VA Class:AM116

AHFS Class:

• Second Generation Cephalosporins 8:12.06.08

Generic Name(s):

• Cefaclor

Associated Monographs

• Cephalosporins General Statement

Cefaclor is a semisynthetic, second generation cephalosporin antibiotic.

Cefaclor is used orally for the treatment of acute otitis media caused by susceptible bacteria; pharyngitis and tonsillitis caused by Streptococcus pyogenes (group A β-hemolytic streptococci); mild to moderate upper and lower respiratory tract infections (including pneumonia) caused by susceptible bacteria; uncomplicated skin and skin structure infections caused by susceptible bacteria; and urinary tract infections (including pyelonephritis and cystitis) caused by susceptible bacteria.167,169 While commercially available cefaclor capsules and oral suspension can be used for any of these infections,167,169 safety and efficacy of cefaclor extended-release tablets have been established only for the treatment of mild to moderate respiratory tract infections (i.e., acute exacerbations of chronic bronchitis, secondary infections of acute bronchitis) caused by susceptible bacteria; pharyngitis and tonsillitis caused by S. pyogenes ; and mild to moderate uncomplicated skin and skin structure infections caused by susceptible Staphylococcus aureus (methicillin-susceptible [oxacillin-susceptible] strains only).168

Acute Otitis Media

Cefaclor capsules and oral suspension are used for the treatment of acute otitis media (AOM) caused by Streptococcus pneumoniae , Haemophilus influenzae , staphylococci, or S. pyogenes (group A β-hemolytic streptococci).167,169 When selecting an anti-infective for treatment of AOM that may involve H. influenzae , clinicians should consider the fact that β-lactamase-negative, ampicillin-resistant (BLNAR) strains of H. influenzae should be considered resistant to cefaclor despite apparent in vitro susceptibility of some strains.167,169

When anti-infective therapy is indicated for the treatment of AOM, the American Academy of Pediatrics (AAP) recommends high-dose amoxicillin or amoxicillin and clavulanate potassium as the drugs of first choice for initial treatment.165 These experts recommend certain cephalosporins (cefdinir, cefpodoxime, cefuroxime, ceftriaxone) as alternatives for initial treatment in penicillin-allergic patients who do not have a history of severe and/or recent penicillin-allergic reactions.165

Results of controlled clinical studies in pediatric patients with AOM indicate that a 10-day regimen of oral cefaclor generally is as effective as a 10-day regimen of oral amoxicillin,131 oral cefixime (no longer commercially available in the US),120,121,128,132 oral cefprozil,120,121 or oral ceftibuten.127

Cefaclor has been effective for the treatment of AOM in some pediatric patients when administered in a 5-day regimen†; however, the shortened regimen appears to be less effective in patients with spontaneous perforation of the tympanic membrane and purulent drainage than in those with intact tympanic membranes.134 In a controlled study in children with AOM who were randomized to received 5 or 10 days of oral cefaclor (20 mg/kg twice daily), the treatment failure rate in those with intact tympanic membranes at the time of diagnosis was 10% in those who received the 5-day regimen and 6% in those who received the 10-day regimen; in those with spontaneous perforation of the tympanic membrane at the time of diagnosis, the failure rate was 53 and 8%, respectively.134 Further study is needed to evaluate use of a 5-day regimen of oral cefaclor for the treatment of AOM.137,138,154 The AAP states that oral anti-infective regimens of less than 10 days' duration are not recommended for the treatment of AOM in children younger than 2 years of age or in patients with severe symptoms.165

For additional information regarding treatment of AOM, including information on diagnosis and management strategies, anti-infectives for initial treatment, duration of initial treatment, and anti-infectives after initial treatment failure, see Acute Otitis Media under Uses: Otitis Media, in the Cephalosporins General Statement 8:12.06.

