Clarithromycin

Clarithromycin is an antibiotic medicine used to treat certain bacterial infections. It belongs to the macrolide group of antibiotics and works by stopping bacteria from making the proteins they need to grow and spread.

This page provides clear, patient-friendly information about how clarithromycin works, how it is typically used in the United Kingdom, common interactions, and practical guidance to help you use it safely and effectively.

Basic product information

How clarithromycin works (mechanism of action)

Clarithromycin helps treat bacterial infections by interfering with the bacteria’s protein production. Specifically, it binds to the 50S ribosomal subunit of susceptible bacteria. This blocks translation and prevents bacteria from building the proteins required for growth.

Clarithromycin may also produce an active metabolite (an additional effect in the body) that contributes to antibacterial activity against certain organisms.

Pharmacokinetics (how the body handles clarithromycin)

“Pharmacokinetics” describes how the medicine is absorbed, distributed, metabolised, and removed from the body.

• Absorption: Clarithromycin is absorbed after oral dosing. Food can influence how much is absorbed and when peak levels occur (see “Food interactions”).
• Distribution: It spreads through body tissues, which is one reason it can be used for infections in areas such as the respiratory tract.
• Metabolism: The liver metabolises clarithromycin, producing an active metabolite in some patients.
• Excretion: The medicine is cleared from the body through liver and kidney routes.
• Half-life: The time it takes for drug levels to reduce by half can vary depending on dose and patient factors.

Your individual suitability may depend on kidney and liver function, age, other medicines, and the specific infection being treated.

Typical uses and indications in the UK

Clarithromycin is used for specific bacterial infections where it is clinically appropriate. It is not effective against viruses such as colds or flu.

Common indications include (examples)

• Respiratory tract infections (for example, infections involving the sinuses or certain lower respiratory infections caused by susceptible bacteria)
• Some skin and soft tissue infections
• Helicobacter pylori infection

In the UK, antibiotic choice is guided by local resistance patterns and clinical guidelines. Clarithromycin may be selected when it is the best option for the specific organism and patient circumstances.

Important note

Antibiotics should be used carefully to reduce the risk of antimicrobial resistance. Using the wrong antibiotic (or stopping too early) can lead to incomplete treatment and recurrence.

Dosage and timing (general guidance)

Dosing depends on the infection type, severity, local guidance, age, kidney/liver function, and the product formulation. Your healthcare professional will determine the most appropriate schedule.

General dosing pattern

• Many adults are prescribed clarithromycin two times daily for a defined course length.
• Treatment duration varies by indication (for example, respiratory infections often use shorter courses than some H. pylori regimens, where combination therapy may be required).

How to take it

• Take clarithromycin at evenly spaced times to maintain steady levels.
• Swallow tablets whole with water unless your product instructions advise otherwise.
• If you have a liquid medicine, shake the bottle and measure carefully using an oral syringe or measuring device.

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 to make up for a missed tablet.

Timing with food: food interactions

Clarithromycin can be taken with or without food, depending on the specific product and how it is tolerated. Food may slow absorption and can reduce peak concentrations, but many patients still achieve effective antibacterial activity.

Practical advice

• If your stomach feels sensitive, taking the dose with food may help reduce nausea or discomfort.
• Try to take each dose at a similar time each day so you keep a consistent routine.
• Follow the instructions supplied with your specific clarithromycin brand or formulation.

Alcohol and medicine interactions

Clarithromycin is not generally associated with a specific “dangerous” interaction with alcohol in the way that some antibiotics are. However, alcohol can worsen side effects such as:

• nausea
• stomach irritation
• dizziness
• fatigue

If you choose to drink alcohol while taking clarithromycin, do so in moderation and consider avoiding alcohol if you feel unwell, dehydrated, or your appetite is poor.

Also, consider that alcohol may interfere with recovery when you are fighting an infection. If you have liver problems or are taking other interacting medicines, it is especially important to ask a pharmacist or clinician for advice.

Important medication interactions (including alcohol-related considerations)

Clarithromycin can interact with several medicines by affecting enzymes involved in drug metabolism. These interactions may increase or decrease drug levels, leading to side effects or reduced effectiveness.

