Action And Clinical Pharmacology: Doxycycline hyclate is a broad-spectrum antibiotic and is active against a wide range of gram-negative and gram-positive organisms. Doxycycline exerts its bacteriostatic effect by the inhibition of protein synthesis.
Indications And Clinical Uses: For the treatment of: Pneumonia: single and multilobe pneumonia and bronchopneumonia due to susceptible strains of S. pneumoniae (formerly D. pneumoniae) and other Streptococci, Staphylococcus, H. influenzae and K. pneumoniae.
Other Respiratory Tract Infections: pharyngitis, tonsillitis, sinusitis, otitis media, bronchitis caused by susceptible strains of b-hemolytic Streptococcus, Staphylococcus, S. pneumoniae (formerly D. pneumoniae), and H. influenzae.
Genitourinary Tract Infections: pyelonephritis, cystitis, urethritis, gonococcal urethritis caused by susceptible strains of Klebsiella species, E. aerogenes, E. coli, Enterococcus, Staphylococcus, Streptococcus and N. gonorrhoeae.
In adult patients with urethritis, cervicitis and vaginitis with a positive test for C. trachomatis and/or U. urealyticum, clinical resolution and absence of detectable organisms have only been observed at completion of oral therapy. Relapses or reinfection can occur. In these cases, limited data suggest that some patients may derive clinical benefit from the oral administration of doxycycline or an alternative therapy. The effect on long-term morbidity has not been established.
Skin and Soft Tissue Infections: impetigo, furunculosis, cellulitis, abscess, wound sepsis, paronychia, caused by susceptible strains of S. aureus and epidermidis (formerly albus), Streptococcus, E. coli, Klebsiella species and E. aerogenes.
Gastrointestinal Infections: caused by susceptible strains of Shigella, Salmonella and E. coli.
Up to 44% of strains of S. pyogenes and 74% of S. faecalis have been found to be resistant to tetracycline drugs.
Appropriate culture and susceptibility studies should be carried out prior to initiation of therapy with doxycycline and if clinically indicated during treatment. Consideration may be given to the initiation of therapy before obtaining results of these tests, however modification of such treatment may be required once the results become available.
Contra-Indications: In individuals who have shown hypersensitivity to tetracyclines and in patients with myasthenia gravis.
Manufacturers’ Warnings In Clinical States: Doxycycline like other tetracyclines, may form a stable calcium complex in any bone-forming tissue, though in vitro it binds calcium less strongly than other tetracyclines. It should be anticipated that the use of doxycycline during tooth development (last trimester of pregnancy, during lactation, neonatal period and early childhood to the age of 8 years) may cause permanent discoloration of the teeth (yellow-gray-brown). Though more commonly associated with long-term use of tetracyclines, this effect has also been known to occur after short courses. Enamel hypoplasia has also been reported. Doxycycline should, therefore, not be used in these age groups unless other drugs are unlikely to be effective or are contraindicated.
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 doxycycline, and treatment should be discontinued at the first evidence of skin erythema.
Pregnancy: Doxycycline should not be administered to pregnant women, unless in the judgment of the physician the potential benefit to the mother outweighs the risk to the fetus. (See Warnings about use during tooth development.)
Results of animal studies indicate that tetracyclines cross the placenta, are found in fetal tissues and can have toxic effects on the developing fetus (often related to retardation of skeletal development). Evidence of embryotoxicity has also been noted in animals treated early in pregnancy.
Lactation: Tetracyclines are excreted in the milk of lactating women. Accordingly the use of doxycycline is not recommended in women while they are breast feeding. (See Warnings about use during tooth development.)
Children: The use of doxycycline in children under 8 years is not recommended because safe conditions for its use have not been established. (See Warnings about use during tooth development.)
Doxycycline, like other tetracyclines, forms a stable calcium complex in any bone-forming tissue. A decrease in the fibula growth rate has been observed in prematures given oral tetracycline in doses of 25 mg/kg every 6 hours. This reaction was shown to be reversible when the drug was discontinued.
