Clarithromycin (for UK use) — Patient-Friendly Information

Clarithromycin is a well-known antibiotic medicine used to treat certain bacterial infections. It belongs to the macrolide class of antibiotics and works by stopping bacteria from making the proteins they need to grow and multiply. This guide explains how clarithromycin works, how it is typically used in the UK, and important safety information for patients and carers.

Important: Antibiotics only treat bacterial infections. They do not work for viruses such as colds and flu. If symptoms do not improve or worsen, seek medical advice promptly.

Basic product information

How clarithromycin works (mechanism of action)

Clarithromycin works by interfering with bacterial protein synthesis. It binds to the 50S ribosomal subunit of susceptible bacteria. This prevents bacteria from producing proteins essential for growth and replication, leading to bacterial death or stopping their ability to multiply.

Clarithromycin is active against a range of bacteria commonly involved in respiratory tract infections and certain other infections. Susceptibility can vary, so appropriate use is important to help ensure effectiveness and reduce antibiotic resistance.

Pharmacokinetics (how the body handles it)

Understanding how clarithromycin moves through the body can help you take it correctly.

• Absorption: Clarithromycin is absorbed after oral administration. The presence of food can affect absorption for some formulations (see the “Food interactions” section below).
• Distribution: It reaches many tissues, including the lungs and upper respiratory tract.
• Metabolism: The liver metabolises part of the dose. A key metabolite is 14-hydroxyclarithromycin (varies by patient factors and formulation).
• Elimination: It is cleared mainly through the liver and kidneys. Reduced kidney or liver function can increase exposure and affect tolerability.
• Half-life: Half-life may be longer at higher doses and may vary between individuals.

If you have kidney problems, liver disease, or are taking multiple interacting medicines, a clinician/pharmacist may adjust guidance for safe use.

Typical uses of clarithromycin in the UK

Clarithromycin is used for bacterial infections where it is considered appropriate based on clinical assessment, local guidance, and likely bacterial causes. Common use areas include:

• Respiratory tract infections (for example, certain bacterial infections of the throat, sinuses, or chest when appropriate)
• Skin and soft tissue infections in selected cases
• Helicobacter pylori eradication as part of combination therapy (used alongside other medicines)
• Other infections where a macrolide is specifically indicated

Note: The exact indication and regimen vary. Selection depends on local antibiotic resistance patterns and individual factors such as allergies, other medicines, and severity of illness.

Indications and when it is commonly considered

In UK clinical practice, clarithromycin may be considered for bacterial infections including:

• Acute bacterial infections of the upper respiratory tract when bacterial causes are suspected
• Community-acquired respiratory infections in selected patients
• Some oral and dental infections in certain circumstances (as part of an overall treatment plan)
• H. pylori infection in combination regimens

Guidance and preferred antibiotics can vary. If you’re unsure why clarithromycin was chosen for you, ask your healthcare professional.

Timing: how to take clarithromycin

Clarithromycin is usually taken at consistent times each day to maintain effective levels.

• Typical schedule: Often twice daily (about 12 hours apart) for many indications.
• Finish the course: Even if you feel better, complete the prescribed course to reduce relapse and resistance risk.
• Missed dose: If you miss a dose, take it when you remember unless it is close to the next dose. Do not take a double dose.
• Vomiting/diarrhoea: If you vomit soon after taking a dose, ask a pharmacist for advice (a repeat dose may or may not be appropriate depending on timing).

Practical tip: Set alarms on your phone to help you stay on schedule, especially if you take it morning and evening.

Dosing: what to expect

Dosing depends on the infection, age, kidney function, and the specific product formulation. The most common adult regimens are often twice daily. For children, dosing is usually based on body weight and formulation type.

• Adults: Common regimens include 500 mg twice daily for many respiratory indications, but duration and exact dose can differ.
• Children: Dosing is typically weight-based using an appropriate liquid formulation.
• H. pylori regimens: Clarithromycin is used with other medicines (such as a proton pump inhibitor and possibly additional antibiotics) for eradication.

Important: Always follow the dosing instructions provided for your specific product and indication. Doses are not one-size-fits-all.

Food interactions: can you take it with meals?

Food can influence clarithromycin absorption. In practice, many products can be taken with food if it helps with stomach tolerance, but it may affect peak levels depending on formulation.

• With food: Taking clarithromycin with meals may reduce some gastrointestinal side effects for some people.
• Consistency matters: If your clinician/pharmacist advises a particular approach (with or without food), keep it consistent throughout your course.
• Follow product instructions: Different formulations (e.g., immediate-release tablets vs. other presentations) may have different food effects.