Pharyngitis and Tonsillitis

Cefaclor capsules, oral suspension, and extended-release tablets are used for the treatment of pharyngitis and tonsillitis caused by susceptible S. pyogenes (group A β-hemolytic streptococci).124,135,152,153,167,168,169 Although cefaclor usually is effective in eradicating S. pyogenes from the nasopharynx,135,167,168,169 efficacy in the prevention of subsequent rheumatic fever has not been established to date.167,168,169

Selection of an anti-infective for the treatment of S. pyogenes pharyngitis and tonsillitis should be based on the drug's spectrum of activity, bacteriologic and clinical efficacy, potential adverse effects, ease of administration, patient compliance, and cost.116,117,146,147 No regimen has been found to date that effectively eradicates group A β-hemolytic streptococci in 100% of patients.117

Because the drugs have a narrow spectrum of activity, are inexpensive, and generally are effective with a low frequency of adverse effects, the AAP,100 Infectious Diseases Society of America (IDSA),116 American Heart Association (AHA),117 and others101 recommend a penicillin regimen (i.e., 10 days of oral penicillin V or oral amoxicillin or a single dose of IM penicillin G benzathine) as the treatment of choice for S. pyogenes pharyngitis and tonsillitis and prevention of initial attacks (primary prevention) of rheumatic fever. Other anti-infectives (e.g., oral cephalosporins, oral macrolides, oral clindamycin) are recommended as alternatives in penicillin-allergic individuals.100,101,116,117

If an oral cephalosporin is used for the treatment of S. pyogenes pharyngitis and tonsillitis, a 10-day regimen of a first generation cephalosporin (cefadroxil, cephalexin) is preferred instead of other cephalosporins with broader spectrums of activity (e.g., cefaclor, cefdinir, cefixime, cefpodoxime, cefuroxime).100,116,117

Although there is some evidence that a shorter duration of therapy with certain oral cephalosporins (e.g., a 5-day regimen of cefadroxil, cefdinir, cefixime, or cefpodoxime proxetil or a 4- or 5-day regimen of cefuroxime axetil) achieves bacteriologic and clinical cure rates equal to or greater than those achieved with the traditional 10-day oral penicillin V regimen,117,146,147,148,149,150,151 the IDSA and AHA state that use of cephalosporin regimens administered for 5 days or less for the treatment of S. pyogenes pharyngitis and tonsillitis cannot be recommended at this time.116,117

A 10-day regimen of oral cefaclor is at least as effective as a 10-day regimen of oral penicillin V or a 10-day regimen of oral amoxicillin and clavulanate potassium for the treatment of S. pyogenes pharyngitis and tonsillitis.124,152 In an open, randomized study in adults and adolescents 12 years of age or older with acute pharyngitis caused by S. pyogenes , a 10-day regimen of oral cefaclor (250 mg 3 times daily) was at least as effective as a 10-day regimen of oral cefprozil (500 mg once daily); the clinical response rate was 85% for both drugs and the bacteriologic eradication rate was 95% in those who received cefaclor and 91% in those who received cefprozil.135 In double-blind, randomized multicenter studies designed to compare efficacy of a 10-day regimen of cefaclor capsules (250 mg 3 times daily) and a 10-day regimen of cefaclor extended-release tablets (375 mg twice daily), the clinical response rates were 98.1 and 96.7%, respectively, and the bacteriologic eradication rates were 94.1 and 93.6%, respectively.153

Respiratory Tract Infections

Cefaclor capsules and oral suspension are used for the treatment of lower respiratory tract infections (including pneumonia) caused by susceptible S. pneumoniae , H. influenzae , or S. pyogenes .167,169 Cefaclor extended-release tablets are used for the treatment of mild to moderate acute exacerbations of chronic bronchitis or secondary infections of acute bronchitis caused by susceptible H. influenzae (non-β-lactamase-producing strains only), Moraxella catarrhalis (including β-lactamase-producing strains), or S. pneumoniae .168 When selecting an anti-infective for treatment of lower respiratory tract infections that may involve H. influenzae , consider the fact that strains of H. influenzae should be considered resistant to cefaclor despite apparent in vitro susceptibility of some strains.167 The manufacturer cautions that data are insufficient to establish efficacy of cefaclor extended-release tablets in the treatment of acute or chronic bronchitis that is known, suspected, or potentially caused by β-lactamase-producing strains of H. influenzae .168

