Erythromycin inhibits microsomal protein synthesis in susceptible organisms by inhibiting the translocation process. Specific binding to the 50S subunit or 70S ribosome occurs in these organisms but there is no binding to the stable 80S mammalian ribosome. Erythromycin is active against many Grampositive bacteria, some Gram-negative bacteria and against mycoplasmas and chlamydia.
Adult and Child over 8 years: 250-500 mg every 6 hours or 0.5-1 gm every 12 hours. This may be increased up to 4 gm daily according to severity of infections.
Child of 2-8 years: 250 mg every 6 hours, doses doubled for severe infections.
Child up to 2 years: 125 mg every 6 hours.
Neonates: 30 to 45 mg/kg daily in 3 divided doses.
Elderly: Same as for adults.
If administration on a twice daily schedule is desirable, one half of the total daily dose may be given every 12 hours, one hour before meal.
Adult: 250 – 500 mg four times daily for 10 – 14 days.
Children: 30 – 50 mg/kg/day in divided doses for 10 – 14 days.
Pertussis: 30 – 50 mg/kg/day in divided doses for 5-14 days depending upon eradication of a positive culture.
Streptococcal infections: In the treatment of group A beta haemolytic streptococcal infections, therapeutic dosage of Erythromycin should be administered for at least 10 days.
Acne: The usual dosage regimen of erythromycin in the treatment of acne is 500 mg twice daily for 3 months. Then the dose is to be reduced to 250 mg twice daily for another 3 months.
Early Syphilis: 500 mg 4 times daily for 14 days.
Uncomplicated genital Chlamydia nongonococcal Urethritis: 500 mg twice daily for 14 days.
Prophylaxis: In continuous prophylaxis of streptococcal infections in person with a rheumatic heart disease, the dosage is 250 mg twice daily.
When Erythromycin is used prior to surgery to prevent endocarditis caused by alpha haemolytic streptococci, a recommended schedule:
For children: 20 mg/Kg 1.5 – 2 hours pre-operatively and 10 mg/kg every 6 hours for 8 doses post-operatively.
For adults: The dose is 1 g, 1.5 – 2 hours pre-operatively and 500 mg every 6 hours for 8 doses post-operatively.