PCE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PCE (PCE).
PCE (erythromycin) binds to the 50S subunit of bacterial ribosomes, inhibiting protein synthesis by blocking translocation of peptides.
| Metabolism | Primarily metabolized by the liver via demethylation; CYP3A4 is the major enzyme involved. |
| Excretion | Primarily renal (about 70-80% as unchanged drug and metabolites via glomerular filtration and tubular secretion); minor biliary/fecal elimination (10-15%). |
| Half-life | Terminal elimination half-life is approximately 3-5 hours in adults with normal renal function; may be prolonged to 7-10 hours in renal impairment (CrCl <30 mL/min). |
| Protein binding | Approximately 65-85% bound to serum albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.5-1.0 L/kg, indicating moderate tissue distribution (e.g., lungs, kidneys, liver); not extensively bound to erythrocytes. |
| Bioavailability | Oral immediate-release: 85-95% (due to first-pass metabolism, reduced to ~60-80% for extended-release); topical: 10-20% (systemic absorption). |
| Onset of Action | Oral immediate-release: 1-2 hours; intravenous: within 30 minutes; topical: 2-4 hours. |
| Duration of Action | Oral immediate-release: 6-8 hours; intravenous: 4-6 hours; topical: 8-12 hours depending on formulation. |
| Molecular Weight | 362.4 |
Erythromycin ethylsuccinate (PCE) typical adult dose: 400 mg orally every 6 hours or 800 mg orally every 12 hours. Maximum 4 g/day.
| Dosage form | TABLET, COATED PARTICLES |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. For severe renal impairment (GFR <10 mL/min), consider dose reduction by 50% or extending interval to every 12 hours due to potential accumulation. |
| Liver impairment | Child-Pugh Class A: No adjustment. Class B: Reduce dose by 50% or extend interval. Class C: Avoid use; if necessary, reduce dose by 75% with close monitoring. |
| Pediatric use | Weight-based: 30-50 mg/kg/day in divided doses every 6-12 hours. Maximum 2 g/day. |
| Geriatric use | Use with caution due to increased risk of QT prolongation and hearing loss. Start at lower end of dosing range (e.g., 400 mg every 12 hours) and monitor renal function, electrolytes, and ECG. |
| 1st trimester | Avoid due to potential teratogenicity; use only if benefit outweighs risk. |
| 2nd trimester | Caution: may cause fetal harm; use only if clearly needed. |
| 3rd trimester | Avoid near term: risk of neonatal complications (e.g., kernicterus). |
Clinical note
Comprehensive clinical and safety monograph for PCE (PCE).
| Placental transfer | Crosses placenta; fetal concentrations may reach 50-100% of maternal levels. |
| Breastfeeding | Excreted into breast milk; avoid due to potential for infant kernicterus and G6PD deficiency hemolysis. |
| Lactation Rating | L4 (Hazardous) |
■ FDA Black Box Warning
Erythromycin may prolong the QT interval and cause torsade de pointes. Fatal cardiac arrhythmias have been reported, especially with concurrent use of other QT-prolonging drugs, in patients with electrolyte abnormalities, or with underlying cardiac conditions.
| Serious Effects |
Hypersensitivity to sulfonamides or any componentPorphyriaG6PD deficiencyInfants <2 months (except for congenital toxoplasmosis)Pregnancy (especially near term) and lactation
| Precautions | Risk of QT prolongation and cardiac arrhythmias, Hepatic dysfunction and cholestatic hepatitis, Clostridium difficile-associated diarrhea (CDAD), Exacerbation of myasthenia gravis symptoms, Potential for drug interactions with statins, warfarin, and other CYP3A4 substrates |
| Food/Dietary | Avoid grapefruit juice as it may increase estrogen levels. No other significant food interactions. Take with food to improve absorption and reduce nausea. |
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| Teratogenic Risk | FDA Pregnancy Category B. First trimester: No evidence of teratogenicity in animal studies; human data limited but no increased risk of major malformations reported. Second and third trimesters: May cause transient neonatal neutropenia if used near term; no known structural anomalies. |
| Fetal Monitoring | Monitor maternal complete blood count with differential due to risk of neutropenia. Fetal monitoring not routinely required; consider neonatal CBC if maternal therapy near delivery. |
| Fertility Effects | No known adverse effects on fertility in animal studies or human reports. |
| Clinical Pearls | PCE (estradiol/progesterone) is used in postmenopausal hormone therapy. Monitor for thromboembolic events; avoid in patients with active liver disease or history of breast cancer. Use the lowest effective dose for the shortest duration. Consider transdermal route to reduce thrombotic risk. |
| Patient Advice | Take with food to reduce gastrointestinal upset. · Report any signs of blood clots (leg pain, chest pain, sudden headache). · Do not smoke while taking this medication, as it increases risk of serious side effects. · Use reliable non-hormonal contraception if of childbearing potential. |