Clarith

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Medically reviewed

Rosario Oropesa

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Clarith

Clarith is a systemic, prescription-only medicine containing the active ingredient Clarithromycin. It is classified as an antibacterial agent belonging to the macrolide antibiotic class, which is a group of drugs used to manage bacterial infections.

Quick Facts Description
Active ingredient Clarithromycin
Form Tablet (Immediate and Extended-Release), Oral Suspension, Solution for Injection
Pharmacological class Macrolide Antibiotic
Common use Combating bacterial infection
Origin Semisynthetic (Derived from Erythromycin)

What is Clarithromycin and Its Classification?

Clarithromycin is chemically defined as a semisynthetic macrolide, indicating it is derived from the natural macrolide erythromycin through chemical modification. This alteration enhances its stability against stomach acid and improves its absorption compared to its parent compound. The resulting bioavailability and spectrum of activity over the original compound make it a clinically recognized option for systemic antibacterial intervention.

The fundamental purpose of the medicine is to stop the growth of susceptible bacteria throughout the body. Clarithromycin achieves this by functioning as a protein synthesis inhibitor; it penetrates the bacterial cell and reversibly binds to the 50S ribosomal subunit, which is a critical part of the bacteria's machinery for assembling necessary proteins. By inhibiting this process, the drug restricts the bacteria's ability to multiply and spread.

Available Forms and General Therapeutic Purpose

Clarithromycin is provided as a single active ingredient product designed for systemic administration and is available in several distinct dosage forms. These preparations include standard and extended-release tablets for oral use, granules for oral suspension to create a liquid format (which is often specifically differentiated for pediatric patients), and a solution for injection intended for intravenous delivery. The availability of these forms allows for the drug to be administered across different patient needs and settings.

The general therapeutic purpose of utilizing these diverse forms is to provide a comprehensive strategy for infection control by delivering the antibacterial agent to the entire system. The systemic activity helps to inhibit the spread of susceptible microorganisms, ultimately facilitating the patient's recovery from bacterial illness.

Regulatory References

  1. Macrolides (StatPearls)
  2. CPIC (Clinical Pharmacogenetics Implementation Consortium)

What side effects are possible with Clarith?

Clarithromycin's official safety profile establishes clear regulatory classifications for adverse reactions and identifies specific patient populations with heightened risk.

Frequency-Classified Adverse Reactions

Adverse reactions are classified by incidence based on clinical and post-marketing data. Common reactions (occurring in ge1/100 to <1/10 patients) typically include Gastrointestinal Disorders (diarrhea, nausea, vomiting, abdominal pain) and Nervous System Disorders (headache, dysgeusia, or taste disturbance, insomnia). Uncommon effects (occurring in ge1/1,000 to <1/100 patients) involve Leukopenia, Jaundice, and ECG QT prolonged. Events such as Fatal Hepatic Failure and certain severe arrhythmias are classified as Not Known (frequency cannot be estimated from available data).

Serious Adverse Reactions

Regulatory documents highlight several serious adverse reactions, including the potential for life-threatening Ventricular Arrhythmias (Torsades de pointes, Ventricular Fibrillation) and severe liver damage, including Fatal Hepatic Failure. Severe Cutaneous Adverse Reactions (SCARs), such as Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN), are also documented. Additionally, like nearly all antibacterial agents, it is associated with the risk of Clostridioides difficile-associated diarrhoea (CDAD).

Safety Constraints and Considerations

Use is contraindicated in patients with known hypersensitivity to macrolides, a history of QT prolongation or ventricular arrhythmias, uncorrected low potassium or magnesium levels (hypokalemia/hypomagnesemia), or Severe Hepatic Failure combined with Renal Impairment. A potential increased long-term risk of cardiovascular mortality following a short course of treatment is a documented concern for patients with pre-existing Coronary Artery Disease. The profile also contains explicit restrictions against concomitant use with certain medications, such as lovastatin, simvastatin, and colchicine, due to documented serious safety consequences.

Overdose and Emergency Response

Clarithromycin (Clarith) overdose typically results in exaggerated adverse reactions, primarily affecting the gastrointestinal tract. However, more serious complications related to heart function are also possible.

Symptoms of Overdose

The most common symptoms associated with a Clarithromycin overdose include:

  • Gastrointestinal: Severe stomach pain, intense nausea, vomiting, and diarrhea.
  • Other Potential Effects: In higher-than-recommended doses, or in sensitive individuals, Clarithromycin may affect heart rhythm, causing a condition known as QT-interval prolongation, which can lead to a fast, pounding, or irregular heartbeat.

