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Tetracycline antibiotic (with anti-ADH effect) Pregnancy: CONTRAINDICATED. SPC §4.6: 'Demeclocycline hydrochloride capsule is contra-indicated during pregnancy and lactation.' Pregnancy: 'Results of animal studies indicate that tetracyclines cross the placenta, are found in foetal tissues and can have toxic effects on the developing foetus (often related to retardation of skeletal development). Evidence of embryotoxicity has also been noted in animals treated early in pregnancy. The use of tetracyclines during tooth development (last half of pregnancy and children to the age of 12 years) may cause permanent discoloration of the teeth (yellow-grey-brown). This adverse reaction is more common during long term use of the drugs but has been observed following repeated short term courses. Enamel hypoplasia has also been reported.' Breast-feeding: 'Tetracyclines have been found in the milk of lactating women who are taking a drug in this class. Permanent tooth discoloration may occur in the developing infant and enamel hypoplasia has been reported. Therefore, demeclocycline hydrochloride capsule should not be administered to lactating women.' Pregnancy and breast-feeding are also listed among the §4.3 contraindications.

Demeclocycline

Brand names: Ledermycin

Used in: Hyponatraemia

Demeclocycline is a tetracycline antibiotic used in endocrinology principally to manage chronic hyponatraemia caused by the syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Adult dose

Dose: 900-1200 mg daily initially, in divided doses; maintenance 600-900 mg daily in divided doses
Route: Oral - capsules. SPC §4.2: 'Demeclocycline hydrochloride capsule should be swallowed whole with plenty of fluid while sitting or standing.' The SPC product is a 150 mg capsule.
Frequency: In divided doses. The SPC does not state how many divisions to use for the SIADH regimen; for its antibiotic indication it specifies '2 or 4 divided doses'. Doses are taken away from food: 'Doses should be taken an hour before or 2 hours after meals as absorption of demeclocycline hydrochloride capsule is impaired by milk and food.'
SCOPE: this is the SPC's regimen for CHRONIC HYPONATRAEMIA DUE TO SIADH - the primary indication of this endocrinology page - and it is licensed for adults only. VERBATIM (SPC §4.2): 'For the treatment of Chronic Hyponatraemia due to SIADH: Adults only Initially: 900mg-l200mg daily in divided doses Maintenance dose: 600-900mg daily in divided doses'. NOTE the fetched text renders the upper initial figure as 'l200mg' with a lower-case letter l in place of the digit 1; it is 1200 mg, which is also what the arithmetic of the 900 mg lower bound and the 600-900 mg maintenance range requires. Confirm against the SPC page if the exact figure is load-bearing. STOPPING (SPC §4.2, verbatim): 'Demeclocycline hydrochloride capsule therapy in the treatment of chronic hyponatraemia due to SIADH should not be withdrawn without commencing other methods of control.' SECONDARY INDICATION on the same page, for completeness (SPC §4.2, antibiotic use, adults, capsules): '600mg daily in 2 or 4 divided doses. For primary atypical pneumonia, the average daily dose is 900mg in 3 divided doses for 6 days.' Duration rules for antibiotic use: 'Antibiotic therapy should be continued for one to three days after characteristic symptoms of fever have subsided. The incidence of rheumatic fever or glomerulonephritis following streptococcal infections suggests that therapy of a streptococcal infection should be continued for 8 full days even though symptoms have subsided.' The US label's adult antibiotic dose differs: 'Usual daily dose - Four divided doses of 150 mg each or two divided doses of 300 mg each' (i.e. 600 mg/day). ELDERLY (SPC §4.2): 'Use with caution in elderly patients.' NO MAXIMUM DOSE IS ASSERTED: the SPC states no ceiling for the SIADH regimen. The only numeric ceiling anywhere in the bundle is conditional on liver disease ('Patients who have known liver disease should not receive more than 1g daily', §4.4) and is therefore recorded under hepaticAdjustment, not as a maxDose for this regimen - note that it sits BELOW the initial SIADH range, so a patient with known liver disease cannot receive the regimen above. §4.4 warns specifically about this indication: 'The treatment of chronic hyponatraemia may necessitate the administration of high doses of demeclocycline hydrochloride capsule for prolonged periods, so increasing the potential for nephrotoxicity (manifested by rises in plasma urea and creatinine) and photoallergic reactions.'

