Reconstitution and Administration
Doxycycline calcium, doxycycline hyclate, and doxycycline monohydrate are administered orally. When oral therapy is not feasible, doxycycline hyclate may be administered by slow IV infusion; however, oral therapy should replace IV therapy as soon as possible. If doxycycline is given IV, the risk of thrombophlebitis should be considered.
Oral Administration
To reduce the risk of esophageal irritation and ulceration, capsules or tablets containing doxycycline hyclate and capsules containing doxycycline monohydrate should be administered with adequate amounts of fluid and probably should not be given at bedtime or to patients with esophageal obstruction or compression. It has been suggested that individuals receiving doxycycline for prevention of malaria can take the drug in the evening (but not at bedtime) to minimize the risk of doxycycline-induced photosensitivity.
If gastric irritation occurs, doxycycline can be taken with food or milk, since such administration usually does not result in clinically important reductions in GI absorption of the drug. If necessary, doxycycline tablets can be ground and mixed with food or drinks.
Results of a limited study in adults indicate that ground doxycycline tablets are most palatable when mixed with chocolate pudding, regular or low-fat chocolate milk, simple syrup with sour apple flavor, apple juice with table sugar, or low-fat milk; the bitterness of the drug is not masked with grape or strawberry jellies or cherry yogurt.
IV Infusion
Doxycycline hyclate powder for IV administration is reconstituted by adding 10 or 20 mL of sterile water for injection or other compatible IV infusion solution to the vials labeled as containing 100 or 200 mg of doxycycline, respectively; resultant solutions contain 10 mg of doxycycline per mL. Each 100 mg of the drug must be further diluted prior to administration with 100 mL to 1 liter of compatible IV infusion fluid to provide solutions containing approximately 0.1-1 mg of doxycycline per mL. IV solutions should not be given IM or subcutaneously, and extravasation should be avoided. Depending on the dose, IV infusions of doxycycline hyclate usually are given over 1-4 hours. The manufacturer states that 1 hour is the minimum recommended time for infusion of 100 mg of doxycycline in a solution containing 0.5 mg of the drug per mL.
Dosage
Dosage of doxycycline calcium, doxycycline hyclate, and doxycycline monohydrate is expressed in terms of doxycycline.
For dosage of doxycycline in the treatment of specific infections, consult the appropriate sections that follow. The usual dosage of doxycycline, as described in this general dosage section, is used when the drug is indicated in infections not specified in the following sections. The usual oral dosage of doxycycline for adults and children older than 8 years of age weighing more than 45 kg is 100 mg every 12 hours on the first day of treatment followed by 100 mg daily given in 1 or 2 divided doses
For severe infections, these patients may receive 100 mg every 12 hours. The usual oral dosage of doxycycline for children older than 8 years of age weighing 45 kg or less is 4.4 mg/kg given in 2 divided doses on the first day of treatment followed by 2.2 mg/kg daily given in 1 or 2 divided doses. For severe infections, oral dosages up to 4.4 mg/kg daily may be used in these children.
The usual IV dosage of doxycycline for adults and children older than 8 years of age weighing more than 45 kg is 200 mg on the first day of treatment given in 1 or 2 infusions followed by 100-200 mg daily. The usual IV dosage of doxycycline for children older than 8 years of age weighing 45 kg or less is 4.4 mg/kg on the first day of treatment given in 1 or 2 infusions followed by 2.2-4.4 mg/kg daily given in 1 or 2 infusions.
Rickettsial Infections
For the treatment of Rocky Mountain spotted fever, endemic (murine) typhus, and rickettsialpox, doxycycline generally is given in the usual oral dosage for at least 3-7 days or until the patient has been afebrile for approximately 2-3 days. Because a single dose of doxycycline (but not other currently available tetracyclines) is usually effective for the treatment of louse-borne (epidemic) typhus, Brill-Zinsser disease, and scrub typhus, many clinicians state that adults should receive 100-200 mg of doxycycline as a single oral dose and children should receive 50 mg as a single oral dose for the treatment of these rickettsial infections.
