Vibramycin (Doxycycline)

Doxycycline is a tetracycline antibiotic used to treat a wide range of susceptible bacterial infections. In Canada, it is also used for selected preventive regimens, such as travel medicine, and for other specialist-guided uses.

How to take

• Take each dose with a full glass of water (about 8 oz / 240 mL).
• Swallow it while sitting or standing. Do not take it right before lying down. This helps reduce the risk of esophageal irritation or ulceration.
• If it upsets your stomach, doxycycline can be taken with food.
• Finish the full course exactly as prescribed (do not stop early unless your prescriber tells you to).

Timing guide: food, minerals, and common add-ons

If you miss a dose

Uses and Administration

Doxycycline is a tetracycline derivative with uses similar to tetracycline. It may sometimes be preferred to other tetracyclines for susceptible infections because its absorption is fairly reliable and its long half-life allows less frequent dosing, often once daily. It also has the advantage that it can be used, with care, in patients with renal impairment. However, relatively high doses may be needed for urinary tract infections because of its low renal excretion.

Tooth infection (dental infection): Antibiotics are not a substitute for dental procedures (for example, drainage or definitive dental treatment). In many cases, urgent dental treatment is prioritized in Canada, and antibiotics are reserved for cases with systemic involvement or a higher risk of spread. A Canadian clinician or dentist may prescribe an antibiotic based on the suspected organisms and your allergy history.

What doxycycline is not for (common misconceptions)

Doxycycline is usually given by mouth as the base or one of its salts, usually the hyclate. Doses are expressed in terms of doxycycline; doxycycline hyclate 115 mg is equivalent to about 100 mg of anhydrous doxycycline.

Typical adult dosing (examples)

The usual adult dose, taken by mouth or given intravenously, is 200 mg of doxycycline on the first day (as a single dose or in divided doses), followed by 100 mg daily. In severe infections, the initial dose may be continued throughout the course of treatment, as prescribed.

Gonorrhea note (Canada): Doxycycline is not a first-line treatment for gonorrhea in current Canadian guidance. Recommended therapy typically includes ceftriaxone; doxycycline may be used only when a clinician is also treating possible chlamydial infection and when appropriate.

For syphilis in penicillin-allergic patients, doxycycline 100 to 200 mg twice daily is given by mouth for at least 14 days; some authorities suggest the same dose for 28 to 30 days in patients with late latent disease (follow specialist guidance).

For malaria prevention, doxycycline chemoprophylaxis should begin 1-2 days before travel to endemic areas, be taken once daily during travel, and continue daily for 4 weeks after leaving the endemic area (follow travel medicine guidance).

Interactions

Minerals and antacids, especially products containing calcium, magnesium, aluminum, iron, zinc, or bismuth, can reduce doxycycline absorption-use the timing guide above. Some medicines that induce liver enzymes (for example, rifampicin and certain antiepileptics) may reduce doxycycline levels. Tell your prescriber about all medications and supplements you take.

Alcohol

Occasional alcohol use is not known to cause a disulfiram-like reaction with doxycycline. However, chronic heavy alcohol use may reduce doxycycline exposure, which could lower how well it works. If you drink heavily or have alcohol use disorder, discuss this with your prescriber.

Adverse Effects and Precautions

Common side effects

• Stomach upset (nausea, vomiting), diarrhea, loss of appetite
• Throat/esophageal irritation (especially if taken without enough water or right before lying down)
• Photosensitivity (sunburning more easily) - use sun protection and stop and get advice if severe skin redness occurs
• Yeast overgrowth/superinfection can happen with antibiotics (get advice if you develop persistent mouth or genital symptoms)

As for Tetracycline

Gastrointestinal side effects with doxycycline are reported to be less common than with tetracycline, and doxycycline may also cause less tooth discolouration. Esophageal ulceration can be a particular problem if capsules or tablets are taken with too little fluid or while lying down. Doxycycline should be taken with a full glass of water, while upright, and well before bedtime. Dispersible tablets or liquid formulations should be used in elderly patients, who may be at greater risk of esophageal injury. Unlike many tetracyclines, doxycycline does not appear to accumulate in patients with impaired renal function, and worsening of impairment may be less likely.

Practical comparison with other tetracyclines

Pharmacokinetics

For the general pharmacokinetics of tetracyclines, see Tetracycline. Doxycycline is absorbed from the gastrointestinal tract; absorption and peak levels may vary by formulation and by study, and can be affected by taking it with multivalent cations (for example, calcium, iron, magnesium, or aluminum).

About 80 to 95% of doxycycline in the circulation is reported to be bound to plasma proteins. Its biological half-life varies from about 12 to 24 hours. Doxycycline is more lipid-soluble than tetracycline. It is widely distributed in body tissues and fluids.

Most of a dose of doxycycline is excreted in the feces after chelation in the intestines. Removal of doxycycline by hemodialysis is insignificant.

Administration in children

In children, the effects on teeth should be considered. Because tetracyclines can affect tooth development, doxycycline use in children 8 years of age or younger should be limited to situations where the potential benefits are expected to outweigh the risks (for example, severe or life-threatening infections as directed by a clinician).

In Canada, dosing in children, when used, is weight-based; follow clinician and public health guidance for specific indications (for example, anthrax exposure).

Doxycycline (Vibramycin) Use in Pets

Veterinarians may advise avoiding giving it with products that contain calcium, magnesium, aluminum, iron, or zinc because these can reduce absorption. As with other tetracyclines, extra caution is used in very young animals because of possible effects on developing teeth and bones. Contact a veterinarian promptly if a pet develops persistent vomiting, diarrhea, or other concerning symptoms during treatment.

Storage

Store at room temperature: 20°C to 25°C (68°F to 77°F). Short-term temperature changes are allowed: 15°C to 30°C (59°F to 86°F). Keep the container tightly closed, protected from light, and out of reach of children.

Doxycycline is a widely used tetracycline antibiotic with convenient dosing and generally reliable absorption. Take it with plenty of water while sitting or standing, avoid taking it at the same time as mineral-containing antacids or supplements, and store it at controlled room temperature. Follow your prescriber's directions, especially for dental infections (where definitive dental treatment is key), sun sensitivity, and if you drink alcohol heavily.