Erythromycin – Antibiotic

What is Erythromycin?

Erythromycin is an antibiotic in the class of antibiotics known as macrolide antibiotics which also includes azithromycin (Zithromax, Zmax) and clarithromycin (Biaxin).

Erythromycin, like all macrolide antibiotics, prevents bacterial cells from growing and multiplying by interfering with their ability to make proteins while not affecting human cells. Bacteria such as Haemophilus influenzae are resistant to erythromycin alone and must be treated with a combination of erythromycin and adequate doses of sulfonamides.

erythromycin Tablet.jpg

Properties and Characteristics of Erythromycin

Drug class Antibiotics
Brand Names  Aktipak, Apo-Erythro-S, Benzamycin, E.E.S., Ery, Ery-tab, Erygel, Eryped, Erythro, Erythrocin, Erythrocin Stearate
Synonyms Erythromycin, 114-07-8, Erythromycin A, E-Mycin, Ilotycin, Abomacetin, Erymax, Erythromycinum, Emgel, Erycette
Molecular Formula C37H67NO13
Molecular Weight 733.9 g/mol
IUPAC Names (3R,4S,5S,6R,7R,9R,11R,12R,13S,14R)-6-[(2S,3R,4S,6R)-4-(dimethylamino)-3-hydroxy-6-methyloxan-2-yl]oxy-14-ethyl-7,12,13-trihydroxy-4-[(2R,4R,5S,6S)-5-hydroxy-4-methoxy-4,6-dimethyloxan-2-yl]oxy-3,5,7,9,11,13-hexamethyl-oxacyclotetradecane-2,10-dione
Structural formula of main components Erythromycin skeletal structure.png
Pure active ingredient Erythromycin
Appearance    Hydrated crystals from water
Melting Point  133-135°C
Solubility         Soluble in water at 2mg/ml
Excretion Excreted in the urine
Available as Gel, Ointment, Solution, Tablet, delayed release, Suspension, Lotion
Storage Topical solutions and gels should be stored at 15 – 30 °C

Tablets should be stored in tight, light-resistant containers at 30 °C or lower

Prescription Prescription is required

Erythromycin Uses

Erythromycin is used to treat:

  • Streptococcal infections of the throat (“strep throat”) and skin
  • Lung infections, for example, pneumonia caused by streptococcal pneumoniae, mycoplasma pneumoniae, and legionella pneumophila (legionnaires disease)
  • Pelvic inflammatory disease
  • Erythrasma
  • Whooping cough
  • Listeriosis
  • Intestinal amebiasis

It is used for the treatment of staphylococcal infections of the skin and as an alternative antibiotic for the treatment of syphilis, gonorrhea, and chlamydia.

Erythromycin is used in patients who are allergic to penicillin for the prevention of recurrent rheumatic fever and infections of the hearts’ valves (endocarditis) in patients with valvular abnormalities of the heart before they undergo dental treatments.

The non-FDA approved uses for erythromycin include acne, Lyme disease, and tetanus. The FDA approved E.E.S in April 1965.

What are the side effects of Erythromycin (MY-E)?

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Call your doctor at once if you have:

  • Severe stomach pain, diarrhea that is watery or bloody (even if it occurs months after your last dose);
  • Headache with chest pain and severe dizziness, fainting, fast or pounding heartbeats;
  • A seizure;
  • Hearing problems (rare);
  • Pancreatitis–severe pain in your upper stomach spreading to your back, nausea and vomiting; or
  • Liver problems–loss of appetite, stomach pain (upper right side), tiredness, easy bruising or bleeding, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Serious side effects may be more likely in older adults, including hearing loss, or a life-threatening fast heart rate.

Call your doctor if a baby using this medicine is vomiting or irritable with feeding.

Common side effects may include:

  • Severe stomach pain, diarrhea that is watery or bloody (even if it occurs months after your last dose);
  • Liver problems; or
  • Abnormal liver function tests.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

Mechanism of action

In order to replicate, bacteria require a specific process of protein synthesis, enabled by ribosomal proteins. Erythromycin acts by inhibition of protein synthesis by binding to the 23S ribosomal RNA molecule in the 50S subunit of ribosomes in susceptible bacterial organisms. It stops bacterial protein synthesis by inhibiting the transpeptidation/translocation step of protein synthesis and by inhibiting the assembly of the 50S ribosomal subunit. This results in the control of various bacterial infections. The strong affinity of macrolides, including erythromycin, for bacterial ribosomes, supports their broad‐spectrum antibacterial activities.

What may interact with this medication?

