Meds and you

Updated 11 February 2013


Doxycycline is a broad-spectrum antibiotic effective in treating a variety of bacterial infections.


Doxycycline is the active ingredient of A-Lennon Doxycycline, Cyclidox, Doximal, Doxitab, Doxycyl, DoxyHexal and Dumoxin.

General information

Doxycycline is a broad-spectrum antibiotic effective in treating a variety of bacterial infections. It is frequently prescribed to treat infections of the urinary, respiratory and gastrointestinal tracts, as well as infections of the eye, skin and certain sexually transmitted diseases caused by organisms that are susceptible to doxycycline.

Doxycycline is also frequently prescribed to prevent malaria is those patients entering a malaria area. It is furthermore often used for the long-term treatment of acne.

It is important to note that this medication is only effective against bacterial infections - if your infection is the result of a viral or fungal infection, it will be ineffective.

Antibiotic resistance - when bacteria develop the ability to defend themselves against the effect of an antibiotic - occurs frequently with many antibiotics. The most common causes of this are when patients do not complete the prescribed course in full, allowing bacteria to recover from treatment, and by using antibiotics for non-bacterial infections such as cold and flu.

Oesophageal irritation and ulceration is a threat with doxycycline and doses should be taken with adequate amounts of fluids, in an upright position and well before retiring.

The absorption of doxycycline is less impaired by food than is the case with other similar antibiotics.

It is however still recommended that doxycycline should be taken at least one hour before, or two hours after a meal. Antacids, milk and milk products, and iron supplements should not be given within two hours of a doxycycline dose as it may reduce the absorption and thus the effect of doxycycline.

Doxycycline combines with calcium in the body and is deposited in the developing and growing bones and teeth of unborn babies and growing children. This often results in yellow-brown staining of both milk- and permanent teeth, and retardation of bone growth. Doxycycline should therefore not be given to children under the age of 12, and pregnant or breastfeeding women.

An increased incidence of an abnormal sunburn reaction in people taking doxycycline has also been noted.

How does doxycycline work?

Tetracycline antibiotics functions by inhibiting bacterial protein synthesis. It thus prevents bacteria from producing specific proteins essential for their survival.

Fast facts

Drug schedule: schedule 4

Available as : doxycycline is available as capsules, enteric coated capsules and tablets

What does it do? Doxycycline has an antibacterial effect

Overdose risk: low

Dependence risk: low

Is doxycycline available as a generic? yes

Is doxycycline available on prescription only? yes

User information

Onset of effect: may take a few days for the full beneficial effect to be reached and several weeks in the case of acne.

Duration of action: up to 24 hours.

Dietary advice: milk and milk products should not be given within 2 hours of doxycycline; medication should be taken with plenty of water.

Stopping this medicine: do not stop taking this medication until you have finished the course as prescribed by your doctor - infection may recur with premature discontinuation.

Prolonged use: there is a slim risk of liver damage during prolonged use of the drug.

Special precautions

Consult your doctor before using this drug if:

  • you have liver disease
  • you have systemic lupus erythematosus
  • you have myasthenia gravis
  • you are taking any other medication

Pregnancy: avoid. Potential risk to the foetus has been reported. Consult your doctor before use, or if you are planning to fall pregnant.

Breastfeeding: avoid. This medication is passed through breast milk and may affect your baby adversely. Consult your doctor before use.

Porphyria: avoid. This medication may cause serious adverse effects. Consult your doctor before use.

Infants and children: this medication is not intended for use in children under the age of 12

The elderly: no special precautions need to be taken.

Driving and hazardous work: no special precautions need to be taken.

Alcohol: avoid concomitant use of alcohol with this medication as the efficacy of doxycycline may be reduced.

Possible side effects

Side effect


Consult your doctor



Only if severe

In all cases







discoloration of teeth






ulceration of mouth/ oesophagus



skin rash/ itch






visual disturbance




Drug interactions


reduced effect of antibiotic; take 2 hours apart


risk of warfarin toxicity

medication for epilepsy such as carbamazepine, phenobarbital and phenytoin

reduced effect of antibiotic


risk of ciclosporin toxicity

iron salts

reduced antibiotic effect; reduced iron absorption

oral contraceptives

contraceptive failure is possible; use alternative contraception

isotretinoin/ acitretin

raised intracranial pressure

sodium bicarbonate

increase ph and reduce antibiotic activity


may reduce effect of antibiotic; space at least 2 hours apart

Food interactions

Milk and milk products should not be given within 2 hours of doxycycline.

Disease interactions

Consult your doctor before using this drug if you have liver disease, you have systemic lupus erythematosus, you have porphyria, or if you have myasthenia gravis.

Overdose action

A small overdose is no cause for concern. In case of intentional large overdose, seek emergency medical attention.

Recommended dosage

Adults: 50 - 200mg as a single dose or 2 divided doses

Interesting fact

Doxycycline has been used in the treatment of certain types of elephantiasis.


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