The overall clinical response rate (cure or improvement) reported in adults with acute bacterial bronchitis or acute bacterial exacerbations of chronic bronchitis treated with cefaclor capsules (250 mg 3 times daily) is 92% and the overall bacteriologic elimination rate is 80-92%.122,125,126 When results are stratified according to causative agent, the bacteriologic elimination rate is 85% for infections caused by H. influenzae and 100% for those caused by H. parainfluenzae † or Klebsiella pneumoniae †; 81% for infections caused by S. pneumoniae ; and 75% for infections caused by M. catarrhalis .125

Skin and Skin Structure Infections

Cefaclor capsules, oral suspension, and extended-release tablets are used for the treatment of uncomplicated skin and skin structure infections caused by Staphylococcus aureus (methicillin-susceptible [oxacillin-susceptible] strains only).136,167,168,169 Cefaclor capsules and oral suspension also can be used for the treatment of uncomplicated skin and skin structure infections caused by S. pyogenes ;167,169 however, the manufacturer states that efficacy of cefaclor extended-release tablets for the treatment of uncomplicated skin or skin structure infections known or suspected of being caused by these bacteria has not been established.168

In a multicenter, randomized study in adults and children 2 years of age or older with mild to moderate bacterial skin and skin structure infections (e.g., carbuncle, cellulitis, folliculitis, furuncle, impetigo, infected dermatitis, paronychia, pyoderma, superficial abscess, wound infection), patients were randomized to receive 5-10 days of therapy with oral cefaclor (250 mg 3 times daily in adults or 20 mg/kg daily in 3 doses) or oral cefprozil (500 mg once daily in adults or 20 mg/kg once daily in children).136 Results of this study indicate that cefaclor and cefprozil are equally effective for these infections and similarly tolerated; a satisfactory clinical response was attained in 92 and 93% of patients, respectively, and the bacteriologic eradication rate was 89 and 91%, respectively.136

Urinary Tract Infections

Cefaclor capsules and oral suspension are used for the treatment of urinary tract infections (including pyelonephritis and cystitis) caused by susceptible Escherichia coli , Klebsiella , Proteus mirabilis , or coagulase-negative staphylococci.167,169

Reconstitution and Administration

Cefaclor is administered orally.167,168,169

Food does not affect the extent of absorption of cefaclor administered as conventional capsules or oral solution,107,108,167,169 and these preparations may be administered without regard to meals.167,169 However, food increases the extent of absorption of cefaclor administered as extended-release tablets.168 (See Pharmacokinetics: Absorption.) The manufacturer recommends that cefaclor extended-release tablets be administered with meals or within 1 hour of eating to enhance GI absorption.168

Cefaclor extended-release tablets should not be cut, crushed, or chewed.168

Reconstitution

Cefaclor powder for oral suspension should be reconstituted at the time of dispensing by adding the amount of water specified on the container to provide a suspension containing 125, 187, 250, or 375 mg of cefaclor per 5 mL.169 The water should be added in 2 portions and the bottle shaken well after each addition.169

The oral suspension should be shaken well prior to administration of each dose.169

Dosage

Cefaclor is commercially available as the monohydrate; dosage is expressed in terms of anhydrous cefaclor.167,168,169

Adult Dosage

Acute Otitis Media

The usual adult dosage of cefaclor administered as capsules or oral suspension for the treatment of acute otitis media is 250 mg every 8 hours; for more severe infections or those caused by less susceptible organisms, 500 mg may be given every 8 hours.167,169 Although the daily dosage of cefaclor capsules or oral suspension usually is administered in 3 equally divided doses, the manufacturer states that daily dosage may be given in 2 equally divided doses at 12-hour intervals for the treatment acute otitis media.167,169

Pharyngitis and Tonsillitis

The usual adult dosage of cefaclor administered as capsules or oral suspension for the treatment of pharyngitis and tonsillitis caused by Streptococcus pyogenes (group A β-hemolytic streptococci) is 250 mg every 8 hours for at least 10 days; for more severe infections or those caused by less susceptible organisms, 500 mg may be given every 8 hours.167,169 Although the daily dosage of cefaclor capsules or oral suspension usually is administered in 3 equally divided doses, the manufacturer states that daily dosage may be given in 2 equally divided doses at 12-hour intervals for the treatment of pharyngitis.167,169

If cefaclor extended-release tablets are used for the treatment of pharyngitis and/or tonsillitis caused by S. pyogenes , the usual adult dosage is 375 mg every 12 hours for 10 days.168