When to Seek Emergency Help

If you suspect an overdose, contact a poison control center immediately. However, call emergency medical services (such as 911) if the individual experiences any of the following severe symptoms:

Symptom Category Signs Requiring Immediate Attention
Cardiovascular Fast, irregular, or pounding heartbeat; fainting or severe dizziness.
Gastrointestinal Severe, bloody, or persistent diarrhea.
Allergic/Systemic Signs of a severe allergic reaction (anaphylaxis), such as difficulty breathing, swelling of the face/throat, or a rapidly spreading skin rash.
Neurological Confusion, hallucinations, or seizures.

Overdose management usually involves symptomatic and supportive care, with prompt medical evaluation being critical.

Therapeutic Uses of Clarith

What Clarith Treats: Main Uses and Benefits

Clarith is commonly used for conditions presenting with acute episodes driven by susceptible bacterial growth. It plays a role in managing symptoms related to physical discomfort and systemic imbalance across several key therapeutic areas.

This medicine is generally applied in situations involving certain distressing symptoms across respiratory infections (like pneumonia and sinusitis), ear and throat infections (such as pharyngitis), skin and soft tissue infections, and is relevant for easing symptoms associated with specific stomach ulcers. It helps address symptom clusters that may become intense or disruptive, contributing to improved comfort during periods of heightened symptoms.

In clinical scenarios where symptoms intensify and short-term symptomatic assistance is needed, the medication supports the patient by easing the overall symptom load. This helps maintain a sense of stability when symptoms are more noticeable and assists with managing the localized pain and inflammation associated with the infection.


Quick Fact: Relief for Inflammatory Discomfort

Clarith is commonly used to help with symptoms related to inflammatory or irritative states, such as localized pain, swelling, and redness in the skin, or persistent cough and sore throat from a bacterial cause.

Regulatory References

  1. NIH MedlinePlus overview on Clarithromycin

Eligibility and Restrictions for Use

Clarithromycin is subject to strict eligibility rules based on regulatory requirements to ensure patient safety.

Populations that Must Not Use Clarith (Contraindicated)

Clarithromycin is strictly contraindicated for individuals with:

  • A known hypersensitivity or allergy to clarithromycin, erythromycin, or any macrolide antibiotic.
  • A history of cholestatic jaundice or hepatic dysfunction caused by previous clarithromycin use.
  • Existing QT prolongation (congenital or acquired) or a history of ventricular cardiac arrhythmias, including Torsades de pointes.
  • Severe hepatic failure combined with renal impairment.
  • Uncorrected hypokalemia (low potassium) or hypomagnesemia (low magnesium) due to the risk of dangerous heart rhythm changes.

Conditional Use and Age Restrictions

Use is restricted or requires caution in other populations:

  • Pregnancy: Use is not recommended unless there is no appropriate alternative, due to potential hazard to the fetus observed in animal studies.
  • Children: Tablets are generally not recommended for children younger than 12 years; liquid formulations are prescribed for children aged 6 months to 12 years. Safety and efficacy are not established for infants younger than 6 months.
  • Impaired Organ Function: Patients with severe renal impairment require a dose reduction. Use requires caution in all patients with impaired hepatic function or pre-existing heart conditions, such as coronary artery disease.

What should I know about interactions with other medicines?

Clarithromycin is a strong inhibitor of the enzyme Cytochrome P450 3A4 (CYP3A4) and the transport protein P-glycoprotein (P-gp), which leads to significantly increased plasma concentrations of many co-administered medicines. This pharmacokinetic effect forms the basis for several clinically important restrictions.

Classification Interacting Medicines/Categories Constraint
Contraindicated Simvastatin, Lovastatin, Ergot Alkaloids (e.g., Ergotamine, Dihydroergotamine), Cisapride, Pimozide, Colchicine (in patients with renal/hepatic impairment), Lomitapide, Ivabradine, Ranolazine, Ticagrelor Do not combine due to risk of serious toxicity (e.g., rhabdomyolysis, vasospasm, QT prolongation).
Requires Close Monitoring/Adjustment Warfarin, Digoxin, Benzodiazepines (e.g., oral Midazolam), CYP3A4 metabolized Statins (e.g., Atorvastatin), Oral Hypoglycemic Agents Requires frequent laboratory checks (e.g., INR, drug levels) or dose reduction of the co-administered drug.

Co-administration with other drugs that prolong the QT interval is also strongly advised against due to the risk of ventricular arrhythmia (torsades de pointes). Separately, when immediate-release clarithromycin is co-administered with Zidovudine, doses must be separated by at least 2 hours to avoid decreased Zidovudine exposure.

Mechanism of Action

Interfering with Bacterial Protein Synthesis

Clarithromycin functions as a protein synthesis inhibitor by directly targeting the bacterial 50S ribosomal subunit. This mechanism involves reversible binding to the 23S rRNA component, physically blocking the translocation step within the ribosome. This interference rapidly inhibits the elongation of the polypeptide chain, thereby suppressing the production of proteins vital for bacterial replication. The physiological consequence of this inhibition is a bacteriostatic effect.


