DOXYCHEL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DOXYCHEL (DOXYCHEL).
Doxycycline inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit, preventing aminoacyl-tRNA from binding to the mRNA-ribosome complex.
| Metabolism | Primarily hepatic via non-enzymatic routes; undergoes enterohepatic circulation. Not significantly metabolized by CYP450 enzymes. |
| Excretion | Renal (20-30%), biliary/fecal (40-60%), with significant enterohepatic circulation; nonrenal elimination accounts for about 70%. |
| Half-life | 12-22 hours (mean ~16 hours); prolonged in severe hepatic impairment (up to 30 hours). |
| Protein binding | 80-90%, primarily to albumin. |
| Volume of Distribution | 0.7-1.5 L/kg (~100 L in 70 kg adult); indicates extensive tissue penetration. |
| Bioavailability | Oral: 60-80% (decreased by food, dairy, antacids). |
| Onset of Action | Oral: 1-2 hours; IV: within minutes. |
| Duration of Action | 12-24 hours; maintains bacteriostatic levels for 12 hours after a single dose. |
100 mg orally or intravenously every 12 hours on day 1, then 100 mg once daily. For severe infections, continue 100 mg every 12 hours.
| Dosage form | FOR SUSPENSION |
| Renal impairment | No dose adjustment required in mild to moderate renal impairment (CrCl >30 mL/min). For CrCl <10 mL/min, reduce dose to 100 mg every 24 hours. Not removed by hemodialysis. |
| Liver impairment | For Child-Pugh Class A and B: no adjustment required. For Child-Pugh Class C: use with caution, reduce dose by 50% or extend interval to every 24 hours. |
| Pediatric use | For children >8 years: 2.2 mg/kg (up to 100 mg) every 12 hours on day 1, then 2.2 mg/kg (up to 100 mg) once daily. Not recommended in children <8 years due to risk of permanent tooth discoloration. |
| Geriatric use | No specific dose adjustment required; monitor renal function and consider lower starting doses due to age-related renal impairment. Avoid in patients with severe renal insufficiency. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for DOXYCHEL (DOXYCHEL).
| Breastfeeding | Doxycycline is excreted into human milk in low concentrations. The M/P ratio is approximately 0.3-0.4. Use during breastfeeding is not recommended due to potential risks of dental staining and bone growth inhibition in the nursing infant. If use is necessary, temporary discontinuation of breastfeeding is advised. Alternatives such as penicillins or cephalosporins are preferred. |
| Teratogenic Risk | Doxycycline is classified as FDA Pregnancy Category D. It should be avoided during pregnancy due to teratogenic effects including permanent tooth discoloration (dental fluorosis) and inhibition of bone growth in the fetus. Risk is highest during the second and third trimesters (weeks 13-40) related to dental and skeletal development. Use during the first trimester may be associated with a small increased risk of neural tube defects and cardiovascular malformations, though data are limited. |
■ FDA Black Box Warning
None officially; however, doxycycline is associated with tooth discoloration and enamel hypoplasia when used in children under 8 years of age and during pregnancy/breastfeeding.
| Serious Effects |
Hypersensitivity to doxycycline or any tetracycline; use in children under 8 years; pregnancy (second and third trimesters); breastfeeding (if nursing infant is at risk).
| Precautions | Esophageal irritation/ulceration (take with adequate fluids), photosensitivity, superinfection (C. difficile), hepatotoxicity (rare), benign intracranial hypertension, use in children <8 years/pregnancy/lactation (tooth discoloration, bone growth inhibition), and tetracycline class effects. |
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| Fetal Monitoring | If doxycycline must be used during pregnancy (e.g., for severe infections with no alternatives), ultrasonography for fetal growth and development should be performed. Monitor for signs of hepatotoxicity, hypersensitivity reactions, and blood dyscrasias. In the neonate, monitor for evidence of dental staining and bone growth impairment. |
| Fertility Effects | Doxycycline may affect fertility by reducing sperm motility and increasing sperm DNA fragmentation in males, although effects are usually reversible upon discontinuation. In females, there is no clear evidence of impaired fertility, but caution is warranted due to potential effects on vaginal flora and superinfection. |