Respiratory Tract Infections

For the treatment of lower respiratory tract infections caused by susceptible bacteria, the usual adult dosage of cefaclor administered as capsules or oral suspension is 250 mg every 8 hours; for more severe infections (e.g., pneumonia) or those caused by less susceptible organisms, 500 mg may be given every 8 hours.167,169

If cefaclor extended-release tablets are used for the treatment of acute bacterial exacerbation of chronic bronchitis or secondary bacterial infections of acute bronchitis caused by susceptible Haemophilus influenzae (non-β-lactamase-producing strains only), Moraxella catarrhalis (including β-lactamase-producing strains), or S. pneumoniae , the usual adult dosage is 500 mg every 12 hours for 7 days.168

Skin and Skin Structure Infections

For the treatment of skin and skin structure infections caused by susceptible Staphylococcus aureus or S. pyogenes , the usual adult dosage of cefaclor administered as capsules or oral suspension is 250 mg every 8 hours; for more severe infections or those caused by less susceptible organisms, 500 mg may be given every 8 hours.167,169

If cefaclor extended-release tablets are used for the treatment of uncomplicated skin and skin structure infections caused by susceptible S. aureus , the usual adult dosage is 375 mg every 12 hours for 7-10 days.168

Urinary Tract Infections

For the treatment of urinary tract infections (including pyelonephritis and cystitis) caused by susceptible bacteria, the usual adult dosage of cefaclor administered as capsules or oral suspension is 250 mg every 8 hours; for more severe infections or those caused by less susceptible organisms, 500 mg may be given every 8 hours.167,169

Pediatric Dosage

General Pediatric Dosage

The American Academy of Pediatrics (AAP) recommends that pediatric patients beyond the neonatal period receive cefaclor in a dosage of 20-40 mg/kg daily in 2 or 3 equally divided doses for the treatment of mild or moderate infections.100 The AAP states that the drug is inappropriate for the treatment of severe infections.100

A maximum cefaclor dosage of 1 g daily is recommended in pediatric patients.167,169

Acute Otitis Media

The usual dosage of cefaclor capsules or oral suspension for the treatment of otitis media in children 1 month of age or older is 40 mg/kg daily in divided doses every 8 or 12 hours.167,169

Pharyngitis and Tonsillitis

The usual dosage of cefaclor capsules or oral suspension for the treatment of pharyngitis or tonsillitis in children 1 month of age or older is 20 mg/kg daily in divided doses every 8 or 12 hours for at least 10 days.167,169 For more severe infections or those caused by less susceptible organisms, 40 mg/kg daily in divided doses every 8 hours can be used.167,169

Respiratory Tract Infections

The usual dosage of cefaclor capsules or oral suspension for the treatment of lower respiratory tract infections in children 1 month of age or older is 20 mg/kg daily in divided doses every 8 hours for 10 days.167,169 For more severe infections or those caused by less susceptible organisms, 40 mg/kg daily in divided doses every 8 hours can be used.167,169

Skin and Skin Structure Infections

The usual dosage of cefaclor capsules or oral suspension for the treatment of skin and skin structure infections in children 1 month of age or older is 20 mg/kg daily in divided doses every 8 hours for 10 days.167,169 For more severe infections or those caused by less susceptible organisms, 40 mg/kg daily in divided doses every 8 hours can be used.167,169

Urinary Tract Infections

The usual dosage of cefaclor capsules or oral suspension for the treatment of urinary tract infections in children 1 month of age or older is 20 mg/kg daily in divided doses every 8 hours for 10 days.167,169 For more severe infections or those caused by less susceptible organisms, 40 mg/kg daily in divided doses every 8 hours can be used.167,169

Dosage in Renal Impairment

Modification of usual cefaclor dosage is not necessary in patients with renal impairment; however, close clinical observation and appropriate laboratory tests are recommended in patients with moderate or severe renal impairment since experience in such patients is limited.167

Adverse Effects

Most adverse effects reported with cefaclor are similar to those reported with other oral cephalosporins.167,168,169 (See Cautions in the Cephalosporins General Statement 8:12.06.) The most frequent adverse effects reported with cefaclor include GI effects (diarrhea, nausea, vomiting), headache, and rash.123,125,127,129,130,132,153,167,168

