PEDIAMYCIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PEDIAMYCIN (PEDIAMYCIN).
Erythromycin is a macrolide antibiotic that binds to the 50S subunit of the bacterial ribosome, inhibiting protein synthesis by blocking translocation of peptidyl-tRNA. It may be bacteriostatic or bactericidal depending on concentration and organism.
| Metabolism | Primarily hepatic via demethylation; CYP3A4 is the major enzyme involved. Also metabolized by CYP2C9, CYP2C19. Elimination half-life ~1.5-2 hours (increased in hepatic impairment). |
| Excretion | PEDIAMYCIN (erythromycin ethylsuccinate) is primarily excreted via the biliary route (60-70% as unchanged drug and metabolites) with significant fecal elimination. Renal excretion accounts for only 5-15% of the dose, mostly as inactive metabolites. Less than 5% is excreted unchanged in urine. |
| Half-life | The terminal elimination half-life is approximately 1.5-2 hours in adults with normal renal function. In patients with severe hepatic impairment, half-life may be prolonged to 5-6 hours. The short half-life necessitates frequent dosing (every 6-8 hours) to maintain therapeutic levels. |
| Protein binding | Erythromycin is 70-90% bound to plasma proteins, primarily to alpha-1-acid glycoprotein (AAG) and albumin. Binding is saturable and concentration-dependent. |
| Volume of Distribution | The apparent volume of distribution is 0.6-0.9 L/kg, indicating distribution into total body water and some tissue binding. Higher Vd in neonates (0.8-1.2 L/kg) due to increased extracellular fluid. |
| Bioavailability | Oral bioavailability of erythromycin ethylsuccinate is 30-65% (mean 45%), reduced by food. Intramuscular bioavailability is approximately 70-80% due to erratic absorption. Intravenous administration yields 100% bioavailability. |
| Onset of Action | Oral: Onset of action occurs within 1-2 hours after a dose, with peak serum concentrations reached 0.5-2.5 hours. Intravenous: Onset is rapid, within minutes, with peak concentrations at the end of infusion. |
| Duration of Action | Duration of action is approximately 6-8 hours after oral administration, supporting a dosing interval of every 6-8 hours. For intravenous therapy, duration is similar due to rapid clearance. |
| Molecular Weight | 733.93 |
250-500 mg orally every 6 hours; maximum 2 g/day.
| Dosage form | GRANULE |
| Renal impairment | GFR >50 mL/min: no adjustment; GFR 10-50 mL/min: 250 mg every 6-8 hours; GFR <10 mL/min: 250 mg every 12-24 hours. |
| Liver impairment | Child-Pugh A: cautious use; Child-Pugh B or C: contraindicated. |
| Pediatric use | Children: 30-50 mg/kg/day orally divided every 6 hours. |
| Geriatric use | Use lowest effective dose; monitor renal function; adjust based on creatinine clearance. |
| 1st trimester | Erythromycin (PEDIAMYCIN) is generally considered safe in the first trimester; no increased risk of major malformations has been observed in human studies, though data are limited. Use only if clearly needed. |
| 2nd trimester | Safe to use in the second trimester when indicated; no known fetal risks. |
| 3rd trimester | Safe to use in the third trimester; however, there is a rare risk of infantile hypertrophic pyloric stenosis (IHPS) if used after 32 weeks or near term. Avoid if alternative antibiotics available. |
Clinical note
Comprehensive clinical and safety monograph for PEDIAMYCIN (PEDIAMYCIN).
| Placental transfer | Erythromycin crosses the placenta, achieving fetal serum concentrations approximately 5-20% of maternal levels. Transfer is moderate and saturable, with higher transfer at therapeutic doses. |
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts. It is generally considered compatible with breastfeeding, but caution is advised due to potential gastrointestinal effects in the infant (e.g., diarrhea, rash). Monitor infant for signs of pyloric stenosis, especially in newborns under 2 weeks of age. |
■ FDA Black Box Warning
Erythromycin has been associated with QT prolongation and rare cases of torsades de pointes. Caution in patients with electrolyte abnormalities, bradycardia, or concomitant use of other QT-prolonging drugs. Also, erythromycin estolate is associated with hepatotoxicity; use with caution in hepatic impairment.
| Serious Effects |
Hypersensitivity to erythromycin or any macrolide antibioticConcomitant use with cisapride, pimozide, or ergotamine/dihydroergotamine (risk of QT prolongation and cardiac arrhythmias)
| Precautions | QT prolongation and cardiac arrhythmias (especially with intravenous use or in patients with risk factors), Hepatic dysfunction (especially with erythromycin estolate), Exacerbation of myasthenia gravis, Clostridium difficile-associated diarrhea, Ototoxicity (especially with high doses or renal impairment), Drug interactions (CYP3A4 inhibitors/inducers, statins, warfarin, digoxin) |
| Food/Dietary | Take on an empty stomach at least 1 hour before or 2 hours after meals. Avoid grapefruit juice as it may increase drug levels. No other specific food restrictions. |
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| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | PEDIAMYCIN (erythromycin) is generally considered low risk in pregnancy. No increased risk of major malformations has been consistently demonstrated in first trimester exposure. However, there is a possible association with pyloric stenosis in infants exposed in utero, though this risk remains small. Fetal monitoring is recommended in advanced pregnancy due to rare reports of fetal distress. |
| Fetal Monitoring | Monitor liver function tests if treatment is prolonged. Fetal heart rate monitoring may be considered in late pregnancy due to rare reports of fetal bradycardia. No specific fetal monitoring is routinely required. |
| Fertility Effects | No adverse effects on fertility have been reported in animal studies or human data. Erythromycin does not appear to impair reproductive function. |
| Clinical Pearls | Monitor for hepatotoxicity and elevated liver enzymes, especially in patients with pre-existing hepatic impairment. Concurrent use with warfarin increases INR; adjust warfarin dose accordingly. Can cause QT prolongation; avoid with other QT-prolonging agents. Administer on an empty stomach to maximize absorption. |
| Patient Advice | Take this medication exactly as prescribed, usually every 6 hours around the clock. · Complete the full course of therapy even if you feel better. · Avoid alcohol and products containing alcohol (e.g., elixirs, some mouthwashes) while taking this medication. · Notify your doctor immediately if you experience jaundice, dark urine, abdominal pain, or unusual bleeding/bruising. · This medication may cause interactions with many other drugs; inform your healthcare provider of all medications you take. |