Erythromycin is a macrolide-class antibiotic medication with broad-spectrum activity against numerous gram-positive and some gram-negative bacteria. As a bacteriostatic agent that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, it serves as an effective alternative for patients with penicillin allergies. This versatile antibiotic is available in multiple formulations including oral tablets, capsules, suspensions, ophthalmic preparations, and topical applications, providing flexibility in treatment approaches across various infection types and patient populations.

Features

• Macrolide-class antibiotic with bacteriostatic action
• Multiple administration routes: oral, topical, ophthalmic
• Various salt forms including erythromycin base, stearate, and ethylsuccinate
• Demonstrated efficacy against streptococci, staphylococci, and atypical pathogens
• Established safety profile with decades of clinical use
• Available in immediate and delayed-release formulations

Benefits

• Effective treatment for respiratory tract infections including pneumonia and bronchitis
• Proven efficacy against skin and soft tissue infections caused by susceptible organisms
• Suitable alternative for penicillin-allergic patients requiring antibiotic therapy
• Multiple formulation options allow for tailored treatment approaches
• Established clinical history with well-characterized pharmacokinetics
• Cost-effective antibiotic option with generic availability

Common use

Erythromycin is commonly prescribed for the treatment of various bacterial infections including upper and lower respiratory tract infections such as pharyngitis, tonsillitis, acute bronchitis, and community-acquired pneumonia. It demonstrates particular effectiveness against infections caused by Streptococcus pyogenes, Streptococcus pneumoniae, and Haemophilus influenzae. Additionally, it is utilized for skin and soft tissue infections including impetigo, erysipelas, and cellulitis when caused by susceptible staphylococcal and streptococcal species. The medication also finds application in the treatment of pertussis (whooping cough), diphtheria, erythrasma, and as prophylaxis against bacterial endocarditis in high-risk patients undergoing dental procedures. Ophthalmologic formulations are employed for the treatment of bacterial conjunctivitis, while topical preparations address acne vulgaris through both antibacterial and anti-inflammatory mechanisms.

Dosage and direction

Dosage varies significantly based on the specific formulation, indication, and patient factors. For adults with mild to moderate infections, the typical oral dosage ranges from 250-500 mg every 6 hours or 400-800 mg every 8 hours for ethylsuccinate formulations. Severe infections may require doses up to 4 grams daily in divided doses. Pediatric dosing is typically calculated as 30-50 mg/kg/day in divided doses, not to exceed adult maximum doses.

For ophthalmic use, apply a 0.5% ointment to the affected eye(s) 2-6 times daily depending on severity. Topical solutions for acne are generally applied twice daily to affected areas. All formulations should be administered at evenly spaced intervals to maintain constant blood levels. Oral doses are preferably taken on an empty stomach (1 hour before or 2 hours after meals) unless gastrointestinal upset occurs, in which case administration with food is acceptable though may slightly decrease absorption.

Precautions

Patients should complete the full prescribed course of therapy even if symptoms improve to prevent development of resistant bacteria. Caution is advised in patients with hepatic impairment as erythromycin is primarily metabolized by the liver and may accumulate. Those with pre-existing liver disease require careful monitoring and potential dosage adjustment. Use with caution in patients with renal impairment, although dosage adjustment is generally not required until significant impairment exists.

Erythromycin may prolong the QT interval, increasing risk of cardiac arrhythmias, particularly in patients with existing cardiac conditions, electrolyte imbalances, or those taking other QT-prolonging medications. Patients should report any symptoms of irregular heartbeat, dizziness, or fainting. Superinfection with nonsusceptible organisms including fungi may occur, requiring appropriate treatment. Pseudomembranous colitis has been reported with nearly all antibacterial agents, including erythromycin, and may range in severity from mild to life-threatening.

Contraindications

Erythromycin is contraindicated in patients with known hypersensitivity to erythromycin or any macrolide antibiotics. Concomitant administration with cisapride, pimozide, ergotamine, dihydroergotamine, or terfenadine is absolutely contraindicated due to potentially fatal drug interactions. Additional contraindications include history of cholestatic jaundice or hepatic dysfunction associated with prior erythromycin use. The medication should not be used in patients with known or suspected electrolyte disturbances, particularly hypokalemia or hypomagnesemia, due to increased risk of QT prolongation. Patients with congenital long QT syndrome or documented ventricular arrhythmias including torsades de pointes should avoid erythromycin therapy.