Serum sickness-like reactions consisting of erythema multiforme or maculopapular pruritic rash or urticaria accompanied by arthritis, arthralgia, irritability, and fever have been reported rarely in patients receiving cefaclor.102,109,112,113,118,119,167,168,169 These reactions differ from serum sickness type III hypersensitivity reactions since they generally are not associated with lymphadenopathy and proteinuria, circulating immune complexes have not been identified, and sequelae have not been reported.109,111,119,167,168,169 Serum sickness-like reactions have been reported most frequently in pediatric patients younger than 6 years of age receiving cefaclor oral suspension for the treatment of acute otitis media, pharyngitis and tonsillitis, or other upper respiratory tract infection and occur most often with second or subsequent courses of the drug.111,115,118,119,167,168,169 Signs and symptoms of the reaction usually are apparent 2-11 days after initiation of cefaclor therapy and begin to subside within a few days after the drug is discontinued.109,113,114,115,118,119,167,168,169 Oral antihistamines and corticosteroids provide symptomatic relief and may enhance resolution of the reaction;115,119,167,168,169 short-term (i.e., 2-3 days) hospitalization has been necessary in some patients because of symptoms (e.g., arthralgia) that ranged from mild to severe.113,119,167,168,169 The true incidence of serum sickness-like reactions in patients receiving cefaclor is unclear but has been estimated to be 0.5% or lower.111,112,113,114,167,168,169 While similar serum sickness-like reactions have been reported rarely in patients receiving other cephalosporins (i.e., cefprozil, cephalexin)102,113,156 or other β-lactam antibiotics (i.e., amoxicillin, loracarbef),112,118,119 these reactions have been reported more frequently with cefaclor than with any other anti-infective agent.112,113,114 Some clinicians recommend that cefaclor not be used in patients who have had a serum sickness-like reaction to the drug;111,115 however, others suggest that a history of a serum sickness-like reaction from cefaclor does not necessarily contraindicate use of other cephalosporins or other β-lactam antibiotics.110,111,119,156

Severe hypersensitivity reactions, including Stevens-Johnson syndrome,167,168 toxic epidermal necrolysis,167,168 and anaphylaxis,157,167,168,169 have been reported rarely with cefaclor. Anaphylactic reactions167,168,169 may be manifested by solitary symptoms, including angioedema,167,168 asthenia,167,168,169 edema (including face and limbs),167,168,169 dyspnea,167,168 paresthesia,167,168,169 syncope,167,168 hypotension,167,168,169 or vasodilation.167,168,169 There has been at least one report of hypersensitivity myocarditis that appeared to be a sensitivity reaction to cefaclor.158 Hypersensitivity reactions rarely may persist for several months.167,168,169

Precautions and Contraindications

Cefaclor shares the toxic potentials of other cephalosporins, and the usual cautions, precautions, and contraindications associated with cephalosporin therapy should be observed. (See Cautions in the Cephalosporins General Statement 8:12.06.)

Prior to initiation of cefaclor therapy, careful inquiry should be made concerning previous hypersensitivity reactions to cephalosporins, penicillins, or other drugs.167,168,169 There is clinical and laboratory evidence of partial cross-allergenicity among cephalosporins and other β-lactam antibiotics, including penicillins and cephamycins.144,167,168 Cefaclor is contraindicated in patients who are hypersensitive to the drug or other cephalosporins and should be used with caution in patients with a history of hypersensitivity to penicillins.167,168,169 Use of cephalosporins should be avoided in patients who have had an immediate-type (anaphylactic) hypersensitivity reaction to penicillins.102,144,167,168,169 If a hypersensitivity reaction occurs during cefaclor therapy, the drug should be discontinued and the patient treated with appropriate therapy (e.g., epinephrine, corticosteroids, and maintenance of an adequate airway and oxygen) as indicated.167,168,169

To reduce development of drug-resistant bacteria and maintain effectiveness of cefaclor and other antibacterials, the drug should be used only for the treatment or prevention of infections proven or strongly suspected to be caused by susceptible bacteria.167,168,169 When selecting or modifying anti-infective therapy, results of culture and in vitro susceptibility testing should be used.167,168,169 In the absence of such data, local epidemiology and susceptibility patterns should be considered when selecting anti-infectives for empiric therapy should be considered.167,168,169

