Demeclocycline

DECLOMYCIN

What it isTetracycline that antagonizes renal antidiuretic-hormone action; SIADH-related hyponatremia.

Why this oneIt deliberately induces nephrogenic diabetes insipidus, correcting water retention in SIADH.

What limits itSlow onset, photosensitivity, and nephrotoxicity limit use; vasopressin antagonists have largely displaced it.

FDA-approved for

FDA dosing	Population	Start	Target	Max
Bacterial infection	Adult	150 mg QID or 300 mg BID	150 mg QID or 300 mg BID	600 mg/day
Bacterial infection	Peds >8 yr	7-13 mg/kg/day divided BID-QID	7-13 mg/kg/day divided BID-QID	600 mg/day
Gonorrhea (penicillin-sensitive)	Adult	600 mg once	then 300 mg q12h x4 days	3 g total

Renal Use cautiously; reduce individual doses and/or extend dosing intervals in renal impairment

Hepatic Use cautiously; reduce individual doses and/or extend dosing intervals in hepatic impairment

Give >=1 h before or 2 h after meals; avoid antacids (Al/Ca/Mg), iron, and dairy which impair absorption
Take with adequate fluid to reduce esophageal irritation; do not lie down immediately after dosing
Continue therapy >=24-48 h after symptoms and fever subside

Fetal harm; permanent tooth discoloration (yellow-gray-brown) and enamel hypoplasia with use during tooth development (last half of pregnancy, infancy, childhood to age 8) - avoid unless other drugs are not likely to be effective or are contraindicated
Reversible decrease in fibula growth rate reported in premature infants
Anti-anabolic effect raises BUN; in renal impairment may cause azotemia, hyperphosphatemia, acidosis, drug accumulation, and possible liver toxicity - use lower doses; consider serum drug levels with prolonged therapy
Photosensitivity/phototoxicity (exaggerated sunburn, severe burns on exposed surfaces) - discontinue at first evidence of skin erythema
Nephrogenic diabetes insipidus syndrome (polyuria, polydipsia, weakness) with long-term therapy - dose-dependent, reversible on discontinuation
CNS symptoms (headache, dizziness, light-headedness, vertigo, blurred vision) - caution with driving or hazardous machinery
C. difficile-associated diarrhea (mild diarrhea to fatal colitis), reported even >2 months after antibacterial use
Pseudotumor cerebri (benign intracranial hypertension) in adults; bulging fontanels in infants - usually resolve on discontinuation but permanent sequelae possible
Overgrowth of nonsusceptible organisms including fungi - discontinue if superinfection occurs

GI: anorexia, nausea, vomiting, diarrhea, esophageal ulceration, hepatotoxicity
Skin: maculopapular/erythematous rash, photosensitivity, erythema multiforme, rare SJS
Tooth discoloration (<8 yr)
Renal toxicity: acute renal failure, nephrogenic diabetes insipidus
Hematologic: hemolytic anemia, thrombocytopenia, neutropenia, eosinophilia
Hypersensitivity: urticaria, angioedema, anaphylaxis

Pregnancy Undefined

Lactation Undefined

NO BOXED WARNINGS

Principal riskNephrotoxicity; photosensitivity

Cost, est. cash$10–$300/month

Generic entry2004

Therapeutic safety burden1 / 4

Overdose danger1 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk2 / 4

Legacy pregnancy categoryD

Defining liabilityAllergy, gastrointestinal effects and agent-specific renal, hepatic, hematologic or interaction risks.