Precautions: In clinical studies to date, administration of doxycycline did not lead to increased serum levels nor to an increase in the serum half-life of doxycycline in patients with impaired renal function. Modification of the dosage for these patients is not necessary. Although no evidence of increased toxicity has been observed in such patients, the potential for increased hepatic or other toxicity should be considered until further data on the metabolic fate of doxycycline under these conditions become available.
Concurrent administration of doxycycline with agents known to be hepatotoxic should be avoided.
The use of antibiotics may occasionally result in overgrowth of nonsusceptible organisms; thus, observation of the patient is essential. There is evidence to suggest that doxycycline may have less effect on the gut flora than other tetracyclines. Nevertheless, it is important to consider the possibility of pseudomembranous colitis due to toxins produced by the overgrowth of C. difficile. Mild cases of pseudomembraneous colitis may respond to drug discontinuance alone. Moderate to severe cases should be managed with fluid, electrolyte and protein supplementation as indicated. When the colitis is not relieved by the discontinuance of doxycycline or when it is severe, consideration should be given to the administration of oral Vancomycin.
Increased intracranial pressure with bulging fontanels has been observed in infants receiving therapeutic doses of tetracycline. Although the mechanism of this phenomenon is unknown the signs and symptoms have disappeared rapidly upon cessation of treatment with no sequelae.
Isolated cases of esophageal injury consisting of esophagitis and esophageal ulceration have been reported in patients receiving doxycycline orally. Most of these patients took medication immediately before going to bed and/or without adequate amount of fluid (see Dosage). If this should occur, doxycycline should be discontinued until healing occurs. Administration of antacids and/or cimetidine has provided relief in the treatment of such cases. To reduce the risk of esophageal injury, patients should be advised to take doxycycline capsules or film-coated tablets with an adequate amount of fluid while standing or sitting upright.
In long-term therapy with doxycycline, periodic laboratory evaluation of organ systems, including hematopoietic, renal and hepatic studies should be performed. Liver function tests should be carried out at regular intervals on patients receiving high doses for prolonged periods of time.
Drug Interactions: Doxycycline should be given with caution to patients receiving oral anticoagulants. Because the tetracyclines have been shown to depress plasma prothrombin activity, patients who are on anticoagulant therapy may require downward adjustment of their anticoagulant dosage.
Antacids containing aluminum, calcium or magnesium impair absorption and should not be given to patients taking doxycycline.
The concurrent use of doxycycline with alcohol, barbiturates, phenytoin and carbamazepine (hepatic enzyme inducers) has been reported to result in a reduction of plasma half-life of doxycycline, thereby reducing the antimicrobial effectiveness of doxycycline. This effect may last for several days after discontinuation of therapy with the interacting agent. Therefore, consideration should be given to re-adjustment of the daily dose of doxycycline when administered concomitantly with alcohol and with drugs known to be enzyme inducers.
It has been reported that concurrent administration of ferrous sulfate (iron) lowered serum concentrations of doxycycline given orally and shortened the serum half-life after a single i.v. injection. In the event that iron and iron-containing products have to be given during treatment with doxycycline, the interval between administration of each drug should be as wide as possible.
It has been reported that when subsalicylate bismuth was given simultaneously and as a multiple-dose regimen before oral doxycycline there was a reduced bioavailability of doxycycline. Also peak serum concentrations of doxycycline were significantly decreased when subsalicylate bismuth was given 2 hours before oral doxycycline but not when given 2 hours after oral doxycycline. Therefore subsalicylate bismuth should not be taken during therapy with oral doxycyline.
Since bacteriostatic drugs may interfere with the bactericidal action of penicillin, it is advisable to avoid giving doxycycline, or any other tetracycline, in conjunction with penicillin.
There have been anecdotal reports that concurrent use of tetracyclines may render oral contraceptives less effective.
Adverse Reactions: Gastrointestinal: As with other broad spectrum antibiotics administered orally and parenterally, gastrointestinal disturbances such as anorexia, nausea, vomiting, diarrhea, glossitis, dysphagia, stomatitis, proctitis and enterocolitis, may occur, but have rarely been sufficiently troublesome to warrant discontinuation of therapy.