Patients should be advised that antibacterials (including cefaclor) should only be used to treat bacterial infections and not used to treat viral infections (e.g., the common cold).167,168,169 Patients also should be advised about the importance of completing the full course of therapy, even if feeling better after a few days, and that skipping doses or not completing therapy may decrease effectiveness and increase the likelihood that bacteria will develop resistance and will not be treatable with cefaclor or other antibacterials in the future.167,168,169

Because Clostridium difficile infection (CDI) and C. difficile -associated diarrhea and colitis (CDAD; also known as antibiotic-associated diarrhea and colitis or pseudomembranous colitis) have been reported with the nearly all anti-infectives, including cephalosporins, it should be considered in the differential diagnosis of patients who develop diarrhea during or following cefaclor therapy.142,167,168,169 Patients should be advised that diarrhea is a common problem caused by anti-infectives and usually ends when the drug is discontinued; however, they should contact a clinician if watery and bloody stools (with or without stomach cramps and fever) occur during or as late as 2 months or longer after the last dose.168,169

Pediatric Precautions

Safety and efficacy of cefaclor capsules and oral suspension have not been established in children younger than 1 month of age.167,169

Safety and efficacy of cefaclor extended-release tablets have not been established in children younger than 16 years of age.168

Geriatric Precautions

Safety and efficacy of cefaclor in geriatric adults (i.e., those older than 65 years of age) are similar to that observed in younger adults.167,168,169

Cefaclor is substantially eliminated by the kidneys.167,169 Although no age-related dosage adjustments are required in geriatric patients,167,168,169 dosage should be selected with caution and renal function monitoring should be considered because of age-related decreases in renal function.167,169

Mutagenicity and Carcinogenicity

Animal studies have not been performed to date to evaluate the mutagenic and carcinogenic potential of cefaclor.167,168,169

Pregnancy, Fertility, and Lactation

Pregnancy

Reproduction studies in mice, rats, and ferrets using doses up to 3-5 times the maximum human dosage (1500 mg daily) based on mg/m² have not revealed evidence of harm to the fetus.168 There are no adequate and controlled studies using cefaclor in pregnant women or during labor and delivery, and the drug should be used during pregnancy only when clearly needed.167,168,169

Fertility

Reproduction studies in animals using cefaclor have not revealed evidence of impaired fertility.168

Lactation

Because low concentrations of cefaclor (0.16-0.21 mcg/mL) have been detected in milk following a single 500-mg oral dose of the drug, cefaclor should be used with caution in nursing women.167,168,169

Acute Toxicity

Overdosage of cefaclor may cause nausea, vomiting, epigastric distress, and diarrhea; the severity of the epigastric distress and diarrhea are dose related.167,168,169 If other symptoms are present, they probably are secondary to an underlying disease state, an allergic reaction, or the effects of other intoxication.167 The manufacturer of cefaclor capsules and oral suspension states that, in the event of cefaclor overdosage, GI decontamination is not necessary unless 5 times the normal dose of cefaclor has been ingested.167,169 The benefits of forced diuresis, peritoneal dialysis, hemodialysis, or charcoal hemoperfusion in treating cefaclor overdosage have not been established.167,168,169

Spectrum

Based on its spectrum of activity, cefaclor is classified as a second generation cephalosporin. While cefaclor is less active in vitro against gram-negative bacteria than other currently available second generation cephalosporins, cefaclor is active against some gram-negative bacteria that are generally resistant to the first generation drugs (e.g., Haemophilus influenzae ). For information on the classification of cephalosporins and closely related β-lactam antibiotics based on spectra of activity, see Spectrum in the Cephalosporins General Statement 8:12.06.

In Vitro Susceptibility Testing

Strains of staphylococci resistant to penicillinase-resistant penicillins (methicillin-resistant [oxacillin-resistant] staphylococci) should be considered resistant to cefaclor, although results of in vitro susceptibility tests may indicate that the organisms are susceptible to the drug.105 In addition, β-lactamase-negative, ampicillin-resistant (BLNAR) strains of H. influenzae should be considered resistant to cefaclor despite the fact that results of in vitro susceptibility tests may indicate that the organisms are susceptible to the drug.105,167,169

For information on interpreting results of in vitro susceptibility testing (disk susceptibility tests, dilution susceptibility tests) when cefaclor susceptibility testing is performed according to the standards of the Clinical and Laboratory Standards Institute (CLSI; formerly National Committee for Clinical Laboratory Standards [NCCLS]), see Spectrum: In Vitro Susceptibility Testing, in the Cephalosporins General Statement 8:12.06.

