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. |
| Molecular Weight | 444.44 Da (doxycycline hyclate), 512.94 Da (doxycycline calcium complex) |
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 | Contraindicated due to risk of fetal skeletal and dental abnormalities. Alternative antibiotics recommended. |
| 2nd trimester | Contraindicated due to risk of permanent tooth discoloration and impaired bone growth in the fetus. |
| 3rd trimester | Contraindicated due to risk of permanent tooth discoloration and impaired bone growth in the fetus. |
Clinical note
Comprehensive clinical and safety monograph for DOXYCHEL (DOXYCHEL).
| Placental transfer | Crosses placenta readily; achieves fetal serum levels approximately 60-75% of maternal levels. |
| Breastfeeding | Excreted in human milk in low concentrations; theoretical risk of dental staining and bone growth suppression in nursing infants. Use only if benefits outweigh risks; monitor infant for gastrointestinal disturbances and rash. |
■ 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 tetracyclinePregnancyLactation (unless short-term use and alternative not available)Children under 8 years of age (unless for specific indications like anthrax)
| 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. |
| Food/Dietary | Avoid concurrent intake of dairy products (milk, yogurt, cheese) and calcium-fortified foods, as calcium chelates doxycycline reducing absorption. Separate administration by at least 2 hours. Also avoid iron-rich foods or supplements and antacids containing aluminum, magnesium, or calcium. High-fat meals may slightly delay absorption but not significantly reduce bioavailability. No other specific food restrictions. |
Loading safety data…
| Lactation Rating |
| L3 (Moderately Safe) - Limited data suggests minimal risk, but caution advised. |
| 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. |
| 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. |
| Clinical Pearls | Doxycycline (DOXYCHEL) is a tetracycline antibiotic with high oral bioavailability. It is photosensitizing; advise patients to avoid excessive sun exposure and use sunscreen. It chelates divalent cations, so avoid concurrent administration with dairy products, antacids, iron, or calcium supplements. Administer with a full glass of water to reduce esophageal irritation. Doxycycline is effective against atypical pathogens (e.g., Mycoplasma, Chlamydia, Rickettsia). It is also used for malaria prophylaxis. In acne, it reduces inflammation and bacterial counts. Monitor for superinfection, especially Clostridioides difficile. Note: Doxycycline can cause permanent tooth discoloration in children <8 years and should be avoided during pregnancy. |
| Patient Advice | Take doxycycline exactly as prescribed, with a full glass of water, and remain upright for at least 30 minutes to prevent esophageal irritation. · Avoid dairy products, antacids, iron supplements, and calcium supplements within 2 hours of taking doxycycline. · Use sunscreen and protective clothing during treatment as doxycycline increases sensitivity to sunlight and risk of sunburn. · Complete the full course even if symptoms improve to prevent resistance. · If you miss a dose, take it as soon as possible, but skip it if near the next dose; do not double dose. · Notify your doctor if you experience severe diarrhea, rash, or signs of liver toxicity (yellowing eyes/skin, dark urine). · Do not use if pregnant, breastfeeding, or in children under 8 years unless specifically directed. |