DECLOMYCIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DECLOMYCIN (DECLOMYCIN).
Binds to the 30S ribosomal subunit, inhibiting aminoacyl-tRNA binding to the mRNA-ribosome complex, thereby blocking protein synthesis.
| Metabolism | Primarily hepatic metabolism (minimal); excreted unchanged in urine and feces via bile. |
| Excretion | Renal: ~50% unchanged; biliary/fecal: ~40% as inactive metabolites; enterohepatic recycling occurs |
| Half-life | Terminal elimination half-life 10-17 hours; prolonged to 18-48 hours in renal impairment |
| Protein binding | 40-80% bound primarily to albumin |
| Volume of Distribution | 1.5-2.0 L/kg; indicates extensive tissue distribution with accumulation in bone and teeth |
| Bioavailability | Oral: 90-100% (administered only orally) |
| Onset of Action | Oral: 1-2 hours for therapeutic serum concentrations |
| Duration of Action | 12-24 hours after single oral dose; sustained due to enterohepatic circulation |
| Molecular Weight | 464.85 |
150 mg orally every 6 hours or 300 mg orally every 12 hours.
| Dosage form | SYRUP |
| Renal impairment | For GFR 50-80 mL/min: administer every 8-12 hours. For GFR 10-50 mL/min: administer every 12-24 hours. For GFR <10 mL/min: administer every 24-48 hours. |
| Liver impairment | No specific adjustment recommended for Child-Pugh A or B; use with caution in severe hepatic impairment (Child-Pugh C) as metabolism may be reduced. |
| Pediatric use | 8-12 mg/kg/day divided every 6-12 hours, not to exceed 600 mg/day. |
| Geriatric use | Use lowest effective dose due to increased risk of renal impairment and photosensitivity; monitor renal function closely. |
| 1st trimester | Avoid. Tetracyclines, including demeclocycline, can cause fetal harm (e.g., retarded skeletal development) when administered to a pregnant woman. They cross the placenta and may cause permanent discoloration of teeth and enamel hypoplasia during the latter part of pregnancy. |
| 2nd trimester | Avoid. Same risks as first trimester. Use only if no alternative and benefit outweighs risk. |
| 3rd trimester | Avoid. Same risks as first and second trimesters. Additionally, may cause maternal hepatotoxicity. |
Clinical note
Comprehensive clinical and safety monograph for DECLOMYCIN (DECLOMYCIN).
| Placental transfer | Crosses the placenta readily, achieving fetal serum levels 50-75% of maternal levels. |
| Breastfeeding | Demeclocycline is excreted into breast milk in small amounts. Theoretical risk of dental staining and bone growth inhibition in nursing infants. Consider alternative agents that are safer. |
■ FDA Black Box Warning
WARNING: Use during tooth development (last half of pregnancy, infancy, and childhood to the age of 8 years) may cause permanent discoloration of teeth (yellow-gray-brown) and enamel hypoplasia. This reaction is more common during long-term use but has been observed following repeated short-term courses. Enamel hypoplasia has also been reported.
| Serious Effects |
Hypersensitivity to demeclocycline or any tetracyclinePregnancy (especially after first trimester)Lactation (unless benefits outweigh risks)Children under 8 years of age (except for anthrax or other life-threatening conditions, if no alternative)Severe hepatic impairmentConcurrent use with isotretinoin (increased risk of intracranial hypertension)
| Precautions | Photosensitivity: exaggerated sunburn reaction may occur; avoid prolonged sun exposure., Superinfection: overgrowth of nonsusceptible organisms, including fungi, may occur., Hepatotoxicity: rare but severe cases reported; monitor liver function., Renal impairment: accumulation may occur; use caution and reduce dose., Central nervous system: dizziness, headache, tinnitus have been reported. |
| Food/Dietary |
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| Lactation Rating | L3 (Moderately Safe) per Hale's classification; avoid if possible. |
| Teratogenic Risk | First trimester: Avoid due to risk of fetal skeletal abnormalities and teeth discoloration. Second and third trimesters: Contraindicated; causes permanent yellow-gray-brown teeth discoloration and enamel hypoplasia; may inhibit fetal bone growth. |
| Fetal Monitoring | Monitor maternal renal and hepatic function, complete blood count, and signs of superinfection. Fetal monitoring with serial ultrasounds for skeletal growth and teeth development if inadvertent exposure. |
| Fertility Effects | May impair fertility in both sexes; in males, reduces sperm motility and count; in females, may disrupt menstrual cycle and ovulation. |
| Avoid dairy products (milk, cheese, yogurt), calcium-fortified juices, antacids, and supplements containing calcium, magnesium, iron, or zinc within 2-3 hours of taking demeclocycline as they impair absorption. Food reduces absorption; take on empty stomach. |
| Clinical Pearls | Declomycin (demeclocycline) is a tetracycline antibiotic. It is also used for syndrome of inappropriate antidiuretic hormone (SIADH) due to its ability to induce nephrogenic diabetes insipidus. Monitor renal function and liver enzymes. Avoid in children <8 years and pregnant/breastfeeding women. Photosensitivity is common; advise sun avoidance. Use with caution in renal impairment; may accumulate. Do not use after expiration date due to risk of Fanconi syndrome. |
| Patient Advice | Take on empty stomach (1 hour before or 2 hours after meals) with full glass of water. · Avoid dairy products, antacids, iron, calcium, magnesium, zinc supplements within 2-3 hours of dose. · Complete full course even if feeling better. · Stop and contact doctor if severe headache, blurred vision, or bulging fontanelles (pseudotumor cerebri). · Use sunscreen and protective clothing; avoid prolonged sun exposure. · Do not use after expiration date; discard properly. · May cause dizziness; avoid driving if affected. · Notify doctor if pregnant or breastfeeding. |