Indications and Usage

To reduce the development of drug-resistant bacteria and maintain effectiveness of doxycycline and other antibacterial drugs, doxycycline 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.

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 Chlamydophila 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.

Tularemia due to Francisella tularensis.

Cholera caused by Vibrio cholerae.

Campylobacter fetus infections caused by Campylobacter 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

Shigella species

Acinetobacter 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.

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.

Dosage and Administration

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 or 50 mg every 6 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 Pediatric Patients above Eight Years of Age

The recommended dosage schedule for pediatric patients 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 pediatric patients over 100 pounds the usual adult dose should be used.

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.

Acute Epididymo-orchitis Caused by N. gonorrhoeae

100 mg, by mouth, twice a day for at least 10 days.

Primary and Secondary Syphilis

300 mg a day in divided doses for at least 10 days.

Uncomplicated Urethral, Endocervical, or Rectal Infection in Adults Caused by Chlamydia trachomatis

100 mg, by mouth, twice a day for at least 7 days.

Nongonococcal Urethritis Caused by C. trachomatis and U. urealyticum

100 mg, by mouth, twice a day for at least 7 days.

Acute Epididymo-orchitis Caused by C. trachomatis

100 mg, by mouth, twice a day for at least 10 days.

Inhalational Anthrax (Post-Exposure)

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

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, doxycycline may be given with food. Ingestion of a high fat meal has been shown to delay the time to peak plasma concentrations by an average of one hour and 20 minutes. However, in the same study, food enhanced the average peak concentration by 7.5% and the area under the curve by 5.7%.

Contraindications

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

Adverse Reactions

Due to oral doxycycline's virtually complete absorption, side effects to 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. 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 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, Stevens-Johnson syndrome, toxic epidermal necrolysis, and erythema multiforme have been reported. 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 with tetracyclines.

Other

Intracranial hypertension (IH, pseudotumor cerebri) has been associated with the use of tetracyclines. (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 are known to occur.

Overdosage

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

Description

Doxycycline is a broad-spectrum antibacterial synthetically derived from oxytetracycline. Doxycycline Capsules USP, 100 mg, 75 mg, and 50 mg capsules contain doxycycline monohydrate equivalent to 100 mg, 75 mg, or 50 mg of doxycycline for oral administration. The chemical designation of the light-yellow crystalline powder is alpha-6-deoxy-5-oxytetracycline.

Structural formula:

Doxycycline has a high degree of lipid 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: colloidal silicon dioxide, magnesium stearate, microcrystalline cellulose and sodium starch glycolate. Hard gelatin capsule contains black iron oxide, gelatin, red iron oxide, titanium dioxide and yellow iron oxide. The capsules are printed with edible ink containing black iron oxide, potassium hydroxide, propylene glycol, shellac and titanium dioxide.

Doxycycline Monohydrate

Clinical Pharmacology

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

Following a 200 mg dose of doxycycline monohydrate, 24 normal adult volunteers averaged the following serum concentration values:

Time (hr):	0.5	1.0	1.5	2.0	3.0	4.0	8.0	12.0	24.0	48.0	72.0
Conc.	1.02	2.26	2.67	3.01	3.16	3.03	2.03	1.62	0.95	0.37	0.15 (mcg/mL)

Average Observed Values
Maximum Concentration	3.61 mcg/mL (± 0.9 sd)
Time of Maximum Concentration	2.60 hr (± 1.10 sd)
Elimination Rate Constant	0.049 per hr (± 0.030 sd)
Half-Life	16.33 hr (± 4.53 sd)

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 to 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 to 22 hours) in individuals with normal and severely impaired renal function.

Hemodialysis does not alter serum half-life.

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. Cross resistance with other tetracyclines is common.

Doxycycline has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section of the package insert.

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

Vibrio fetus

Yersinia pestis

Gram-Positive Bacteria

Bacillus anthracis

Streptococcus pneumoniae

Anaerobes

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 Methods

When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antimicrobial drugs used in resident hospitals to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting the most effective antimicrobial.

Dilution techniques

Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized test method (broth and/or agar).^1,2,4,6,7The MIC values should be interpreted according to criteria provided in Table 1.

Diffusion techniques

Quantitative methods that require measurement of zone diameters can also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The zone size provides an estimate of the susceptibility of bacteria to antimicrobial compounds. The zone size should be determined using a standard test method.^1,3,4 This procedure uses paper disks impregnated with 30 mcg doxycycline to test the susceptibility of bacteria to doxycycline. The disk diffusion interpretive criteria are provided in Table 1.

Anaerobic Techniques

For anaerobic bacteria, the susceptibility to doxycycline can be determined by a standardized test method.⁵ The MIC values obtained should be interpreted according to the criteria provided in Table 1.