Examples of medicines that commonly interact

• Some cholesterol-lowering medicines (statins) (especially when clarithromycin raises statin levels, increasing risk of muscle-related side effects)
• Antiarrhythmic medicines and other drugs that can affect heart rhythm
• Medicines that prolong the QT interval (a measure seen on an ECG related to electrical timing in the heart)
• Warfarin and other blood thinners (possible effect on bleeding risk)
• Oral diabetes medicines (for example, medicines that may affect blood sugar control)
• Digoxin (possible increase in digoxin levels)
• Other antibiotics or drugs that may interact depending on regimen

What to do

• Tell your pharmacist or prescriber about all medicines you take, including over-the-counter products and herbal remedies.
• If you start clarithromycin, check whether any of your existing medicines should be adjusted.
• If you experience new symptoms such as unusual bruising, fast or irregular heartbeat, severe muscle pain, or fainting, seek medical advice promptly.

Safety profile: who should be careful

Most people tolerate clarithromycin well, but side effects and risks vary by individual. The sections below highlight common issues and when to seek help.

Common side effects

• Nausea
• Diarrhoea or loose stools
• Abdominal discomfort or indigestion
• Headache
• Altered taste

Allergic reactions (seek urgent advice)

Stop taking clarithromycin and seek urgent medical help if you develop signs of allergy such as:

• swelling of the face, lips, tongue, or throat
• difficulty breathing or wheezing
• severe rash or hives
• faintness or severe dizziness

Serious but less common risks

• Liver problems: Rare cases of hepatitis or liver enzyme abnormalities may occur. Seek advice if you develop yellowing of the skin/eyes (jaundice), dark urine, or severe fatigue with abdominal pain.
• Heart rhythm effects: Clarithromycin can be associated with changes in heart rhythm in certain circumstances, especially with other QT-prolonging medicines or in people with existing rhythm problems.
• Severe diarrhoea: If you get persistent watery diarrhoea, blood in stools, or severe abdominal cramps, contact a clinician promptly. Antibiotics can rarely contribute to inflammation of the bowel.
• Drug interactions: Some interactions can lead to significant side effects; this is why it’s important to review your medicines list.

Who should seek advice before use

• People with a history of QT prolongation, certain rhythm disorders, or low potassium/magnesium levels
• People with liver impairment
• People with kidney impairment (dose adjustment may be needed)
• Anyone taking interacting medicines (particularly statins, blood thinners, or antiarrhythmics)
• Those who have previously had an allergic reaction to macrolides

Practical use tips for patients

• Finish the course: Even if you feel better, complete the prescribed time period to reduce the risk of relapse.
• Stay hydrated: Drinking enough fluids can help manage side effects like nausea or diarrhoea.
• Track symptoms: Note improvements and any side effects. If symptoms worsen after starting therapy, contact a healthcare professional.
• Take consistently: Use alarms or phone reminders to avoid missed doses.
• Be cautious with interactions: Check with a pharmacist if you start new medicines (including antifungals, migraine meds, or heart medicines).
• Do not share antibiotics: Antibiotics should be used only for the person and infection they were intended for.

When to seek medical advice during treatment

Contact a healthcare professional urgently if you experience:

• signs of severe allergic reaction
• severe or persistent diarrhoea
• fainting, severe dizziness, palpitations, or chest pain
• yellowing of the skin/eyes, dark urine, or intense abdominal pain
• no improvement after a few days or symptoms worsening despite treatment

Alternative options (what may be used instead)

Antibiotic choice depends on the infection, likely bacteria, severity, and local resistance. If clarithromycin is not suitable due to interactions, allergies, side effects, or the likely organism, clinicians may consider alternative antibiotics or different management strategies.

Possible alternatives (examples)

• Other macrolides (such as azithromycin) in selected cases
• Penicillins (if appropriate and suitable)
• Cephalosporins (depending on the infection and allergy history)
• Doxycycline or clindamycin in certain situations

The “best” alternative varies. A pharmacist or clinician can advise based on your medical history, current medicines, and local guidance.

UK market and legal context (patient-friendly)

In the United Kingdom, clarithromycin is an antibiotic that is regulated to support safe use and help reduce antibiotic resistance. Availability and supply depend on local prescribing and pharmacy regulations, as well as your clinical needs.

