Doxycycline

Oral
Susceptible infections
Adult: 200 mg as a single dose or in 2 divided doses (at 12-hour interval) on the first day, then 100 mg once daily. Severe infections: 200 mg daily.
Child: <45 kg: 4.4 mg/kg in 2 divided doses on the first day then, 2.2 mg/kg. For severe infections: 2.2 mg/kg 12 hourly; ≥45 kg: Same as adult dose.

Oral
Nongonococcal urethritis
Adult: 100 mg bid for 7 days.

Oral
Sexually transmitted diseases
Adult: 100 mg bid for 7 days.

Oral
Uncomplicated gonorrhoea
Adult: 100 mg bid for 7 days.

Oral
Epididymo-orchitis
Adult: Infection caused by Chlamydia trachomatis or Neisseria gonorrhoeae 100 mg bid for at least 10 days.

Oral
Syphilis
Adult: 300 mg daily in divided doses for at least 10 days.

Oral
Relapsing fever and louse-borne typhus
Adult: 100 or 200 mg as a single dose.

Oral
Prophylaxis of scrub typhus
Adult: 200 mg as a single dose.

Oral
Chloroquine resistant falciparum malaria acute attack
Adult: In combination with quinine: 200 mg daily for at least 7 days.

Oral
Prophylaxis of malaria
Adult: As dispersible tab: 100 mg daily starting 1-2 days before travel to malarial areas, continued daily during the stay and for 4 weeks after leaving the malarial area.
Child: ≥12 years <45 kg: 2.2 mg/kg once daily; ≥45 kg: Same as adult dose.

Oral
Treatment and postexposure prophylaxis of inhalation anthrax
Adult: Postexposure prophylaxis: 100 mg bid for 60 days. Treatment: 100 mg bid for 7-10 days (cutaneous); 200 mg as a single dose then 100 mg 12 hourly, in combination with a bactericidal agent, for 2 weeks until clinically stable (systemic).
Child: <45 kg: 2.2 mg/kg bid for 60 days; ≥45 kg: Same as adult dose.

Oral
Traveller's diarrhoea
Adult: As prophylaxis: 200 mg as a single dose or in 2 divided doses on the first day of travel, then 100 mg once daily throughout the stay in the area.

Oral
Leptospirosis
Adult: As prophylaxis: 200 mg once weekly throughout the stay in the area, then 200 mg on the last day of trip.

Oral
Acne
Adult: 40 mg or 50 mg (depending on the preparation) daily for 6-12 weeks.

Oral
Periodontitis
Adult: As film-coated tab: 20 mg bid for up to 3 months.

Intravenous
Susceptible infections
Adult: 200 mg on day 1 followed by 100-200 mg daily depending on the severity of infection.
Reconstitution: IV: Dilute a 100 or 200 mg vial with 10 or 20 mL of sterile water for inj or other compatible IV infusion solution, respectively, to a final concentration of 10 mg/mL. Further dilute each 100 or 200 mg with 100-1000 or 200-2000 mL, respectively, of compatible IV infusion fluid to a final concentration of approx 0.1-1 mg/mL.

Topical/Cutaneous
Periodontitis
Adult: As 10% controlled-release subgingival preparation: Inject into the periodontal pocket, may be repeated 4 months after initial treatment.

May be taken with or without food. Take w/ a full glass of water & remain upright for at least 30 min. Take w/ food or milk if GI irritation occurs.

Hypersensitivity to doxycycline and other tetracycline congeners. Known or suspected achlorhydria (film-coated tab). Children <8 years (except for anthrax). Pregnancy and lactation. Concomitant use of methoxyflurane.

Patient with coexisting venereal disease, myasthenia gravis, SLE; history or predisposition to oral candidosis (film-coated tab). Hepatic and renal impairment. Patient Counselling Avoid exposure to direct sunlight or UV light. Monitoring Parameters Before treatment, perform sensitivity testing. Monitor CBC, LFT and renal function.

Significant: Microbial overgrowth including fungi, pseudomembranous colitis, oesophagitis, oesophageal ulceration, benign intracranial hypertension, discolouration of teeth, enamel hypoplasia, photosensitivity, exfoliative dermatitis, erythema multiforme, drug reaction with eosinophilia and systemic symptoms, Jarisch-Herxheimer reaction (if with spirochete infection); rarely, transient increases in LFT, porphyria. Blood and lymphatic system disorders: Haemolytic anaemia, neutropenia, eosinophilia, thrombocytopenia. Cardiac disorders: Tachycardia, pericarditis. Ear and labyrinth disorders: Tinnitus. Eye disorders: Blurred vision, diplopia, scotomata. Gastrointestinal disorders: Stomatitis, nausea, vomiting, diarrhoea, dyspepsia, abdominal pain, pancreatitis. General disorders and administration site conditions: Peripheral oedema. Hepatobiliary disorders: Jaundice. Immune system disorders: Angioneurotic oedema, urticaria, serum sickness. Investigations: Brown/black discolouration of thyroid tissue, increased serum AST. Metabolism and nutrition disorders: Anorexia. Musculoskeletal and connective tissue disorders: Arthralgia, myalgia. Nervous system disorders: Headache. Reproductive system and breast disorders: Vaginitis. Respiratory, thoracic and mediastinal disorders: Dyspnoea. Skin and subcutaneous tissue disorders: Rashes, photo-onycholysis, skin hyperpigmentation. Vascular disorders: Hypotension.
Potentially Fatal: Anaphylactoid reactions, Stevens-Johnson syndrome, toxic epidermal necrolysis, Clostridium difficile-associated disease (CDAD), hepatotoxicity.

Risk of pseudotumour cerebri with isotretinoin. Risk of breakthrough bleeding with oral contraceptives. Prolonged prothrombin time with anticoagulants (e.g. warfarin). Decreased exposure with antacids containing Al, Ca or Mg, Zn, Fe salts, bismuth preparations, carbamazepine, phenobarbital, phenytoin and primidone. May increase the exposure of ciclosporin. May interfere with the bactericidal action of penicillin. Drugs that induce hepatic enzymes (e.g. rifampicin) may decrease the half-life of doxycycline.
Potentially Fatal: Concurrent use with methoxyflurane may result in renal toxicity.

May decrease absorption with food including milk. Decreased half-life with alcohol.

May interfere with fluorescence test for urinary catecholamines.

Doxycycline, a tetracycline congener, is bacteriostatic against a broad range of gram-positive and gram-negative bacteria. It inhibits protein synthesis by inhibiting the 30S ribosomal subunit of bacteria.
Absorption: Readily and almost completely absorbed from the gastrointestinal tract. Bioavailability: Approx 93%. Time to peak plasma concentration: 2 hours.
Distribution: Widely distributed into body tissues (with strong affinity to lung and renal tissues) and fluids. Crosses the placenta and enters breast milk. Plasma protein binding: Approx 80-95%.
Excretion: Via urine (23%-40%); faeces (30%). Plasma elimination half-life: 12-24 hours.

Intravenous: Store between 20-25°C. Protect reconstituted solution from light. Oral: Store between 20-25°C. Topical/Cutaneous: Store between 20-25°C.

Acne Treatment Preparations / Tetracyclines

A01AB22 - doxycycline ; Belongs to the class of local antiinfective and antiseptic preparations. Used in the treatment of diseases of the mouth.
J01AA02 - doxycycline ; Belongs to the class of tetracyclines. Used in the systemic treatment of infections.