Vibramycin is a broad-spectrum antibiotic synthetically derived from oxytetracycline, and is available as Vibramycin Monohydrate (doxycycline monohydrate); Vibramycin Hyclate and Vibra-Tabs (doxycycline hydrochloride hemiethanolate hemihydrate); and Vibramycin Calcium (doxycycline calcium) for oral administration.

The structural formula of doxycycline monohydrate is

with a molecular formula of C₂₂H₂₄N₂O₈•H₂O and a molecular weight of 462.46. The chemical designation for doxycycline is 4-(Dimethylamino)-1,4,4a,5,5a,6,11,12a- octahydro-3,5,10,12,12a-pentahydroxy-6-methyl-1,11-dioxo-2-naphthacenecarboxamide monohydrate. The molecular formula for doxycycline hydrochloride hemiethanolate hemihydrate is (C₂₂H₂₄N₂O₈•HCl)₂•C₂H₆O•H₂O and the molecular weight is 1025.89. Doxycycline is a light-yellow crystalline powder. Doxycycline hyclate is soluble in water, while doxycycline monohydrate is very slightly soluble in water.

Doxycycline has a high degree of lipoid solubility and a low affinity for calcium binding. It is highly stable in normal human serum. Doxycycline will not degrade into an epianhydro form.

Inert ingredients in the syrup formulation are: apple flavor; butylparaben; calcium chloride; carmine; glycerin; hydrochloric acid; magnesium aluminum silicate; povidone; propylene glycol; propylparaben; raspberry flavor; simethicone emulsion; sodium hydroxide; sodium metabisulfite; sorbitol solution; water.

Inert ingredients in the capsule formulations are: hard gelatin capsules (which may contain Blue 1 and other inert ingredients); magnesium stearate; microcrystalline cellulose; sodium lauryl sulfate.

Inert ingredients for the oral suspension formulation are: carboxymethylcellulose sodium; Blue 1; methylparaben; microcrystalline cellulose; propylparaben; raspberry flavor; Red 28; simethicone emulsion; sucrose.

Inert ingredients for the tablet formulation are: ethylcellulose; hypromellose; magnesium stearate; microcrystalline cellulose; propylene glycol; sodium lauryl sulfate; talc; titanium dioxide; Yellow 6 Lake.

Last updated on RxList: 3/4/2008

To reduce the development of drug-resistant bacteria and maintain effectiveness of Vibramycin and other antibacterial drugs, Vibramycin should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

Treatment

Doxycycline is indicated for the treatment of the following infections:

• Rocky Mountain spotted fever, typhus fever and the typhus group, Q fever, rickettsialpox, and tick fevers caused by Rickettsiae.
• Respiratory tract infections caused by Mycoplasma pneumoniae.
• Lymphogranuloma venereum caused by Chlamydia trachomatis.
• Psittacosis (ornithosis) caused by Chlamydia psittaci.
• Trachoma caused by Chlamydia trachomatis, although the infectious agent is not always eliminated as judged by immunofluorescence.
• Inclusion conjunctivitis caused by Chlamydia trachomatis.
• Uncomplicated urethral, endocervical or rectal infections in adults caused by Chlamydia trachomatis.
• Nongonococcal urethritis caused by Ureaplasma urealyticum.
• Relapsing fever due to Borrelia recurrentis.

Doxycycline is also indicated for the treatment of infections caused by the following gram-negative microorganisms:

• Chancroid caused by Haemophilus ducreyi.
• Plague due to Yersinia pestis (formerly Pasteurella pestis).
• Tularemia due to Francisella tularensis (formerly Pasteurella tularensis).
• Cholera caused by Vibrio cholerae (formerly Vibrio comma).
• Campylobacter fetus infections caused by Campylobacter fetus (formerly Vibrio fetus).
• Brucellosis due to Brucella species (in conjunction with streptomycin).
• Bartonellosis due to Bartonella bacilliformis.
• Granuloma inguinale caused by Calymmatobacterium granulomatis.

Because many strains of the following groups of microorganisms have been shown to be resistant to doxycycline, 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).
• Shigellaspecies.
• Acinetobacter species (formerly Mima species and Herellea species).
• Respiratory tract infections caused by Haemophilus influenzae.
• Respiratory tract and urinary tract infections caused by Klebsiella species.

Doxycycline is indicated for treatment of infections caused by the following gram-positive microorganisms when bacteriologic testing indicates appropriate susceptibility to the drug:

• Upper respiratory infections caused by Streptococcus pneumoniae (formerly Diplococcus pneumoniae).

