Doxycycline

• Doxycycline treats pneumonia and other respiratory tract infections such as pharyngitis, tonsillitis, sinusitis, otitis media, and bronchitis caused by susceptible bacteria.
• Doxycycline treats urinary and genital tract infections, including chlamydia and gonococcal urethritis, caused by susceptible organisms.
• Doxycycline treats skin and soft tissue infections such as impetigo, cellulitis, and wound infections caused by susceptible bacteria.
• Doxycycline treats gastrointestinal infections caused by susceptible bacteria such as Shigella and Salmonella species.
• Culture and susceptibility testing should be performed before, and when appropriate during, treatment to confirm the bacteria are susceptible to doxycycline.

• Doxycycline should not be used in pregnant women unless the potential benefit to the mother clearly outweighs the risk to the baby.
• Tetracyclines like doxycycline cross the placenta and can affect the developing baby, particularly bone and tooth development.
• Use during the last trimester of pregnancy may permanently discolor the baby's teeth (yellow-gray-brown) and can affect bone growth.

• Doxycycline is excreted into breast milk.
• Doxycycline is not recommended for breastfeeding women due to the risk of permanent tooth discoloration and effects on bone development in the nursing infant.

• No data specific to older adults are available, and no specific dosage adjustment is described for this population.

• Doxycycline is not authorized for use in children under 8 years of age because it can cause permanent yellow-gray-brown discoloration of developing teeth and can affect bone growth.
• Doxycycline should not be used in this age group unless other appropriate antibiotics are unlikely to work or cannot be used.
• A decrease in bone (fibula) growth rate has been observed in premature infants given tetracyclines, though this effect reversed after stopping the drug.

• For most susceptible infections in adults, the usual dose is a 200 mg loading dose on the first day, followed by 100 mg once daily thereafter.
• For more severe infections, particularly chronic urinary tract infections, 200 mg daily may be given throughout treatment.
• For uncomplicated gonococcal infections, a specific 4-day regimen is used, starting with a higher first-day dose.
• For chlamydia or ureaplasma genital infections, the usual dose is 100 mg twice daily for at least 10 days.
• Treatment should continue for at least 24 to 48 hours after fever and symptoms have resolved.
• For streptococcal infections, treatment should continue for 10 days to reduce the risk of rheumatic fever or kidney inflammation.
• No dosage adjustment is needed for patients with impaired kidney function.
• If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next dose, in which case it should be skipped; doses should not be doubled.

If overdose is suspected, seek emergency medical attention immediately or contact your regional Poison Control Centre without delay.

• Specific information on the symptoms of doxycycline overdose is not available in the product monograph.
• Treatment of overdose should be symptomatic, and gastric lavage (stomach pumping) may be considered for a recent oral overdose.
• Dialysis does not significantly remove doxycycline from the blood and would not be expected to help in an overdose.

• Nausea may occur.
• Vomiting may occur.
• Diarrhea may occur.
• Loss of appetite may occur.
• Stomach pain or heartburn (dyspepsia) may occur.
• Vaginal yeast infection may occur.
• Skin sensitivity to sunlight (photosensitivity) may occur.
• Headache may occur.

Serious side effects require immediate discussion with the prescriber or emergency care.

• Esophagitis and esophageal ulcers, sometimes severe, have occurred, especially when the capsule or tablet was taken with too little water or right before lying down.
• Clostridioides difficile-associated diarrhea and colitis, ranging from mild diarrhea to severe or life-threatening colitis, may occur during or after treatment.
• Benign intracranial hypertension (pseudotumor cerebri), which can cause headache and vision changes and rarely permanent vision loss, has been reported.
• Serious allergic reactions, including anaphylaxis and angioedema, have been reported.
• Severe skin reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms (DRESS), have been reported.
• Liver problems, including hepatitis, autoimmune hepatitis, and liver failure, have been reported.
• Blood disorders such as hemolytic anemia, low platelet counts, and low white blood cell counts have been reported.
• Autoimmune reactions, including a lupus-like syndrome, have been reported with prolonged use.
• Seek urgent medical attention for difficulty or pain swallowing, chest pain, severe headache with vision changes, severe rash, or signs of a severe allergic reaction.

• Use with caution in patients with a history of gastrointestinal disease, particularly esophageal disorders such as strictures.
• Use with caution in patients taking other drugs known to be toxic to the liver.
• Use with caution in patients exposed to strong sunlight or UV light, due to the risk of an exaggerated sunburn reaction; use of sunscreen is recommended.
• Use with caution in patients with a history of autoimmune conditions, such as lupus.
• Doxycycline should not be used during tooth development, from the last trimester of pregnancy through about age 8, unless other drugs are unlikely to work or cannot be used.
• Doxycycline does not treat viral infections, and unnecessary use increases the risk of antibiotic resistance.

• Contraindicated in patients with known hypersensitivity to doxycycline, any ingredient in the formulation, or any other tetracycline antibiotic.
• Contraindicated in patients with myasthenia gravis.
• Contraindicated in patients taking isotretinoin, due to the shared risk of benign intracranial hypertension.

• Antacids containing aluminum, calcium, or magnesium impair doxycycline absorption and should not be taken at the same time.
• Iron-containing products reduce doxycycline absorption; doses should be spaced as far apart as possible if both must be used.
• Barbiturates, phenytoin, carbamazepine, and rifampin can reduce doxycycline blood levels by speeding up its breakdown in the liver, potentially reducing its effectiveness.
• Alcohol can reduce doxycycline blood levels through the same mechanism, potentially diminishing its antibiotic effect.
• Combining doxycycline with isotretinoin should be avoided due to the shared risk of benign intracranial hypertension.
• Doxycycline may enhance the blood-thinning effect of oral anticoagulants such as warfarin, requiring dose adjustment and monitoring.
• Doxycycline may make oral contraceptives less reliable, based on anecdotal reports.
• Bismuth subsalicylate can reduce doxycycline absorption and should not be taken during treatment.
• Doxycycline should generally be avoided with penicillin antibiotics, as it may interfere with penicillin's bactericidal action.
• The combination of tetracyclines with the anesthetic methoxyflurane has been linked to fatal kidney toxicity.

• Doxycycline should be taken with food or a meal to reduce the chance of stomach upset.

• Doxycycline should be taken with or after a meal, with a full glass of water.
• Doses should not be taken right before bedtime; the patient should remain upright for 1 to 2 hours after each dose to reduce the risk of esophageal irritation.

• Store doxycycline capsules at room temperature (15°C to 30°C) in a tightly closed, light-resistant container.
• Store doxycycline tablets at 15°C to 30°C in a tightly closed container, protected from light.

• Take doxycycline with food and a full glass of water, and stay upright for 1 to 2 hours afterward.
• Avoid direct sun and UV light exposure, and use sunscreen, as doxycycline can make skin sunburn more easily.
• Do not take antacids, iron supplements, or calcium products at the same time as doxycycline.
• Finish the entire course of medicine as prescribed, even if you feel better.