinate preparations is unaffected or possibly even enhanced by presence of food. When administered topically, drug is absorbed minimally.
Distribution: Distributed widely to most body tissues and fluids except CSF, where it’s distributed only in low levels. Drug crosses the placental barrier. About 80% of base and 96% of erythromycin estolate are protein-bound.
Metabolism: Metabolized partially in the liver to inactive metabolites.
Excretion: Excreted mainly unchanged in bile. Only small drug amounts (less than 5%) are excreted in urine; some drug appears in breast milk. In patients with normal renal function, plasma half-life is about 11/2 hours. Drug isn’t dialyzable.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug or other macrolides. Erythromycin estolate is contraindicated in patients with hepatic disease. Use erythromycin salts cautiously in patients with impaired hepatic function.

Interactions
Drug-drug. Carbamazepine: Increases carbamazepine levels and increases risk of toxicity. Monitor patient and carbamazepine levels closely.
Clindamycin, lincomycin: May be antagonistic. Avoid use together.
Cyclosporine: Increases cyclosporine levels and may cause nephrotoxicity. Monitor patient closely.
Digoxin: Increases digoxin levels. Monitor patient for digitalis toxicity.
Disopyramide: Increases disopyramide levels and increases risk of arrhythmias and lengthened QT intervals. Monitor patient’s ECG.
Fluoroquinolones, sparfloxacin: Increases risk of life-threatening arrhythmias, including torsades de pointe. Avoid use together.
Isotretinoin: May cause cumulative dryness and excessive skin irritation. Monitor patient carefully.
Midazolam, triazolam: Increases effects of these drugs. Use together cautiously.
Oral anticoagulants: Causes excessive anticoagulant effect. Monitor PT and INR closely.
Theophylline: Increases theophylline levels and decreases erythromycin levels. Use together cautiously.
Drug-herb. Pill-bearing spurge: Inhibits CYP3A enzymes and alters drug metabolism. Discourage use together.
Drug-lifestyle. Abrasive or medicated soaps or cleansers, acne preparations or other preparations containing peeling agents (benzoyl peroxide, resorcinol, salicylic acid, sulfur, tretinoin), alcohol-containing products (aftershave, perfumed toiletries, cosmetics, shaving creams or lotions), astringent soaps or cosmetics, medicated cosmetics or cover-ups: May cause cumulative dryness, resulting in excessive dryness. Tell patient to use together cautiously.

Adverse reactions
CNS: fever (with oral or systemic administration).
CV: ventricular arrhythmias; venous irritation, thrombophlebitis (after I.V. injection).
EENT: bilateral reversible hearing loss (with high systemic or oral doses in patients with renal or hepatic insufficiency); slowed corneal wound healing, blurred vision (with ophthalmic administration).
GI: abdominal pain, cramping, nausea, vomiting, diarrhea (with oral or systemic administration).
Hepatic: cholestatic jaundice (with estolate).
Skin: urticaria, rash, eczema (with oral or systemic administration); urticaria, dermatitis (with ophthalmic administration); sensitivity reactions, erythema, burning, dryness, pruritus, irritation, peeling, oily skin (with topical application).
Other: overgrowth of nonsusceptible bacteria or fungi; anaphylaxis; hypersensitivity reactions, including itching and burning eyes (with ophthalmic administration).

Effects on lab test results
None reported.

Overdose and treatment
No information available.

Special considerations
• Perform culture and sensitivity tests before treatment starts and then as needed.
• Base and stearate forms aren’t available as liquid.
• Absorption of estolate and ethylsuccinate preparations is unaffected or possibly even enhanced by presence of food.
• Erythromycin estolate may cause serious hepatotoxicity (reversible cholestatic jaundice) in adults.
• Don’t administer erythromycin lactobionate with other drugs because of chemical instability. Reconstituted solutions are acidic and should be completely administered within 8 hours of preparation.
• Drug may cause overgrowth of nonsusceptible bacteria or fungi.
• Although drug is bacteriostatic, it may be bactericidal in high levels or against highly susceptible organisms.
• Monitor liver function tests for increased serum bilirubin, AST, and alkaline phosphatase levels. Other erythromycin salts can cause less severe hepatotoxicity. (Patients who develop hepatotoxicity from erythromycin estolate may react similarly to any erythromycin preparation.)
Pregnant patients
• Use drug during pregnancy only when clearly indicated.
Breast-feeding patients
• Although drug appears in breast milk, no adverse reactions have been reported. Use cautiously in breast-feeding women.

Patient education
• Instruct patient to take oral form with full glass of water 1 hour before or 2 hours after meals; enteric-coated tablets may be taken with meals.
• Advise patient not to take drug with fruit juice. If patient takes chewable tablets, tell him not to swallow them whole.
• If patient uses topical solution, instruct patient to wash, rinse, and dry affected areas before applying it. Warn patient not to apply solution near eyes, nose, mouth, or other mucous membranes.
• Instruct patient to wash hands before and after applying ophthalmic ointment. Instruct him to clean eye area of excess exudate before applying ointment. Warn him not to allow tube to touch the eye or surrounding tissue. Instruct him to promptly report signs of sensitivity, such as itching eyelids and constant burning.
• Tell patient to take drug exactly as directed and to continue taking it for prescribed period, even after he feels better.
• Instruct patient to report adverse reactions promptly.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use