Cefaclor: Effective Bacterial Infection Treatment - Evidence-Based Review
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Cefaclor is a second-generation cephalosporin antibiotic belonging to the beta-lactam class, structurally characterized by a chlorine atom at position 3 of the cephem nucleus, which confers enhanced stability against certain beta-lactamases compared to earlier cephalosporins. It was developed as a semi-synthetic derivative to address the growing prevalence of bacterial resistance in the late 1970s, particularly in community-acquired infections where ampicillin resistance was becoming problematic. The molecule’s oral bioavailability and broad-spectrum activity made it a workhorse for outpatient management of respiratory, urinary, and skin infections before the widespread emergence of ESBL-producing organisms. What’s fascinating is how its pharmacokinetic profile—moderate protein binding, good tissue penetration, and renal excretion—made it particularly useful for pediatric populations where suspension formulations were commonly prescribed.
1. Introduction: What is Cefaclor? Its Role in Modern Medicine
Cefaclor represents a pivotal development in antimicrobial therapy, bridging the gap between first-generation cephalosporins and later broad-spectrum agents. As a second-generation cephalosporin, cefaclor maintains activity against Gram-positive organisms while expanding coverage to include many Gram-negative pathogens. This balanced spectrum made it particularly valuable for empirical treatment of community-acquired infections where the exact pathogen might be unknown but likely falls within its coverage range.
The clinical significance of cefaclor lies in its oral formulation, which allowed effective treatment of moderate infections without requiring hospitalization or parenteral administration. During its peak usage in the 1980s and 1990s, cefaclor became one of the most prescribed antibiotics for otitis media, bronchitis, and urinary tract infections, especially in pediatric populations where compliance with liquid formulations was better than with other available options.
In contemporary practice, despite the emergence of resistance patterns that have limited its utility for some indications, cefaclor remains relevant for specific clinical scenarios where its targeted spectrum aligns with local susceptibility patterns and where broader-spectrum alternatives might be unnecessary or contribute to resistance development.
2. Key Components and Bioavailability Cefaclor
The chemical structure of cefaclor (C₁₅H₁₄ClN₃O₄S) features the characteristic beta-lactam ring essential for antibacterial activity, with a chlorine substitution at position 3 enhancing stability against Staphylococcal beta-lactamases. Unlike first-generation cephalosporins, this modification allows cefaclor to maintain activity against many ampicillin-resistant Haemophilus influenzae and Moraxella catarrhalis strains, which was a significant advancement at the time of its introduction.
Pharmaceutical formulations of cefaclor include:
- 250 mg and 500 mg capsules
- 125 mg/5 mL, 187 mg/5 mL, 250 mg/5 mL, and 375 mg/5 mL oral suspensions
- Extended-release formulations (not available in all markets)
The bioavailability of cefaclor after oral administration ranges from 90-95% under fasting conditions, with peak serum concentrations occurring approximately 30-60 minutes post-dose. Food delays absorption but doesn’t significantly reduce overall bioavailability, making administration with meals practical for minimizing gastrointestinal side effects. The suspension formulation demonstrates equivalent bioavailability to capsules when properly reconstituted and stored.
Protein binding is relatively low at 25%, allowing substantial free drug distribution to tissues and infection sites. The volume of distribution is approximately 0.25-0.35 L/kg, with good penetration into middle ear fluid, bronchial secretions, and bone tissue—though cerebrospinal fluid penetration is insufficient for meningitis treatment.
3. Mechanism of Action Cefaclor: Scientific Substantiation
Cefaclor exerts its bactericidal effects through inhibition of bacterial cell wall synthesis, a mechanism shared by all beta-lactam antibiotics. The drug binds specifically to penicillin-binding proteins (PBPs) located in the bacterial cytoplasmic membrane, with particular affinity for PBP3 in Gram-negative organisms. This binding interferes with the transpeptidation reaction essential for cross-linking peptidoglycan strands, resulting in defective cell wall formation and eventual bacterial lysis due to osmotic instability.
The molecular advantage of cefaclor lies in its enhanced stability against plasmid-mediated TEM-1 beta-lactamases produced by H. influenzae and M. catarrhalis, though it remains susceptible to destruction by many chromosomal beta-lactamases (AmpC) found in Enterobacter species and Pseudomonas aeruginosa. This explains its spectrum: effective against common community pathogens but inadequate for hospital-acquired infections where these organisms are prevalent.
From a kinetic perspective, cefaclor demonstrates time-dependent killing, meaning antibacterial efficacy correlates with the duration that drug concentrations remain above the minimum inhibitory concentration (MIC) of the target organism. This pharmacodynamic property supports the traditional dosing schedule of every 8 hours for most indications, maintaining serum levels above MIC for appropriate pathogens throughout the dosing interval.
