BMA Concise Guide to Medicine & Drugs


Brand names Doxylar, Efracea, Periostat, Vibramycin, Vibramycin-D

Used in the following combined preparations None


Drug group Tetracycline antibiotic

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Doxycycline is a tetracycline antibiotic. It is used to treat infections of the urinary, respiratory, and gastrointestinal tracts. It is also prescribed for treatment of some oral and dental infections, sexually transmitted diseases, skin, eye, and prostate infections, acne, and malaria prevention (in some parts of the world).

Doxycycline is less likely to cause diarrhoea than other tetracyclines, and its absorption is not significantly impaired by milk and food. It can therefore be taken with meals to reduce side effects such as nausea or indigestion. It is also safer than most other tetracyclines for people with impaired kidney function. Like other tetracyclines, it can stain developing teeth and may affect development of bone; it is therefore usually avoided in children under 12 years old and pregnant women.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, dispersible tablets, capsules.

Frequency and timing of doses 1–2 x daily with plenty of water, or with or after food, in a sitting or standing position, well before going to bed to avoid risk of throat irritation.

Dosage range 100–200mg daily.

Onset of effect 1–12 hours; several weeks (acne).

Duration of action Up to 24 hours; several weeks (acne).

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take as soon as you remember. If your next dose is due within 6 hours, take a single dose now and skip the next.

Stopping the drug Take the full course. Even if you feel better, the original infection may still be present and symptoms may recur if treatment is stopped too soon.

Exceeding the dose An occasional unintentional extra dose is unlikely to be a cause for concern. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.


Adverse effects from doxycycline are rare, although it may cause nausea, vomiting, or diarrhoea. If a rash, itching, or abnormal sensitivity of the skin to light occur, stop taking the drug and talk to your doctor. If you experience headache or visual disturbances, stop taking the drug and consult your doctor urgently.


Penicillin antibiotics Doxycycline interferes with the antibacterial action of these drugs.

Barbiturates, carbamazepine, and phenytoin All of these drugs reduce the effectiveness of doxycycline. Doxycycline dosage may need to be increased.

Oral contraceptives There is a slight risk of doxycycline reducing the effectiveness of oral contraceptives. Discuss with your doctor.

Oral anticoagulant drugs Doxycycline may increase the anticoagulant action of these drugs.

Antacids and preparations containing iron, calcium, or magnesium may impair absorption of this drug. Do not take within 2–3 hours of doxycycline.

Ciclosporin and lithium Doxycycline may increase levels of these drugs in the blood.


Be sure to tell your doctor if:

· You have a long-term liver problem.

· You have previously suffered an allergic reaction to a tetracycline antibiotic.

· You have porphyria.

· You have systemic lupus erythematosus.

· You have myasthenia gravis.

· You have a history of angioedema.

· You are taking other medicines.

Pregnancy Not used in pregnancy. May discolour the teeth of the developing baby.

Breast-feeding The drug passes into the breast milk and may lead to discoloration of the baby’s teeth and may also have other adverse effects. Discuss with your doctor.

Infants and children Not recommended under 12 years. Reduced dose necessary for older children.

Over 60 No special problems. Dispersible tablets should be used because they are less likely to cause oesophageal irritation or ulceration.

Driving and hazardous work No known problems.

Alcohol Excessive amounts may decrease the effectiveness of doxycycline.

Surgery and general anaesthetics Notify your doctor or dentist that you are taking doxycycline.


Not usually prescribed long term, except for acne.