Q Fever
For the treatment of acute Q fever, the US Centers for Disease Control and Prevention (CDC) and other clinicians recommend that doxycycline be given in a dosage of 100 mg twice daily for 2-3 weeks. For the treatment of acute Q fever in patients with preexisting valvular heart disease, the CDC recommends a doxycycline dosage of 200 mg daily given in conjunction with hydroxychloroquine (465 mg [600 mg of hydroxychloroquine sulfate] daily; dosage adjusted to maintain plasma concentrations at 1 ± 0.2 mcg/mL); the recommended duration of treatment is 1 year to prevent progression of acute disease to endocarditis.
For the treatment of chronic Q fever endocarditis, the same regimen of doxycycline and hydroxychloroquine should be given for 1.5-3 years. It has been suggested that doxycycline given in a dosage of 100 mg every 12 hours for 5-7 days may be effective as prophylaxis against Q fever and may prevent clinical disease if initiated 8-12 days after exposure; however, such prophylaxis is not effective and may only prolong the onset of disease if given immediately (1-7 days) after exposure.
Chlamydial Infections
The US Centers for Disease Control and Prevention (CDC) states that individuals with Chlamydia psittaci infection (psittacosis) usually respond to oral doxycycline given in a dosage of 100 mg twice daily. Although fever and symptoms usually are controlled within 48-72 hours, therapy should be continued for at least 10-14 days after defervescence to prevent relapse. For initial treatment of severely ill patients, an IV regimen of doxycycline hyclate in a dosage of 4.4 mg/kg daily given in 2 divided doses (maximum 100 mg per dose) may be indicated. When oral doxycycline is used for the treatment of trachoma, an oral doxycycline dosage of 2.5-4 mg/kg once daily for 36-40 days has been suggested; however, optimum therapy has not been established, and treatment may be difficult.
For the treatment of uncomplicated urethral, endocervical, or rectal infections caused by Chlamydia trachomatis in adults, adolescents, or children 8 years of age or older, the recommended dosage of oral doxycycline is 100 mg twice daily for 7 days. For the treatment of nongonococcal urethritis caused by C. trachomatis or Ureaplasma urealyticum in adults, the recommended dosage of oral doxycycline is 100 mg twice daily for 7 days.
Nongonococcal urethritis caused by Mycoplasma has been successfully treated in adults with 100 mg of doxycycline given orally 1 or 2 times daily for 1-3 weeks. For the treatment of genital, inguinal, or anorectal infections caused by a lymphogranuloma venereum serotype of C. trachomatis in adults, the CDC and some clinicians recommend an oral doxycycline dosage of 100 mg twice daily for 21 days. When doxycycline is indicated in the treatment of other chlamydial or mycoplasmal infections, the usual dosage of the drug is generally used.
Granuloma Inguinale (Donovanosis)
For the treatment of granuloma inguinale (donovanosis) caused by Calymmatobacterium granulomatis, the CDC recommends that adults and adolescents receive oral doxycycline in a dosage of 100 mg twice daily. The drug should be continued until all lesions have healed completely; a minimum of 3 weeks of treatment usually is necessary. If lesions do not respond within the first few days of therapy, some experts recommend that a parenteral aminoglycoside (e.g., 1 mg/kg of gentamicin IV every 8 hours) be added to the regimen. Use of a parenteral aminoglycoside in addition to doxycycline should be strongly considered when treating donovanosis in HIV-infected patients.
Gonorrhea and Associated Infections
Some manufacturers state that when oral doxycycline is used as an alternative for the treatment of uncomplicated gonorrhea, adults should receive 100 mg twice daily for 7 days or, alternatively, an initial 300-mg dose of the drug can be given followed by a second 300-mg dose 1 hour later.
Although tetracyclines are not included in current CDC recommendations for the treatment of uncomplicated or disseminated gonorrhea, the CDC and many clinicians recommend use of doxycycline for presumptive treatment of coexisting chlamydial infections in patients being treated for gonococcal infections. When oral doxycycline is used for the treatment of urogenital chlamydial infections, including presumptive treatment, it is given in a dosage of 100 mg twice daily for 7 days.