Do not take this medication with any of the following:

  • Astemizole
  • Certain medications for cholesterol like atorvastatin, cerivastatin, lovastatin, simvastatin
  • Certain medications for fungal infections like fluconazole, itraconazole, ketoconazole, posaconazole, voriconazole
  • Certain medications for irregular heart beat like amiodarone, disopyramide, dronedarone, flecainide, procainamide, propafenone, quinidine
  • Certain medications for psychotic disturbances like mesoridazine, pimozide, thioridazine
  • Chloroquine
  • Cisapride
  • Droperidol
  • Eplerenone
  • Ergot alkaloids like ergotamine, dihydroergotamine
  • Methadone
  • Other antibiotics like grepafloxacin or sparfloxacin
  • Red yeast rice
  • Sirolimus
  • Terfenadine
  • Vinblastine

This medication may also interact with the following:

  • Alfentanil
  • Birth control
  • Bromocriptine
  • Carbamazepine
  • Certain medications for anxiety or sleep
  • Certain medications that treat or prevent blood clots like warfarin
  • Cyclosporine
  • Digoxin
  • Dofetilide
  • Other medications that prolong the QT interval (cause an abnormal heart rhythm)
  • Phenytoin
  • Theophylline
  • Valproate
  • Ziprasidone

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.


The dose of this medicine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For oral dosage forms (granules for suspension, suspension, and tablets)

For treatment of bacterial infections:

  • Adults—400 milligrams (mg) every 6 hours or 800 mg every 12 hours. Depending on the severity of your infection, your doctor may increase your dose as needed up to 4000 mg per day.
  • Children—Dose is based on body weight and must be determined by your doctor. The dose is usually 30 to 50 milligrams (mg) per kilogram (kg) of body weight per day, divided in equal doses and taken every 6 hours. Depending on the severity of your infection, your doctor may increase your dose as needed.

For oral dosage form (PCE® tablets)

For prevention of recurring attacks of rheumatic fever:

  • Adults—250 milligrams (mg) 2 times a day.
  • Children—Use and dose must be determined by your doctor.

For treatment of bacterial infections:

  • Adults—333 milligrams (mg) every 8 hours or 500 mg every 12 hours. Depending on the severity of your infection, your doctor may increase your dose as needed up to 4000 mg per day.
  • Children—Dose is based on body weight and must be determined by your doctor. The dose is usually 30 to 50 milligrams (mg) per kilogram (kg) of body weight per day, divided in equal doses. Depending on the severity of your infection, your doctor may increase your dose as needed.


In case of overdosage, erythromycin should be discontinued. Overdosage should be handled with the prompt elimination of unabsorbed drug and all other appropriate measures should be instituted.

Erythromycin is not removed by peritoneal dialysis or hemodialysis.


Erythromycin can sometimes cause harmful effects in people who have certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether erythromycin is a good treatment option for you.

Talk with your doctor about your health history before you take erythromycin. Factors to consider include those described below.

Age 65 years and older. Adults ages 65 years and older have a higher risk of reversible hearing loss as a side effect from taking erythromycin. This risk may be even higher if you’re in this age group and have a liver or kidney problem.

Older adults also have a higher risk of irregular heart rhythm, which is a rare but serious side effect erythromycin can cause. To learn more about whether erythromycin is safe to take at your age, talk with your doctor.

Heart problems. In rare cases, erythromycin can cause heart rhythm problems, including long QT syndrome. You may have a higher risk if you already have a heart problem, especially if you have arrhythmia. If you have a heart condition, talk with your doctor about whether erythromycin is right for you.

Low potassium or low magnesium. While rare, erythromycin may cause heart rhythm problems, such as long QT syndrome. You may be at higher risk if you already have low levels of potassium or magnesium in your blood. Your doctor will determine if it is safe for you to take erythromycin.

Liver or kidney problems. Erythromycin can cause kidney or liver problems. You may have a higher risk of these side effects if you already have a liver or kidney problem. It’s also possible that taking erythromycin could worsen your condition worse.

Myasthenia gravis. Taking erythromycin if you have myasthenia gravis could worsen the symptoms of your condition. If you have this condition, talk with your doctor about the risks and benefits of using erythromycin.

Due to the risks, your doctor may prescribe a different antibiotic, if possible, to treat your infection.

Seizures. Convulsions in people taking erythromycin have been reported since the drug became available for use. If you have a condition that causes seizures, such as epilepsy, you may have a higher risk of this side effect if you take erythromycin.

Allergic reaction. If you’ve had an allergic reaction to erythromycin or any of its ingredients, your doctor will likely not prescribe erythromycin. Ask them what other medications are better options for you.

Erythromycin and alcohol

It’s recommended that you avoid consuming alcohol while taking erythromycin. This is because alcohol may make erythromycin less effective at treating your infection.

If you have questions about drinking alcohol while taking erythromycin, talk with your doctor.

Pregnancy and breastfeeding

Erythromycin is generally considered safe to take during pregnancy after the first trimester. (The first trimester refers to the first 12 weeks of pregnancy). When used during the first trimester, there have been rare reports of heart abnormalities in newborns. But it’s not known for certain whether this is caused by erythromycin or other factors.

Erythromycin passes into breast milk in small amounts. It’s generally considered safe to breastfeed while using this drug unless your doctor advises against it. If you breastfeed while taking erythromycin, you should monitor your breastfed child for irritability, diarrhea, and diaper rash.

If you have other questions about using erythromycin while pregnant or breastfeeding, talk with your doctor.

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