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) |
| Molecular Weight | 496.9 |
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 | Avoid; associated with fetal skeletal development retardation and enamel hypoplasia; risk of hepatotoxicity in pregnant women. |
| 2nd trimester | Avoid; causes permanent tooth discoloration and enamel hypoplasia in fetus; contraindicated after 4th month. |
| 3rd trimester | Avoid; same risks as t2; also potential inhibition of fetal bone growth. |
Clinical note
Antacids and calcium supplements decrease absorption Can cause photosensitivity and tooth discoloration in children.
| Placental transfer | Crosses placenta; achieves fetal serum concentrations 60-70% of maternal levels. |
| Breastfeeding | Excreted in breast milk; may cause tooth discoloration and bone growth inhibition in nursing infants; use only if no alternative. |
| Lactation Rating |
■ 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 tetracyclinesPregnancy (especially second and third trimesters)LactationChildren under 8 years (risk of permanent tooth discoloration)Severe hepatic impairment
| 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…
| L4 - Possibly Hazardous |
| 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. |
| 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. |
| Food/Dietary | Milk, dairy products, calcium-fortified foods, antacids, iron preparations, and magnesium-containing laxatives reduce oxytetracycline absorption. Take on an empty stomach; avoid food for at least 1 hour before and 2 hours after dosing. Do not take with any calcium, iron, magnesium, or aluminum-containing products. |
| Clinical Pearls | Avoid in children under 8 years due to permanent tooth discoloration and bone growth impairment. Contraindicated in pregnancy and lactation. Administer on an empty stomach (1 hour before or 2 hours after meals) to maximize absorption. Monitor for photosensitivity reactions; advise sun avoidance. Use with caution in renal impairment; dose adjustment may be necessary. Can cause hepatotoxicity in high doses or in patients with pre-existing liver disease. Check for tetracycline allergy before prescribing. |
| Patient Advice | Take this medication on an empty stomach, at least 1 hour before or 2 hours after meals, with a full glass of water. · Avoid taking with dairy products, antacids, iron supplements, or calcium supplements as they reduce absorption. · Do not take if you are pregnant, planning to become pregnant, or breastfeeding. · Use effective sun protection as this drug increases sensitivity to sunlight and risk of severe sunburn. · Complete the full course of therapy even if you feel better to prevent bacterial resistance. · Report any signs of liver toxicity (yellowing of skin/eyes, dark urine, abdominal pain) or severe diarrhea to your healthcare provider. · Store at room temperature away from moisture and heat. Do not use after expiration date. |