Erythromycin: A Macrolide Antibiotic

Erythromycin treats bacterial infections including respiratory, skin, and sexually transmitted diseases. It works by inhibiting protein synthesis in bacteria. This antibiotic is often prescribed for penicillin-allergic patients due to its different chemical structure.

How Erythromycin Works

The drug binds to bacterial ribosomes, blocking protein production. This bacteriostatic action stops bacterial growth, allowing the immune system to eliminate the infection. It's effective against gram-positive and some gram-negative bacteria.

Common Medical Uses

Erythromycin treats pneumonia, Legionnaires' disease, and pertussis. It's also used for acne, chlamydia, and prevention of neonatal conjunctivitis. Gastrointestinal motility applications exist at lower doses.

Dosage Forms Available

Available as tablets, capsules, ointments, and IV solutions. Typical adult doses range from 250-500mg every 6 hours. Pediatric erythromycin comes as suspensions or chewable tablets.

Potential Side Effects

Common issues include nausea, diarrhea, and stomach pain. Serious but rare effects include hearing loss, liver problems, and QT prolongation. Allergic reactions require immediate discontinuation.

Important Precautions

Use cautiously with liver disease or myasthenia gravis. Avoid grapefruit juice which increases drug levels. Monitor for superinfections like candidiasis during prolonged use.

Drug Interactions to Consider

Erythromycin inhibits liver enzymes, increasing levels of statins, warfarin, and theophylline. Concurrent use with cisapride or pimozide is contraindicated due to arrhythmia risk.

Administration Guidelines

Take oral forms with food to reduce stomach upset, except enteric-coated tablets. Complete the full course even if symptoms improve. Do not crush delayed-release formulations.

Resistance Concerns

Bacterial resistance occurs via ribosomal modification or efflux pumps. Avoid unnecessary use and follow susceptibility testing when available.

Special Populations

Dose adjustment needed for severe renal impairment. Pregnancy category B - benefits often outweigh risks. Secreted in breast milk but generally compatible with breastfeeding.

Storage Requirements

Store tablets at room temperature. Refrigerate liquid suspensions and discard after 14 days. Protect all forms from moisture and light.

Historical Significance

Discovered in 1952, erythromycin was the first macrolide antibiotic. It remains valuable despite newer alternatives like azithromycin and clarithromycin.

What infections does erythromycin treat best?

Erythromycin is particularly effective for atypical pneumonias (like Legionnaires'), pertussis, and chlamydia. It's also first-line for campylobacter gastroenteritis and erythrasma skin infections.

Why does erythromycin cause stomach upset?

It stimulates motilin receptors in the gut, increasing contractions. Taking with food or using enteric-coated forms reduces this effect. Nausea typically improves after a few doses.

Can erythromycin be used for acne?

Yes, both oral and topical forms treat acne. However, P. acnes resistance is common, so combination therapy with benzoyl peroxide or retinoids is often preferred.

How soon after taking erythromycin can I drink alcohol?

Avoid alcohol during treatment as it may increase nausea and liver stress. Wait 48 hours after finishing the course before consuming alcohol.

Does erythromycin affect birth control?

Unlike some antibiotics, erythromycin doesn't reduce contraceptive effectiveness. However, diarrhea/vomiting may impact absorption of oral contraceptives.

Is erythromycin safe for infants?

Yes, it's commonly prescribed for whooping cough prophylaxis and chlamydial conjunctivitis in newborns. Pediatric suspensions allow precise dosing by weight.

What's the difference between erythromycin and azithromycin?

Azithromycin has longer action allowing once-daily dosing, better stomach tolerance, and broader coverage. However, erythromycin remains cheaper and effective for specific infections.

Can I take erythromycin with dairy products?

Unlike tetracyclines, dairy doesn't significantly affect absorption. However, taking with food may help minimize gastrointestinal side effects.

Why is erythromycin used before surgery?

Sometimes prescribed for bowel prep due to its prokinetic effects. It also serves as antibiotic prophylaxis for penicillin-allergic patients undergoing certain procedures.

How should I store erythromycin eye ointment?

Keep at room temperature (15-30°C). Don't freeze. Discard 28 days after opening. Avoid touching the tube tip to prevent contamination.