ERYTHROCIN STEARATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ERYTHROCIN STEARATE (ERYTHROCIN STEARATE).
Erythromycin binds to the 50S subunit of the bacterial ribosome, inhibiting protein synthesis by blocking the translocation step. It may also act as a motilin receptor agonist, stimulating gastrointestinal motility.
| Metabolism | Primarily metabolized by CYP3A4 in the liver; also a potent inhibitor of CYP3A4. Small amount excreted unchanged in bile and urine. |
| Excretion | Primarily biliary-fecal (90-95% as unchanged drug and metabolites); renal excretion accounts for 2-15%. |
| Half-life | 1.5-2 hours in adults; prolonged to 5-6 hours in severe hepatic impairment. In anuria, half-life not significantly affected. |
| Protein binding | 65-90% bound, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.6-0.9 L/kg, indicating distribution into total body water; higher in tissues due to intracellular uptake. |
| Bioavailability | Oral: 30-65% (stearate salt); bioavailability reduced by food. Not administered parenterally as stearate. |
| Onset of Action | Oral (stearate salt): 1-2 hours (peak serum concentration at 2-4 hours). |
| Duration of Action | Approximately 6 hours for susceptible organisms; bacteriostatic effect persists while serum levels above MIC. |
250-500 mg orally every 6 hours for mild to moderate infections; up to 4 g/day for severe infections.
| Dosage form | TABLET |
| Renal impairment | No adjustment needed for mild to moderate renal impairment. For severe renal impairment (GFR <10 mL/min), consider dose reduction to 250-500 mg every 8-12 hours. |
| Liver impairment | Caution in severe hepatic impairment (Child-Pugh Class C); dose reduction may be necessary, but no specific guidelines. Monitor liver function. |
| Pediatric use | 30-50 mg/kg/day orally in 3-4 divided doses; maximum 2 g/day. |
| Geriatric use | No specific dose adjustment; use lower end of dosing range due to age-related decline in renal function. Monitor for ototoxicity and QT prolongation. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ERYTHROCIN STEARATE (ERYTHROCIN STEARATE).
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts; M/P ratio approximately 0.5. Considered compatible with breastfeeding by AAP. Monitor infant for gastrointestinal disturbances or rash. |
| Teratogenic Risk | FDA pregnancy category B. No evidence of teratogenicity in animal studies. Limited human data; no increased risk of major malformations reported. Avoid in first trimester unless clearly needed. Use during second and third trimester only if benefit outweighs risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
There is no FDA black box warning for erythromycin.
| Serious Effects |
["Hypersensitivity to erythromycin or any macrolide antibiotic","Concomitant use with cisapride, pimozide, ergot alkaloids, or HMG-CoA reductase inhibitors (statins) metabolized by CYP3A4 (e.g., lovastatin, simvastatin) due to increased risk of rhabdomyolysis","Pre-existing QT prolongation or history of torsades de pointes","Use with caution in patients with electrolyte disturbances (hypokalemia, hypomagnesemia) and those taking other QT-prolonging drugs"]
| Precautions | ["QT prolongation and risk of torsades de pointes, especially with concurrent use of other QT-prolonging drugs or in patients with electrolyte abnormalities, bradycardia, or underlying cardiac disease","Hepatotoxicity including cholestatic hepatitis","Infantile hypertrophic pyloric stenosis (IHPS) in neonates exposed to erythromycin","Clostridioides difficile-associated diarrhea (CDAD)","Myasthenia gravis exacerbation","Hypersensitivity reactions","Use caution in hepatic impairment"] |
| Food/Dietary |
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| No specific monitoring required for erythromycin. In pregnancy, monitor for gastrointestinal intolerance, QT prolongation (ECG if risk factors), and signs of hepatotoxicity (rare). |
| Fertility Effects | No known adverse effects on fertility. Erythromycin does not impair reproductive function in animal studies. |
| Take on empty stomach 1 hour before or 2 hours after meals. Avoid alcohol; may cause disulfiram-like reaction. Grapefruit juice increases bioavailability and risk of QT prolongation. |
| Clinical Pearls | Erythromycin stearate is a macrolide antibiotic with prokinetic properties; may cause QT prolongation especially with other QT-prolonging drugs or electrolyte abnormalities. Administer on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption. Avoid concurrent use with statins (except pravastatin and rosuvastatin) due to increased risk of rhabdomyolysis. |
| Patient Advice | Take this medication on an empty stomach with a full glass of water. · Do not take with grapefruit juice as it may increase side effects. · Report any signs of liver problems (dark urine, jaundice) or irregular heartbeat. · Complete the full course even if you feel better. |