VIBRAMYCIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VIBRAMYCIN (VIBRAMYCIN).
Inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit, preventing addition of amino acids to the growing peptide chain. Bacteriostatic.
| Metabolism | Hepatic metabolism is minimal; primarily excreted unchanged in urine and feces. Not significantly metabolized by CYP450 enzymes. |
| Excretion | Approximately 40% excreted unchanged in urine via glomerular filtration; 20-25% eliminated in feces via biliary secretion; remainder metabolized. Renal clearance is about 30 mL/min. |
| Half-life | Terminal elimination half-life is 16-18 hours in patients with normal renal function. Prolonged to 20-36 hours in severe renal impairment; no significant change in hepatic impairment. |
| Protein binding | 80-90% bound primarily to albumin. |
| Volume of Distribution | 0.75-1.0 L/kg; indicates extensive tissue penetration, especially into skin, lung, and bile. |
| Bioavailability | Oral: 90-100% (almost completely absorbed); Intravenous: 100%. |
| Onset of Action | Oral: 1-2 hours; Intravenous: immediately after infusion (peak effect at 1-2 hours). |
| Duration of Action | 24 hours for once-daily dosing; sustained tissue levels persist for 48-72 hours after last dose due to long half-life. |
| Molecular Weight | 444.43 Da |
100 mg orally or intravenously every 12 hours on day 1, then 100 mg once daily; severe infections: 100 mg every 12 hours.
| Dosage form | CAPSULE |
| Renal impairment | No dose adjustment required in mild to moderate renal impairment; in severe renal impairment (CrCl <10 mL/min), consider extending interval to every 24 hours and monitor serum levels. |
| Liver impairment | No specific guidelines; use with caution in severe hepatic impairment; consider dose reduction or extended interval based on clinical response and liver function tests. |
| Pediatric use | Children ≥8 years: 4.4 mg/kg (up to 200 mg) orally or IV divided every 12 hours on day 1, then 2.2 mg/kg (up to 100 mg) once daily; for severe infections: 4.4 mg/kg daily in divided doses. Not recommended for children <8 years due to tooth discoloration. |
| Geriatric use | No specific dose adjustment required; monitor renal function as elderly may have age-related decline; consider lower starting doses for frail patients. |
| 1st trimester | Avoid. Use only if no alternative, as tetracyclines may cause fetal harm (e.g., delayed skeletal development). |
| 2nd trimester | Avoid. Risk of permanent tooth discoloration and enamel hypoplasia; also may inhibit bone growth. |
| 3rd trimester | Avoid. Same risks as t2; use only if no safer alternative. |
Clinical note
Comprehensive clinical and safety monograph for VIBRAMYCIN (VIBRAMYCIN).
| Placental transfer | Doxycycline crosses the placenta; fetal serum levels are approximately 60-100% of maternal levels. |
| Breastfeeding | Doxycycline is excreted into breast milk in low concentrations. Theoretical risk of tooth discoloration and bone growth inhibition in nursing infants; however, absorption is limited by milk calcium binding. Use caution, especially in prolonged courses. American Academy of Pediatrics considers doxycycline compatible with breastfeeding for short-term use. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to doxycycline or any tetracyclinePregnancy (especially second and third trimesters)Children under 8 years of age (risk of permanent tooth discoloration)
| Precautions | Photosensitivity: exaggerated sunburn reaction, Tooth discoloration in children <8 years, Bone growth inhibition in premature infants, Esophageal injury: take with adequate fluids, Central nervous system effects: dizziness, headache, Pseudotumor cerebri: benign intracranial hypertension, Superinfection: Clostridioides difficile colitis, Hepatotoxicity, especially in pregnancy or with pre-existing hepatic impairment, Renal impairment: dose adjustment may be necessary |
| Food/Dietary | Avoid dairy products (milk, cheese, yogurt), calcium-fortified juices, and antacids containing calcium, magnesium, or aluminum within 2 hours of dosing. Iron supplements, zinc, and bismuth subsalicylate also reduce absorption. |
Loading safety data…
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | First trimester: Avoid due to risk of skeletal and dental abnormalities (tetracycline class effect). Second and third trimesters: Contraindicated; may cause permanent tooth discoloration (yellow-gray-brown) and enamel hypoplasia in the fetus, as well as reversible inhibition of bone growth. Associated with the use of tetracyclines during pregnancy; Vibramycin (doxycycline) is classified as FDA pregnancy category D (positive evidence of human fetal risk). |
| Fetal Monitoring | Monitor maternal hepatic function, renal function, and complete blood cell count due to potential hematologic toxicity. Monitor for signs of photosensitivity. In pregnancy, if exposure occurs, fetal ultrasound may be considered to assess bone growth and dental development, though no specific monitoring is required. Assess for maternal superinfection (e.g., pseudomembranous colitis). |
| Fertility Effects | Doxycycline has no established direct effect on human fertility. In animal studies, tetracyclines have been associated with reversible impairment of spermatogenesis at high doses, but clinical significance is unclear. No evidence of female fertility impairment. Use during pregnancy may affect fetal development but not fertility per se. |
| Clinical Pearls | Avoid in children <8 years due to permanent tooth discoloration and bone growth inhibition. Dose adjustment required in renal impairment. Can cause photosensitivity; instruct patients to avoid excessive sun exposure. Use with caution in patients with myasthenia gravis or lupus erythematosus. Administer with a full glass of water to reduce esophageal irritation. |
| Patient Advice | Take with a full glass of water to prevent throat irritation. · Avoid taking with dairy products, antacids, or iron supplements within 2 hours. · Do not take before bedtime to reduce risk of esophageal ulceration. · Finish the entire course even if you feel better. · Stop use and seek medical attention if you develop a severe headache, vision changes, or signs of intracranial hypertension. · Avoid prolonged sun exposure and use sunscreen. · Report any signs of allergic reaction, including rash, hives, or difficulty breathing. |