| Indication | Doxycycline is indicated for use in respiratory tract infections caused by Mycoplasma pneumoniae, Haemophilus influenzae, Streptococcus pneumoniae, Legionella spp., or Klebsiella spp. It is also used for prophylaxis of malaria. Doxycycline is indicated for a variety of bacterial infections, from Mycobacterium fortuitum and M. marinum, to susceptible E. coli and Brucella spp. It can be used as an alternative to treating plague, tetanus, Campylobacter fetus |
| Pharmacodynamics | Doxycycline, a long-acting tetracycline derived from oxytetracycline, is used to inhibit bacterial protein synthesis and treat non-gonococcal urethritis and cervicitis, exacerbations of bronchitis in patients with COPD, and adult periodontitis. |
| Mechanism of action | Doxycycline, like minocycline, is lipophilic and can pass through the lipid bilayer of bacteria. Doxycycline reversibly binds to the 30 S ribosomal subunits and possibly the 50S ribosomal subunit(s), blocking the binding of aminoacyl tRNA to the mRNA and inhibiting bacterial protein synthesis. Doxycycline prevents the normal function of the apicoplast of Plasmodium falciparum, a malaria causing organism. |
| Absorption | Completely absorbed following oral administration. |
| Volume of distribution | Not Available |
| Protein binding | >90% |
| Metabolism | Hepatic |
| Route of elimination | They are concentrated by the liver in the bile and excreted in the urine and feces at high concentrations in a biologically active form. |
| Half life | 18-22 hours |
| Clearance | Not Available |
| Toxicity | Symptoms of overdose include anorexia, nausea, diarrhoea, glossitis, dysphagia, enterocolitis and inflammatory lesions (with monilial overgrowth) in the anogenital region, skin reactions such as maculopapular and erythematous rashes, exfoliative dermatitis, photosensitivity, hypersensitivity reactions such as urticaria, angioneurotic oedema, anaphylaxis, anaphyl-actoid purpura, pericarditis, and exacerbation of systemic lupus erythematosus, benign intracranial hypertension in adults disappearing on discontinuation of the medicine, haematologic abnormalities such as haemolytic anaemia, thrombocytopenia, neutropenia, and eosinophilia. LD50=262 mg/kg (I.P. in rat). |
