Classifications: antibiotic; tetracycline;
Therapeutic: tetracycline antibiotic

Prototype: Tetracycline
Pregnancy Category: D


150 mg capsules; 150 mg, 300 mg tablets


Demeclocycline is a broad-spectrum, tetracycline antibiotic. It is pumped through the inner cytoplasmic membrane of bacteria. Demeclocycline blocks the binding of transfer RNA (tRNA) to the messenger RNA (mRNA) of the bacteria. Therefore, bacterial protein synthesis is inhibited and bacterial cells are destroyed.

Therapeutic Effect

Effective against both gram-positive and gram-negative bacteria.


Similar to those of tetracycline.

Unlabeled Uses

Treatment of chronic SIADH (syndrome of inappropriate antidiuretic hormone) secretion.


Hypersensitivity to any of the tetracyclines; severe renal or hepatic disease; cirrhosis, common bile duct obstruction; period of tooth development in fetus; pregnancy (category D), lactation, children <8 y (causes permanent yellow discoloration of teeth, enamel hypoplasia, and retarded bone growth).

Cautious Use

Mild or moderate impaired renal or hepatic function; nephrogenic diabetes insipidus; use of capsule or tablet formulations in patients with esophageal compression or obstruction.

Route & Dosage

Adult: PO 150 mg q6h or 300 mg q12h (max: 2.4 g/d)
Child (>8 y): PO 8–12 mg/kg/d divided q8–12h

Adult: PO 600 mg followed by 300 mg q12h for 4 d

Adult: PO 600–1200 mg/d in 3–4 divided doses


  • Give not less than 1 h before or 2 h after meals. Foods rich in iron (e.g., red meat or dark green vegetables) or calcium (e.g., milk products) impair absorption.
  • Concomitant therapy: Do not give antacids with tetracyclines.
  • Check expiration date before giving drug. Renal damage and death have resulted from use of outdated tetracyclines.
  • Request physician order to give with light meal if gastric distress is a problem. Absorption may be reduced; keep meal dairy free.
  • Store in tight, light-resistant containers, preferably at 15°–30° C (59°–86° F) unless otherwise directed. Tetracyclines form toxic products when outdated or exposed to light, heat, or humidity.

Adverse Effects (≥1%)

Body as a Whole: Hypersensitivity [photosensitivity, pericarditis, anaphylaxis (rare)]. GI: Nausea, vomiting, diarrhea, esophageal irritation or ulceration, enterocolitis, abdominal cramps, anorexia. Urogenital: Diabetes insipidus, azotemia, hyperphosphatemia. Skin: Pruritus, erythematous eruptions, exfoliative dermatitis.

Diagnostic Test Interference

Like other tetracyclines, demeclocycline may cause false increases in urine catecholamines (fluorometric methods); false decreases in urine urobilinogen; and false-negative urine glucose with glucose oxidase methods (e.g., Clinistix, TesTape).


Drug: antacids, iron preparation, calcium, magnesium, zinc, kaolin-pectin, sodium bicarbonate can significantly decrease demeclocycline absorption; effects of desmopressin and demeclocycline antagonized; increases digoxin absorption, increasing risk of digoxin toxicity; methoxyflurane increases risk of renal failure. Food: Dairy products significantly decrease demeclocycline absorption; food may decrease drug absorption also.


Absorption: 60–80% absorbed from GI tract. Peak: 3–4 h. Distribution: Concentrated in liver; crosses placenta; distributed into breast milk. Metabolism: In liver; enterohepatic circulation. Elimination: 40–50% excreted in urine and 31% in feces in 48 h. Half-Life: 10–17 h.

Nursing Implications

Assessment & Drug Effects

  • Lab tests: C&S prior to initial therapy and periodically during prolonged therapy. With prolonged therapy, add periodic evaluations of serum drug levels, electrolytes, and renal, hepatic, and hematopoietic systems.
  • Monitor I&O ratio and pattern and record weights in patients with impaired kidney or liver function, or on prolonged or high dose therapy. Some patients develop diabetes insipidus-like syndrome (SIADH).

Patient & Family Education

  • Do not use antacids while taking this drug.
  • Take drug on an empty stomach to enhance absorption. Because esophageal irritation and ulceration have been reported, take each dose with a full glass (240 mL) of water; remain upright for at least 90 s after taking medication; and avoid taking drug within 1 h of lying down or bedtime.
  • Notify physician if gastric distress is a problem; a snack or light meal free of dairy products may be added to the regimen.
  • Report symptoms of superinfections; this is VERY important (see Appendix F).
  • Demeclocycline-induced phototoxic reaction can be unusually severe. Avoid sunlight as much as possible and use sunscreen.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2023 Last Updated On: 01/19/2023 (0)
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