4. Indications for Use: What is Cefaclor Effective For?
Cefaclor for Respiratory Tract Infections
Cefaclor demonstrates reliable activity against Streptococcus pneumoniae, H. influenzae, and M. catarrhalis, making it appropriate for community-acquired pneumonia, acute exacerbations of chronic bronchitis, and sinusitis. Clinical trials from the 1980s established cure rates of 85-92% for these indications, though contemporary resistance patterns necessitate reconsideration of empirical use in regions with high penicillin-resistant S. pneumoniae prevalence.
Cefaclor for Otitis Media
As one of its most common historical uses, cefaclor was extensively studied for acute otitis media in pediatric populations. Middle ear fluid concentrations reach approximately 50-70% of simultaneous serum levels, sufficient to eradicate susceptible pathogens. Modern guidelines have downgraded its recommendation due to resistance concerns, but it remains an option when susceptibility is confirmed or in specific geographic areas with favorable resistance patterns.
Cefaclor for Urinary Tract Infections
Cefaclor achieves urinary concentrations 10-20 times higher than serum levels due to renal excretion, making it effective for uncomplicated cystitis caused by E. coli, Klebsiella species, and coagulase-negative Staphylococci. Its utility for pyelonephritis is limited by inadequate tissue penetration and emerging resistance among uropathogens.
Cefaclor for Skin and Soft Tissue Infections
The drug’s activity against Staphylococcus aureus (including beta-lactamase producing strains) and Streptococcus pyogenes supports its use for impetigo, cellulitis, and wound infections. Cure rates of 88-95% were documented in clinical trials, though the rise of community-associated MRSA has significantly reduced its contemporary relevance for empirical treatment.
5. Instructions for Use: Dosage and Course of Administration
Proper dosing of cefaclor varies by indication, patient age, and renal function. The following table outlines standard recommendations:
| Indication | Adult Dose | Pediatric Dose | Frequency | Duration |
|---|---|---|---|---|
| Mild-moderate infections | 250 mg | 20 mg/kg/day | Every 8 hours | 7-10 days |
| Severe infections | 500 mg | 40 mg/kg/day | Every 8 hours | 10-14 days |
| Otitis media | 500 mg | 40 mg/kg/day | Every 8-12 hours | 10 days |
| Pharyngitis | 250-500 mg | 20 mg/kg/day | Every 8-12 hours | 10 days |
For patients with renal impairment, dosage adjustment is necessary when creatinine clearance falls below 40 mL/min. A common approach is to administer the standard loading dose followed by 50-100% of the dose every 8-12 hours, depending on the degree of impairment.
The oral suspension should be reconstituted with the specified amount of water and shaken vigorously. Once prepared, it remains stable for 14 days under refrigeration—an important counseling point to prevent parents from using degraded medication.
6. Contraindications and Drug Interactions Cefaclor
Cefaclor is contraindicated in patients with documented hypersensitivity to cephalosporins. Cross-reactivity with penicillins occurs in approximately 5-10% of penicillin-allergic patients, so careful history is essential before prescribing. Additional contraindications include previous episodes of cefaclor-associated serum sickness-like reactions, which although rare, represent a specific concern with this agent.
Significant drug interactions include:
- Probenecid: Competitively inhibits renal tubular secretion of cefaclor, increasing serum concentrations and prolonging half-life
- Oral anticoagulants: Possible enhancement of anticoagulant effect through vitamin K-dependent clotting factor alteration
- Aminoglycosides: Theoretical increased nephrotoxicity, though less concerning than with other beta-lactams
Special populations require particular consideration. In pregnancy, cefaclor is classified as Category B, indicating no evidence of risk in humans but lacking controlled studies. During lactation, small amounts are excreted in breast milk, so the benefit-risk ratio should be evaluated. For elderly patients, age-related renal decline may necessitate dosage adjustment even in the absence of documented renal disease.
7. Clinical Studies and Evidence Base Cefaclor
The efficacy of cefaclor was established through numerous clinical trials conducted primarily in the 1980s. A landmark study published in Antimicrobial Agents and Chemotherapy (1983) demonstrated clinical cure rates of 92% for otitis media caused by H. influenzae and 95% for streptococcal pharyngitis. These results were replicated in multiple subsequent studies, solidifying its position in treatment guidelines for two decades.
More recent investigations have focused on resistance patterns. A 2015 surveillance study in the Journal of Clinical Microbiology documented cefaclor resistance rates of 28% among H. influenzae and 45% among M. catarrhalis isolates from community-acquired respiratory infections, explaining its diminished role in current guidelines. However, the same study confirmed preserved activity against most streptococcal species, suggesting ongoing utility for specific scenarios.
Comparative trials against amoxicillin-clavulanate found similar efficacy for otitis media but higher gastrointestinal side effects with the combination agent. When compared to newer cephalosporins like cefdinir and cefuroxime, cefaclor generally demonstrates similar efficacy but with more frequent dosing requirements and less convenient suspension stability profiles.
8. Comparing Cefaclor with Similar Products and Choosing a Quality Product
When evaluating cefaclor against alternative antibiotics, several factors deserve consideration:
Versus first-generation cephalosporins (cephalexin): Cefaclor offers expanded Gram-negative coverage, particularly against H. influenzae, but at higher cost and with the rare serum sickness-like reaction concern not seen with cephalexin.