Possible side effect

Gastrointestinal disturbances are the most frequently reported side effects, including nausea, vomiting, abdominal pain, diarrhea, and anorexia. These effects are often dose-related and may be mitigated by administration with food. Less common gastrointestinal effects include pseudomembranous colitis, pancreatitis, and hepatotoxicity manifesting as elevated liver enzymes, cholestatic jaundice, or hepatitis.

Allergic reactions ranging from mild skin rashes to severe reactions including anaphylaxis may occur. Cardiac effects include QT prolongation, ventricular tachycardia, and torsades de pointes, particularly in patients with risk factors. Ototoxicity manifested as reversible hearing loss, usually at high doses or in patients with renal impairment, has been reported. Other potential adverse effects include superinfection, crystalluria, and various neurological symptoms including headache, dizziness, and vertigo.

Drug interaction

Erythromycin significantly inhibits cytochrome P450 3A4 enzyme system, leading to numerous important drug interactions. Concurrent use with CYP3A4 substrates including statins (particularly simvastatin and lovastatin), benzodiazepines, buspirone, carbamazepine, cyclosporine, disopyramide, and many others may lead to increased levels of these medications and potential toxicity.

The interaction with drugs that prolong QT interval (antiarrhythmics, antipsychotics, antidepressants) may produce additive effects and increase arrhythmia risk. Erythromycin may enhance effects of oral anticoagulants, potentially increasing bleeding risk. Concomitant administration with ergot derivatives may cause acute ergot toxicity. The antibiotic may reduce efficacy of oral contraceptives, necessitating additional contraceptive measures. Absorption may be impaired by antacids containing aluminum or magnesium, requiring separation of administration by at least 2 hours.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next scheduled dose. In that case, the missed dose should be skipped and the regular dosing schedule resumed. Patients should never double the dose to make up for a missed one. Maintaining consistent blood levels is important for therapeutic efficacy, so efforts should be made to adhere to the prescribed dosing schedule. If multiple doses are missed or uncertainty exists about proper dosing, patients should consult their healthcare provider for guidance.

Overdose

Erythromycin overdose may produce effects including severe nausea, vomiting, diarrhea, and abdominal pain. Hearing loss, which may be permanent, has been reported with massive overdosage. QT prolongation and associated cardiac arrhythmias represent the most serious potential consequences of overdose. Management is primarily supportive and symptomatic, with particular attention to cardiac monitoring. Gastric lavage may be considered if performed soon after ingestion. There is no specific antidote for erythromycin overdose. Hemodialysis is not effective for removal of the drug due to extensive tissue binding and large volume of distribution. Patients suspected of overdose should receive immediate medical attention with continuous cardiac monitoring for at least 24 hours or until QT interval normalizes.

Storage

Store erythromycin products at room temperature (15-30°C or 59-86°F) unless otherwise specified by the manufacturer. Protect from excessive moisture and light. Oral suspensions should be kept tightly closed and refrigerated, with careful attention to expiration dates as reconstituted formulations have limited stability. Do not freeze liquid formulations. Keep all medications out of reach of children and pets. Properly discard any unused medication after the completion of therapy or upon reaching the expiration date, following local regulations for medication disposal.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Individual patient needs may vary, and healthcare providers should make treatment decisions based on specific clinical circumstances. Always consult with a qualified healthcare professional before starting, changing, or stopping any medication. The prescribing physician should be consulted for specific dosage recommendations and treatment duration based on the infection being treated, pathogen susceptibility, and patient-specific factors. This information may not include all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects.

Reviews

Clinical studies and decades of use demonstrate erythromycin’s effectiveness against susceptible organisms, with particular value as an alternative for penicillin-allergic patients. Many clinicians appreciate its established safety profile and multiple formulation options. However, the high incidence of gastrointestinal side effects and significant drug interaction potential are frequently noted limitations. The development of bacterial resistance, particularly among streptococcal species, has increased over time, necessitating careful consideration of local resistance patterns when prescribing. Overall, erythromycin remains a valuable therapeutic option within the antibiotic armamentarium when used appropriately for susceptible infections.