Dose adjustments

Renal

The UK SPC CONTRAINDICATES demeclocycline in renal impairment outright - §4.3: 'The use of Demeclocycline is contraindicated in ... patients with renal impairment.' §4.4 nonetheless carries dose guidance for where it is used: 'Demeclocycline hydrochloride capsule should be used with caution in patients with renal or hepatic dysfunction, or in conjunction with other potentially hepatotoxic or nephrotoxic drugs' and 'Lower doses are indicated in cases of renal impairment to avoid excessive systemic accumulation and if therapy is prolonged, serum level determinations are advisable.' §4.4 also notes 'The anti-anabolic action of the tetracyclines may cause an increase in BUN.' The US label is less absolute: 'Tetracyclines should be used cautiously in patients with impaired renal function. Total dosage should be decreased by reduction of recommended individual doses and/or by extending time intervals between doses.' No numeric renally-adjusted regimen is given in either source. Relevant to this page: §4.4 warns that the prolonged high dosing needed for chronic hyponatraemia itself increases 'the potential for nephrotoxicity (manifested by rises in plasma urea and creatinine)', and §4.8 lists 'reversible nephrogenic diabetes insipidus (prolonged and/or at high dosages)'.

Hepatic

SPC §4.4: 'Demeclocycline hydrochloride capsule should be used with caution in patients with renal or hepatic dysfunction, or in conjunction with other potentially hepatotoxic or nephrotoxic drugs' and, as an explicit numeric ceiling, 'Patients who have known liver disease should not receive more than 1g daily.' That 1 g/day cap is below the initial SIADH range of 900-1200 mg daily, so the initial regimen cannot be given in full to a patient with known liver disease. US label: 'Tetracyclines should be used cautiously in patients with impaired liver function. Total dosage should be decreased by reduction of recommended individual doses and/or by extending time intervals between doses.'

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • SPC §4.3: 'Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.'
  • SPC §4.3: acute porphyria
  • SPC §4.3: patients who are pregnant or breast-feeding
  • SPC §4.3: children under 12 years of age
  • SPC §4.3: 'patients with a history of hypersensitivity to tetracyclines'
  • SPC §4.3: patients with renal impairment
  • US label CONTRAINDICATIONS: 'This drug is contraindicated in persons who have shown hypersensitivity to any of the tetracyclines or any of the components of the product formulation.'
  • Not a contraindication but a stated incompatibility, SPC §4.5: 'Demeclocycline hydrochloride capsule should not be used with penicillins.'
  • Not a contraindication but a specific hazard, SPC §4.4: 'Concurrent use with the anaesthetic methoxyflurane increases the risk of kidney failure.'

