Klacid

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Klacid

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Medically reviewed

Marina Burgos

Last updated on 10/01/2026

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 Klacid

Quick Facts

Property Description
Active ingredient Clarithromycin
Forms Tablets, Modified-Release (MR) Tablets, oral suspension, powder for injection
Pharmacological class Macrolide antibiotic (Antibacterial agent)
General purpose Fighting systemic bacterial proliferation in the body
Origin Semi-synthetic (derived from Erythromycin)

What Type of Medicine is Klacid (Clarithromycin)?

Klacid is a brand name for the drug substance Clarithromycin, which is classified as a potent systemic anti-infective medicine belonging to the macrolide antibiotic pharmacological class. The active substance is semi-synthetic, chemically derived from Erythromycin A. This structural modification enhances its acid stability and oral absorption. This semi-synthetic origin results in a drug that is recognized for achieving reliable concentrations at the site of infection compared to its predecessor.

As a prescription-only medicine, Clarithromycin is an established antibacterial agent utilized to combat a broad spectrum of susceptible microbial organisms. It is considered an essential medicine for its recognized value and effectiveness in global health protocols.


Composition and Distinctive Forms

The core active ingredient is Clarithromycin, which is formulated as a single active ingredient product. The Klacid brand provides several key pharmaceutical forms designed for effective delivery: standard film-coated tablets, specialized modified-release tablets (such as Klacid MR), granules for oral suspension (often preferred for children), and a powder for solution for injection.

Differentiation Factor: The availability of the Modified-Release (MR) tablet is a distinctive feature designed to slowly release the Clarithromycin content over an extended period. This structural variety ensures the systemic anti-infective action can be initiated efficiently through either oral or intravenous routes, depending on the patient's needs.


What is the General Purpose of This Antibacterial Agent?

The general purpose of Clarithromycin is to serve as a defense mechanism against bacterial pathogens. The drug works by binding to the 50S ribosomal subunit inside the bacteria, which blocks the production of essential proteins required for microbial growth.

This fundamental mechanism allows the medicine to exert either a bacteriostatic effect (halting growth) or a bactericidal effect (directly killing the microbes). This action is critical for helping the body resolve active bacterial illnesses—such as those commonly occurring in the respiratory tract and skin—by neutralizing the infectious cause at a cellular level.

Regulatory References

  1. World Health Organization Essential Medicines List

What side effects are possible with Klacid?

Possible Side Effects and Safety Information

The regulatory safety profile for Klacid (Clarithromycin) classifies documented adverse reactions by frequency and the body system affected, consistent with official government prescribing information.

Documented Adverse Reactions

Side effects are primarily observed in the Gastrointestinal and Nervous Systems.

Classification Examples of Reactions
Common (1 to 10 in 100) Diarrhea, Nausea, Vomiting, Abdominal pain, Headache, Insomnia, Dysgeusia (taste perversion).
Uncommon (1 to 10 in 1,000) Increased hepatic enzyme levels (Investigations), Leukopenia (Blood disorders), Gastritis.

Serious Safety Concerns and Constraints

Official labeling highlights several serious adverse reactions, which are reported as rare post-marketing events, with frequency often categorized as Not Known.

Serious Reactions include severe Hepatotoxicity (e.g., hepatic failure), Cardiotoxicity (e.g., QT prolongation, Torsades de Pointes), and severe hypersensitivity like Stevens-Johnson Syndrome (SJS). Clostridioides difficile-associated diarrhea (CDAD) is also a documented risk with antibacterial use.

Safety Constraints are explicitly stated for certain conditions. Use is contraindicated in patients with known QT prolongation or ventricular arrhythmias. It is also contraindicated in individuals with severe hepatic failure combined with renal impairment.

Furthermore, the safety profile notes special considerations for co-medication: use with certain drugs like Lovastatin and Simvastatin is prohibited due to the risk of rhabdomyolysis, and a potential long-term mortality risk has been noted in patients with Coronary Artery Disease.

Overdose and Emergency Response

The regulatory profile for Klacid (Clarithromycin) overdose describes acute manifestations and severe systemic risks, which dictate mandated emergency actions. All overdose information is based on official government regulatory documents.