UK antibiotic stewardship aims to ensure antibiotics are used only when needed and for the right duration. Guidance is provided by professional bodies and public health organisations, and local resistance patterns are considered when selecting antibiotics.

Recent guidance (high level)

UK antimicrobial guidance continues to emphasise:

• using antibiotics only when there is evidence or strong suspicion of bacterial infection
• selecting the narrowest effective antibiotic where possible
• reviewing treatment if there is no response
• reducing unnecessary antibiotic use in conditions usually caused by viruses

If you are unsure whether your symptoms are likely bacterial, speak to a healthcare professional before using antibiotics.

Delivery and availability from an online pharmacy (UK)

Availability of clarithromycin can vary by formulation, strength, and stock levels. When ordering online from a UK pharmacy, delivery timelines depend on:

• stock availability
• your delivery address and chosen delivery method
• processing time for order verification steps required by UK regulations

You can typically expect clear product details on the listing (such as strength, formulation, and pack size). If a product is temporarily unavailable, the pharmacy may offer options such as an alternative brand, a different pack size, or advice on next steps.

Storage and handling

• Store tablets and suspensions according to the label instructions.
• Keep medicines out of sight and reach of children.
• Do not use after the expiry date shown on the packaging.
• If you have liquid clarithromycin, follow instructions on whether refrigeration is required after opening (product instructions vary).

FAQ about clarithromycin (UK)

1. What is clarithromycin used for?

Clarithromycin is used for certain bacterial infections, commonly including some respiratory tract infections and some skin/soft tissue infections. It can also be part of combination treatment for Helicobacter pylori infection.

2. How long does clarithromycin take to work?

Many people begin to feel an improvement within a few days, but this depends on the infection and severity. If you have no improvement or you feel worse, contact a healthcare professional.

3. Can I take clarithromycin with food?

Often yes. Food may affect absorption and timing, and some people prefer taking it with meals to reduce stomach upset. Follow the instructions supplied with your exact product.

4. Is it safe to drink alcohol while taking clarithromycin?

Moderate alcohol is not usually associated with a direct dangerous interaction, but alcohol can worsen side effects and delay recovery. If you feel unwell, it’s best to avoid alcohol and stay hydrated.

5. What should I do if I miss a dose?

Take it when you remember unless it is almost time for the next dose. Do not double up. If you are unsure, ask your pharmacist.

6. What are the common side effects?

Common side effects include nausea, diarrhoea, abdominal discomfort, headache, and altered taste. Most are mild, but contact a clinician if symptoms are severe or persistent.

7. Can clarithromycin cause diarrhoea?

Yes. Mild diarrhoea can occur. However, seek urgent medical advice if you develop severe watery diarrhoea, blood in stools, or significant abdominal cramps.

8. Are there important interactions I should know about?

Yes. Clarithromycin can interact with medicines including certain statins, blood thinners, antiarrhythmics, digoxin, and some medicines affecting heart rhythm. Always review your medicines list with a pharmacist.

9. Who should not take clarithromycin or should seek advice first?

You should get advice first if you have significant liver problems, a history of heart rhythm issues, kidney impairment, or take interacting medicines. Also seek advice if you have had an allergic reaction to macrolide antibiotics.

10. What happens if my symptoms don’t improve?

If symptoms do not improve after a few days or they worsen, contact a healthcare professional. You may need reassessment, a different treatment, or testing.

11. Is clarithromycin effective for viral infections?

No. Antibiotics like clarithromycin only treat bacterial infections and do not treat viral illnesses such as colds and flu.

12. What are practical tips to help me complete the course?

Use reminders, take doses at consistent times, stay hydrated, and complete the full course even if you feel better—unless a clinician tells you to stop.

Summary

Clarithromycin is a macrolide antibiotic used in the UK for selected bacterial infections. It works by blocking bacterial protein production and can be taken reliably with consideration of timing and food effects. As with all antibiotics, it is important to use it appropriately, be aware of interactions—particularly with heart rhythm–related medicines and certain other drugs—and seek medical advice for serious side effects.