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 the following infections:

• Uncomplicated gonorrhea caused by Neisseria gonorrhoeae.
• Syphilis caused by Treponema pallidum.
• Yaws caused by Treponema pertenue.
• Listeriosis due to Listeria monocytogenes.
• Vincent's infection caused by Fusobacterium fusiforme.
• Actinomycosis caused by Actinomyces israelii.
• Infections caused by Clostridium species.

In acute intestinal amebiasis, doxycycline may be a useful adjunct to amebicides. In severe acne, doxycycline may be useful adjunctive therapy.

Prophylaxis

Doxycycline is indicated for the prophylaxis of malaria due to Plasmodium falciparum in short-term travelers ( < 4 months) to areas with chloroquine and/or pyrimethamine- sulfadoxine resistant strains. See DOSAGE AND ADMINISTRATION section and Information for Patients subsection of the PRECAUTIONS section.

THE USUAL DOSAGE AND FREQUENCY OF ADMINISTRATION OF DOXYCYCLINE DIFFERS FROM THAT OF THE OTHER TETRACYCLINES. EXCEEDING THE RECOMMENDED DOSAGE MAY RESULT IN AN INCREASED INCIDENCE OF SIDE EFFECTS. Adults: The usual dose of oral doxycycline is 200 mg on the first day of treatment (administered 100 mg every 12 hours) followed by a maintenance dose of 100 mg/day. The maintenance dose may be administered as a single dose or as 50 mg every 12 hours.

In the management of more severe infections (particularly chronic infections of the urinary tract), 100 mg every 12 hours is recommended.

For children above eight years of age: The recommended dosage schedule for children weighing 100 pounds or less is 2 mg/lb of body weight divided into two doses on the first day of treatment, followed by 1 mg/lb of body weight given as a single daily dose or divided into two doses, on subsequent days. For more severe infections up to 2 mg/lb of body weight may be used. For children over 100 lb the usual adult dose should be used.

The therapeutic antibacterial serum activity will usually persist for 24 hours following recommended dosage.

When used in streptococcal infections, therapy should be continued for 10 days.

Administration of adequate amounts of fluid along with capsule and tablet forms of drugs in the tetracycline class is recommended to wash down the drugs and reduce the risk of esophageal irritation and ulceration. (See ADVERSE REACTIONS.)

If gastric irritation occurs, it is recommended that doxycycline be given with food or milk. The absorption of doxycycline is not markedly influenced by simultaneous ingestion of food or milk.

Studies to date have indicated that administration of doxycycline at the usual recommended doses does not lead to excessive accumulation of the antibiotic in patients with renal impairment.

Uncomplicated gonococcal infections in adults (except anorectal infections in men): 100 mg, by mouth, twice a day for 7 days. As an alternate single visit dose, administer 300 mg stat followed in one hour by a second 300 mg dose. The dose may be administered with food, including milk or carbonated beverage, as required.

Uncomplicated urethral, endocervical, or rectal infection in adults caused by Chlamydia trachomatis: 100 mg by mouth twice a day for 7 days.

Nongonococcal urethritis (NGU) caused by C. trachomatis or U. urealyticum: 100 mg by mouth twice a day for 7 days.

Syphilis - early: Patients who are allergic to penicillin should be treated with doxycycline 100 mg by mouth twice a day for 2 weeks.

Syphilis of more than one year's duration: Patients who are allergic to penicillin should be treated with doxycycline 100 mg by mouth twice a day for 4 weeks.

Acute epididymo-orchitis caused by N. gonorrhoeae: 100 mg, by mouth, twice a day for at least 10 days.

Acute epididymo-orchitis caused by C. trachomatis: 100 mg, by mouth, twice a day for at least 10 days.

For prophylaxis of malaria: For adults, the recommended dose is 100 mg daily. For children over 8 years of age, the recommended dose is 2 mg/kg given once daily up to the adult dose. Prophylaxis should begin 1-2 days before travel to the malarious area. Prophylaxis should be continued daily during travel in the malarious area and for 4 weeks after the traveler leaves the malarious area.

Inhalational anthrax (post-exposure):

ADULTS: 100 mg of doxycycline, by mouth, twice a day for 60 days. CHILDREN: weighing less than 100 lb (45 kg); 1 mg/lb (2.2 mg/kg) of body weight, by mouth, twice a day for 60 days. Children weighing 100 lb or more should receive the adult dose.

