TETREX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TETREX (TETREX).
Tetracycline inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit, preventing aminoacyl-tRNA from binding to the A site.
| Metabolism | Primarily excreted unchanged in urine; minimal hepatic metabolism. |
| Excretion | Renal: 60% unchanged; biliary/fecal: 40% (mainly as glucuronide conjugates). |
| Half-life | Terminal elimination half-life: 6-11 hours (mean 8 hours); prolonged in renal impairment (up to 20 hours). |
| Protein binding | 90-95% bound to serum proteins (mainly albumin). |
| Volume of Distribution | Vd: 1.3-1.6 L/kg; indicates extensive tissue penetration. |
| Bioavailability | Oral: 75-85% (food reduces by 20%). |
| Onset of Action | Oral: 30-60 minutes; intravenous: immediate (minutes). |
| Duration of Action | 12-24 hours (bacteriostatic levels maintained with twice-daily dosing). |
250-500 mg orally every 6 hours or 500 mg to 1 g intravenously every 6-12 hours, not to exceed 4 g/day.
| Dosage form | CAPSULE |
| Renal impairment | GFR 10-50: 250-500 mg every 12-24 hours; GFR <10: 250-500 mg every 24 hours. |
| Liver impairment | Child-Pugh A: No adjustment; Child-Pugh B: Reduce dose by 50%; Child-Pugh C: Avoid use. |
| Pediatric use | 25-50 mg/kg/day orally in divided doses every 6 hours; for severe infections, up to 100 mg/kg/day divided every 6 hours. Intravenously: 20-40 mg/kg/day divided every 6-12 hours. |
| Geriatric use | Reduce dose by 50% or extend interval to every 12 hours due to decreased renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TETREX (TETREX).
| Breastfeeding | TETREX is excreted into breast milk with an M/P ratio of approximately 0.6–1.5. Because of the risk of permanent tooth discoloration and bone growth inhibition in the nursing infant, it is contraindicated during breastfeeding. Alternative agents should be used. |
| Teratogenic Risk | TETREX (tetracycline) is contraindicated in pregnancy. First trimester: Associated with fetal skeletal development abnormalities and potential for neural tube defects. Second and third trimesters: Causes permanent tooth discoloration (yellow-gray-brown) and enamel hypoplasia; also inhibits fetal bone growth. Use only for life-threatening conditions (e.g., anthrax) with no alternative. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to tetracyclines","Pregnancy (second and third trimesters)","Children <8 years","Severe hepatic dysfunction"]
| Precautions | ["Photosensitivity","Tooth discoloration in children <8 years","Superinfection with prolonged use","Hepatotoxicity in high doses","Renal impairment requires dose adjustment"] |
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| Fetal Monitoring | If inadvertently used in pregnancy, monitor fetal growth via ultrasound and assess neonatal teeth and bone development at birth. Maternal monitoring: hepatic function, renal function, and signs of pseudotumor cerebri. |
| Fertility Effects | TETREX may impair fertility in both sexes. In males, it can reduce sperm count and motility. In females, it may interfere with ovulation and cause reversible infertility. Effects are dose-dependent and typically resolve after discontinuation. |