lia recurrentis) . the following gram-negative microorganisms: haemophilus ducreyi (chancroid). yersinia pestis (formerly pasteurella pestis ) and francisella tularensis (formerly pasteurella tularensis ). bartonella bacilliformis . bacteroides species. vibrio cholerae (formerly vibrio comma ) and campylobacter fetus (formerly vibrio fetus ). brucella species (in conjunction with streptomycin). because many strains of the following groups of microorganisms have been shown to be resistant to tetracyclines, culture and susceptibility testing are recommended. doxycycline is indicated for treatment of infections caused by the following gram-negative microorganisms when bacteriologic testing indicates appropriate susceptibility to the drug: escherichia coli . enterobacter aerogenes (formerly aerobacter aerogenes ). shigella species. acinetobacter species (formerly mima species and herellea species). haemophilus influenzae (respiratory infections). klebsiella species (respiratory and urinary infections). doxycycline is indicated for treatment of infections caused by the following gram-positive microorganisms when bacteriologic testing indicates appropriate susceptibility to the drug: streptococcus species: up to 44 percent of strains of streptococcus pyogenes and 74 percent of enterococcus faecalis (formerly streptococcus faecalis ) have been found to be resistant to tetracycline drugs. therefore, tetracyclines should not be used for streptococcal disease unless the organism has been demonstrated to be sensitive. for upper respiratory infections due to group a beta-hemolytic streptococci, penicillin is the usual drug of choice, including prophylaxis of rheumatic fever. streptococcus pneumoniae (formerly diplococcus pneumoniae ). staphylococcus aureus , respiratory, skin and soft tissue infections. tetracyclines are not the drugs of choice in the treatment of any type of staphylococcal infections. anthrax due to bacillus anthracis , including inhalational anthrax (post-exposure): to reduce the incidence or progression of disease following exposure to aerosolized bacillus anthracis . when penicillin is contraindicated, doxycycline is an alternative drug in the treatment of infections due to: neisseria gonorrhoeae and n. meningitidis . treponema pallidum and treponema pertenue (syphilis and yaws). listeria monocytogenes . clostridium species. fusobacterium fusiforme (vincent's infection). actinomyces species. in acute intestinal amebiasis, doxycycline may be a useful adjunct to amebicides. doxycycline is indicated in the treatment of trachoma, although the infectious agent is not always eliminated, as judged by immunofluorescence.

le produces toxins a and b which contribute to the development of cdad. hypertoxin producing strains of c. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. cdad must be considered in all patients who present with diarrhea following antibiotic use. careful medical history is necessary since cdad has been reported to occur over two months after the administration of antibacterial agents. if cdad is suspected or confirmed, ongoing antibiotic use not directed against c. difficile may need to be discontinued. appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of c. difficile, and surgical evaluation should be instituted as clinically indicated. severe skin reactions, such as exfoliative dermatitis, erythema multiforme, stevens-johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms (dress) have been reported in patients receiving doxycycline (see adverse reactions ). if severe skin reactions occur, doxycycline should be discontinued immediately and appropriate therapy should be instituted. intracranial hypertension (ih, pseudotumor cerebri) has been associated with the use of tetracyclines including doxycycline. clinical manifestations of ih include headache, blurred vision, diplopia, and vision loss; papilledema can be found on fundoscopy. women of childbearing age who are overweight or have a history of ih are at greater risk for developing tetracycline associated ih. concomitant use of isotretinoin and doxycycline should be avoided because isotretinoin is also known to cause pseudotumor cerebri. although ih typically resolves after discontinuation of treatment, the possibility for permanent visual loss exists. if visual disturbance occurs during treatment, prompt ophthalmologic evaluation is warranted. since intracranial pressure can remain elevated for weeks after drug cessation patients should be monitored until they stabilize. photosensitivity manifested by an exaggerated sunburn reaction has been observed in some individuals taking tetracyclines. patients apt to be exposed to direct sunlight or ultraviolet light, should be advised that this reaction can occur with tetracycline drugs, and treatment should be discontinued at the first evidence of skin erythema. the anti-anabolic action of the tetracyclines may cause an increase in bun. studies to date indicate that this does not occur with the use of doxycycline in patients with impaired renal function.