Vibramycin Hyclate (doxycycline hyclate) is available in capsules containing doxycycline hyclate equivalent to:

50 mg doxycycline
bottles of 50 (NDC 0069-0940-50)

The capsules are white and light blue and are imprinted with "VIBRA" on one half and "PFIZER 094" on the other half.

100 mg doxycycline
bottles of 50 (NDC 0069-0950-50)

The capsules are light blue and are imprinted with "VIBRA" on one half and "PFIZER 095" on the other half.

Vibra-Tabs (doxycycline hyclate) is available in salmon colored film-coated tablets containing doxycycline hyclate equivalent to:

100 mg doxycycline
bottles of 50 (NDC 0069-0990-50)

The tablets are imprinted on one side with "VIBRA-TABS" and "PFIZER 099" on the other side.

Vibramycin Calcium Syrup (doxycycline calcium) oral suspension is available as a raspberry-apple flavored oral suspension. Each teaspoonful (5 mL) contains doxycycline calcium equivalent to 50 mg of doxycycline: 1 pint (473 mL) bottles (NDC 0069-0971-93).

Vibramycin Monohydrate (doxycycline monohydrate) for Oral Suspension is available as a raspberry-flavored, dry powder for oral suspension. When reconstituted, each teaspoonful (5 mL) contains doxycycline monohydrate equivalent to 25 mg of doxycycline: 2 oz (60 mL) bottles (NDC 0069-0970-65).

All products are to be stored below 86°F (30°C) and dispensed in tight, light-resistant containers (USP).

Pfizer Labs, Division of Pfizer Inc, NY, NY 10017. April 2007. FDA Rev date: 2/6/2008

Last updated on RxList: 3/4/2008

Due to oral doxycycline's virtually complete absorption, side effects of the lower bowel, particularly diarrhea, have been infrequent. The following adverse reactions have been observed in patients receiving tetracyclines:

Gastrointestinal: anorexia, nausea, vomiting, diarrhea, glossitis, dysphagia, enterocolitis, and inflammatory lesions (with monilial overgrowth) in the anogenital region. Hepatotoxicity has been reported rarely. These reactions have been caused by both the oral and parenteral administration of tetracyclines. Rare instances of esophagitis and esophageal ulcerations have been reported in patients receiving capsule and tablet forms of the drugs in the tetracycline class. Most of these patients took medications immediately before going to bed. (See DOSAGE AND ADMINISTRATION.)

Skin: maculopapular and erythematous rashes. Exfoliative dermatitis has been reported but is uncommon. Photosensitivity is discussed above. (See WARNINGS.)

Renal toxicity: Rise in BUN has been reported and is apparently dose related. (See WARNINGS.)

Hypersensitivity reactions: urticaria, angioneurotic edema, anaphylaxis, anaphylactoid purpura, serum sickness, pericarditis, and exacerbation of systemic lupus erythematosus.

Blood: Hemolytic anemia, thrombocytopenia, neutropenia, and eosinophilia have been reported.

Other: bulging fontanels in infants and intracranial hypertension in adults. (See PRECAUTIONS - General.)

When given over prolonged periods, tetracyclines have been reported to produce brown-black microscopic discoloration of the thyroid gland. No abnormalities of thyroid function studies are known to occur.

Because tetracyclines have been shown to depress plasma prothrombin activity, patients who are on anticoagulant therapy may require downward adjustment of their anticoagulant dosage.

Since bacteriostatic drugs may interfere with the bactericidal action of penicillin, it is advisable to avoid giving tetracyclines in conjunction with penicillin.

Absorption of tetracyclines is impaired by antacids containing aluminum, calcium, or magnesium, and iron-containing preparations.

Absorption of tetracyclines is impaired by bismuth subsalicylate.

Barbiturates, carbamazepine, and phenytoin decrease the half-life of doxycycline.

The concurrent use of tetracycline and Penthrane® (methoxyflurane) has been reported to result in fatal renal toxicity.

Concurrent use of tetracycline may render oral contraceptives less effective.

Drug/Laboratory Test Interactions

False elevations of urinary catecholamine levels may occur due to interference with the fluorescence test.