If you’re unsure whether your specific brand/formulation should be taken with food, check the patient information leaflet included with your product or ask a pharmacist.

Alcohol and medicine interactions

Alcohol

Clarithromycin itself is not typically described as requiring strict alcohol abstinence. However, alcohol may:

• Worsen stomach upset (nausea, diarrhoea)
• Increase drowsiness or reduce your ability to rest and recover
• Make dehydration more likely if you are unwell

Practical advice: For best tolerance and recovery, it’s sensible to limit alcohol during the course, especially if you feel unwell.

Medicine interactions (important)

Clarithromycin can interact with several medicines, sometimes in ways that can be serious. The key issue is that clarithromycin can affect how the liver processes certain drugs, potentially increasing their levels.

Tell your pharmacist/doctor if you take any of the following (this is not an exhaustive list):

• Statins (cholesterol-lowering medicines, e.g., simvastatin or similar): risk of muscle-related side effects may increase.
• Warfarin (and other blood thinners): may increase bleeding risk; monitoring may be required.
• Antiarrhythmics (heart rhythm medicines): may affect heart rhythm.
• Certain antihistamines and antipsychotics: QT prolongation risk can increase.
• Some anti-reflux/anti-seizure medicines and other antibiotics: interaction patterns vary.
• Medicines containing ergot alkaloids (migraine treatments): can be unsafe with macrolides.
• Oral hypoglycaemics/insulin: blood sugar may change in some cases.

Do not start or stop other medicines while on clarithromycin without checking first. If you have questions about a specific medicine, ask a pharmacist and have the medicine name(s) to hand.

Safety profile: what to watch for

Like all medicines, clarithromycin can cause side effects. Many are mild and manageable, but some require urgent action.

Common side effects

• Diarrhoea
• Nausea and/or indigestion
• Abdominal discomfort
• Headache
• Altered taste (sometimes)

Less common but important risks

• Severe or persistent diarrhoea (especially with fever or blood/mucus): could indicate antibiotic-associated colitis.
• Allergic reactions: rash, swelling of face/lips, breathing difficulty.
• Heart rhythm effects: clarithromycin can rarely affect heart rhythm (QT prolongation), especially in people with existing risk factors or interacting medicines.
• Liver problems: signs include yellowing of skin/eyes, dark urine, severe tiredness, or persistent nausea.
• Effects on hearing: rarely, ringing in the ears or hearing changes have been reported.

Seek urgent medical help if

• You develop swelling of the face, throat tightness, or difficulty breathing
• You have severe watery diarrhoea or diarrhoea with blood
• You experience fainting, a very fast or irregular heartbeat, or severe dizziness
• You notice symptoms of liver injury (yellow skin/eyes, dark urine)

If you have any concerns, contact a healthcare professional promptly.

Practical use tips for getting the best results

• Use a medication organiser: A box or blister organiser can help you avoid missed doses.
• Stay hydrated: Especially if you develop diarrhoea or feel generally unwell.
• Take with adequate water: This helps tablet swallowing and reduces irritation.
• Don’t double up: If you miss a dose, follow missed-dose advice rather than taking extra.
• Track side effects: Note new symptoms (timing, severity) and tell your pharmacist or doctor.
• Respect the course length: Stopping early can allow infection to return.
• Consider probiotics cautiously: Some people take probiotics to reduce diarrhoea; ask a pharmacist for advice on timing and suitability, especially if you are immunocompromised.

What to do if symptoms don’t improve

Some infections begin improving within a couple of days, but this varies by condition and severity. If your symptoms:

• do not improve after a reasonable time, or
• get worse, or
• you develop high fever or severe shortness of breath,

you should seek medical advice. You may need reassessment, additional tests, or a different antibiotic based on likely bacteria.

Alternative options (if clarithromycin is unsuitable)

Depending on the infection, alternatives may be considered. Choice depends on local guidance, infection type, severity, patient factors (including allergies and interactions), and resistance patterns.

Possible alternatives may include:

• Other macrolides (e.g., azithromycin) in selected cases
• Doxycycline for certain respiratory or skin infections where appropriate
• Amoxicillin or other penicillin-type antibiotics (where suitable)
• Clindamycin in specific skin/soft tissue infections in selected patients

Important: Do not switch antibiotics on your own. If clarithromycin is not appropriate (for example, due to interactions, intolerance, or treatment failure), a clinician should choose an alternative.

