ERYMAX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ERYMAX (ERYMAX).
Erythromycin acts by binding to the 50S subunit of the bacterial ribosome, inhibiting protein synthesis. It also acts as a motilin receptor agonist, stimulating gastrointestinal motility.
| Metabolism | Primarily metabolized by the liver via CYP3A4 enzyme system. Erythromycin is a substrate and inhibitor of CYP3A4. |
| Excretion | Renal excretion of unchanged drug: 10–15%; biliary/fecal excretion: 85–90% as active metabolites. |
| Half-life | Terminal elimination half-life: 1.5–2 hours in adults; prolonged to 4–6 hours in hepatic impairment; requires dosing adjustment in cirrhosis. |
| Protein binding | 75–85% bound primarily to albumin. |
| Volume of Distribution | 1.2–1.6 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: 50–60% (first-pass metabolism); IM: 80–90%; IV: 100%. |
| Onset of Action | Oral: 30–45 minutes; Intravenous: 5–10 minutes; Intramuscular: 15–30 minutes. |
| Duration of Action | 4–6 hours for most clinical effects; extended to 8–12 hours with sustained-release formulations. |
| Molecular Weight | 733.93 |
250-500 mg orally every 6 hours or 500-1000 mg intravenously every 6 hours.
| Dosage form | SOLUTION |
| Renal impairment | CrCl 10-50 mL/min: 250-500 mg every 6-12 hours; CrCl <10 mL/min: 250-500 mg every 12-24 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | 30-50 mg/kg/day orally divided every 6-8 hours; 20-40 mg/kg/day intravenously divided every 6 hours. |
| Geriatric use | Start at low end of dosing range (250 mg orally every 6 hours) and adjust based on renal function; monitor for QT prolongation and electrolyte disturbances. |
| 1st trimester | Erymax (erythromycin) is generally considered safe in the first trimester. No increased risk of major birth defects has been observed. However, use only if clearly needed. |
| 2nd trimester | Safe in the second trimester. No known fetal risks. |
| 3rd trimester | Safe in the third trimester. Erythromycin is used for prevention of neonatal group B streptococcal infection. Caution: rare association with infantile hypertrophic pyloric stenosis if used after 36 weeks? (Inconsistent evidence). |
Clinical note
Comprehensive clinical and safety monograph for ERYMAX (ERYMAX).
| Placental transfer | Erythromycin crosses the placenta; fetal serum concentrations are approximately 5-20% of maternal levels. It is extensively bound to plasma proteins, limiting transfer. |
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts. Generally considered compatible with breastfeeding; however, monitor for potential gastrointestinal effects in the infant (e.g., diarrhea, candidiasis). The American Academy of Pediatrics classifies it as a drug usually compatible with breastfeeding. |
■ FDA Black Box Warning
Increased risk of infantile hypertrophic pyloric stenosis (IHPS) when used in neonates and young infants.
| Serious Effects |
Hypersensitivity to erythromycin or any macrolide antibioticConcomitant use with ergotamine or dihydroergotamineConcurrent use with cisapride, pimozide, astemizole, terfenadine (risk of QT prolongation and torsades de pointes)
| Precautions | QT interval prolongation and risk of torsades de pointes, especially in patients with pre-existing QT prolongation, electrolyte imbalances, bradycardia, or concomitant use of other QT-prolonging drugs., Hepatotoxicity, including cholestatic hepatitis, particularly with erythromycin estolate., Clostridioides difficile-associated diarrhea (CDAD)., Exacerbation of myasthenia gravis., Infantile hypertrophic pyloric stenosis (IHPS) in neonates., Drug interactions due to CYP3A4 inhibition (e.g., with statins, warfarin, benzodiazepines)., Ototoxicity, especially with high doses or renal impairment. |
| Food/Dietary | Avoid grapefruit juice and grapefruit products as they inhibit CYP3A4 and increase erythromycin levels. Take with food to minimize GI upset. Avoid alcohol as it may worsen GI irritation. |
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| Lactation Rating | L2 (Probably Compatible, or L1 if topical) |
| Teratogenic Risk | No evidence of teratogenicity in human studies; animal studies show no fetal harm at therapeutic doses. Risk Category B (FDA). First trimester: no increased malformation risk. Second/third trimester: no known adverse effects. |
| Fetal Monitoring | No specific monitoring required; observe for maternal gastrointestinal effects. |
| Fertility Effects | No known adverse effects on fertility in animal or human studies. |
| Clinical Pearls | ERYMAX (erythromycin base in a delayed-release matrix) is a macrolide antibiotic with activity against atypical pathogens. It is a CYP3A4 inhibitor and can increase levels of statins, warfarin, and other drugs. Prolonged QT interval risk exists; avoid use with other QT-prolonging agents. May cause gastrointestinal distress; administer with food to improve tolerance. Not effective against MRSA. |
| Patient Advice | Take with food to reduce stomach upset. · Complete the full course even if you feel better. · Avoid taking with grapefruit juice as it may increase side effects. · Report any signs of liver issues (yellowing skin/eyes, dark urine) or hearing loss (especially with high doses). · If you are on blood thinners (warfarin) or statins, discuss with your doctor as dose adjustments may be needed. |