Ery-Max (Erythromycin)
Macrolide Antibiotic Oral Suspension for Bacterial Infections
Quick Facts About Ery-Max
Key Takeaways About Ery-Max
- Versatile macrolide antibiotic: Ery-Max treats a wide range of bacterial infections including atypical pneumonia, pertussis, chlamydial infections, and serves as a key penicillin alternative
- Complete the full course: Even if symptoms improve quickly, finishing all prescribed doses prevents bacterial regrowth and reduces the risk of antibiotic resistance
- Important cardiac warning: Ery-Max must not be used by patients with long QT syndrome or low potassium/magnesium levels due to the risk of serious heart rhythm disturbances
- Numerous drug interactions: Erythromycin inhibits CYP3A4 and interacts with many medications including statins, warfarin, digoxin, and theophylline – always inform your doctor of all medicines you take
- Reconstituted suspension storage: Once prepared, the oral suspension lasts 14 days in the refrigerator or 5 days at room temperature – shake well before each dose
What Is Ery-Max and What Is It Used For?
Ery-Max is a macrolide antibiotic containing erythromycin ethylsuccinate. It works by blocking bacterial protein synthesis, binding to the 50S ribosomal subunit and preventing bacteria from producing the essential proteins they need to grow and multiply. This bacteriostatic action allows the body's immune system to eliminate the infection.
Erythromycin was first isolated in 1952 from Saccharopolyspora erythraea (formerly Streptomyces erythraeus) and has been a cornerstone of antibiotic therapy for over seven decades. It belongs to the macrolide class of antibiotics, which are characterised by a large macrocyclic lactone ring in their chemical structure. Ery-Max uses the ethylsuccinate ester form of erythromycin, a prodrug that is hydrolysed in the body to release the active erythromycin base.
The World Health Organization (WHO) includes erythromycin on its Model List of Essential Medicines, recognising its importance in global healthcare. It remains particularly valuable in settings where penicillin allergy limits treatment options and in treating infections caused by atypical organisms that do not respond to beta-lactam antibiotics.
Primary Indications
Ery-Max is indicated for the treatment of several specific infections where erythromycin has proven clinical efficacy:
- Atypical pneumonia: Caused by Mycoplasma pneumoniae, Legionella pneumophila, or Chlamydophila pneumoniae – organisms that lack a cell wall and are inherently resistant to penicillin
- Whooping cough (pertussis): Caused by Bordetella pertussis; erythromycin is a first-line agent for both treatment and post-exposure prophylaxis
- Diphtheria: Used as an adjunct to diphtheria antitoxin to eliminate Corynebacterium diphtheriae from the upper respiratory tract
- Genital chlamydial infections: Treatment of Chlamydia trachomatis infections of the urogenital tract, particularly when tetracyclines are contraindicated
- Neonatal chlamydial infections: Eye infections (ophthalmia neonatorum) and pneumonia in newborns caused by Chlamydia trachomatis acquired during birth
Alternative to Penicillin
For patients who are allergic to penicillin, Ery-Max provides a critical therapeutic alternative for common infections including:
- Acute otitis media (middle ear infection) – particularly common in children
- Streptococcal pharyngitis (tonsillitis/strep throat) – for eradication of Group A Streptococcus
- Community-acquired pneumonia – caused by Streptococcus pneumoniae and other susceptible organisms
- Skin and soft tissue infections – including impetigo, erysipelas, and cellulitis caused by susceptible staphylococci and streptococci
According to the European Medicines Agency (EMA) and international prescribing guidelines, the choice of antibiotic should always be guided by local resistance patterns, culture and sensitivity results where available, and patient-specific factors including allergy history and concurrent medications.
What Should You Know Before Taking Ery-Max?
Before starting Ery-Max, your doctor must evaluate your medical history for heart rhythm disorders, liver problems, and current medications. Erythromycin has important contraindications and numerous drug interactions that can cause serious adverse effects, including potentially life-threatening cardiac arrhythmias.
