Ilosone (erythromycin estolate) is a well-established macrolide antibiotic indicated for the treatment of a wide range of bacterial infections. With its bacteriostatic action, it inhibits protein synthesis in susceptible organisms, providing a reliable therapeutic option for both community-acquired and certain hospital-managed infections. Its estolate formulation offers enhanced oral bioavailability, making it a practical choice for outpatient management. Trusted by clinicians for decades, Ilosone remains a relevant option in the antimicrobial arsenal.

Features

• Active ingredient: Erythromycin estolate
• Available formulations: 250 mg and 500 mg tablets; oral suspension (125 mg/5 mL and 250 mg/5 mL)
• Pharmacologic class: Macrolide antibiotic
• Mechanism of action: Binds to the 50S ribosomal subunit, inhibiting bacterial protein synthesis
• Spectrum: Effective against Gram-positive bacteria, some Gram-negative organisms, and atypical pathogens
• Prescription status: Rx-only

Benefits

• Provides broad-spectrum coverage against common respiratory, skin, and soft tissue pathogens
• Offers convenient oral dosing, supporting patient compliance and outpatient treatment
• Suitable for patients with penicillin allergies, serving as an alternative therapeutic option
• Demonstrates good tissue penetration, including lung and skin concentrations
• Established safety profile with extensive clinical use history
• Available in multiple formulations to accommodate pediatric and adult dosing needs

Common use

Ilosone is commonly prescribed for the treatment of mild to moderate bacterial infections caused by susceptible strains. Typical indications include upper and lower respiratory tract infections such as pharyngitis, tonsillitis, acute otitis media, bronchitis, and community-acquired pneumonia. It is also effective for skin and soft tissue infections including impetigo, erysipelas, and cellulitis. Additionally, Ilosone may be used for pertussis (whooping cough) treatment and prophylaxis, as well as for diphtheria carrier eradication. Some off-label uses include treatment of chlamydial infections in pregnancy and erythrasma. The appropriate use should always be guided by culture and susceptibility testing when possible.

Dosage and direction

Adults: The usual dosage is 250 mg every 6 hours, or 500 mg every 12 hours. For more severe infections, 500 mg every 6 hours may be prescribed. Maximum daily dose should not exceed 4 grams.

Children: 30-50 mg/kg/day in divided doses every 6-8 hours. For more severe infections, the dose may be doubled.

Administration: Tablets should be swallowed whole with a full glass of water. The oral suspension should be shaken well before each use and may be taken with or without food, though administration with food may reduce gastrointestinal upset. Complete the full course of therapy even if symptoms improve earlier to prevent development of resistant bacteria.

Dosage adjustments may be necessary in patients with hepatic impairment. Duration of treatment typically ranges from 7 to 14 days depending on the infection type and severity.

Precautions

Patients should be advised to complete the entire course of therapy despite feeling better. Hepatic function should be monitored during prolonged therapy (longer than two weeks) as erythromycin estolate has been associated with cholestatic hepatitis. Use with caution in patients with pre-existing liver disease. May prolong the QT interval; use caution in patients with known QT prolongation, electrolyte abnormalities, or those taking other QT-prolonging drugs. Superinfections with nonsusceptible organisms, including fungi, may occur. Pseudomembranous colitis has been reported with nearly all antibacterial agents; consider this diagnosis in patients who present with diarrhea. Caution should be exercised when prescribing to patients with myasthenia gravis as exacerbations have been reported.

Contraindications

Ilosone is contraindicated in patients with known hypersensitivity to erythromycin or any macrolide antibiotics. Should not be used in patients with pre-existing liver disease or hepatic dysfunction. Contraindicated in patients taking drugs that are extensively metabolized by CYP3A4 and that prolong QT interval (e.g., cisapride, pimozide, ergot alkaloids). Not recommended for patients with history of hepatitis or jaundice associated with previous erythromycin use. Avoid concurrent administration with colchicine in patients with renal or hepatic impairment.

Possible side effect

Common side effects (≥1%) include nausea, vomiting, abdominal pain, diarrhea, and loss of appetite. Less frequently reported effects include skin rash, itching, and urticaria. Hepatic side effects may include elevated liver enzymes, cholestatic jaundice, and hepatitis, particularly with prolonged use. Ototoxicity, manifesting as reversible hearing loss, has been reported, usually at high doses or in patients with renal impairment. Cardiac effects including QT prolongation and ventricular arrhythmias have been observed. Other reported adverse reactions include pseudomembranous colitis, pancreatitis, and psychiatric disturbances including confusion and hallucinations in elderly patients.

Drug interaction

Ilosone interacts significantly with drugs metabolized by cytochrome P450 3A4 enzyme system. It may increase concentrations of theophylline, digoxin, carbamazepine, cyclosporine, hexobarbital, and phenytoin. Concurrent use with simvastatin, lovastatin, or other statins metabolized by CYP3A4 may increase risk of rhabdomyolysis. Potentially fatal interactions may occur with ergot derivatives, pimozide, cisapride, and terfenadine. May enhance effects of oral anticoagulants requiring more frequent INR monitoring. Concurrent administration with azole antifungals or other macrolides may increase risk of QT prolongation. Antacids containing aluminum or magnesium may decrease absorption.

Missed dose

If a dose is missed, it should be taken as soon as remembered. However, if it is almost time for the next scheduled dose, the missed dose should be skipped and the regular dosing schedule resumed. Patients should not double the dose to make up for a missed one. Maintaining consistent antibiotic levels is important for therapeutic efficacy, so adherence to the prescribed schedule should be emphasized.

Overdose

Symptoms of overdose may include severe nausea, vomiting, diarrhea, and abdominal pain. Hepatotoxicity may occur, manifesting as jaundice, dark urine, or clay-colored stools. Ototoxicity with hearing loss, especially in patients with renal impairment, may be seen. Cardiac effects including QT prolongation and torsades de pointes have been reported. Management is primarily supportive with careful monitoring of hepatic and cardiac function. Gastric lavage may be considered if ingestion was recent. Not removed by hemodialysis. Specific antidote is not available.

Storage

Store at room temperature (15-30°C or 59-86°F) in a dry place protected from light and moisture. Keep the container tightly closed. Do not freeze the oral suspension. Discard any unused oral suspension after 14 days of reconstitution. Keep out of reach of children. Do not use beyond the expiration date printed on the packaging.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Ilosone is a prescription medication that should be used only under the supervision of a qualified healthcare professional. The prescribing physician should be consulted for specific medical advice, diagnosis, and treatment recommendations. Individual patient response may vary, and not all side effects or interactions are listed here. Healthcare providers should reference the complete prescribing information before administration.

Reviews

Clinical studies and decades of use demonstrate Ilosone’s efficacy in treating susceptible bacterial infections. Many clinicians appreciate its role as an alternative for penicillin-allergic patients. Some reviews note the gastrointestinal side effect profile as a limitation, though this is often manageable with dose timing adjustments. The estolate formulation is recognized for its reliable absorption characteristics. While newer macrolides have emerged, Ilosone maintains its position in therapeutic guidelines for specific indications. Patient satisfaction generally correlates with successful infection resolution, though individual tolerance varies.