Last updated on RxList: 3/4/2008

THE USE OF DRUGS OF THE TETRACYCLINE CLASS DURING TOOTH DEVELOPMENT (LAST HALF OF PREGNANCY, INFANCY AND CHILDHOOD TO THE AGE OF 8 YEARS) MAY CAUSE PERMANENT DISCOLORATION OF THE TEETH (YELLOW-GRAY-BROWN). This adverse reaction is more common during long-term use of the drugs, but it has been observed following repeated short-term courses. Enamel hypoplasia has also been reported. TETRACYCLINE DRUGS, THEREFORE, SHOULD NOT BE USED IN THIS AGE GROUP, EXCEPT FOR ANTHRAX, INCLUDING INHALATIONAL ANTHRAX (POST-EXPOSURE), UNLESS OTHER DRUGS ARE NOT LIKELY TO BE EFFECTIVE OR ARE CONTRAINDICATED.

Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including VIBRAMYCIN, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.

C. difficile 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.

All tetracyclines form a stable calcium complex in any bone-forming tissue. A decrease in 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.

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. If any tetracycline is used during pregnancy or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to the fetus.

The antianabolic 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.

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.

Vibramycin Syrup contains sodium metabisulfite, a sulfite that may cause allergic-type reactions, including anaphylactic symptoms and life-threatening or less severe asthmatic episodes in certain susceptible people. The overall prevalence of sulfite sensitivity in the general population is unknown and probably low. Sulfite sensitivity is seen more frequently in asthmatic than in non-asthmatic people.

General

As with other antibiotic preparations, use of this drug may result in overgrowth of nonsusceptible organisms, including fungi. If superinfection occurs, the antibiotic should be discontinued and appropriate therapy instituted.

Bulging fontanels in infants and benign intracranial hypertension in adults have been reported in individuals receiving tetracyclines. These conditions disappeared when the drug was discontinued.

Incision and drainage or other surgical procedures should be performed in conjunction with antibiotic therapy, when indicated.

Doxycycline offers substantial but not complete suppression of the asexual blood stages of Plasmodium strains.

Doxycycline does not suppress P. falciparum's sexual blood stage gametocytes. Subjects completing this prophylactic regimen may still transmit the infection to mosquitoes outside endemic areas.

Prescribing Vibramycin in the absence of proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

Laboratory Tests

In venereal disease, when co-existent syphilis is suspected, dark field examinations should be done before treatment is started and the blood serology repeated monthly for at least 4 months.

In long-term therapy, periodic laboratory evaluation of organ systems, including hematopoietic, renal, and hepatic studies, should be performed.

Carcinogenesis, Mutagenesis, Impairment Of Fertility

Long-term studies in animals to evaluate carcinogenic potential of doxycycline have not been conducted. However, there has been evidence of oncogenic activity in rats in studies with the related antibiotics, oxytetracycline (adrenal and pituitary tumors), and minocycline (thyroid tumors).

Likewise, although mutagenicity studies of doxycycline have not been conducted, positive results in in vitro mammalian cell assays have been reported for related antibiotics (tetracycline, oxytetracycline).

Doxycycline administered orally at dosage levels as high as 250 mg/kg/day had no apparent effect on the fertility of female rats. Effect on male fertility has not been studied.

Pregnancy: Teratogenic Effects. Pregnancy Category D:

There are no adequate and well-controlled studies on the use of doxycycline in pregnant women. The vast majority of reported experience with doxycycline during human pregnancy is short-term, first trimester exposure. There are no human data available to assess the effects of long-term therapy of doxycycline in pregnant women such as that proposed for treatment of anthrax exposure. An expert review of published data on experiences with doxycycline use during pregnancy by TERIS - the Teratogen Information System - concluded that therapeutic doses during pregnancy are unlikely to pose a substantial teratogenic risk (the quantity and quality of data were assessed as limited to fair), but the data are insufficient to state that there is no risk^a. A case-control study (18,515 mothers of infants with congenital anomalies and 32,804 mothers of infants with no congenital anomalies) shows a weak but marginally statistically significant association with total malformations and use of doxycycline anytime during pregnancy. Sixty-three (0.19%) of the controls and fifty-six (0.30%) of the cases were treated with doxycycline. This association was not seen when the analysis was confined to maternal treatment during the period of organogenesis (i.e., in the second and third months of gestation) with the exception of a marginal relationship with neural tube defect based on only two exposed cases^b.

A small prospective study of 81 pregnancies describes 43 pregnant women treated for 10 days with doxycycline during early first trimester. All mothers reported their exposed infants were normal at 1 year of age^c.

Nonteratogenic Effects: (See WARNINGS).