of primary and secondary syphilis, the recommended dosage is 300 mg daily for at least 10 days. in the treatment of inhalational anthrax (post-exposure) the recommended dose is 100 mg of doxycycline, twice a day. parenteral therapy is only indicated when oral therapy is not indicated and should not be continued over a prolonged period of time. oral therapy should be instituted as soon as possible. therapy must continue for a total of 60 days. pediatric patients for all pediatric patients weighing less than 45 kg with severe or life-threatening infections (e.g., anthrax, rocky mountain spotted fever), the recommended dosage is 2.2 mg/kg of body weight administered every 12 hours. children weighing 45 kg or more should receive the adult dose (see warnings and precautions ). for pediatric patients with less severe disease (greater than 8 years of age and weighing less than 45 kg), the recommended dosage schedule is 4.4 mg/kg of body weight divided into two doses on the first day of treatment, followed by a maintenance dose of 2.2 mg/kg of body weight (given as a single daily dose or divided into twice daily doses). for pediatric patients weighing over 45 kg, the usual adult dose should be used. in the treatment of inhalational anthrax (post-exposure) the recommended dose is 2.2 mg/kg of body weight, twice a day in children weighing less than 45 kg. parenteral therapy is only indicated when oral therapy is not indicated and should not be continued over a prolonged period of time. oral therapy should be instituted as soon as possible. therapy must continue for a total of 60 days. general the duration of infusion may vary with the dose (100 to 200 mg/day), but is usually one to four hours. a recommended minimum infusion time for 100 mg of a 0.5 mg/ml solution is one hour. therapy should be continued for at least 24 to 48 hours after symptoms and fever have subsided. the therapeutic antibacterial serum activity will usually persist for 24 hours following recommended dosage. intravenous solutions should not be injected intramuscularly or subcutaneously. caution should be taken to avoid the inadvertent introduction of the intravenous solution into the adjacent soft tissue.

ura, pericarditis and exacerbation of systemic lupus erythematosus, drug reaction with eosinophilia and systemic symptoms (dress). other bulging fontanels in infants and intracranial hypertension in adults (see warnings ). blood hemolytic anemia, thrombocytopenia, neutropenia and eosinophilia have been reported. when given over prolonged periods, tetracyclines have been reported to produce brown-black microscopic discoloration of thyroid glands. no abnormalities of thyroid function studies are known to occur.

ot alter this serum half-life of doxycycline. population pharmacokinetic analysis of sparse concentration-time data of doxycycline following standard of care intravenous and oral dosing in 44 pediatric patients (2-18 years of age) showed that allometrically -scaled clearance (cl) of doxycycline in pediatric patients ≥2 to ≤8 years of age (median [range] 3.58 [2.27-10.82] l/h/70 kg, n=11) did not differ significantly from pediatric patients ˃8 to 18 years of age (3.27 [1.11-8.12] l/h/70 kg, n=33). for pediatric patients weighing ≤45 kg, body weight normalized doxycycline cl in those ≥2 to ≤8 years of age (median [range] 0.071 [0.041-0.202] l/kg/h, n=10) did not differ significantly from those ˃8 to 18 years of age (0.081 [0.035-0.126] l/kg/h, n=8) in pediatric patients weighing ˃45 kg, no clinically significant differences in body weight normalized doxycycline cl were observed between those ≥2 to ≤8 years of age (0.050 l/kg/h, n=1) and those ˃8 to 18 years of age (0.044 [0.014-0.121] l/kg/h, n=25). no clinically significant difference in cl between oral and iv dosing was observed in the small cohort of pediatric patients who received the oral (n=19) or iv (n=21) formulation alone. microbiology mechanism of action doxycycline inhibits bacterial protein synthesis by binding to the 30s ribosomal subunit. doxycycline has bacteriostatic activity against a broad range of gram-positive and gram-negative bacteria. resistance cross resistance with other tetracyclines is common. antimicrobial activity doxycycline has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections (see indications and usage ). gram-negative bacteria acinetobacter species bartonella bacilliformis brucella species enterobacter aerogenes escherichia coli francisella tularensis haemophilus ducreyi haemophilus influenzae klebsiella granulomatis klebsiella species neisseria gonorrhoeae shigella species vibrio cholerae campylobacter fetus yersinia pestis gram-positive bacteria bacillus anthracis listeria monocytogenes streptococcus pneumoniae anaerobic bacteria clostridium species fusobacterium fusiforme propionibacterium acnes other bacteria nocardiae and other aerobic actinomyces species borrelia recurrentis chlamydophila psittaci chlamydia trachomatis mycoplasma pneumoniae rickettsiae treponema pallidum treponema pallidum subspecies pertenue ureaplasma urealyticum parasites balantidium coli entamoeba species plasmodium falciparum * *doxycycline has been found to be active against the asexual erythrocytic forms of plasmodium falciparum but not against the gametocytes of p. falciparum. the precise mechanism of action of the drug is not known. susceptibility testing for specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by fda for this drug, please see: https://www.fda.gov/stic.

by doxycycline or other antibacterial drugs in the future. diarrhea is a common problem caused by antibacterial drugs, which usually ends when the antibacterials are discontinued. sometimes after starting treatment with antibacterial drugs, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibacterial drug. if this occurs, patients should contact their physician as soon as possible.