ERYTHROMYCIN LACTOBIONATE
Clinical safety rating: safe
Inhibits CYP3A4 increasing levels of many drugs (eg statins carbamazepine) May cause QT prolongation and subsequent arrhythmias.
Erythromycin lactobionate inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, preventing the translocation of peptides. It may also act as a motilin receptor agonist, enhancing gastrointestinal motility.
| Metabolism | Erythromycin is primarily metabolized in the liver via demethylation by cytochrome P450 3A4 (CYP3A4), resulting in inactive metabolites. It is also a substrate for P-glycoprotein and undergoes extensive hepatic and biliary excretion. |
| Excretion | Primarily biliary excretion (80-90% as unchanged drug and metabolites); renal excretion accounts for 10-15% of the dose. Fecal elimination is minimal (<5%). |
| Half-life | Terminal elimination half-life: 1.4-2.0 hours in adults with normal renal function. In patients with anuria, half-life may be prolonged up to 4.8-6.0 hours. |
| Protein binding | Approximately 70-80% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution: 0.6-1.1 L/kg, indicating wide distribution into tissues and body fluids (excluding cerebrospinal fluid unless meninges inflamed). |
| Bioavailability | Intravenous administration results in 100% bioavailability. Not orally administered as lactobionate salt due to acid lability; erythromycin base or esters are used orally with 30-65% bioavailability. |
| Onset of Action | Intravenous administration: Onset of action occurs within 1-2 hours following infusion. |
| Duration of Action | Duration of action: Approximately 6-12 hours. Bacteriostatic effects persist for several hours post-infusion; clinical effect wanes as serum concentrations fall below MIC. |
1-4 g/day IV divided every 6 hours; maximum 4 g/day. Infuse over 20-60 minutes.
| Dosage form | INJECTABLE |
| Renal impairment | No adjustment required for GFR >10 mL/min; for GFR <10 mL/min, reduce dose by 50% or extend interval to every 8-12 hours. |
| Liver impairment | Child-Pugh Class B or C: reduce dose by 50% or administer every 12 hours. |
| Pediatric use | 15-50 mg/kg/day IV divided every 6 hours; maximum 2 g/day. |
| Geriatric use | No specific dose adjustment; use with caution due to increased risk of QT prolongation and hearing loss; monitor renal function and hearing. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Inhibits CYP3A4 increasing levels of many drugs (eg statins carbamazepine) May cause QT prolongation and subsequent arrhythmias.
| FDA category | Human |
| Breastfeeding | Erythromycin is excreted into human breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.5. At typical maternal doses, the amount ingested by the infant is unlikely to cause adverse effects. However, theoretical risks include alteration of infant gut flora and potential for allergy. Caution is advised, especially in infants with hepatic or renal impairment. The American Academy of Pediatrics considers it compatible with breastfeeding. |
■ FDA Black Box Warning
WARNING: INCREASED RISK OF INFANTILE HYPERTROPHIC PYLORIC STENOSIS (IHPS) IN NEONATES. Erythromycin has been associated with IHPS when used in neonates. Its use in infants less than 6 weeks of age should be limited to proven infections, and parents should be informed of the potential risk.
| Common Effects | Nausea |
| Serious Effects |
["Hypersensitivity to erythromycin or any macrolide antibiotic.","Concomitant use with ergotamine or dihydroergotamine (risk of ergotism).","Concurrent use with cisapride, pimozide, or certain statins (e.g., lovastatin, simvastatin) due to risk of serious cardiac arrhythmias or rhabdomyolysis.","Hepatic disease or impaired hepatic function (relative contraindication).","Preexisting QT interval prolongation or electrolyte disturbances (relative contraindication)."]
| Precautions | ["Hepatotoxicity, particularly in patients with hepatic impairment or concurrent use of other hepatotoxic drugs.","QT interval prolongation and risk of torsades de pointes, especially with IV administration, electrolyte abnormalities, or concomitant use of other QT-prolonging agents.","Pyloric stenosis in neonates (see black box warning).","Severe allergic reactions including anaphylaxis and Stevens-Johnson syndrome.","Clostridioides difficile-associated diarrhea (CDAD).","Ototoxicity, primarily with high doses or renal impairment.","Myasthenia gravis exacerbation."] |
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| Teratogenic Risk |
| Erythromycin lactobionate is generally considered low risk during pregnancy. No teratogenic effects have been consistently demonstrated in human studies; however, as with all drugs, administration should be limited to clear indications. FDA pregnancy category B. There is no evidence of increased risk of major birth defects from exposure during any trimester. |
| Fetal Monitoring | Monitor for maternal gastrointestinal side effects (nausea, vomiting, diarrhea) and signs of allergic reaction. In neonates, monitor for infantile hypertrophic pyloric stenosis if used during breastfeeding, although risk is low. No specific fetal monitoring required beyond routine prenatal care. |
| Fertility Effects | No known effects on human fertility. Erythromycin does not have established reproductive toxicity in animal studies. Reports of reversible male infertility related to erythromycin are not confirmed. |
| Food/Dietary | Grapefruit juice inhibits CYP3A4 and may increase erythromycin levels; avoid concurrent consumption. No other significant food interactions reported. |
| Clinical Pearls | Erythromycin lactobionate is a macrolide antibiotic used intravenously for serious infections, including Legionnaires' disease and pertussis. It prolongs QT interval; monitor ECG and electrolytes. Avoid concurrent use with other QT-prolonging drugs. Rapid infusion can cause cardiac arrhythmias; infuse over 20-60 minutes. Hepatotoxicity may occur, especially with estolate salt, but lactobionate is less associated. Monitor liver function tests in prolonged therapy. Erythromycin is a CYP3A4 inhibitor; check for drug interactions, especially with statins, warfarin, and colchicine. |
| Patient Advice | This medication is given intravenously for serious bacterial infections. · Report any symptoms of irregular heartbeat, fainting, or dizziness immediately. · Avoid grapefruit juice and grapefruit products during treatment. · Take all doses as prescribed; do not stop early even if you feel better. · Inform your doctor of all medications you are taking, including over-the-counter drugs and herbal supplements. · Possible side effects include nausea, vomiting, diarrhea, and abdominal pain. · Contact your healthcare provider if you experience severe diarrhea, jaundice, or hearing loss. |