Labor and Delivery

The effect of tetracyclines on labor and delivery is unknown.

Nursing Mothers

Tetracyclines are excreted in human milk; however, the extent of absorption of tetracyclines, including doxycycline, by the breastfed infant is not known. Short-term use by lactating women is not necessarily contraindicated; however, the effects of prolonged exposure to doxycycline in breast milk are unknownd. Because of the potential for serious adverse reactions in nursing infants from doxycycline, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother. (See WARNINGS.)

Pediatric Use

See WARNINGS and DOSAGE AND ADMINISTRATION.

REFERENCES

3.   ^aFriedman JM and Polifka JE. Teratogenic Effects of Drugs. A Resource for Clinicians (TERIS). Baltimore, MD: The Johns Hopkins University Press, 2000: 149- 195.
      ^bCziezel AE and Rockenbauer M. Teratogenic study of doxycycline. Obstet Gynecol 1997; 89: 524-528.
      ^cHorne HW Jr and Kundsin RB. The role of mycoplasma among 81 consecutive pregnancies: a prospective study. Int J Fertil 1980; 25: 315-317.
      dHale T. Medications and Mothers Milk. 9th edition. Amarillo, TX: Pharmasoft Publishing, 2000: 225-226.

Last updated on RxList: 3/4/2008

In case of overdosage, discontinue medication, treat symptomatically and institute supportive measures. Dialysis does not alter serum half-life and thus would not be of benefit in treating cases of overdosage.

This drug is contraindicated in persons who have shown hypersensitivity to any of the tetracyclines.

Last updated on RxList: 3/4/2008

Tetracyclines are readily absorbed and are bound to plasma proteins in varying degree. They are concentrated by the liver in the bile, and excreted in the urine and feces at high concentrations and in a biologically active form. Doxycycline is virtually completely absorbed after oral administration.

Following a 200 mg dose, normal adult volunteers averaged peak serum levels of 2.6 mcg/mL of doxycycline at 2 hours decreasing to 1.45 mcg/mL at 24 hours. Excretion of doxycycline by the kidney is about 40%/72 hours in individuals with normal function (creatinine clearance about 75 mL/min.). This percentage excretion may fall as low as 1-5%/72 hours in individuals with severe renal insufficiency (creatinine clearance below 10 mL/min.). Studies have shown no significant difference in serum half-life of doxycycline (range 18-22 hours) in individuals with normal and severely impaired renal function.

Hemodialysis does not alter serum half-life.

Results of animal studies indicate that tetracyclines cross the placenta and are found in fetal tissues.

Microbiology

The tetracyclines are primarily bacteriostatic and are thought to exert their antimicrobial effect by the inhibition of protein synthesis. The tetracyclines, including doxycycline, have a similar antimicrobial spectrum of activity against a wide range of gram-positive and gram-negative organisms. Cross-resistance of these organisms to tetracyclines is common.

Gram-Negative Bacteria

• Neisseria gonorrhoeae
• Calymmatobacterium granulomatis
• Haemophilus ducreyi
• Haemophilus influenzae
• Yersinia pestis (formerly Pasteurella pestis)
• Francisella tularensis (formerly Pasteurella tularensis)
• Vibrio cholerae (formerly Vibrio comma)
• Bartonella bacilliformis
• Brucella species

Because many strains of the following groups of gram-negative microorganisms have been shown to be resistant to tetracyclines, culture and susceptibility testing are recommended:

• Escherichia coli
• Klebsiella species
• Enterobacter aerogenes
• Shigella species
• Acinetobacter species (formerly Mima species and Herellea species)
• Bacteroides species

Gram-Positive Bacteria

Because many strains of the following groups of gram-positive microorganisms have been shown to be resistant to tetracycline, culture and susceptibility testing are recommended. Up to 44 percent of strains of Streptococcus pyogenes and 74 percent of Streptococcus faecalis have been found to be resistant to tetracycline drugs. Therefore, tetracycline should not be used for streptococcal disease unless the organism has been demonstrated to be susceptible.