For the treatment of acute, sexually transmitted epididymitis caused by N. gonorrhoeae and/or C. trachomatis in adults and children 8 years of age and older, the CDC, other clinicians, and the manufacturer recommend that oral doxycycline be given in a dosage of 100 mg twice daily for 10 days as follow-up to a single 250-mg dose of ceftriaxone. For the treatment of proctitis likely to be caused by N. gonorrhoeae and/or chlamydia, adults and adolescents should receive 100 mg of oral doxycycline twice daily for 7 days after a single 125-mg IM dose of ceftriaxone.
Pelvic Inflammatory Disease
For the treatment of acute pelvic inflammatory disease (PID) in adults or adolescents when N. gonorrhoeae or C. trachomatis is suspected as the primary pathogen and a parenteral regimen is indicated, the CDC and many clinicians suggest the use of an IV or oral doxycycline dosage of 100 mg twice (every 12 hours) daily in conjunction with either cefoxitin (2 g IV every 6 hours) or cefotetan (2 g IV every 12 hours).
This initial regimen may be discontinued 24 hours after there is clinical improvement and oral doxycycline is then given in a dosage of 100 mg twice daily to complete 14 days of therapy. If tubo-ovarian abscess is present, many clinicians would include clindamycin or metronidazole with oral doxycycline to provide more effective coverage against anaerobes. Another parenteral regimen recommended by the CDC and many clinicians for the treatment of PID includes parenteral clindamycin (900 mg IV every 8 hours) and gentamicin (loading dose of 2 mg/kg IV or IM followed by 1.5 mg/kg every 8 hours or, alternatively, single daily dosing) for the initial phase, followed by oral doxycycline in a dosage of 100 mg twice daily to complete a total of 14 days of therapy. If tubo-ovarian abscess is present, many clinicians substitute oral clindamycin (450 mg 4 times daily) for oral doxycycline in the second phase of therapy.
An alternative parenteral regimen recommended by the CDC for the treatment of PID is ampicillin and sulbactam (3 g IV every 6 hours) and oral or IV doxycycline given in a dosage of 100 mg every 12 hours; this regimen has good coverage against C. trachomatis, N. gonorrhoeae, and anaerobes and is effective for patients with tubo-ovarian abscess. When an oral regimen is indicated for the treatment of acute PID in adults or adolescents, the CDC and many clinicians recommend a single IM dose of ceftriaxone, cefoxitin (with oral probenecid), or an equivalent second or third generation cephalosporin (e.g., ceftizoxime, cefotaxime) and oral doxycycline given in a dosage of 100 mg twice daily for 14 days with or without oral metronidazole (500 mg twice daily for 14 days).
The CDC states that clinical trials of outpatient regimens have provided little information regarding intermediate and long-term outcomes, and patients who do not respond to an oral regimen within 72 hours should be hospitalized to confirm the diagnosis and receive a parenteral regimen.
Brucellosis
For the treatment of brucellosis, some clinicians recommend that adults receive 200 mg of doxycycline orally daily for 4 days followed by 100 mg orally daily for 6-7 days, When streptomycin is used in conjunction with doxycycline in adults, 1 g of streptomycin is given IM once or twice daily during the first week of therapy and once daily for at least one additional week of therapy.
Alternatively, usual dosages of tetracyclines have been given for more prolonged periods (i.e., 4-6 weeks). When the infection is severe or when endocarditis, meningitis, or osteomyelitis are present, IM streptomycin (20 mg/kg daily in 2 divided doses; maximum 1 g daily) or gentamicin (5 mg/kg daily in 3 divided doses) can be administered during the first 7-14 days of doxycycline therapy. To decrease the risk of relapse in patients with brucellosis, rifampin (15-20 mg/kg daily in 1 or 2 divided doses; maximum 600-900 mg daily) can be administered concomitantly with doxycycline (with or without an aminoglycoside).
Cholera
For the treatment of cholera, in conjunction with fluid and electrolyte replacement, the usual oral dosage of doxycycline has been given for 3 days. Some clinicians suggest that doxycycline can be given as a single 300-mg dose for the treatment of cholera.
