Medication Name and Type

Erythromycin is a macrolide antibiotic. It is generally used to treat various bacterial infections. It is available in multiple forms including tablets, capsules, topical solutions, and ophthalmic ointments.

Mechanism of Action

Erythromycin works by inhibiting bacterial protein synthesis. It binds to the 50S subunit of bacterial ribosomes, thus blocking the translocation of peptides. This effectively halts bacterial growth and multiplication.

Indications and Uses

Erythromycin is prescribed for respiratory tract infections, skin and soft tissue infections, pertussis, and diphtheria. It is also used for gastrointestinal infections caused by susceptible strains of bacteria.

Pharmacokinetics

Erythromycin has variable oral bioavailability due to acid lability. It is metabolized primarily in the liver by the cytochrome P450 enzyme system. The drug has a half-life of around 1.5 to 2 hours. It is excreted mainly in the bile.

Dose Administration

Typical dosages for adults range from 250mg to 500mg every 6 to 12 hours. Pediatric doses are often calculated based on weight. Dosage adjustment may be necessary for patients with hepatic impairment. Topical forms are applied directly to the affected area, whereas ophthalmic ointments are typically used multiple times a day in the infected eye.

Drug Interactions

Erythromycin can interact with numerous medications including warfarin, theophylline, and statins. These interactions can lead to either increased levels of erythromycin or the concomitant drug, resulting in potential toxicity. It is a known inhibitor of the cytochrome P450 enzyme system.

Side Effects

Common side effects include gastrointestinal upset, such as nausea and diarrhea. More serious, but less common, side effects can include hepatotoxicity and ototoxicity. Skin reactions such as rash can also occur.

Special Populations

Pregnant women should use erythromycin cautiously as it is classified as Category B. Erythromycin estolate is generally avoided in pregnancy due to potential hepatotoxicity. In breastfeeding women, the medication is excreted into breast milk but is considered compatible with breastfeeding by most guidelines.

Formulations Available

Erythromycin is available in oral tablets and capsules, often in 250mg and 500mg strengths. It is also available as a topical gel, ointment, and eye ointment. Intravenous formulations are less common but available for severe infections.

Storage Guidelines

Oral tablets and capsules should be stored at room temperature, away from moisture and light. Topical and ophthalmic formulations also need to be kept at specified temperatures and should not be frozen. Always check manufacturer’s guidelines.

Patient Counseling Information

Patients should be instructed to complete the full course of therapy. They should be made aware of the potential side effects and be advised to report any serious or unusual symptoms. It is important to take the medication on an empty stomach for better absorption unless gastrointestinal upset occurs.

Monitoring Criteria

Liver function tests should be performed periodically in patients on prolonged therapy. Additionally, hearing assessments may be necessary if signs of ototoxicity occur. Regular monitoring of complete blood counts and kidney function tests may also be warranted in specific cases.

Antibiotic Resistance

Erythromycin resistance is increasingly common in certain strains of bacteria such as Staphylococcus aureus. Resistance mechanisms often involve methylation of the ribosomal binding site or efflux mechanisms. Clinicians should consider local resistance patterns when prescribing.

Compatibility and Stability

Compatible with most intravenous fluids if the intravenous form is used. It should, however, not be mixed with aminoglycosides as this may lead to precipitation. The drug is generally stable under normal storage conditions, but reconstituted solutions should be used promptly.

Disposal Instructions

Unused or expired erythromycin should be disposed of in accordance with local regulations. Patients should be instructed not to flush medications down the toilet unless specifically directed.

Alternative Therapies

For patients who are allergic or have intolerances, alternative antibiotics such as azithromycin or clarithromycin may be considered. In cases of severe systemic infections, parenteral antibiotics like vancomycin or linezolid may be required.

Healthcare Professional Considerations

Pharmacists and healthcare providers should review the patient’s complete medication profile to avoid drug interactions. Special attention should be given to medications metabolized by the cytochrome P450 system.

Cost and Availability

Erythromycin is generally affordable and widely available. Generic versions are cost-effective compared to brand names. Insurance coverage for the medication often varies.