• Streptococcus pyogenes
• Streptococcus pneumoniae
• Enterococcus group (Streptococcus faecalis and Streptococcus faecium)
• Alpha-hemolytic streptococci (viridans group)

Other Microorganisms

• Rickettsiae
• Chlamydia psittaci
• Chlamydia trachomatis
• Mycoplasma pneumoniae
• Ureaplasma urealyticum
• Borrelia recurrentis
• Treponema pallidum
• Treponema pertenue
• Clostridium species
• Fusobacterium fusiforme
• Actinomyces species
• Bacillus anthracis
• Propionibacterium acnes
• Entamoeba species
• Balantidium coli
• 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 tests: Diffusion techniques: Quantitative methods that require measurement of zone diameters give the most precise estimate of the susceptibility of bacteria to antimicrobial agents. One such standard procedure¹ which has been recommended for use with disks to test susceptibility of organisms to doxycycline uses the 30-mcg tetracycline-class disk or the 30-mcg doxycycline disk. Interpretation involves the correlation of the diameter obtained in the disk test with the minimum inhibitory concentration (MIC) for tetracycline or doxycycline, respectively.

Reports from the laboratory giving results of the standard single-disk susceptibility test with a 30-mcg tetracycline-class disk or the 30-mcg doxycycline disk should be interpreted according to the following criteria:

Zone Diameter (mm)		Interpretation
tetracycline	doxycycline
≥ 19	≥ 16	Susceptible
15-18	13-15	Intermediate
≤ 14	≤ 12	Resistant

A report of "Susceptible" indicates that the pathogen is likely to be inhibited by generally achievable blood levels. A report of "Intermediate" suggests that the organism would be susceptible if a high dosage is used or if the infection is confined to tissues and fluids in which high antimicrobial levels are attained. A report of "Resistant" indicates that achievable concentrations are unlikely to be inhibitory, and other therapy should be selected.

Standardized procedures require the use of laboratory control organisms. The 30-mcg tetracycline-class disk or the 30-mcg doxycycline disk should give the following zone diameters:

Organism	Zone Diameter (mm)
	tetracycline	doxycycline
E. coli ATCC 25922	18-25	18-24
S. aureus ATCC 25923	19-28	23-29

Dilution techniques: Use a standardized dilution method² (broth, agar, microdilution) or equivalent with tetracycline powder. The MIC values obtained should be interpreted according to the following criteria:

MIC (mcg/mL)	Interpretation
≤ 4	Susceptible
8	Intermediate
≥ 16	Resistant

As with standard diffusion techniques, dilution methods require the use of laboratory control organisms. Standard tetracycline powder should provide the following MIC values:

Organism	MIC (mcg/mL)
E. coli ATCC 25922	1.0-4.0
S. aureus ATCC 29213	0.25-1.0
E. faecalis ATCC 29212	8-32
P. aeruginosa ATCC 27853	8-32

Animal Pharmacology And Animal Toxicology

Hyperpigmentation of the thyroid has been produced by members of the tetracycline class in the following species: in rats by oxytetracycline, doxycycline, tetracycline PO4, and methacycline; in minipigs by doxycycline, minocycline, tetracycline PO4, and methacycline; in dogs by doxycycline and minocycline; in monkeys by minocycline.

Minocycline, tetracycline PO4, methacycline, doxycycline, tetracycline base, oxytetracycline HCl, and tetracycline HCl were goitrogenic in rats fed a low iodine diet. This goitrogenic effect was accompanied by high radioactive iodine uptake. Administration of minocycline also produced a large goiter with high radioiodine uptake in rats fed a relatively high iodine diet.

Treatment of various animal species with this class of drugs has also resulted in the induction of thyroid hyperplasia in the following: in rats and dogs (minocycline); in chickens (chlortetracycline); and in rats and mice (oxytetracycline). Adrenal gland hyperplasia has been observed in goats and rats treated with oxytetracycline.

REFERENCES

1.   National Committee for Clinical Laboratory Standards, Performance Standards for Antimicrobial Disk Susceptibility Tests, Fourth Edition. Approved Standard NCCLS Document M2-A4, Vol. 10, No. 7 NCCLS, Villanova, PA, April 1990.

2.   National Committee for Clinical Laboratory Standards, Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically, Second Edition. Approved Standard NCCLS Document M7-A2, Vol. 10, No. 8 NCCLS, Villanova, PA, April 1990.

3.   ^aFriedman JM and Polifka JE. Teratogenic Effects of Drugs. A Resource for Clinicians (TERIS). Baltimore, MD: The Johns Hopkins University Press, 2000: 149- 195.
      ^bCziezel AE and Rockenbauer M. Teratogenic study of doxycycline. Obstet Gynecol 1997; 89: 524-528.
      ^cHorne HW Jr and Kundsin RB. The role of mycoplasma among 81 consecutive pregnancies: a prospective study. Int J Fertil 1980; 25: 315-317.
      dHale T. Medications and Mothers Milk. 9th edition. Amarillo, TX: Pharmasoft Publishing, 2000: 225-226.