Contraindications
Ery-Max must not be used in the following situations:
- Allergy to erythromycin or macrolides: Known hypersensitivity to erythromycin or any other macrolide antibiotic (e.g., azithromycin, clarithromycin)
- Long QT syndrome: Congenital long QT syndrome or acquired QT prolongation on ECG
- Electrolyte imbalances: Abnormally low levels of potassium (hypokalaemia) or magnesium (hypomagnesaemia) in the blood
- Family history of cardiac arrhythmia: Personal or family history of ventricular arrhythmia or torsades de pointes
Ery-Max must not be taken together with the following medicines due to the risk of serious or life-threatening cardiac arrhythmias or other dangerous reactions:
- Terfenadine or astemizole – antihistamines (risk of QT prolongation and torsades de pointes)
- Cisapride – gastrointestinal motility agent (risk of fatal arrhythmia)
- Pimozide – antipsychotic (risk of cardiac arrest)
- Ergotamine or dihydroergotamine – migraine/hypotension agents (risk of severe vasospasm and ischaemia)
- Disopyramide – antiarrhythmic (risk of QT prolongation)
- Domperidone – antiemetic (risk of QT prolongation)
- Statins – cholesterol-lowering drugs (risk of rhabdomyolysis)
- Lomitapide – lipid-lowering agent (risk of elevated liver transaminases and hepatotoxicity)
Warnings and Precautions
Speak with your doctor before taking Ery-Max if you have any of the following conditions or circumstances:
- Impaired liver function: Erythromycin is extensively metabolised by the liver. Hepatic impairment can lead to drug accumulation and increased risk of side effects, including cholestatic hepatitis. Your doctor may need to adjust the dose or monitor liver function during treatment.
- Myasthenia gravis: Erythromycin may exacerbate symptoms of myasthenia gravis, a neuromuscular disorder. Cases of worsening muscle weakness have been reported.
- Heart conditions: If you have any form of heart disease or are taking other medications known to affect the heart rhythm, inform your doctor. Erythromycin can prolong the QT interval on an ECG, increasing the risk of ventricular arrhythmias.
- Use in infants: If your infant vomits or becomes irritable during feeding while taking Ery-Max, contact your doctor immediately. This could indicate infantile hypertrophic pyloric stenosis (IHPS), a condition where the muscle at the outlet of the stomach thickens and blocks food from passing. IHPS has been associated with erythromycin use in neonates, particularly in the first two weeks of life.
Pregnancy and Breastfeeding
Ery-Max should not be used during pregnancy or when planning pregnancy unless specifically prescribed by your doctor after a careful risk-benefit assessment. Research data on the risk of birth defects from erythromycin use during pregnancy are conflicting. Some studies have reported an association with cardiac malformations when erythromycin is taken during early pregnancy, though other studies have not confirmed this finding.
Erythromycin is excreted in breast milk, but at concentrations that are generally considered unlikely to affect a breastfed infant. Nevertheless, consult your doctor before using Ery-Max during breastfeeding, especially with prolonged use, as the infant could develop gastrointestinal disturbances or sensitisation to the antibiotic.
Ery-Max has no known effects on the ability to drive or operate machinery. However, if you experience dizziness or any other side effects that could impair your alertness, avoid driving until these symptoms resolve.
Important Information About Excipients
Ery-Max oral suspension contains sucrose (sugar) at approximately 396 mg per ml. If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicine. Because the suspension contains sugar, thorough and regular tooth brushing and dental care are important during treatment.
This medicine contains less than 1 mmol (23 mg) sodium per 20 ml, meaning it is essentially sodium-free and suitable for patients on sodium-restricted diets.
How Does Ery-Max Interact with Other Drugs?
Erythromycin is a potent inhibitor of the cytochrome P450 3A4 (CYP3A4) enzyme system in the liver. This means it can significantly increase blood levels of many other medications, potentially leading to serious or life-threatening adverse effects. Always inform your doctor and pharmacist of all medicines you are taking.
The CYP3A4 enzyme is responsible for metabolising approximately 50% of all clinically used drugs. When erythromycin inhibits this enzyme, co-administered drugs that are CYP3A4 substrates accumulate in the body, often reaching toxic concentrations. This is the basis for the majority of erythromycin's drug interactions and explains why the list of interacting medications is extensive.