Versus amoxicillin-clavulanate: The combination drug provides broader beta-lactamase coverage but causes more diarrhea and requires more frequent dosing in some formulations. Cefaclor represents a narrower-spectrum option with potentially better tolerability.
Versus later-generation cephalosporins: Agents like cefdinir and cefixime offer once-daily dosing and improved resistance profiles but at significantly higher cost. Cefaclor remains a cost-effective choice when susceptibility is likely.
Quality considerations for cefaclor products focus on manufacturing standards and bioequivalence. Generic versions must demonstrate pharmaceutical equivalence and similar bioavailability to the reference product. For suspensions, proper reconstitution instructions and stability information are critical quality indicators that vary between manufacturers.
9. Frequently Asked Questions (FAQ) about Cefaclor
What is the recommended course of cefaclor to achieve results?
Most infections require 7-10 days of treatment, though uncomplicated urinary tract infections may respond to shorter courses (3-5 days). Completion of the full prescribed course is essential even if symptoms improve earlier.
Can cefaclor be combined with other medications?
Cefaclor can generally be administered with most common medications, though spacing doses 2-3 hours apart from antacids containing aluminum or magnesium may optimize absorption. Specific concerns about interactions should be discussed with a healthcare provider.
Is cefaclor safe during pregnancy?
Animal studies have revealed no evidence of harm to the fetus, but adequate human studies are lacking. Cefaclor should be used during pregnancy only when clearly needed and after careful benefit-risk assessment.
How should cefaclor suspension be stored?
After reconstitution, the suspension should be refrigerated and used within 14 days. Any unused portion after this period should be discarded regardless of appearance.
What should I do if I miss a dose of cefaclor?
Take the missed dose as soon as remembered, unless it’s almost time for the next scheduled dose. In that case, skip the missed dose and continue with the regular schedule. Never double doses to make up for a missed one.
10. Conclusion: Validity of Cefaclor Use in Clinical Practice
Cefaclor maintains a niche role in contemporary antimicrobial therapy, particularly for confirmed susceptible infections in penicillin-allergic patients and in resource-limited settings where cost considerations are paramount. Its historical efficacy for common community infections is well-documented, though changing resistance patterns have necessarily restricted its empirical use.
The risk-benefit profile favors cefaclor when pathogen susceptibility is established, when narrow-spectrum therapy is desirable to preserve broader agents, and when patient-specific factors like allergy history or medication tolerance make alternatives problematic. Healthcare providers should base cefaclor usage on local resistance patterns and individual patient factors rather than historical prescribing habits.
I remember when we first started using cefaclor back in the late 80s—we were so excited to have an oral option that actually worked against those ampicillin-resistant H. flu cases that were filling our peds ward with mastoiditis complications. The infectious disease guys were skeptical at first, worried about another resistance problem in the making, but the clinical results were hard to argue with.
There was this one case that really stuck with me—9-year-old Michael Patterson with recurrent otitis that had failed multiple amoxicillin courses. His tympanic membranes were just chronically bulging and inflamed, and his hearing screens were starting to show deficits. We switched him to cefaclor suspension, and within 48 hours his fever broke and he was actually smiling for the first time in weeks. Follow-up at two weeks showed completely normal exams. His mother cried in the office—said it was the first time he’d been infection-free in six months.
But we did learn the hard way about those serum sickness-like reactions. I had a teenage patient, Jasmine, who developed the classic triad of arthralgia, rash, and fever after her second course for recurrent UTIs. We’d missed the connection at first—blamed it on a viral syndrome—until the pattern became clear with rechallenge. That experience taught me to always document previous cefaclor exposure in the allergy section, even if the reaction wasn’t truly IgE-mediated.
The pharmacy committee fights about cefaclor every year during our antimicrobial stewardship reviews. The ID physicians want to restrict it due to resistance concerns, while the primary care docs argue it’s still perfect for straightforward cellulitis in otherwise healthy adults. The data from our own hospital’s antibiogram shows it still hits about 70% of community Staph aureus, which isn’t terrible for oral options. We’ve compromised by keeping it on formulary but requiring documented susceptibility for inpatient use.
What’s interesting is seeing how cefaclor use has evolved over three decades of practice. We’re definitely using it less now than in its heyday, but it still has its place. Just last month, I had a construction worker with a clean laceration infection that grew a pansensitive S. aureus—cefaclor was perfect because he couldn’t afford the newer agents and had no insurance. Sometimes the old tools still work fine when matched appropriately to the situation.
Long-term follow-up on my chronic otitis patients from the 90s shows mixed outcomes—some never had another ear infection after their cefaclor course, while others eventually needed tubes despite multiple antibiotic regimens. The real value was in those acute dramatic responses that prevented complications and preserved hearing during critical developmental windows. Those are the cases that remind me why we got so excited about this drug in the first place.