Last updated on RxList: 3/4/2008

Patients taking doxycycline for malaria prophylaxis should be advised:

-that no present-day antimalarial agent, including doxycycline, guarantees protection against malaria.

-to avoid being bitten by mosquitoes by using personal protective measures that help avoid contact with mosquitoes, especially from dusk to dawn (e.g., staying in well- screened areas, using mosquito nets, covering the body with clothing, and using an effective insect repellent).

-that doxycycline prophylaxis:

-should begin 1-2 days before travel to the malarious area,

-should be continued daily while in the malarious area and after leaving the malarious area,

-should be continued for 4 further weeks to avoid development of malaria after returning from an endemic area,

-should not exceed 4 months.

All patients taking doxycycline should be advised:

-to avoid excessive sunlight or artificial ultraviolet light while receiving doxycycline and to discontinue therapy if phototoxicity (e.g., skin eruption, etc.) occurs.

Sunscreen or sunblock should be considered (See WARNINGS.)

-to drink fluids liberally along with doxycycline to reduce the risk of esophageal

irritation and ulceration. (See ADVERSE REACTIONS.)

-that the absorption of tetracyclines is reduced when taken with foods, especially those which contain calcium. However, the absorption of doxycycline is not markedly influenced by simultaneous ingestion of food or milk. (See DRUG INTERACTIONS.)

-that the absorption of tetracyclines is reduced when taking bismuth subsalicylate (See DRUG INTERACTIONS.)

-that the use of doxycycline might increase the incidence of vaginal candidiasis.

Patients should be counseled that antibacterial drugs including Vibramycin should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When Vibramycin is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by Vibramycin or other antibacterial drugs in the future.

Diarrhea is a common problem caused by antibiotics which usually ends when the antibiotic is discontinued. Sometimes after starting treatment with antibiotics, 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 antibiotic. If this occurs, patients should contact their physician as soon as possible.

Last updated on RxList: 3/4/2008

IMPORTANT NOTE: This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your health care professional. Always seek the advice of your health care professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your health care professional. This information does not contain any assurances that this product is safe, effective, or appropriate for you.

DOXYCYCLINE - ORAL

(dox-ee-SYE-kleen)

COMMON BRAND NAME(S): Vibra-Tabs, Vibramycin

USES: This medication is used to treat a wide variety of bacterial infections, including those that cause acne. This medication is known as a tetracycline antibiotic. It works by stopping the growth of bacteria.

This medication is also used to prevent malaria.

This antibiotic treats only bacterial infections. It will not work for viral infections (e.g., common cold, flu). Unnecessary use or overuse of any antibiotic can lead to its decreased effectiveness.

OTHER USES: This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used to treat a certain skin condition (rosacea).

HOW TO USE: Take this medication by mouth as directed. Doxycycline is best taken on an empty stomach with a full glass of water (8 ounces or 240 milliliters), 1 hour before or 2 hours after meals. Some manufacturers state it can be taken with food or milk if you develop an upset stomach, however doxycycline might be less effective if taken with food or milk (or other products high in calcium). Do not lie down for 30 minutes after taking this medication.

If you are taking the delayed-release capsules, swallow them whole. Do not crush or chew the capsules. If you have difficulty swallowing the capsule, the capsule may be opened and the contents sprinkled onto cool applesauce and taken immediately as directed. Do not prepare a supply in advance. Do not chew the food/medication mixture because doing so may cause the drug to be released too quickly, increasing side effects. Drink a glass of cool water after each dose to ensure complete swallowing of the medication.

The liquid suspension form of this medicine must be shaken well before using. For liquid products, use a medication measuring device to carefully measure the prescribed dose. Do not use a household spoon because you may not get the correct dose.

Take this medication 2-3 hours before or after taking any medications containing magnesium, aluminum, calcium, iron, or zinc. Some examples include quinapril, certain forms of didanosine (chewable/dispersible buffered tablets or pediatric oral solution), vitamins/minerals, antacids, sucralfate, and bismuth subsalicylate. These medications react with doxycycline, preventing its full absorption into your bloodstream.

The dosage is based on your medical condition and response to therapy.

Antibiotics work best when the amount of medicine in your body is kept at a constant level. Therefore, take this drug at evenly spaced intervals throughout the day and night.