Side effects

  • Skin, SPC §4.8 and §4.4: photosensitivity, erythematous and maculo-papular rashes, pruritus, bullous dermatoses, exfoliative dermatitis, skin discolouration, serious skin reactions. §4.4: 'Demeclocycline hydrochloride capsule has the greatest potential of the tetracycline analogues for causing photo-allergic reactions in hypersensitive persons. Such patients should be warned to avoid direct exposure to natural or artificial sunlight and to discontinue therapy at the first sign of skin discomfort.'
  • Renal and urinary, SPC §4.8: 'Renal dysfunction, especially in patients with pre-existing renal impairment, acute renal failure or nephritis, reversible nephrogenic diabetes insipidus (prolonged and/or at high dosages)'
  • Gastrointestinal, SPC §4.8: 'Nausea, vomiting, diarrhoea, dysphagia, oesophagitis, oesphageal ulceration, candidiasis, pseudomembranous colitis (Clostridium difficile overgrowth) glossitis, stomatitis, vaginitis, or staphylococcal enterocolitis, pancreatitis'. §4.8 footnote c: oesophageal ulceration occurs 'In patients taking oral tetracyclines in solid dose form, usually where medication was taken immediately before retiring or with inadequate fluids.'
  • Hepatobiliary, SPC §4.8: 'Hepatitis, jaundice, hepatic failure'; investigations: 'Transient increases in liver function test values'
  • Blood and lymphatic, SPC §4.8: 'Haemolytic anaemia, thrombocytopenia, neutropenia, agranulocytosis, aplastic anaemia and eosinophilia'
  • Immune, SPC §4.8: 'Hypersensitivity reactions including urticaria, Stevens-Johnson syndrome, angioneurotic oedema, anaphylaxis, anaphylactoid purpura, pericarditis and exacerbation of systemic lupus erythematosus'
  • Nervous system, SPC §4.8: 'Headache, dizziness, bulging fontanelles (in infants), benign intracranial hypertension (in juveniles and adults), raised intracranial pressure (such as severe or persistent headache or blurred vision), myasthenia'. Footnote b: 'While the condition and related symptoms usually resolve soon after discontinuation of the tetracycline, the possibility of permanent sequelae exists.'
  • Eye and ear, SPC §4.8: visual disturbances; impaired hearing
  • SPC §4.4: 'Exacerbation of pre-existing SLE has been reported with tetracyclines. Demeclocycline hydrochloride capsule may increase muscle weakness in patients with myasthenia gravis.'
  • SPC §4.8 footnote a: 'When given over prolonged periods, tetracyclines have been reported to produce brown-black discoloration of the thyroid gland. No abnormalities of thyroid function are known to occur.'
  • Overgrowth of resistant organisms, SPC §4.4: discontinue 'if there are signs/symptoms of overgrowth of resistant organisms including candida, enteritis, glossitis, stomatitis, vaginitis, pruritis ani or staphylococcal enterocolitis'

Monitoring

  • Renal function - §4.4 warns the prolonged high dosing used for chronic hyponatraemia increases 'the potential for nephrotoxicity (manifested by rises in plasma urea and creatinine)', so plasma urea and creatinine are the stated markers
  • Periodic organ-system laboratory evaluation on long-term therapy, §4.4, verbatim: 'In long term therapy, periodic laboratory evaluation of organ systems, including haematopoietic, renal and hepatic studies should be performed.'
  • Serum drug levels where treatment is prolonged in renal impairment, §4.4: 'if therapy is prolonged, serum level determinations are advisable'
  • Skin - photoallergic reactions; §4.4 directs that susceptible patients 'be warned to avoid direct exposure to natural or artificial sunlight and to discontinue therapy at the first sign of skin discomfort'
  • Signs of overgrowth of resistant organisms (candida, enteritis, glossitis, stomatitis, vaginitis, pruritus ani, staphylococcal enterocolitis), §4.4 - discontinue if they appear
  • Anticoagulant effect where a coumarin or phenindione is co-prescribed, §4.5: 'Tetracyclines depress plasma prothrombin activity and reduced doses of concomitant anti-coagulants such as Coumarins and phenindione may be required.'
  • NOTE - neither fetched source specifies a serum sodium monitoring schedule for the SIADH regimen, despite sodium being the treatment target. Take the sodium monitoring interval from a hyponatraemia guideline, not from this bundle.

Clinical monograph

How it works

In this setting it acts on the renal collecting ducts to reduce responsiveness to antidiuretic hormone, producing a reversible nephrogenic diabetes insipidus that promotes water excretion.

Prescribing in practice

  • It can be nephrotoxic, particularly in hepatic impairment, so renal function must be monitored and it is avoided in significant liver disease.
  • As a tetracycline it causes photosensitivity and is contraindicated in pregnancy and young children because of effects on teeth and bone.
  • Absorption is reduced by dairy products and by calcium, iron or antacids, which should be separated from dosing.

Monitoring

Monitor serum sodium and renal function during treatment for SIADH.

Counselling the patient

  • Avoid strong sun exposure and use sun protection because of photosensitivity.
  • Take separately from milk, indigestion remedies and iron or calcium supplements.
  • Attend for blood tests to check sodium and kidney function.

Evidence & guidelines

Demeclocycline is an established option for chronic SIADH where fluid restriction is insufficient; use should follow the SPC.

Reference: SmPC Ledermycin; UK Hyponatraemia Guidance (Spasovski et al. ESE 2014); Verbalis et al. Am J Med 2013; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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