Market and legal context for the UK (including guidance on antibiotic use)

Antibiotic stewardship is a major priority in the United Kingdom. The goal is to use antibiotics appropriately to treat bacterial infections while reducing antibiotic resistance and preventing unnecessary exposure to side effects.

In the UK:

• Antibiotic guidance is informed by clinical bodies and evidence-based recommendations.
• Respiratory infection management is commonly guided by local NHS pathways and national recommendations, which emphasise correct diagnosis, watchful waiting where appropriate, and targeted antibiotic selection.
• Rational prescribing helps ensure antibiotics remain effective.

Recent emphasis: Over recent years, UK healthcare has continued to highlight the need for careful antibiotic use, including attention to resistance, avoiding unnecessary broad-spectrum use, and reviewing antibiotic choice when symptoms do not improve.

Recent guidance (overview)

Clinical guidance for antibiotics can change based on updated resistance patterns and new evidence. In general, current UK practice focuses on:

• Using antibiotics only when bacterial infection is likely.
• Selecting the narrowest effective option whenever possible.
• Considering local resistance and patient factors such as allergy history and interactions.
• Reviewing treatment if there is no improvement.

For the most up-to-date recommendations for specific infections, consult NHS guidance or speak with a healthcare professional.

Delivery, availability, and how to receive your medicine

As an online pharmacy, we aim to make it straightforward for you to receive your medicine safely and promptly. Availability can vary depending on formulation and stock levels.

• Dispatch times: Orders are typically processed quickly during business days. Dispatch may vary based on stock and verification.
• Delivery options: Delivery methods and estimated times can differ depending on your postcode and carrier.
• Packaging: Medicines are supplied in appropriate packaging to protect the product during transit.
• Storage: Once delivered, store as instructed on the outer packaging or leaflet (commonly at room temperature away from heat and moisture; keep out of sight and reach of children).

If you need your medicine urgently, contact the pharmacy support team to check the most reliable delivery options for your area.

Safety and special considerations

Who should be extra cautious?

• People with heart rhythm disorders or known QT prolongation risk
• People with low potassium or magnesium levels
• People with liver impairment
• People with kidney impairment
• People taking interacting medicines (especially those affecting heart rhythm, blood thinning, or drug metabolism)
• Pregnancy or breastfeeding: clarithromycin may be considered in some situations, but individual risk/benefit should be assessed by a clinician

Underlying conditions and monitoring

Depending on your health background, you may need additional monitoring (for example, if you are on blood thinners, have liver issues, or are at risk for heart rhythm changes).

FAQ

1) What is clarithromycin used for?

Clarithromycin is an antibiotic used to treat certain bacterial infections, such as some respiratory tract infections and skin infections, and it can also be part of combination therapy to eradicate Helicobacter pylori.

2) How quickly should I feel better?

Many people begin to feel improvement within a few days, but it depends on the infection type and severity. If you don’t improve or you worsen, seek medical advice.

3) Can I take clarithromycin with food?

Food can affect absorption for some formulations. Many people find it easier on the stomach when taken with meals, but for best results follow the instructions for your exact product.

4) What if I miss a dose?

Take the missed dose when you remember unless it is close to the next dose. Do not take a double dose to make up for the missed one.

5) Are there interactions with other medicines?

Yes. Clarithromycin can interact with several commonly used medicines, including some blood thinners, statins, heart rhythm medicines, and other drugs. Always check with a pharmacist if you’re taking other medicines or supplements.

6) Can I drink alcohol while taking clarithromycin?

There is no universal requirement to completely avoid alcohol, but alcohol may worsen stomach upset and reduce recovery. Limiting alcohol during the course is a sensible approach, especially if you feel unwell.

7) What side effects are common?

Common side effects include diarrhoea, nausea, indigestion, abdominal discomfort, and headache.

8) When should I stop taking it and get help?

Seek urgent medical help if you develop signs of a serious allergic reaction (swelling, breathing difficulty), severe diarrhoea (especially with blood or fever), fainting or severe dizziness, or symptoms suggesting liver problems (yellow skin/eyes, dark urine).

9) What if the infection doesn’t clear?

If symptoms persist or worsen, you may need reassessment. It could be due to the infection not being bacterial, resistance, or the need for a different treatment.

10) Is clarithromycin suitable for everyone?

Not always. People with certain heart conditions, liver/kidney problems, or those taking interacting medicines may need special advice. If you have concerns, speak to a pharmacist.

Disclaimer: This information is for general guidance and does not replace advice from a healthcare professional. Always refer to the patient information leaflet supplied with your medicine and seek medical advice for personalised care.