Table 1: Susceptibility Test Interpretive Criteria for Doxycycline and Tetracycline
Bacteria Organisms susceptible to tetracycline are also considered susceptible to doxycycline. However, some organisms that are intermediate or resistant to tetracycline may be susceptible to doxycycline.	Minimal Inhibitory Concentration (mcg/mL)			Zone Diameter (mm)			Agar Dilution (mcg/mL)
S	I	R	S	I	R	S	I	R
Acinetobacter spp.
Doxycycline	≤4	8	≥16	≥13	10 to 12	≤9	-	-	-
Tetracycline	≤4	8	≥16	≥15	12 to 14	≤11	-	-	-
Anaerobes
Tetracycline	-	-	-	-	-	-	≤4	8	≥16
Bacillus anthracis The current absence of resistance isolates precludes defining any results other than “Susceptible”. If isolates yielding MIC results other than susceptible, they should be submitted to a reference laboratory for further testing.
Doxycycline	≤1	-	-	-	-	-	-	-	-
Tetracycline	≤1	-	-	-	-	-	-	-	-
Brucella species
Doxycycline	≤1	-	-	-	-	-	-	-	-
Tetracycline	≤1	-	-	-	-	-	-	-	-
Enterobacteriaceae
Doxycycline	≤4	8	≥16	≥14	11 to 13	≤10	-	-	-
Tetracycline	≤4	8	≥16	≥15	12 to 14	≤11	-	-	-
Franciscella tularensis
Doxycycline	≤4	-	-	-	-	-	-	-	-
Tetracycline	≤4	-	-	-	-	-	-	-	-
Haemophilus influenzae
Tetracycline	≤2	4	≥8	≥29	26 to 28	≤25	-	-	-
Mycoplasma pneumoniae
Tetracycline	-	-	-	-	-	-	≤2	-	-
Neisseria gonorrhoeae Gonococci with 30 mcg tetracycline disk zone diameters of <19 mm usually indicate a plasmid-mediated tetracycline resistant Neisseria gonorrhoeae isolate. Resistance in these strains should be confirmed by a dilution test (MIC ≥ 16 mcg/mL).
Tetracycline	-	-	-	≥38	31 to 37	≤30	≤0.25	0.5 to 1	≥2
Norcardiae and other aerobic Actinomyces species
Doxycycline	≤1	2 to 4	≥8	-	-	-	-	-	-
Streptococcus pneumoniae
Doxycycline	≤ 0.25	0.5	> 1	> 28	25 to 27	< 24	-	-	-
Tetracycline	<1	2	> 4	> 28	25 to 27	< 24	-	-	-
Vibrio cholerae
Doxycycline	≤4	8	≥16	-	-	-	-	-	-
Tetracycline	≤4	8	≥16	-	-	-	-	-	-
Yersinia pestis
Doxycycline	≤4	8	≥16	-	-	-	-	-	-
Tetracycline	≤4	8	≥16	-	-	-	-	-	-
Ureaplasma urealyticum
Tetracycline	-	-	-	-	-	-	≤1	-	≥2

A report of Susceptible (S) indicates that the antimicrobial is likely to inhibit growth of the pathogen if the antimicrobial compound reaches the concentrations at the infection site necessary to inhibit growth of the pathogen. A report of Intermediate (I) indicates that the result should be considered equivocal, and, if the bacteria is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug product is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone that prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of Resistant (R) indicates that the pathogen is not likely to inhibit growth of the pathogen if the antimicrobial compound reaches the concentrations usually achievable at the infection site; other therapy should be selected.

Quality Control

Standardized susceptibility test procedures require the use of laboratory controls to monitor and ensure the accuracy and precision of supplies and reagents used in the assay, and the techniques of the individuals performing the test.^{1,2,3,4,5,6,7} Standard doxycycline and tetracycline powders should provide the following range of MIC values noted in Table 2. For the diffusion technique using the 30 mcg doxycycline disk the criteria in Table 2 should be achieved.

Table 2: Acceptable Quality Control Ranges for Susceptibility Testing for Doxycycline and Tetracycline
QC Strain	Minimal Inhibitory Concentration (mcg/mL)	Zone Diameter (mm)	Agar Dilution (mcg/mL)
Enterococcus faecalis ATCC 29212
Doxycycline	2 to 8	-	-
Tetracycline	8 to 32	-	-
Escherichia coli ATCC 25922
Doxycycline	0.5 to 2	18 to 24	-
Tetracycline	0.5 to 2	18 to 25	-
Eggerthella lenta ATCC 43055
Doxycycline	2 to 16	-	-
Haemophilus influenzae ATCC 49247
Tetracycline	4 to 32	14 to 22	-
Neisseria gonorrhoeae ATCC 49226
Tetracycline	-	30 to 42	0.25 to 1
Staphylococcus aureus ATCC 25923
Doxycycline	-	23 to 29	-
Tetracycline	-	24 to 30	-
Staphylococcus aureus ATCC 29213
Doxycycline	0.12 to 0.5	-	-
Tetracycline	0.12 to 1	-	-
Streptococcus pneumoniae ATCC 49619
Doxycycline	0.015 to 0.12	25 to 34	-
Tetracycline	0.06 to 0.5	27 to 31	-
Bacteroides fragilis ATCC 25285
Tetracycline	-	-	0.12 to 0.5
Bacteroides thetaiotaomicron ATCC 29741
Doxycycline	2 to 8	-	-
Tetracycline	-	-	8 to 32
Mycoplasma pneumoniae ATCC 29342
Tetracycline	0.06 to 0.5	-	0.06 to 0.5
Ureaplasma urealyticum ATCC 33175
Tetracycline	-	-	≥ 8

How Supplied / Storage and Handling

Doxycycline capsules USP, 100 mg are brown opaque cap and yellow opaque body imprinted with "LU" on cap in white ink and "M73" on the body in black ink filled with light yellow to grey colored blend.

Each capsule contains doxycycline monohydrate USP equivalent to 100 mg doxycycline.

Doxycycline capsules USP, 100 mg is available in:

Bottle of 2 capsules NDC 63187-672-02

Bottle of 6 capsules NDC 63187-672-06

Bottle of 10 capsules NDC 63187-672-10

Bottle of 14 capsules NDC 63187-672-14

Bottle of 20 capsules NDC 63187-672-20

Bottle of 30 capsules NDC 63187-672-30

Bottle of 40 capsules NDC 63187-672-40

Store at 25°C (77°F); excursions permitted to 15 to 30°C (59 to 86°F) [see USP controlled room temperature]. Protect from light.

Dispense in a tight, light-resistant container as defined in the USP/NF.

Professional Information — DOXYCYCLINE