Continue to take this medication until the full prescribed amount is finished, even if symptoms disappear after a few days. Stopping the medication too early may allow bacteria to continue to grow, which may result in a relapse of the infection.

Inform your doctor if your condition persists or worsens over the next two weeks.

When using to prevent malaria, this medication is usually taken once daily. Take the first dose of this medication 1-2 days before travel to an area where you may be exposed to malaria, or take as directed by your doctor. Continue to take this medication daily while in the malarial area. Upon returning home you should keep taking this medication for 4 more weeks. If you are unable to finish this course of doxycycline, contact your doctor.

If this medication is being used to prevent malaria, it is important to understand that it is still possible to get the disease even if you have used this medication. Tell your doctor immediately if you develop a fever. It is best to start treating malaria early.

SIDE EFFECTS: Stomach upset, mild diarrhea, nausea, headache, or vomiting may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: stomach pain, yellowing of the eyes/skin, vision changes, mental/mood changes.

Doxycycline may make you more sensitive to sunlight (photosensitive) while you are taking it and for 1-2 days after you finish it. Avoid prolonged/direct sun exposure, tanning booths, and sunlamps during this time. Use sunscreen and wear protective clothing if you must be out in the sun. Symptoms of photosensitivity include sunburn that is much quicker/more severe than usual and tingling of the hands/feet/nose.

This medication may rarely cause a severe intestinal condition (pseudomembranous colitis) due to a type of resistant bacteria. This condition may occur during treatment or weeks to months after treatment has stopped. Do not use anti-diarrhea products or narcotic pain medications if you have any of the following symptoms because these products may make them worse. Tell your doctor immediately if you develop: persistent diarrhea, abdominal or stomach pain/cramping, blood/mucus in your stool.

Use of this medication for prolonged or repeated periods may result in oral thrush or a new vaginal yeast infection (oral or vaginal fungal infection). Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms.

A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: rash, itching, swelling, severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

Contact your doctor for medical advice about side effects. The following numbers do not provide medical advice, but in the US you may report side effects to the Food and Drug Administration (FDA) at 1-800-FDA-1088. In Canada, you may call Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking doxycycline, tell your doctor or pharmacist if you are allergic to it; or to any other tetracycline; or if you have any other allergies.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: liver problems, kidney problems, trouble swallowing, esophagus problems (e.g., hiatal hernia, GERD).

Before having surgery, tell your doctor or dentist that you are taking this medication.

This drug should not be used by children under 8 because treatment may lead to permanently discolored teeth or other problems. Caution is also advised in older children for similar reasons. Consult your doctor or pharmacist for more details.

This drug is not recommended for use during pregnancy. Consult your doctor before using this medication.

This drug passes into breast milk and has had undesirable effects on nursing infants. Therefore, taking this medication while breast-feeding is not recommended. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Your healthcare professionals (e.g., doctor or pharmacist) may already be aware of any possible drug interactions and may be monitoring you for it. Do not start, stop or change the dosage of any medicine before checking with them first.

This drug should not be used with the following medications because very serious interactions may occur: strontium, acitretin, tretinoin taken by mouth.

If you are currently using either of these medications listed above, tell your doctor or pharmacist before starting doxycycline.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: anti-seizure medications (e.g., carbamazepine, phenytoin), barbiturates (e.g., phenobarbital), digoxin, isotretinoin, other antibiotics, warfarin, live bacterial vaccines.

This medicine may decrease the effectiveness of birth control pills. This can result in pregnancy. You may need to use additional form(s) of reliable birth control while using this medication. Consult your doctor or pharmacist for details.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

OVERDOSE: If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US national poison hotline at 1-800-222-1222. Canadian residents should call their local poison control center directly.

NOTES: Do not share this medication with others.

It is important to avoid being bitten by mosquitoes when trying to prevent malaria. Avoid contact with mosquitoes, especially from dusk to dawn, by staying in well-screened areas, wearing protective clothing, and using insect repellent and bed nets.

This medication has been prescribed for your current condition only. Do not use it later for another infection unless told to do so by your doctor. A different medication may be necessary in those cases.

MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

STORAGE: Store at room temperature away from light and moisture. Different brands/strengths of this medication may have different storage requirements. Read the package labeling or ask your pharmacist for the storage requirements for the product you are using. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

Information last revised July 2008 Copyright(c) 2008 First DataBank, Inc.