Documented Manifestations and Severe Outcomes Overdose commonly presents with pronounced gastrointestinal distress, including severe abdominal pain, nausea, vomiting, and diarrhea. Transient sensory changes, such as taste perversion, may also occur. A critical concern documented in regulatory labeling is the potential for QT interval prolongation and severe cardiac arrhythmias, including Torsades de Pointes, which can be life-threatening. Additionally, overdose carries a risk of hepatic dysfunction, potentially progressing to fatal hepatic failure. Increased susceptibility to QT prolongation is noted for elderly patients, and toxicity is increased in those with severe hepatic and renal impairment.

Mandatory Emergency Actions Regulatory documents require specific actions if overdose is suspected. Individuals must seek immediate medical attention or contact a poison control center. Emergency services must be called immediately if there is collapse, difficulty breathing, or seizure activity. The drug should be discontinued immediately upon observation of severe toxicity signs, such as acute hypersensitivity or signs of hepatitis. Treatment is defined as symptomatic and supportive, and ECG monitoring is warranted due to the arrhythmia risk. No specific antidote is known.

Therapeutic Uses of Klacid

What Klacid Treats: Main Uses and Benefits

Klacid (Clarithromycin) is commonly used to help with bacterial infections across several key systems, providing symptomatic support and supporting pathogen management. It is relevant in clinical settings marked by increased discomfort or tension and is commonly used to help with symptomatic relief during acute or disruptive episodes.

This antibiotic is applied across conditions such as pharyngitis, acute otitis media, community-acquired pneumonia, uncomplicated skin and soft tissue infections, and is considered relevant to help address Helicobacter pylori in peptic ulcer disease. This use may assist with supportive relief, contributing to easing the overall symptom load and helping patients cope more steadily with symptom fluctuations that interfere with daily comfort.

“This application is relevant for easing the overall symptomatic burden in complex situations and may assist with maintaining functional stability.”


Quick Fact: Symptomatic Focus in Acute Episodes

Symptom Domain Conditions Managed Patient Benefit
Inflammatory Distress Respiratory Tract Infections, Skin Infections Contributes to easing physical discomfort
Pathogen Burden H. pylori Eradication, MAC Manifestations Supports functional stability

Regulatory References

  1. NIH MedlinePlus overview

Eligibility and Restrictions for Use

Eligibility Map: Who can and cannot use Klacid — Official Regulatory Information

Official regulatory documents define strict population eligibility for Klacid (Clarithromycin) based on a patient's pre-existing conditions, organ function, and age.

Eligibility Scope

Category Official Regulatory Statement
Populations for whom use is contraindicated Patients with known Hypersensitivity to macrolides. Individuals with a history of QT prolongation or ventricular cardiac arrhythmia. Patients experiencing Severe Hepatic Failure combined with Renal Impairment or uncorrected Hypokalaemia.
Populations for whom use is not recommended Use is generally Not Advised during pregnancy, especially in the first trimester. Infants younger than 6 months of age have not established safety and efficacy.

Condition-specific Eligibility Rules

Category Official Regulatory Statement
Age-related eligibility rules Adults and Adolescents (12+ years) are eligible for standard use. Children younger than 12 years must use the oral suspension, as tablets are not suitable.
Condition-specific eligibility rules Severe Renal Insufficiency ( CrCl < 30 mL/ min) requires Conditional Use where a dose adjustment is mandatory. Caution is advised for patients with Impaired Hepatic Function or certain Cardiac Conditions (e.g., severe cardiac insufficiency).

The eligibility profile strictly defines absolute prohibitions and conditional use requirements. These formal, label-based restrictions determine precisely which populations can and cannot use the medicine under labeled conditions.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Klacid (Clarithromycin) interactions are structured by its classification as a potent inhibitor of the CYP3A4 enzyme and the P-glycoprotein (P-gp) transporter. This pharmacological action significantly increases the systemic exposure and plasma concentrations of numerous co-administered medicinal products. The official regulatory profile establishes several Contraindicated Combinations due to the high risk of serious adverse reactions.