Legionella Infections
In the treatment of Legionella pneumophila infections when erythromycin was contraindicated or was ineffective, the usual oral dosage of doxycycline has been given either alone or in conjunction with rifampin.
Other Mycobacterial Infections
The American Thoracic Society (ATS) has recommended that oral doxycycline be given in a dosage of 100 mg twice daily for at least 3 months for the treatment of cutaneous Mycobacterium marinum infections and states that a minimum of 4-6 weeks of therapy is necessary to determine whether or not the infection is responding.
Anthrax Postexposure Prophylaxis
If doxycycline is used for postexposure prophylaxis following suspected or confirmed exposure to aerosolized anthrax spores in the context of biologic warfare or bioterrorism, the CDC and other experts (e.g., US Working Group on Civilian Biodefense) recommend that adults and children older than 8 years of age weighing more than 45 kg receive a dosage of 100 mg orally twice daily and children 8 years of age or younger and children weighing 45 kg or less receive a dosage of 2.2 mg/kg orally twice daily. Anti-infective prophylaxis be continued until exposure to B. anthracis has been excluded.
If exposure is confirmed, postexposure vaccination with anthrax vaccine (if available) may be indicated in conjunction with prophylaxis. Because of the possible persistence of anthrax spores in lung tissue following an aerosol exposure, the CDC and other experts recommend that anti-infective prophylaxis be continued for 60 days. Because of potential adverse effects from prolonged use of doxycycline in infants and children, amoxicillin is an alternative to complete the 60-day regimen when susceptibility to penicillin is known.
Treatment of Inhalational Anthrax
For the initial treatment of inhalational anthrax, the usual dosage of doxycycline for adults and children weighing more than 45 kg is 100 mg IV every 12 hours and the usual dosage for children weighing 45 kg or less is 2.2 mg/kg IV every 12 hours. If meningitis is suspected, IV doxycycline may be less optimal than IV ciprofloxacin because of poor distribution into CSF. Oral therapy should be substituted for IV therapy as soon as the patient’s clinical condition improves. If oral doxycycline is used for the treatment of inhalational anthrax to complete a treatment regimen initiated with IV doxycycline or when a parenteral regimen is not available (e.g., when there are supply or logistic problems because large numbers of individuals require treatment in a mass casualty setting), the usual oral dosage for adults and children weighing more than 45 kg is 100 mg twice daily and the usual oral dosage for children weighing 45 kg or less is 2.2 mg/kg twice daily.
The CDC and other experts (e.g., US Working Group on Civilian Biodefense) recommend that treatment of inhalational anthrax be initiated with a multiple-drug regimen that includes ciprofloxacin or doxycycline and 1 or 2 other anti-infectives predicted to be effective. IV therapy with a multiple-drug parenteral regimen may not be possible if large numbers of individuals require treatment in a mass casualty setting; in these circumstances, some experts recommend that treatment with an oral regimen recommended for postexposure prophylaxis is an option.
Because of the possible persistence of anthrax spores in lung tissue following an aerosol exposure, the CDC and other experts recommend that anti-infective therapy of inhalational anthrax that occurs as the result of exposure to anthrax spores in the context of biologic warfare or bioterrorism should be continued for 60 days. In infants and children with inhalation anthrax who have clinical improvement while receiving the initial parenteral regimen, an oral regimen of 1 or 2 anti-infectives (including either doxycycline or ciprofloxacin) may be used to complete the first 14-21 days of therapy.
Because of potential adverse effects from prolonged use of doxycycline in infants and children, amoxicillin is an option for completion of the remaining 60 days of therapy, but is not recommended for initial therapy.
