Erythromycin Drug Profile

What is Erythromycin?

Erythromycin is a macrolide antibiotic that has been used for over 60 years to treat bacterial infections. It belongs to a class of antibiotics derived from natural compounds produced by certain bacteria and fungi. Erythromycin is particularly useful for treating respiratory tract infections, skin infections, and infections in patients who are allergic to penicillin.

Uses

Erythromycin is prescribed for several types of bacterial infections:

Respiratory tract infections: Including pneumonia, bronchitis, and whooping cough (pertussis), particularly those caused by atypical bacteria like Mycoplasma pneumoniae.

Skin and soft tissue infections: Such as cellulitis, impetigo, and infected wounds caused by susceptible bacteria including Staphylococcus and Streptococcus species.

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Sexually transmitted infections: Used as an alternative treatment for chlamydia and gonorrhea, especially in patients allergic to first-line antibiotics.

Eye infections: Available as an ophthalmic ointment for treating bacterial conjunctivitis and preventing eye infections in newborns.

Gastrointestinal motility disorders: At lower doses, erythromycin can stimulate stomach emptying and is sometimes used off-label for gastroparesis.

How it works

Erythromycin works by binding to the 50S ribosomal subunit of bacteria, which prevents them from making essential proteins needed for survival and reproduction. This action either kills bacteria directly or stops their growth, allowing the body’s immune system to eliminate the infection. The antibiotic is generally bacteriostatic, meaning it stops bacterial growth rather than immediately killing bacteria.

Side effects

Common side effects include:

• Nausea and vomiting
• Abdominal cramping and pain
• Diarrhea
• Loss of appetite
• Heartburn
• Skin rash or itching
• Headache
• Dizziness

Serious side effects requiring immediate medical attention:

• Severe diarrhea or signs of Clostridioides difficile infection
• Irregular heartbeat or QT prolongation
• Severe allergic reactions including difficulty breathing or swelling
• Signs of liver problems such as yellowing of skin or eyes
• Severe stomach pain or persistent vomiting

Warnings and precautions

Liver function monitoring: Erythromycin can cause liver toxicity, particularly with prolonged use or in patients with existing liver disease. Regular liver function tests may be necessary.

Heart rhythm concerns: The medication can prolong the QT interval on ECG, potentially leading to dangerous heart rhythm abnormalities, especially in patients with existing heart conditions.

Pregnancy and breastfeeding: Generally considered safe during pregnancy (FDA Category B) and is often preferred over other antibiotics in pregnant women allergic to penicillin. It passes into breast milk but is usually considered compatible with breastfeeding.

Kidney impairment: Dose adjustments may be necessary in patients with severe kidney disease, as the drug can accumulate and increase the risk of side effects.

Myasthenia gravis: Erythromycin may worsen muscle weakness in patients with this neuromuscular condition.

Interactions

Warfarin: Erythromycin increases bleeding risk by enhancing warfarin’s anticoagulant effects through enzyme inhibition.

Statins (lovastatin, simvastatin): Concurrent use increases the risk of muscle toxicity and rhabdomyolysis by increasing statin blood levels.

Digoxin: Erythromycin can increase digoxin levels, potentially leading to dangerous heart rhythm problems.

Theophylline: The antibiotic reduces theophylline clearance, increasing the risk of toxicity including seizures and heart arrhythmias.

Carbamazepine: Erythromycin increases carbamazepine levels, potentially causing dizziness, confusion, and other neurological side effects.

Cyclosporine: Combined use can increase cyclosporine levels and nephrotoxicity risk in transplant patients.

Ergot alkaloids: This combination can cause severe vasoconstriction and ergot toxicity.

Other QT-prolonging medications: Concurrent use with drugs like quinidine or certain antipsychotics increases the risk of dangerous heart rhythm abnormalities.

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Dosage

Adult dosages vary depending on the infection type and severity. For most infections, the typical oral dose ranges from 250-500 mg every 6 hours or 333-500 mg every 8 hours. Severe infections may require up to 4 grams daily in divided doses. Intravenous administration typically involves 15-20 mg/kg daily divided into multiple doses. Treatment duration usually ranges from 7-14 days depending on the infection. Dosage should always be determined by a healthcare provider based on individual factors including kidney function, infection severity, and patient response.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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