Erythromycin (Oral route)

From Drugs Prescribing Information
Jump to: navigation, search



  • Eryc (United States, Australia, Canada)
  • Ery-Tab United States



The chemical structure is characterized by a lactone ring to which sugars are attached.


Erythromycin is a macrolide antibiotic produced by Streptomyces erythraeus. The mechanism of action of macrolides is inhibition of bacterial protein biosynthesis, and they are thought to do this by binding to the P-site of the 50 S subunit of bacterial ribosomes and preventing translocation of AA-peptide from A site to P site.

Erythromycin also mimics the agonistic action of the gastrointestinal polypeptide motilin at motilin receptors in the gastric antrum and proximal duodenum. The result is an increased motility during the interdigestive period.

Macrolides are especially used in people who are allergic to penicillins


Erythromycin has a wide spectrum of activity against many gram-positive micro-organisms, and is used in the prevention and treatement of infections such as:

  • Throat and sinus infections.
  • Chest infections, such as bronchitis and pneumonia.
  • Ear infections.
  • Mouth and dental infections.
  • Eye infections.
  • Skin and tissue infections, such as acne.
  • Stomach and intestinal infections.
  • Prevention of infection following burns, operations or dental procedures.
  • Other infections, such as sexually transmitted diseases, bone infections or scarlet fever

[edit] DOSAGE

Erythromycin is well absorbed and may be given without regard to meals. Optimum blood levels are obtained in a fasting state (administration at least one half hour and preferably two hours before or after a meal)

ADULTS: The usual dose is 250 mg every 6 hours taken one hour before meals. If twice-a-day dosage is desired, the recommended dose is 500 mg every 12 hours. Dosage may be increased up to 4 grams per day, according to the severity of the infection. Twice-a-day dosing is not recommended when doses larger than 1 gram daily are administered.

CHILDREN: Age, weight, and severity of the infection are important factors in determining the proper dosage. The usual dosage is 30 to 50 mg/kg/day in divided doses. For the treatment of more severe infections, this dose may be doubled.

The usual duration of therapy is 5 to 14 days depending on the type of infection


  • Erythromycin is contraindicated in patients with known hypersensitivity to this antibiotic. Allergic reactions ranging from urticaria to anaphylaxis have occurred. Skin reactions ranging from mild eruptions to erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis have been reported rarely.
  • Erythromycin is contraindicated in patients taking terfenadine, astemizole,cisapride, pimozide, ergotamine, or dihydroergotamine


Hepatotoxicity : hepatic dysfunction, including increased liver enzymes, and hepatocellular and/or cholestatic hepatitis, with or without jaundice may occur

QT Prolongation : Erythromycin has been associated with prolongation of the QT interval and infrequent cases of arrhythmia. Cases of torsades de pointes have been spontaneously reported during postmarketing surveillance in patients receiving erythromycin. Fatalities have been reported. Erythromycin should be avoided in patients with known prolongation of the QT interval, patients with ongoing proarrhythmic conditions such as uncorrected hypokalemia or hypomagnesemia, clinically significant bradycardia, and in patients receiving Class IA (quinidine, procainamide) or Class III (dofetilide, aminodarone, sotalol) antiarrhythmic agents. Elderly patients may be more susceptible to drug-associated effects on the QT interval.


Erythromycin is a strong inhibitor of CYP3A4 and can cause clinically important drug interactions with drugs that are mainly metabolized by CYP3A4 and which have a narrow therapeutic index

Serious adverse reactions have been reported in patients taking erythromycin concomitantly with:

  • colchicine toxicity with colchicine; this interaction is potentially life-threatening, and may occure while using both drugs at their recommended doses
  • rhabdomyolysis with simvastatin, lovastatin, and atorvastatin; patients should be carefully monitored for creatine kinase (CK) and serum transaminase levels.
  • hypotension with calcium channel blockers metabolized by CYP3A4 (for example, verapamil, amlodipine, diltiazem)
  • Digoxin: Concomitant administration of erythromycin and digoxin has been reported to result in elevated digoxin serum levels.
  • oral anticoagulants: increased anticoagulant effects
  • triazolam and alprazolam: Erythromycin has been reported to decrease the clearance of triazolam and midazolam, and thus, may increase the pharmacologic effect of these drugs
  • Erythromycin has been reported to increase the systemic exposure of sildenafil. Reduction of sildenafil dosage should be considered.
  • Concomitant administration of cisapride, pimozide, astemizole, or terfenadine is contraindicated


  • Pregnancy Category B (US). It should be used during pregnancy only if clearly needed.
  • Nursing Mothers: Erythromycin is excreted in human milk. Caution should be exercised when erythromycin is administered to a nursing woman.


The most frequent side effects are gastrointestinal and are dose-related. They include nausea, vomiting, abdominal pain, diarrhea and anorexia. Symptoms of hepatitis, hepatic dysfunction and/or abnormal liver function test results may occur

Erythromycin has been associated with QT prolongation and ventricular arrhythmias, including ventricular tachycardia and torsade de pointes (see WARNINGS).


Macrolides: Mechanisms of Action
Acne Treatments



Oral antibiotics Clindamycin (Oral route)   Doxycycline   Erythromycin (Oral route)   Josamycin   Lymecycline   Minocycline   Tetracycline
Topical antibiotics Clindamycin (Topical)   Erythromycin (Topical)
Topical retinoids Adapalene   Tazarotene   Tretinoin
Oral retinoids Isotretinoin (Oral)
Oral contraceptives Estradiol valerate/Dienogest   Ethinyl Estradiol/Cyproterone acetate
Topical Antibacterial/Keratolytic Benzoyl peroxide   Hydrogen Peroxide Cream
Topical combination products Clindamycin/Benzoyl peroxide   Adapalene/Benzoyl peroxide   Clindamycin/Tretinoin   Miconazole/Benzoyl peroxide   Erythromycin/Benzoyl peroxide   Erythromycin/Isotretinoin