Treatment of Cutaneous Anthrax
For the treatment of cutaneous anthrax that occurs as the result of exposure to anthrax spores in the context of biologic warfare or bioterrorism, the CDC and other experts (e.g., US Working Group on Civilian Biodefense) recommend that adults and children older than 8 years of age weighing more than 45 kg receive doxycycline in a dosage of 100 mg orally every 12 hours and that children 8 years of age or younger and children weighing 45 kg or less receive 2.2 mg/kg orally every 12 hours. Although 5-10 days of anti-infective therapy has been recommended for the treatment of mild, uncomplicated cutaneous anthrax that occurs as the result of natural or endemic exposures to anthrax, the CDC and other experts recommend that therapy be continued for 60 days if the cutaneous infection occurred as the result of exposure to aerosolized anthrax spores since the possibility of inhalational anthrax would also exist.
Anti-infective therapy may limit the size of the cutaneous anthrax lesion and the lesion usually becomes sterile within the first 24 hours of treatment, but it will still progress through the black eschar stage despite effective treatment. Although oral therapy may be adequate for the treatment of mild, uncomplicated cutaneous anthrax, a multiple-drug parenteral regimen is recommended for initial treatment of cutaneous anthrax when there are signs of systemic involvement, extensive edema, or head and neck lesions. Cutaneous anthrax in infants and children younger than 2 years of age should be treated IV initially. When a parenteral regimen is indicated for the treatment of cutaneous anthrax, IV dosages recommended for the treatment of inhalational anthrax should be used.
If infants and children have clinical improvement while receiving the initial parenteral regimen, an oral regimen of 1 or 2 anti-infectives (including either doxycycline or ciprofloxacin) may be used to complete the first 7-10 days of therapy.
Because of potential adverse effects from prolonged use of doxycycline in infants and children, amoxicillin is an option for completion of the remaining 60 days of therapy, but is not recommended for initial therapy. Treatment of GI and Oropharyngeal Anthrax The CDC and other experts (e.g., US Working Group on Civilian Biodefense) state that doxycycline dosage regimens recommended for the treatment of inhalational anthrax also are recommended for the treatment of GI and oropharyngeal anthrax.
Plague Treatment
If doxycycline is used for the treatment of pneumonic plague that occurs as the result of exposure to Yersinia pestis in the context of biologic warfare or bioterrorism, some experts (e.g., the US Working Group on Civilian Biodefense, US Army Medical Research Institute of Infectious Diseases) recommend that adults and children weighing 45 kg or more receive a dosage of 100 mg IV every 12 hours or 200 mg IV once daily and that children weighing less than 45 kg receive doxycycline in a dosage of 2.2 mg/kg IV every 12 hours (maximum 200 mg daily). Prompt initiation of anti-infective therapy (within 18-24 hours of symptom onset) is essential in the treatment of pneumonic plague.
Treatment of pneumonic plague should be initiated with a parenteral regimen, although an oral regimen may be substituted when the patient’s condition improves or if parenteral therapy is unavailable. Anti-infective therapy usually is continued for 10 days; some experts recommend a duration of 10-14 days.
Postexposure Prophylaxis
For postexposure prophylaxis following a high-risk exposure to Y. pestis, including exposure that occurs in the context of biologic warfare or bioterrorism, some experts recommend that adults and children weighing 45 kg or more receive doxycycline in a dosage of 100 mg orally every 12 hours and that children weighing less than 45 kg receive 2.2 mg/kg orally every 12 hours. For high-risk exposures to pneumonic plague, the Advisory Committee on Immunization Practices (ACIP) has recommended that adults 18 years of age and older receive 100-200 mg daily in 2 equally divided doses and that children 9-17 years of age receive 2-4 mg/kg daily in 2 equally divided doses.
Postexposure prophylaxis should be continued for 7 days. Some experts recommend that postexposure anti-infective prophylaxis be given to all asymptomatic individuals with exposure to plague aerosol and all asymptomatic individuals who have had household, hospital, or other close contact (within about 2 m) with an individual who has pneumonic plague; however, any exposed individual who develops a temperature of 38.°C or higher or new cough should promptly receive a parenteral anti-infective for treatment of the disease.