Modulation of Host Biological Signals

Clarithromycin also exhibits a distinct, non-antibacterial action involving the modulation of inflammatory mediators and influencing the function of certain host immune cells, such as neutrophils. This mechanism contributes to the dampening of excessive inflammatory signaling within affected pathways.


Mechanism Evasion and Constraints

The antibacterial mechanism is constrained by bacterial countermeasures, chiefly target site methylation and the use of active efflux pumps. These processes lead to the functional failure of ribosomal inhibition, resulting in the continued, unimpaired proliferation of the bacterial population.

Dosage and Administration Information

How Clarith is Used: Administration Guidelines

The usage of Clarith (Clarithromycin) is characterized by standardized parameters for its systemic administration. These parameters cover the dose, frequency, route, and conditions of intake for use.


Administration and Dosage

Clarith is administered for systemic delivery via two main routes: oral and intravenous (IV) infusion. The dose and frequency depend on the formulation used:

  • Immediate-Release (IR) Oral Forms: The standard adult dose is typically 250 mg to 500 mg taken twice daily (every 12 hours). The total treatment course generally lasts 7 to 14 days.
  • Extended-Release (ER) Oral Forms: The dose is typically 1000 mg (often two 500 mg tablets) taken once daily. These are taken with food and swallowed whole; they are not to be crushed, broken, or chewed.
  • Intravenous (IV) Infusion: This route is usually utilized for severely ill patients, administered as a 500 mg dose twice daily via a slow infusion over 60 minutes. IV therapy is typically limited to a short period (2 to 5 days) before switching to oral therapy.

Specific Use Instructions

Population / Condition Instruction
Pediatric Dosing Based on body weight, typically 7.5 mg/kg twice daily using the oral suspension.
Renal Impairment For adults with significantly reduced kidney function (CrCl < 30 mL/min), the total dose is reduced by one-half.
IR Tablets / Suspension Can be taken with or without food (oral suspension is shaken well before use).
IV Administration Is given over 60 minutes and is not to be administered as a bolus or intramuscular injection.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Clarith

Evidence for Use in Respiratory and Ear/Throat Infections

Clarithromycin was studied for use in acute conditions such as community-acquired pneumonia, acute sinusitis, and pharyngitis. The research typically involves controlled clinical trials (RCTs) which were evaluated in populations of adults and children with mild-to-moderate infections. These trials monitored short-term outcomes related to physical discomfort and systemic or functional imbalance, such as changes in clinical symptom scores and clearance rates of the specific bacteria causing the infection.

Findings describe patterns observed in the studies where measurements of clinical change were observed during the defined time intervals. Research highlights changes measured in symptom intensity over the short term. However, data show patterns related to rising macrolide resistance in some common respiratory bacteria. This means the outcomes measured in studies may vary depending on the local bacteria patterns at the time and location of the study.

Evidence for Use in Managing Stomach Ulcers (H. pylori)

Clarithromycin was evaluated in numerous trials as part of a multi-drug regimen known as Triple Therapy, which was studied for its application in the organism clearance process for Helicobacter pylori (a bacterium associated with stomach ulcers). These trials typically research examined short-term changes and monitored the organism clearance rate, which is the primary outcome reflecting daily functioning or activity level in this context.

Studies report how symptoms evolved in the observed populations by measuring the rate at which the H. pylori organism was observed in post-treatment tests. Findings indicate that when the H. pylori strain was susceptible to Clarithromycin, the combination therapy reported high measurements of clearance rates. However, research describes that this clearance rate may drop significantly in geographical areas where resistance to Clarithromycin was observed in the bacterium.

Long-Term Studies and Extended Follow-up Data

Research has explored the outcomes related to systemic or functional imbalance over extended periods, sometimes for up to a decade, particularly in patients previously treated with a short course of Clarithromycin. These observational settings evaluating daily-life functioning were conducted to monitor for any delayed patterns or associations.

Long-term effects are not fully established and findings were mixed across different long-term cohort studies. The findings observed in one large, placebo-controlled trial reflect the specific conditions under which they were conducted and may not be observed across all patient groups, and the certainty remains low for the broader population without pre-existing health issues.

Key Studies & References

  1. Macrolides (Classification and Mechanism of Action)
  2. MedlinePlus: Clarithromycin Overview and Common Uses

Frequently Asked Questions (FAQ)

Common questions about Clarith (FAQ)


Q: Is Clarith the same as [Commonly known competitor drug]?

Clarith is the proprietary name given to the active ingredient clarithromycin. According to official regulatory documents, it belongs to the macrolide class of antibiotics. While other drugs in this class may treat similar conditions, clarithromycin is a chemically distinct compound from other antibacterial medicines.