Formal Restrictions and Classifications

Co-administration is strictly contraindicated with certain HMG-CoA Reductase Inhibitors (like Lovastatin and Simvastatin) due to the heightened risk of myopathy and rhabdomyolysis. Additionally, simultaneous use with certain QT-prolonging agents (e.g., Pimozide, Terfenadine) and Ergot Alkaloids is formally prohibited due to the risk of severe cardiac events or acute ergot toxicity.

Other documented interactions require caution. Co-administration with oral anticoagulants carries a formal risk of serious hemorrhage. Use with oral hypoglycemic agents or insulin is associated with a risk of significant hypoglycemia. Clarithromycin Modified-Release tablets must be administered with food as a mandatory requirement for proper absorption, though standard formulations can be taken without regard to meals. Colchicine is specifically contraindicated in patients with existing hepatic or renal impairment.

Mechanism of Action

Targeting the Bacterial Protein Factory

The action of Clarithromycin is characterized by a primary antimicrobial mechanism. The drug functions as an inhibitor of bacterial protein synthesis by binding reversibly to the 50S ribosomal subunit, specifically obstructing the Nascent Polypeptide Exit Tunnel (NPET). This steric blockade prevents the formation and release of essential proteins, leading to a functional inhibition of microbial growth (bacteriostasis).

The major active metabolite, 14-hydroxyclarithromycin, acts synergistically with the parent compound, contributing to enhanced and prolonged ribosomal inhibition within this critical pathway.


️ Modulating Host Inflammatory Responses

Clarithromycin also engages a non-antimicrobial mechanism involving host immune cell signaling. The molecule accumulates in immune cells, modulating pathways, such as NF-κB, which regulate the inflammatory cascade. This action involves the suppression of pro-inflammatory signaling (e.g., cytokine release). This mechanism contributes to the modulation of the host's inflammatory response.

Dosage and Administration Information

Klacid (Clarithromycin) is administered via two primary routes: orally, using immediate-release tablets, extended-release tablets, or suspension; and intravenously via slow infusion for patients requiring initial parenteral therapy.

The standard dosing for immediate-release (IR) forms is typically 250 mg to 500 mg taken twice daily (every 12 hours). The extended-release (ER) tablets, designed for once-daily use, are administered as 1000 mg. Pediatric patients generally use the oral suspension and are dosed by body weight at 15 mg/kg/day divided every 12 hours.

The administration instructions are dependent on the form: IR tablets and the suspension may be taken without regard to meals. However, ER tablets must be consumed with food and must be swallowed whole—they should not be crushed, broken, or chewed.

Treatment duration is typically 6 to 14 days. IV administration is generally limited to 2 to 5 days, after which patients transition to the oral form. Critically, for patients with severe renal impairment (creatinine clearance below 30 mL/min), official labeling requires the standard dosage to be reduced by one-half. If a dose is missed, it should be skipped if it is almost time for the next scheduled dose to avoid doubling the intake.

Recent Clinical Evidence

Research evidence / Overview of Studies for Klacid (Clarithromycin)

Klacid (Clarithromycin) was studied in research contexts involving specific clinical situations where bacterial infection was present. These studies help show what has been observed so far regarding how symptoms evolve in the observed populations and what questions may still require further research. The evidence is derived from established sources, including governmental regulators and peer-reviewed scientific literature.


Evidence for Acute Respiratory and Skin Infections

Research has extensively examined Klacid in research contexts involving fluctuating or unstable symptoms related to specific acute respiratory and skin conditions. The goal of these studies was to explore changes measured during the study period, such as outcomes related to physical discomfort.

Studies for Upper and Lower Respiratory Conditions

The research base for respiratory conditions, including acute ear infections, throat infections, sinusitis, and community-acquired pneumonia, largely involves short-term, randomized controlled trials (RCTs). Researchers monitored outcomes related to physical discomfort and outcomes reflecting daily functioning or activity level, comparing Klacid against alternative antibiotic agents. Findings describe patterns observed in the studies where research highlights changes measured during the study period in outcomes related to inflammatory or irritative states. The available data mainly focuses on the short-term change observed during the 7- to 14-day treatment period. What remains uncertain are long-term outcomes and the durability of symptom clearance following the acute illness. Furthermore, the results apply only to the populations studied, and the rising global rates of bacterial resistance to macrolides can limit the real-world applicability of some historical trial findings over time.


