OXYTETRACYCLINE HYDROCHLORIDE
Clinical safety rating: avoid
Positive evidence of fetus risks but benefits may outweigh risks in some cases
Oxytetracycline binds reversibly to the 30S ribosomal subunit, inhibiting protein synthesis by blocking the attachment of aminoacyl-tRNA to the mRNA-ribosome complex.
| Metabolism | Hepatic metabolism via glucuronidation; minimal CYP450 involvement; primarily excreted unchanged in urine and feces. |
| Excretion | Renal (60-70% unchanged by glomerular filtration); biliary/fecal (20-35%) |
| Half-life | 6-10 hours (prolonged to 48-100 hours in renal impairment; consider dose adjustment in CrCl <50 mL/min) |
| Protein binding | 25-40% (primarily albumin) |
| Volume of Distribution | 1.3-1.7 L/kg (large Vd due to tissue binding; concentrates in bone, teeth, liver, and tumors; minimal CNS penetration) |
| Bioavailability | Oral: 60-80% (decreased by food, dairy, divalent cations); IM: ~100% (but painful and not recommended); IV: 100% |
| Onset of Action | Oral: 1-2 hours; IV: immediate (within minutes); IM: 1-2 hours (time to therapeutic serum concentrations) |
| Duration of Action | 12-24 hours (dependent on dose; sustained release formulations may extend to 24-48 hours; accumulation in bone and teeth may persist) |
250-500 mg orally every 6 hours or 1-2 g/day divided every 12 hours intravenously.
| Dosage form | CAPSULE |
| Renal impairment | GFR 50-90 mL/min: no adjustment; GFR 10-50 mL/min: administer every 12-24 hours; GFR <10 mL/min: administer every 24 hours or avoid use due to anti-anabolic effects. |
| Liver impairment | Child-Pugh Class A: no adjustment; Class B: reduce dose by 50%; Class C: contraindicated or avoid use. |
| Pediatric use | Children >8 years: 25-50 mg/kg/day orally divided every 6 hours; intravenous: 15-25 mg/kg/day divided every 12 hours. Not recommended in children <8 years due to tooth discoloration. |
| Geriatric use | Use with caution, consider reduced renal function; adjust dose based on creatinine clearance; may increase risk of azotemia and nephrotoxicity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Antacids and calcium supplements decrease absorption Can cause photosensitivity and tooth discoloration in children.
| Breastfeeding | Excreted into breast milk in low concentrations; M/P ratio approximately 0.6. Theoretical risk of dental staining and bone growth inhibition in nursing infants, but considered compatible with breastfeeding by American Academy of Pediatrics. Monitor infant for gastrointestinal disturbances and rash. |
| Teratogenic Risk | First trimester: limited data suggest low risk; animal studies show no clear teratogenicity. Second and third trimesters: associated with reversible skeletal growth retardation, permanent tooth discoloration, and enamel hypoplasia due to calcium chelation and deposition in developing bones and teeth. Avoid after 25 weeks gestation unless no alternative. |
■ FDA Black Box Warning
NOT APPROVED FOR USE IN PEDIATRIC PATIENTS <8 YEARS OF AGE DUE TO RISK OF PERMANENT TOOTH DISCOLORATION AND ENAMEL HYPOPLASIA.
| Common Effects | acne |
| Serious Effects |
["Hypersensitivity to oxytetracycline or any tetracycline","Pediatric patients <8 years of age (absolute for routine use)","Pregnancy (relative, especially second and third trimesters)","Lactation (avoid due to excretion in breast milk and potential for tooth discoloration in infant)","Severe hepatic impairment (relative, caution required)"]
| Precautions | ["Use during tooth development may cause permanent tooth discoloration and enamel hypoplasia; avoid in children <8 years unless no alternative.","Photosensitivity reactions: avoid prolonged sun exposure; discontinue if erythema occurs.","Superinfection: prolonged use may result in overgrowth of nonsusceptible organisms, including fungi; discontinue and treat appropriately.","Hepatotoxicity: associated with high doses or pre-existing liver disease; monitor liver function.","Renal impairment: dose adjustment recommended due to accumulation and potential nephrotoxicity.","Pregnancy: use only if clearly needed; potential for fetal harm (category D)"] |
Loading safety data…
| Fetal Monitoring | Monitor maternal renal function and liver function tests periodically. Fetal monitoring: growth ultrasound in third trimester given risk of skeletal effects if prolonged exposure. Assess infant for tooth discoloration after birth if exposed in late pregnancy. |
| Fertility Effects | No significant adverse effects on fertility in animal studies; limited human data. Impaired spermatogenesis reported at high doses in some animal models, but clinical significance unclear. No evidence of negative impact on female fertility. |