Q: How quickly does Clarith start working after the first dose?

Official documents describe that Clarith works by having a bacteriostatic effect, meaning it stops the growth of susceptible bacteria by preventing them from creating vital proteins. The time it takes for a patient to observe a change in their symptoms or functional status depends on the specific infection and the individual's biological response.


Q: Do I need to avoid certain foods or drinks while using Clarith?

Official product information notes that the extended-release (ER) forms of the tablets must be taken with food. Regulatory documents also indicate a potential interaction with grapefruit or grapefruit juice. Studies indicate this may delay drug absorption, though it does not typically change the overall amount of medicine absorbed by the body.


Q: What is the longest period of time Clarith is usually prescribed for?

For acute bacterial infections, the standard course of treatment typically lasts 7 to 14 days. However, official documents describe that treatment for certain long-term conditions, particularly Mycobacterium infections, may require administration for a period that extends up to several months.


Q: Can Clarith cause a metallic or strange taste in the mouth?

Official safety information documents dysgeusia or a 'taste disturbance' as a common adverse reaction. This adverse reaction is often characterized by patients as a metallic or strange flavor.


Q: Does Clarith cause sensitivity to sunlight?

Official adverse reaction lists do not commonly list photosensitivity or 'sunlight sensitivity' with a defined frequency. Regulatory documents focus on other dermatological reactions that have been reported.


Q: Is Clarith generally safe for older adults (seniors)?

Regulatory documents state that elderly patients may be more susceptible to drug-associated effects, such as a prolonged QT interval. The official safety profiles document an increased risk of certain adverse cardiac events in this population.


Q: What happens if I miss a dose of Clarith?

Guidance found in patient information sections of regulatory sources states that if a dose is missed, it should be taken as soon as it is remembered. However, if it is nearly time for the next scheduled dose, the missed dose should be skipped, and the regular schedule resumed. Official guidance states that two doses should not be taken at the same time.


Q: Is it possible to develop a resistance to Clarith over time?

Official warnings state that the misuse or overuse of antibacterial drugs like Clarith can lead to the growth of non-susceptible bacteria and the development of antibiotic resistance. This outcome may make the drug ineffective for fighting future bacterial illnesses.


Q: Why is Clarith used in combination with other drugs for some conditions?

Official indications describe its use in a multi-drug regimen, such as the Triple Therapy for H. pylori infections. This strategy is typically employed to increase the overall effectiveness of the treatment and manage the risk of the bacteria developing resistance to a single drug.


Q: Is there a link between Clarith use and hearing changes?

Official safety data has documented hearing loss as an adverse reaction in the 'uncommon' or 'not known' frequency category. Regulatory sources note that this hearing loss is usually reversible after the medicine is stopped.


Q: Can Clarith affect blood sugar levels?

Official drug interaction warnings advise caution for patients taking insulin or other oral hypoglycemic agents. Co-administration may cause changes in blood sugar, including hypoglycemia (low blood sugar), which is a documented concern.


Q: Can Clarith affect your mood or cause anxiety?

Official adverse reaction lists document psychiatric disorders, including anxiety and insomnia (difficulty sleeping), as events that have been reported in patients taking the medicine.


Q: Is the efficacy of Clarith affected by alcohol use?

General patient guidelines from official sources often note that no significant interaction has been documented between Clarith and alcohol that affects the drug's efficacy.


Q: Can Clarith treatment cause yeast infections?

Official warnings note that the use of antibacterial agents may result in the overgrowth of non-susceptible organisms, including fungi. This outcome can lead to conditions such as oral or vaginal yeast infections.


Q: What are the known potential interactions between Clarith and grapefruit?

Official warnings highlight a potential interaction with grapefruit or grapefruit juice. Research indicates it may delay the absorption of the drug, but does not typically affect the overall amount of drug absorbed.


Q: Does Clarith contain gluten or common allergens?

The inactive ingredients for Clarith formulations are listed in regulatory documents. Some formulations contain lactose as an inactive ingredient, and official information encourages reviewing the full ingredient list.

How should Clarith be stored and disposed of?

How to Store and Dispose of Clarithromycin

Storage and disposal must align strictly with regulatory requirements to maintain product stability and safety.

Storage Requirements

  • Tablets: Store at controlled room temperature, typically 20 C to 25 C (68 F to 77 F). The container must be kept tightly closed and protected from light and moisture.
  • Oral Suspension: The liquid must not be refrigerated or frozen. Store at room temperature, and discard any unused portion 14 days after reconstitution.

Safety and Disposal

All forms must be stored out of the reach and sight of children. Unused or expired clarithromycin must be thrown away according to local regulations. Do not dispose of the medicine by flushing it down a toilet or pouring it into a drain unless specific advice is given by a health authority.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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