Isolated cases of esophagitis and esophageal ulcerations in patients receiving capsule and tablet form of doxycycline have been reported (see Precautions and Dosage).
Hypersensitivity: Hypersensitivity reactions consisting of urticaria, angioneurotic edema, anaphylaxis, anaphylactoid purpura, pericarditis, serum sickness, and exacerbation of systemic lupus erythematosus have been reported.
Maculopapular and erythematous rashes have been reported. Exfoliative dermatitis has also been reported but is uncommon.
Photosensitivity: Photosensitivity reaction is discussed under Warnings.
CNS: Bulging fontanels in infants and benign intracranial hypertension in adults have been reported in patients receiving full therapeutic dosages. These conditions disappeared rapidly when the drug was discontinued.
Hepatic and Renal: As with other tetracyclines, elevation of AST or ALT values, or elevated BUN (apparently dose related) have been reported, the significance of which is not known.
Hematologic: anemia, thrombocytopenia, neutropenia, eosinophilia, leukopenia.
Symptoms And Treatment Of Overdose: Symptoms and Treatment: Specific information on symptoms or treatment of overdosage with doxycycline is not available. Treatment, therefore, should be symptomatic and gastric lavage may be considered for overdosage with the oral preparation. Dialysis does not alter serum half-life and thus would not be of benefit in treating cases of overdosage.
Dosage And Administration: The preferred route of administration is oral. I.V. administration should ony be used for patients in whom oral administration is not feasible (e.g., patients with dysphagia, nausea, gastrointestinal intolerance, unconsciousness, traumatic or surgical wounds of the gastrointestinal tract or intestinal obstruction). Oral therapy should be substituted as soon as possible.
Capsules and film-coated tablets should be given with or after a meal in order to minimize the possibility of gastric upset. Antacids and iron preparations impair absorption and should not be given concomitantly to patients taking oral doxycycline.
Capsules and film-coated tablets should be given to patients with adequate amounts of fluid while standing or sitting upright to reduce the risk of esophageal injury.
Adults: The recommended dosage of oral doxycycline for the majority of susceptible infections is a single loading dose of 200 mg on the first day of treatment followed by a maintenance dosage of 100 mg once daily at the same time each day thereafter.
In severe infections a single daily dose of 200 mg may be used throughout.
Therapy should be continued for at least 24 to 48 hours after symptoms and fever have subsided. It should be noted, however, that effective antibacterial levels are usually present 24 to 36 hours following discontinuance of therapy.
When used in streptococcal infections, therapy should be continued for 10 days to prevent the development of rheumatic fever or glomerulonephritis.
For treatment of uncomplicated acute gonococcal infections, the recommended dosage is 200 mg starting and 100 mg at bedtime, the first day, followed by 100 mg b.i.d. for 3 days.
For treatment of uncomplicated urethral, endocervical, or vaginal infections in adults associated with C. trachomatis and U. urealyticum: 100 mg, by mouth, twice a day for at least 10 days.
No alteration in recommended dosage schedule need be made when treating patients with impaired renal function.
Availability And Storage: Vibra-Tabs: Each orange, film-coated tablet contains: doxycycline hyclate equivalent to doxycycline 100 mg. Nonmedicinal ingredients: microcrystalline cellulose, ethylcellulose, hydroxypropylmethylcellulose, magnesium stearate/sodium lauryl sulfate, propylene glycol, talc, titanium dioxide, FD & C Yellow #6 and aluminum hydroxide. Bottles of 100 and 250.
Vibramycin Capsules: Each blue, hard gelatin capsule contains: doxycycline hyclate equivalent to doxycycline 100 mg. Nonmedicinal ingredients: microcrystalline cellulose, magnesium stearate/ sodium lauryl sulfate; capsule shell: gelatin, sulfur dioxide, titanium dioxide and FD & C Blue #1. Bottles of 50 and 200.
Store at a temperature 15 to 30°C. Protect from light.
VIBRA-TABS Pfizer Doxycycline Hyclate Antibiotic