Vibramycin (Doxycycline)

Doxycycline is a tetracycline antibiotic used to treat a wide range of bacterial infections when the bacteria are susceptible to it. In the UK, it is also used for some preventive treatments, such as certain travel medicine uses, and for other specialist-led indications.

How to take

• Take each dose with a full glass of water (about 240 mL).
• Swallow it while sitting or standing; do not take it right before lying down. This helps reduce the risk of irritation or ulceration of the oesophagus.
• If it upsets your stomach, doxycycline can be taken with food.
• Complete the 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 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 given, with care, to patients with renal impairment. However, relatively high doses may be needed for urinary tract infections because renal excretion is low.

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

What doxycycline is not for (common misconceptions)

Doxycycline is usually given by mouth as the base or one of its various 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, either by mouth or 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, if prescribed.

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

For syphilis in patients who are allergic to penicillin, 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, aluminium, 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, so tell your prescriber about all medicines 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 make it less effective. 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), diarrhoea, loss of appetite
• Throat or oesophageal irritation (especially if taken without enough water or right before lying down)
• Photosensitivity (you may burn more easily in the sun) - use sun protection and stop the medicine and seek advice if severe skin redness occurs
• Yeast overgrowth or superinfection can happen with antibiotics (seek advice if you develop persistent symptoms affecting the mouth or genitals)

As for tetracycline

Gastrointestinal problems with doxycycline are reported to be less common than with tetracycline, and doxycycline may also cause less tooth discolouration. Oesophageal 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 oesophageal 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 study, and can be affected by taking it with multivalent cations (for example, calcium, iron, magnesium or aluminium).

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 faeces after chelation in the intestines. Removal of doxycycline by haemodialysis is insignificant.

Administration in children

In children, the effects on teeth should be considered. Because tetracyclines can affect tooth development, doxycycline use in children aged 8 years or under 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 the UK, dosing in children, when used, is weight-based; follow a clinician's and public health guidance for specific indications (for example, anthrax exposure).

Doxycycline (Vibramycin) use in pets

Veterinarians may advise avoiding giving it at the same time as products containing calcium, magnesium, aluminium, 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, diarrhoea or other concerning symptoms while on 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 the reach of children.

Doxycycline is a widely used tetracycline antibiotic with convenient dosing and generally reliable absorption. Take it with plenty of water while upright, 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.