Evidence for Specialized and Combination Uses

Klacid was evaluated in unique clinical scenarios where it was observed in studies as only one component of a multi-drug regimen, or for specific, less-common infectious challenges.

Research in Helicobacter pylori Eradication Regimens

The evidence base for addressing the bacterium H. pylori in peptic ulcer disease involved Randomized Controlled Trials (RCTs) that explored Klacid only as part of a combination therapy. Researchers monitored the main outcome of microbiological eradication, or whether the bacterium was cleared from the body several weeks after the treatment ended. The findings indicate that outcomes related to systemic or functional imbalance was associated with the specific regimen used. However, findings were mixed regarding outcomes across different global regions, and data show patterns related to high variability depending on local resistance levels. If the bacterium is already resistant to Klacid, the likelihood of successful clearance can be severely limited.

Frequently Asked Questions (FAQ)

Common questions about Klacid (FAQ)

Q: Is Klacid the same as other antibiotics like penicillin?

A: Klacid (clarithromycin) is an antibiotic, but it belongs to the macrolide class, which is chemically distinct from the penicillin class of antibiotics. Due to this difference, official clinical guidelines often use clarithromycin as an alternative for people who have a known allergy to penicillin.

Q: What kind of bacteria does Klacid target?

A: Klacid's official labeling indicates that it is used against specific susceptible bacteria that cause infections in the body. This includes common pathogens like Haemophilus influenzae, Streptococcus pneumoniae, and Staphylococcus aureus. It is also used as part of a combination treatment for the bacterium Helicobacter pylori.

Q: How long does it usually take to start feeling better after taking Klacid?

A: Information from treatment guidelines suggests that improvement in symptoms is typically observed within a few days of starting the medicine. For some conditions, such as certain skin problems, the onset of noticeable improvement may take about seven days. The full course of treatment must still be completed.

Q: Can Klacid interact with common over-the-counter pain relievers?

A: Official interaction checks performed on the active ingredient did not find documented interactions between Klacid and widely used non-prescription pain relievers like acetaminophen or ibuprofen. Reviewing all medications and supplements with a healthcare professional before starting treatment is generally advised.

Q: Can I take Klacid if I have a history of liver problems?

A: Regulatory documents indicate that the medicine may worsen pre-existing liver problems or cause new liver dysfunction. Official guidance states that treatment should be stopped and a healthcare professional contacted if signs or symptoms of liver disease (hepatic disease) develop.

Q: Is Klacid an anti-inflammatory drug?

A: Klacid is officially classified as a macrolide antimicrobial or antibacterial agent. However, its documented actions also include a secondary, non-antimicrobial mechanism that modulates the host's inflammatory response.

Q: Can Klacid cause changes in mood or sleep?

A: According to official safety information, Klacid commonly causes difficulty sleeping (insomnia). More rarely, serious effects related to the central nervous system, such as confusion or hallucinations, have been reported.

Q: What foods should I avoid while taking Klacid?

A: Official drug instructions state that patients should continue their normal diet unless a healthcare provider directs them otherwise. Specific food-drug interactions are generally not required for the standard tablets or suspension, which can often be taken without regard to meals.

Q: What are the signs of a serious allergic reaction to Klacid?

A: Signs of a serious allergic reaction may include rash, hives, itching, or swelling of the face, throat, or tongue. These symptoms can also involve difficulty breathing or swallowing. The appearance of these signs requires prompt medical assessment.

Q: How does Klacid affect the normal bacteria in the gut?

A: Like many antibiotics, Klacid can disrupt the normal, healthy balance of bacteria in the gut (gut flora). This disruption is a documented risk factor for developing Clostridioides difficile-associated diarrhea (CDAD), which can range from mild to severe.

Q: Can people with a known heart condition use Klacid?

A: Klacid is strictly contraindicated (prohibited) for people with a history of QT prolongation or ventricular cardiac arrhythmia. In the presence of existing heart disease or a slow heartbeat, consultation with a healthcare professional is necessary to discuss specific risks.

Q: Do existing studies track how quickly Klacid clears the infection?

