Tuesday 26 March 2013

Doxycycline pharmacology


DOXYCYCLINE
Pharmacology
Mechanism of Action
General Dosage
Indications:
Doxycycline is first line choice of drug in:
1.      Venereal diseases:
·        Chlamydial nonspecific urethritis: 100 mg BID for > 7 days.
·        Granuloma inguinale: 100mg doxycycline for 3 weeks.
2.      Atypical pneumonia: duration of illness is reduced by tetracycline therapy.
3.      Cholera: tetracyclines have adjuvant value by reducing the stool volume.
4.      Brucellosis: doxycycline 200mg/day + rifampicin 600mg/day for 6 weeks.
5.      Plague
6.      Relapsing fever
7.      Rickettsial infection: typhus, rocky mountain spotted fever, Q fever.
Doxycycline is second line choice of drug in:
1.      Syphilis:
Early syphilis – 200 mg/day in divided doses for 14 days
Late syphilis -  200 mg/day in divided doses for 28 days
2.      Leptospirosis: 100mg doxycycline twice daily for 7 days.
3.      Endometritis, peritonitis : 100 mg BID IV + ceftriaxone 2 g every 6 hrly for 4 days then orally 100 mg BD for 10 to 14 days
4.      Gonorrhoea: 100mg doxycycline twice daily for 7 days.
 
 
Other situations in which doxycycline may be used:
1.      UTI
2.      Secondary community acquired pneumonia (100 mg BID)
3.      Malaria
4.      Acne vulgaris
5.      Amoebiasis
 
Adverse Effects
Frequency Not Defined
Pregnancy & Lactation
Tetracyclines are primarily bacteriostatic; inhibits the protein synthesis by binding to 30s ribosomes in susceptible organism. Subsequent to such binding, attachment of aminoacyl-t-RNA to the mRNA-ribosome complex is interfered. As a result, the peptide chain fails to grow.
Children:
For Anthrax
Oral, IV (use oral dose when possible) < 8 years : 2.2 mg/kg every 12 hrs for 60 days
Ø  >8 years and < 45 kgs : 2.2 mg/kg every 12 hrs for 60 days
Ø  >8 years and > 45 kgs: 100 mg every 12 hrs for 60 days
For susceptible infections
Children > 8 years (<45kg) oral, IV : 2-5 mg/kg/day in 1-2 divided doses not to exceed 200 mg/day
Children > 8 years (>40 kgs) and adults oral, IV : 100 – 200 mg /day in 1-2 divided doses
Cardiovascular: Pericarditis
Gastrointestinal: Hepatotoxicity, glossitis, anorexia, diarrhoea, dysphagia, epigastric pain,nausea,vomiting.
Hematology: Hemolytic anaemia, eosinophilia, neutropenia, thrombocytopenia
Nephrology: Increased BUN
Neurologic: Bulging fontanels (infants), intracranial hypertension
Skeletomuscular: Teeth discoloration (children)
Skin: Exfoliative dermatitis, rash, urticaria, erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis, exfoliative dermatitis, photosensitivity, rash
Other: SLE exacerbation
Pregnancy Category: D
Lactation: enters breast milk, do not breastfeed

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