In addition to CYP3A4 inhibition, erythromycin can also inhibit P-glycoprotein (P-gp), a membrane transporter that pumps drugs out of cells. This dual inhibition further increases the bioavailability and tissue concentrations of certain co-administered medications.
Major Interactions (Avoid Concurrent Use)
| Drug | Category | Risk |
|---|---|---|
| Terfenadine, Astemizole | Antihistamines | QT prolongation, torsades de pointes, cardiac arrest |
| Cisapride | GI motility agent | QT prolongation, fatal ventricular arrhythmia |
| Pimozide | Antipsychotic | QT prolongation, sudden cardiac death |
| Ergotamine, Dihydroergotamine | Ergot alkaloids | Severe vasospasm, peripheral ischaemia, gangrene |
| Disopyramide | Antiarrhythmic | QT prolongation, ventricular tachycardia |
| Domperidone | Antiemetic | QT prolongation, serious cardiac arrhythmia |
| Statins (e.g., simvastatin, lovastatin) | Lipid-lowering | Rhabdomyolysis, acute kidney injury |
| Lomitapide | Lipid-lowering | Severe hepatotoxicity, elevated transaminases |
Significant Interactions Requiring Dose Adjustment or Monitoring
| Drug | Category | Effect / Recommendation |
|---|---|---|
| Warfarin, Rivaroxaban | Anticoagulants | Increased anticoagulant effect, risk of bleeding; monitor INR/clotting |
| Digoxin | Cardiac glycoside | Increased digoxin levels; monitor serum concentration |
| Theophylline | Bronchodilator | Increased theophylline levels; risk of toxicity (nausea, arrhythmia) |
| Carbamazepine | Antiepileptic | Increased carbamazepine levels; risk of neurotoxicity (dizziness, ataxia) |
| Cyclosporine, Tacrolimus | Immunosuppressants | Increased levels of immunosuppressant; nephrotoxicity risk |
| Midazolam, Alprazolam, Triazolam | Benzodiazepines | Increased sedation and respiratory depression |
| Sildenafil | PDE5 inhibitor | Increased sildenafil exposure; higher risk of adverse effects |
| Phenytoin, Phenobarbital | Antiepileptics | Altered drug levels in both directions; monitor levels |
| Methylprednisolone | Corticosteroid | Increased corticosteroid effect; risk of Cushing-like symptoms |
| Zopiclone | Hypnotic | Increased sedation; may need dose reduction |
| Hydroxychloroquine, Chloroquine | Antimalarials | Increased risk of QT prolongation and cardiac arrhythmia |
| Vinca alkaloids | Chemotherapy | Increased toxicity of anticancer agents |
| Rifampicin, Rifabutin | Anti-tuberculosis | Decreased erythromycin efficacy (CYP3A4 induction) |
| St John’s Wort | Herbal supplement | Decreased erythromycin efficacy; avoid concurrent use |
| Felodipine | Calcium channel blocker | Increased blood pressure-lowering effect; risk of hypotension |
This list is not exhaustive. Additional interactions may occur with other CYP3A4 substrates not listed above. Always provide your doctor and pharmacist with a complete list of all prescription medications, over-the-counter drugs, vitamins, and herbal products you are using before starting Ery-Max.
Ery-Max (erythromycin ethylsuccinate) can be taken immediately before or together with a meal. Unlike erythromycin base or stearate, the ethylsuccinate ester is well absorbed regardless of food intake. Grapefruit juice may increase erythromycin levels via CYP3A4 inhibition in the gut wall; however, this interaction is considered less clinically significant than with some other CYP3A4 substrates.
What Is the Correct Dosage of Ery-Max?
The dose of Ery-Max is determined by your doctor and individualised based on the type and severity of infection, your body weight (especially in children), and other patient-specific factors. Always follow your doctor's instructions exactly and complete the full course of treatment.
Ery-Max is supplied as granules that are reconstituted by the pharmacist into an oral suspension at a concentration of 100 mg erythromycin per ml. The bottle must be shaken well before each use to ensure uniform distribution of the active ingredient throughout the suspension.
