RONDOMYCIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for RONDOMYCIN (RONDOMYCIN).
Binds to the 30S ribosomal subunit, inhibiting protein synthesis by blocking the attachment of aminoacyl-tRNA to the mRNA-ribosome complex.
| Metabolism | Primarily hepatic via CYP450 isoenzymes; undergoes enterohepatic recirculation. |
| Excretion | Renal (40-50% unchanged), biliary/fecal (10-20% as metabolites and unchanged drug). Approximately 30% undergoes enterohepatic circulation. |
| Half-life | Terminal elimination half-life is 6-8 hours in patients with normal renal function; may extend to 20-30 hours in severe renal impairment. |
| Protein binding | 65-75% bound to serum proteins (albumin). |
| Volume of Distribution | 0.9-1.1 L/kg; indicates distribution into total body water and tissues. |
| Bioavailability | Oral: approximately 60-70% (first-pass metabolism reduces bioavailability). |
| Onset of Action | Oral: 1-2 hours (therapeutic plasma levels). |
| Duration of Action | 12-24 hours (typical dosing interval is 12 hours). |
150 mg orally twice daily or 300 mg orally once daily.
| Dosage form | SYRUP |
| Renal impairment | CrCl >50 mL/min: no adjustment; CrCl 10-50 mL/min: 150 mg every 24 hours; CrCl <10 mL/min: 150 mg every 48 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: contraindicated. |
| Pediatric use | 8-12 years: 4 mg/kg initially, then 2 mg/kg orally twice daily; >12 years: adult dosing. |
| Geriatric use | No specific adjustment; monitor renal function and reduce dose if CrCl <50 mL/min. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for RONDOMYCIN (RONDOMYCIN).
| Breastfeeding | RONDOMYCIN is excreted in breast milk. The milk-to-plasma ratio (M/P) is not specifically reported for methacycline but for tetracyclines is approximately 0.6-0.8. The amount ingested by a nursing infant is low but may lead to tooth discoloration and bone growth inhibition in the infant. Alternative agents are preferred during breastfeeding. |
| Teratogenic Risk | RONDOMYCIN (methacycline) is a tetracycline antibiotic. Tetracyclines cross the placenta and can cause fetal harm. First trimester: No well-controlled studies, but animal data suggest risk; avoid unless no alternative. Second and third trimesters: Use is contraindicated due to risk of permanent tooth discoloration (yellow-gray-brown) and enamel hypoplasia in the fetus. Also associated with reduced fibula growth and skeletal development. Risk is greatest after 20 weeks gestation. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to tetracyclines; pregnancy; breastfeeding; children under 8 years of age; severe hepatic impairment; concomitant use with isotretinoin (risk of pseudotumor cerebri).
| Precautions | Photosensitivity reactions; hepatotoxicity; renal impairment; use in pregnancy (Category D) may cause fetal harm; tooth discoloration and enamel hypoplasia in children <8 years; esophageal ulceration; superinfection with resistant organisms; exacerbation of systemic lupus erythematosus; intracranial hypertension; caution in patients with myasthenia gravis. |
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| Fetal Monitoring | Monitor maternal renal and hepatic function, complete blood count, and signs of hepatotoxicity or superinfection. For the fetus, no specific monitoring is required if used early in pregnancy; however, avoid use during second and third trimesters. If inadvertent exposure occurs, document gestational age. |
| Fertility Effects | Tetracyclines have been associated with reversible impairment of spermatogenesis in animal studies. In females, no specific effects on fertility are reported. However, use during pregnancy is not recommended; for men, temporary reduction in sperm count is possible but reversible upon discontinuation. |