Tularemia Treatment
If doxycycline is used for the treatment of tularemia that occurs as the result of exposure to Francisella tularensis in the context of biologic warfare or bioterrorism, some experts (e.g., US Working Group on Civilian Biodefense) recommend that adults and children weighing 45 kg or more receive 100 mg IV twice daily and that children weighing less than 45 kg receive 2.2 mg/kg IV twice daily. Treatment should be continued for 14-21 days. Although therapy should be initiated with IV doxycycline, oral doxycycline can be substituted when the patient’s condition improves.
Postexposure Prophylaxis
If doxycycline is used for postexposure prophylaxis following a high-risk laboratory exposure to F. tularensis (e.g., spill, centrifuge accident, needlestick injury) or in individuals exposed to the organism in the context of biologic warfare or bioterrorism, some experts (e.g., the US Working Group on Civilian Biodefense, US Army Medical Research Institute of Infectious Diseases) recommend that adults and children weighing 45 kg or more receive a dosage of 100 mg orally twice daily and that children weighing less than 45 kg receive a dosage of 2.2 mg/kg orally twice daily.
The recommended duration of postexposure prophylaxis is 14 days. Travelers’ Diarrhea For the prevention of travelers’ diarrhea, oral doxycycline has been given in a dosage of 100 mg daily. However, the CDC and other experts no longer recommend use of anti-infectives for prophylaxis of travelers’ diarrhea in most individuals traveling to areas of risk and other anti-infectives (e.g., fluoroquinolones, azithromycin) are preferred when prophylaxis is indicated in certain high-risk groups or when an anti-infective is indicated for the treatment of traveler’s diarrhea.
Spirochetal Infections Syphilis
While parenteral penicillin G is the drug of choice for all stages of syphilis, the CDC and at least one manufacturer state that nonpregnant adults or adolescents with primary or secondary syphilis who are hypersensitive to penicillin can receive 100 mg of doxycycline orally twice daily for 14 days. In addition, nonpregnant adults or adolescents with early latent syphilis (syphilis of less than 1-year duration) can receive 100 mg of oral doxycycline twice daily for 14 days and those with late latent syphilis, syphilis of unknown duration, or tertiary syphilis (except neurosyphilis) can receive 100 mg twice daily for 4 weeks.
Although the American Academy of Pediatrics (AAP) states that these doxycycline regimens also can be employed in children 8 years of age or older with primary, secondary, or latent syphilis (not tertiary or neurosyphilis) who are hypersensitive to penicillin, the CDC states that infants and children with syphilis who are hypersensitive to penicillin should be desensitized, if necessary, and treated with penicillin. Care should be taken to ensure optimal compliance with these regimens since patient compliance with multiple-day tetracycline regimens may be poor. If compliance with the doxycycline regimen and serologic follow-up cannot be ensured, patients with a history of penicillin hypersensitivity should be desensitized, if necessary, and treated with penicillin.
Leptospirosis
For the treatment of leptospirosis, oral doxycycline has been given in a dosage of 100 mg twice daily for 7 days.
Lyme Disease
For the prevention of Lyme disease in individuals in Lyme disease-endemic areas who are bitten by an I. scapularis tick (particularly a nymphal tick) that is at least partially engorged with blood, some evidence suggests that administration of a single 200-mg oral dose of doxycycline within 72 hours of removal of the tick may be effective. However, the accurate and timely identification of tick species or stage of development and determination of the infection status of the tick as well as assessment of the degree of tick engorgement are often difficult, and the Infectious Diseases Society of America (IDSA), American Academy of Pediatrics (AAP), and other clinicians currently do not recommend routine anti-infective prophylaxis or serologic testing for individuals after a tick bite.
For the treatment of early localized or early disseminated Lyme disease associated with erythema migrans in the absence of neurologic involvement (i.e., meningitis or radiculopathy) or third-degree AV heart block, the IDSA, AAP, and other clinicians recommend an oral doxycycline dosage of 100 mg twice daily for 14-21 days in adults and 1-2 mg/kg (maximum dose: 100 mg) in 2 divided doses for 14-21 days in children 8 years of age or older; doxycycline currently is considered a drug of choice for the treatment of early Lyme disease in these individuals.