General Dosing Guidelines
Adults
The typical adult dose of erythromycin ethylsuccinate is 400 mg (4 ml) every 6 hours or 800 mg (8 ml) every 12 hours. For severe infections, doses up to 4 g per day may be used under medical supervision. According to international guidelines (BNF, FDA), the total daily dose should generally not exceed 4 g of erythromycin base equivalent.
Children
Paediatric dosing is based on body weight. The typical recommended dose is 30–50 mg/kg/day of erythromycin ethylsuccinate, divided into 2–4 doses. For severe infections, the dose may be increased to up to 100 mg/kg/day under specialist supervision. Your doctor will calculate the exact dose based on your child's weight and the specific infection being treated.
Elderly Patients
No specific dose adjustment is routinely required for elderly patients. However, elderly patients may be more susceptible to QT prolongation and hepatotoxicity. Lower doses and careful monitoring are advisable, particularly in those with impaired liver or kidney function or who are taking multiple medications.
Patients with Hepatic Impairment
Since erythromycin is primarily metabolised by the liver, patients with impaired liver function may require dose reduction and regular monitoring of liver enzymes. Use with caution, as erythromycin can cause cholestatic hepatitis.
Duration of Treatment
The duration of treatment depends on the type of infection. Typical treatment courses include:
- Respiratory tract infections: 7–14 days
- Pertussis (whooping cough): 14 days
- Chlamydial infections: 7–14 days, depending on the site and severity
- Skin and soft tissue infections: 7–10 days
- Diphtheria carrier state: 7–10 days
It is crucial to complete the full prescribed course of Ery-Max, even if you start to feel better after just a few days. Stopping treatment early allows surviving bacteria to regrow and potentially develop resistance. Antimicrobial resistance is recognised by the WHO as one of the top 10 global public health threats facing humanity.
Missed Dose
If you forget to take a dose of Ery-Max, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a forgotten one. If you are unsure about what to do, consult your doctor or pharmacist.
Overdose
If you or your child has taken more Ery-Max than prescribed, contact your doctor, hospital emergency department, or poison control centre immediately. Symptoms of erythromycin overdose may include severe nausea, vomiting, diarrhoea, abdominal discomfort, and potentially hearing loss (which is usually reversible). In severe cases, liver damage and cardiac arrhythmias may occur. Keep the medicine bottle available to show the healthcare provider.
What Are the Side Effects of Ery-Max?
Like all antibiotics, Ery-Max can cause side effects, although not everyone experiences them. The most common side effects are gastrointestinal disturbances including stomach pain, nausea, and diarrhoea. Erythromycin acts as a motilin receptor agonist in the gut, which stimulates gastric motility and is the primary cause of its GI side effects.
Most side effects of Ery-Max are mild and resolve after completing the course of treatment. However, some side effects can be serious and require immediate medical attention. The following overview categorises side effects by their frequency of occurrence, based on data from clinical trials and post-marketing surveillance.
- Severe skin reactions: red, scaly rash with bumps under the skin and blisters (acute generalised exanthematous pustulosis), rash with potential mouth sores (erythema multiforme), or widespread skin and mucous membrane involvement with fever (Stevens-Johnson syndrome or toxic epidermal necrolysis)
- Signs of a severe allergic reaction: difficulty breathing, swelling of face, lips, tongue or throat, widespread hives
- Sudden skin rash, fever, and/or facial swelling
- Prolonged or severe diarrhoea (may indicate Clostridioides difficile infection)
Common
- Stomach pain and abdominal cramps
- Nausea
- Diarrhoea
- Skin rash
Uncommon
- Urticaria (hives)
Rare
- Elevated liver enzymes (transaminases)
- Increased bilirubin levels
- Intrahepatic cholestasis (bile flow obstruction in the liver)
- Anaphylactic reaction (severe, life-threatening allergic reaction)
- Cardiac arrhythmia (irregular heartbeat)
- Reversible hearing loss (usually dose-related, occurring at high doses)
Frequency Not Known
- QTc interval prolongation on ECG
- Ventricular arrhythmia
- Torsades de pointes (a specific type of life-threatening irregular heartbeat)
- Cardiac arrest
- Stevens-Johnson syndrome
- Toxic epidermal necrolysis
- Acute generalised exanthematous pustulosis
- Infantile hypertrophic pyloric stenosis (in neonates)
Gastrointestinal Effects
The gastrointestinal side effects of erythromycin are among the most common reasons patients discontinue treatment. Erythromycin stimulates motilin receptors in the gastrointestinal tract, which are receptors that normally control the migrating motor complex – the pattern of smooth muscle contractions that moves food through the digestive system. This prokinetic effect causes increased gastric and intestinal motility, leading to nausea, abdominal cramping, and diarrhoea.