A: For specific uses, such as in the multi-drug regimen for Helicobacter pylori infection, clinical studies monitored the main outcome of microbiological eradication, checking whether the bacterium was cleared several weeks after the treatment ended.

Q: Can Klacid cause sun sensitivity or a rash?

A: Safety documents list rash and hives as possible side effects. While the official documents do not commonly list sun sensitivity (photosensitivity) as a frequent reaction, general caution regarding sun exposure is prudent.

Q: What is the likelihood of developing C. difficile infection from Klacid?

A: While diarrhea is a common side effect, the more serious condition of severe bowel inflammation caused by C. difficile is listed as an uncommon side effect. Patients are alerted to this serious potential risk associated with antibiotic use.

Q: Can I stop taking Klacid once my symptoms disappear?

A: Official patient guidance stresses the importance of completing the full prescribed treatment course. The medicine should be continued until the full course is finished, even if symptoms resolve, to help prevent the infection from returning.

Q: Can Klacid affect the results of blood tests?

A: Yes, regulatory information shows that the medicine can cause abnormal blood test results. This includes reporting increased hepatic enzyme levels (indicating liver activity) and certain blood disorders like Leukopenia.

Q: Is it safe to drink coffee while taking Klacid?

A: While there is no direct contraindication against combining coffee with the medicine, official patient guidance notes that for individuals who experience difficulty sleeping (insomnia), avoiding coffee in the evening may be advised.

Q: Why do doctors prescribe Klacid instead of amoxicillin?

A: Clarithromycin is often prescribed as an alternative to amoxicillin or penicillin because it is a different class of antibiotic. This makes it a suitable option for individuals who have a known allergy or sensitivity to the penicillin class of drugs.

Q: Can Klacid be used for dental infections?

A: Clinical guidelines indicate that the medicine is used to treat various infections, including those affecting the mouth. For certain dental abscesses, it is used as an alternative for patients who have a penicillin allergy.

Q: Does Klacid affect birth control pills?

A: According to official health guidance, Klacid does not stop hormonal contraception from working. However, if a patient experiences severe gastrointestinal issues like vomiting or severe diarrhea, this may reduce the effectiveness of the contraceptive pill.

Q: How long after finishing the course of Klacid can side effects still occur?

A: Some side effects can occur long after the treatment course is complete. For example, severe diarrhea caused by C. difficile may occur up to two months after finishing the medicine. Furthermore, a potential long-term risk has been noted for patients with coronary artery disease, persisting for one to ten years.

Q: Is it normal to feel dizzy or lightheaded while on Klacid?

A: Official safety information states that the medicine may cause patients to feel dizzy, confused, or disoriented. Dizziness is also noted as an uncommon symptom that can be associated with allergic reactions.

Q: Is Klacid safe for older adults (seniors)?

A: Official regulatory documents confirm that the standard dosing for elderly patients is generally the same as for adults. However, due to certain age-related health risks, consultation with a healthcare professional may be appropriate.

Q: Can Klacid make existing fungal infections worse?

A: The use of this antibiotic may indirectly increase the likelihood of developing a yeast infection (such as oral or vaginal thrush). This is due to the antibiotic disrupting the body's normal bacterial balance.

Q: Does Klacid have any known interactions with herbal supplements?

A: Official health guidance states there is not enough information to confirm the safety of taking the medicine with herbal remedies or supplements. It is recommended that patients check with a healthcare professional before taking herbal remedies or supplements with this medication.

How should Klacid be stored and disposed of?

Klacid (clarithromycin) must be stored and handled according to specific official instructions to maintain its stability.

Official Storage Conditions

Formulation Temperature Requirement Handling Constraint
Tablets Room temperature, 20 C to 25 C (Do not exceed 30 C) Protect from light and moisture
Oral Suspension (Mixed) Store between 15 C and 30 C Do not refrigerate; discard after 14 days

The medicine must be kept in its tightly closed original container and stored out of the sight and reach of children. The granules for oral suspension must be stored below 25 C before mixing.

Disposal Mandates

Expired or unused Klacid must be disposed of safely. Do not flush the medicine down the toilet or pour it into a drain unless specific instruction is given by a regulatory body. Unused product must be discarded by following local regulatory requirements or specific disposal guidelines from national health authorities.

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

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