These oral doxycycline regimens also are recommended for patients with early disseminated Lyme disease associated with mild carditis (e.g., first- or second-degree AV heart block) or isolated facial nerve palsy, although some clinicians recommend longer periods of treatment (21-28 days).
For the treatment of Lyme arthritis without objective evidence of neurologic involvement (e.g., meningitis or radiculopathy), oral doxycycline 100 mg twice daily for 28 days in adults or 1-2 mg/kg (maximum dose: 100 mg) twice daily for 28 days in children 8 years of age or older generally is recommended. For adults with acute neurologic manifestations (e.g., meningitis, radiculopathy) of Lyme disease who are intolerant of cephalosporins and penicillin, some clinicians suggest that an oral or IV doxycycline dosage of 100-200 mg twice daily for 14-28 days may be adequate, although experience in the US with such a regimen for Lyme meningitis is limited.
Other Spirochetal Infections
When doxycycline is indicated in the treatment of other spirochetal infections, the usual dosage of the drug is generally used. Prophylaxis in Sexual Assault Victims The CDC currently states that if empiric anti-infective prophylaxis is indicated in adolescent or adult victims of sexual assault, a single 2-g oral dose of metronidazole is given in conjunction with a single 125-mg IM dose of ceftriaxone, followed by oral doxycycline given in a dosage of 100 mg twice daily for 7 days.
Malaria
Prevention of Malaria
For prevention of malaria in individuals traveling to areas with chloroquine-resistant Plasmodium falciparum, the CDC, WHO, and others recommend that adults receive 100 mg of doxycycline once daily and that children 8 years of age or older receive 2 mg/kg (maximum 100 mg) once daily. Chemoprophylaxis should be initiated 1-2 days prior to entering a malarious area and continued for 4 weeks after leaving the area.
Treatment of Malaria
When doxycycline is used in conjunction with quinine sulfate for the treatment of malaria caused by chloroquine-resistant P. falciparum or P. vivax, some clinicians recommend that adults receive 100 mg of doxycycline twice daily for 7 days given in conjunction with quinine sulfate (650 mg every 8 hours for 3-7 days). Children 8 years of age or older should receive doxycycline in a dosage of 2 mg/kg daily for 7 days given in conjunction with quinine sulfate (25 mg/kg daily in 3 divided doses for 3-7 days). Periodontitis For the treatment of periodontitis as an adjunct to scaling and root planing, the usual dosage of oral doxycycline is 20 mg twice daily. Daily doses should be taken at 12-hour intervals, usually in the morning and evening, and doses preferably should be taken at least 1 hour prior to or 2 hours after meals. The manufacturer states that safety of oral doxycycline for the adjunctive treatment of periodontitis has not been established beyond 12 months and efficacy has not been established beyond 9 months of therapy.
Pleural Effusions
When used as a sclerosing agent to control pleural effusions associated with metastatic tumors, 500 mg of doxycycline has been diluted with 25-30 mL of 0.9% sodium chloride injection and instilled into the pleural space through a thoracostomy tube following drainage of the accumulated pleural fluid; the tube is then clamped and the fluid subsequently removed. The pleurodesis procedure has been repeated in some patients to achieve control of the effusion, although repeated administration may have limited effects. Prior to instillation of doxycycline in patients with effusions, the pleural cavity is drained by thoracentesis (needle aspiration) or via the thoracostomy tube by gravity or suction (i.e., closed chest tube drainage).
Efficacy of the procedure may be reduced if the sclerosing agent is introduced into the pleural cavity when fluid drainage from the chest tube exceeds 100 mL per 24 hours. To achieve pleurodesis in patients who have recurrent malignant pleural effusions, doxycycline also has been administered as a less concentrated solution (500 mg diluted with 250 mL of 0.9% sodium chloride injection) via chest tube lavage and drainage. For this procedure, the tube has been clamped for 24 hours and the entire procedure repeated daily until the drainage volume approximates the amount of solution instilled.
Dosage in Renal Impairment
Unlike other currently available tetracycline derivatives, usual dosage of doxycycline may be used in patients with impaired renal function.