Taking Ery-Max with food can help reduce nausea and stomach discomfort. If GI side effects are persistent or severe, consult your doctor – they may adjust the dosing schedule or consider alternative antibiotics.
Vaginal Yeast Infections
Like all antibiotics, Ery-Max can disrupt the normal bacterial flora of the body, potentially leading to overgrowth of Candida species. This may manifest as vaginal itching, discharge, or oral thrush. If you develop symptoms of a yeast infection during or after treatment, consult your doctor or pharmacist for appropriate antifungal treatment.
Cardiac Effects
Erythromycin can affect the electrical activity of the heart by blocking the hERG (human ether-a-go-go-related gene) potassium channels, which prolongs the QT interval on an electrocardiogram (ECG). In rare cases, this can trigger dangerous ventricular arrhythmias, including torsades de pointes, which can progress to ventricular fibrillation and cardiac arrest. The risk is highest in patients with pre-existing QT prolongation, electrolyte abnormalities, or who are taking other QT-prolonging medications.
How Should You Store Ery-Max?
Once reconstituted by the pharmacist, Ery-Max oral suspension has a limited shelf life. Store it in the refrigerator (2–8°C) for up to 14 days, or at room temperature (up to 25°C) for up to 5 days. Always shake the bottle well before use.
Proper storage of Ery-Max is essential to maintain the potency and safety of the medication. The reconstituted oral suspension contains erythromycin in a liquid medium that is susceptible to degradation over time, particularly at higher temperatures.
Storage Instructions
- Refrigerated storage (2–8°C / 36–46°F): The reconstituted suspension is stable for up to 14 days
- Room temperature storage (up to 25°C / 77°F): The reconstituted suspension is stable for up to 5 days
- Keep the bottle tightly closed when not in use
- Keep out of the sight and reach of children
- Do not use after the expiry date printed on the bottle (EXP). The expiry date refers to the last day of that month
Disposal
Do not dispose of Ery-Max by pouring it down the drain or throwing it in household waste. Return any unused or expired medication to your pharmacy for safe disposal. These measures help protect the environment and prevent the release of antibiotics into water systems, which can contribute to antimicrobial resistance in environmental bacteria.
What Does Ery-Max Contain?
Each millilitre of reconstituted Ery-Max oral suspension contains erythromycin ethylsuccinate equivalent to 100 mg of erythromycin, along with several inactive ingredients including sucrose, flavouring agents, and stabilisers.
Active Ingredient
The active substance is erythromycin ethylsuccinate, an ester prodrug of erythromycin. Each 1 ml of the reconstituted oral suspension contains erythromycin ethylsuccinate equivalent to 100 mg of erythromycin base. The ethylsuccinate ester form was developed to improve the acid stability and oral bioavailability of erythromycin compared to the base form.
Inactive Ingredients (Excipients)
- Sucrose (sugar): 396 mg per ml – serves as a sweetener and provides the suspension's palatable taste. Important consideration for patients with sugar intolerances or diabetes
- Carmellose sodium: A cellulose derivative used as a suspending and thickening agent to keep the erythromycin particles evenly distributed
- Magnesium aluminium silicate: Used as a suspending agent and stabiliser
- Sodium citrate: Functions as a buffering agent to maintain the appropriate pH of the suspension
- Cherry flavouring: Added to improve the taste and palatability of the suspension, particularly important for paediatric patients
- Purified water: The vehicle for the suspension
Packaging
Ery-Max is supplied as granules in glass bottles of 50 ml and 100 ml. The pharmacist reconstitutes the granules with purified water to produce the ready-to-use oral suspension. The glass bottle provides optimal protection against light and moisture degradation.
