BMA Concise Guide to Medicine & Drugs


Brand names Clarosip, Febzin XL, Klaricid, Klaricid XL, Mycifor XL

Used in the following combined preparations None


Drug group Antibiotic

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic No


Clarithromycin is a macrolide antibiotic similar to erythromycin, from which it is derived. It has similar actions and uses to erythromycin, but is slightly more active. Clarithromycin is used for upper respiratory tract infections, such as middle ear infections, sinusitis, and pharyngitis, and lower respiratory tract infections, including whooping cough, bronchitis, and pneumonia, as well as for skin and soft tissue infections. Given with anti-ulcer drugs and other antibiotics, it is used to eradicate Helicobacter pylori, the bacterium that causes many peptic ulcers.

Prolonged use of clarithromycin is not usually necessary.


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

How taken/used Tablets, liquid, granules, injection.

Frequency and timing of doses 2 x daily, up to 14 days; 1 x daily (XL preparations).

Adult dosage range 500mg–1g daily.

Onset of effect 1–4 hours.

Duration of action 1–12 hours; 24 hours (XL preparations).

Diet advice None.

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

Missed dose Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.

Stopping the drug Take the full course. Even if you feel better, the 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.


Clarithromycin is generally well tolerated. Gastrointestinal disturbances, such as nausea, vomiting, diarrhoea, and indigestion, are the most common side effects. Hearing loss is a rare possibility but usually reverses on stopping the drug. If you experience severe headaches, severe joint or muscle pain, an altered sense of taste or smell, anxiety, insomnia, confusion, or hallucinations, discuss with your doctor. If a rash or jaundice develops, stop taking the drug and consult your doctor.


Warfarin, midazolam, disopyramide, lovastatin, rifabutin, ciclosporin, tacrolimus, sildenafil, ergotamine, and valproate Blood levels and effects of these drugs are increased by clarithromycin.

Carbamazepine, phenytoin, theophylline, digoxin, and colchicine Blood levels and toxicity of these drugs are increased by clarithromycin.

Pimozide, disopyramide, and quinidine may cause cardiac arrhythmias if taken with clarithromycin.

Lipid-lowering drugs whose names end in ‘statin’ There is a risk of rhabdomyolysis (muscle damage) with clarithromycin.

Zidovudine Blood levels of zidovudine are reduced if this drug is taken at the same time as clarithromycin.


Be sure to tell your doctor if:

· You have liver or kidney problems.

· You have had an allergic reaction to erythromycin or clarithromycin.

· You have a heart problem.

· You have porphyria.

· You are taking other medicines.

Pregnancy Safety has not been established. Discuss with your doctor.

Breast-feeding Clarithromycin passes into the breast milk and may affect the baby. Discuss with your doctor.

Infants and children Reduced dose necessary.

Over 60 No special problems.

Driving and hazardous work No known problems.

Alcohol No known problems.


In courses of over 14 days, there is a risk of developing antibiotic-resistant infections.