Pharmacokinetics

Absorption

Cefaclor is acid-stable and is well absorbed from the GI tract. Following oral administration of cefaclor capsules in healthy, fasting adults with normal renal function, peak serum concentrations of cefaclor are attained within 30-60 minutes and average 5-7 mcg/mL following a single 250-mg dose, 13-15 mcg/mL following a single 500-mg dose, and 23-25 mcg/mL following a single 1-g dose. When 500 mg of cefaclor is administered as capsules, peak plasma concentrations are attained 0.9 hours after the dose and average 16.8 mcg/mL in fasting individuals; however, in nonfasting individuals, peak plasma concentrations are attained 1.5 hours after the dose and average 9.3 mcg/mL.

In nonfasting individuals who receive 375 mg of cefaclor as an extended-release tablet, peak plasma concentrations of the drug average 3.7 mcg/mL and are attained 2.7 hours after the dose.168 Following oral administration 500 mg of cefaclor as an extended-release tablet in fasting individuals, peak plasma concentrations of the drug are attained 1.5 hours after the dose and average 5.4 mcg/mL; when the same dose is given to nonfasting individuals, peak plasma concentrations are attained 2.5 hours after the dose and average 8.2 mcg/mL.168

Peak serum concentrations are lower and attained later when cefaclor capsules are administered with food, although the total amount of drug absorbed is unchanged.107,108,167 Administration of cefaclor extended-release tablets with food increases the extent of absorption and peak plasma concentrations of the drug.168

In one study in infants younger than 18 months of age, peak serum concentrations of cefaclor ranged from 2-14 mcg/mL 1 hour after a single oral dose of 10 mg/kg and 1.2-23 mcg/mL 1 hour after a single oral dose of 15 mg/kg.

Elimination

The serum half-life of cefaclor is 0.6-1 hour in adults with normal renal function167,169 and 2.3-2.8 hours in anuric patients.167,168,169 In one study, the serum half-life of cefaclor was 1.3 hours in an adult with a creatinine clearance of 55 mL/minute, 2.5 hours in an adult with a creatinine clearance of 10.5 mL/minute, and 5.6 hours in an adult with a creatinine clearance of 8 mL/minute. In another study in functionally anephric patients who were given multiple doses of the drug, the serum half-life averaged 2.9 hours.

Cefaclor is excreted unchanged in urine. Approximately 50-85% of a single oral dose is excreted within 8 hours in adults with normal renal function; the major portion of the dose is excreted within the first 2 hours. In adults with normal renal function, peak concentrations of cefaclor average 600 mcg/mL, 900 mcg/mL, and 1.9 mg/mL in urine collected over an 8-hour period following a single 250-mg, 500-mg, or 1-g dose, respectively.

Chemistry and Stability

Chemistry

Cefaclor is a semisynthetic cephalosporin antibiotic.167,168,169

Cefaclor is commercially available for oral administration as capsules,167 powder for oral suspension,169 and extended-release tablets168 containing cefaclor monohydrate; potency is expressed on the anhydrous basis.167,168,169 Cefaclor occurs as a crystalline powder and is sparingly soluble in water.

Stability

Cefaclor capsules should be stored at 20-25°C and protected from moisture.167

Cefaclor powder for oral suspension should be stored at 20-25°C.169 After reconstitution, the suspension should be stored in a tight container in the refrigerator; any unused suspension should be discarded after 14 days.169

Cefaclor extended-release tablets should be stored in tight, light-resistant containers at 20-25°C.168

Additional Information

For further information on chemistry, mechanism of action, spectrum, resistance, pharmacokinetics, uses, cautions, drug interactions, laboratory test interferences, and dosage and administration of cefaclor, see the Cephalosporins General Statement 8:12.06.

Only references cited for selected revisions after 1984 are available electronically.

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