Frequently Asked Questions About Ery-Max
Ery-Max (erythromycin) is a macrolide antibiotic used to treat several types of bacterial infections including atypical pneumonia (caused by Mycoplasma, Legionella, or Chlamydophila), whooping cough (pertussis), diphtheria, genital and neonatal chlamydial infections, and – in penicillin-allergic patients – ear infections, tonsillitis, community-acquired pneumonia, and skin and soft tissue infections.
Yes, Ery-Max oral suspension can be taken immediately before or together with a meal. The erythromycin ethylsuccinate form is well absorbed even when taken with food, and eating may help reduce the gastrointestinal side effects such as nausea and stomach cramps that are common with erythromycin.
The most common side effects are gastrointestinal: stomach pain, nausea, diarrhoea, and skin rash. These occur because erythromycin stimulates motilin receptors in the gut, increasing intestinal motility. Most side effects are mild and resolve after completing the treatment course. Contact your doctor if side effects are severe or persistent.
Ery-Max should generally not be used during pregnancy unless specifically prescribed by your doctor after weighing the benefits against the risks. Some studies have reported conflicting data regarding the risk of cardiac malformations when erythromycin is used in early pregnancy. If you are pregnant or planning to become pregnant, discuss alternative antibiotics with your doctor.
Completing the full course ensures that all bacteria causing the infection are eliminated. Stopping early, even if you feel better, allows surviving bacteria to regrow and potentially develop resistance to erythromycin. This not only increases the risk of your infection returning but also contributes to the global problem of antimicrobial resistance, which the WHO identifies as one of the top public health threats worldwide.
Once mixed with water by the pharmacist, store Ery-Max in the refrigerator (2–8°C) and use within 14 days. If stored at room temperature (up to 25°C), use within 5 days. Always shake the bottle well before measuring each dose. Discard any remaining suspension after the storage period has expired and return it to your pharmacy.
References
- World Health Organization (WHO). Model List of Essential Medicines – 23rd List (2023). Geneva: WHO; 2023.
- European Medicines Agency (EMA). Erythromycin – Summary of Product Characteristics. EMA; 2024.
- British National Formulary (BNF). Erythromycin: Indications, dose, contraindications, side effects, interactions. NICE; 2025.
- U.S. Food and Drug Administration (FDA). Erythromycin Ethylsuccinate Prescribing Information. FDA; 2023.
- Periti P, Mazzei T, Mini E, Novelli A. Adverse effects of macrolide antibacterials. Drug Saf. 1993;9(5):346-364. doi:10.2165/00002018-199309050-00004
- Ray WA, Murray KT, Meredith S, et al. Oral erythromycin and the risk of sudden death from cardiac causes. N Engl J Med. 2004;351(11):1089-1096. doi:10.1056/NEJMoa040582
- Maheshwai N. Are young infants treated with erythromycin at risk for developing hypertrophic pyloric stenosis? Arch Dis Child. 2007;92(3):271-273. doi:10.1136/adc.2006.110007
- Pottegård A, Broe A, Hallas J, et al. Use of macrolides during pregnancy and risk of cardiac malformations: A nationwide, register-based cohort study. Eur Heart J. 2023;44(28):2604-2613.
- Koutsostathis N, Bhatt DL. Drug interactions of macrolide antibiotics. Ann Intern Med. 2020;172(8):553-554.
- WHO. Antimicrobial Resistance: Global Report on Surveillance. Geneva: World Health Organization; 2023.
Editorial Team
Medical Content
Written by licensed physicians specialising in infectious disease and clinical pharmacology. Content follows EMA, FDA, WHO, and BNF guidelines.
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Independently reviewed by the iMedic Medical Review Board. All claims verified against peer-reviewed sources using the GRADE evidence framework.
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Evidence Level 1A based on systematic reviews, meta-analyses of RCTs, and international clinical guidelines. No commercial funding or pharmaceutical sponsorship.
Last Updated
Published September 22, 2025. Last medically reviewed January 26, 2026. Next review scheduled within 12 months.
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