Cefaclor

Absorption

Well absorbed after oral administration, independent of food intake.

Toxicity

Symptoms of overdose include diarrhea, nausea, stomach upset, and vomiting.

Description

Cefaclor differs from cephalexin primarily in the bio-isosteric replacement of methyl by chlorine at C-3 and is quite acid stable, allowing oral administration. It also is quite stable to metabolism. It is less active against Gram-negative bacteria compared with the other second-generation cephalosporins but is more active against Gram-negative bacteria compared with the first-generation drugs.

Description

Cefaclor is a cephalosporin antibiotic that is active against S. pyogenes, S. pneumoniae, S. aureus, P. mirabilis, S. typhi, E. coli, and H. influenzae (MICs = 0.25, 0.25-2, 1-2, 1, 0.5, 1, and 2-4 μg/ml, respectively). It is protective against S. pyogenes, S. pneumoniae, S. aureus, P. mirabilis, S. typhi, E. coli, and H. influenzae infections in mice (ED₅₀s = 0.08-30.2 mg/kg). Formulations containing cefaclor have been used in the treatment of various bacterial infections.

Chemical properties

white crystalline solid

Originator

Ceclor,Lilly,US,1979

The Uses of Cefaclor

Cefaclor belongs to the family of antibiotics known as the cephalosporins (cefalosporins). The cephalosporins are broad-spectrum antibiotics that are used for the treatment of septicaemia, pneumonia, meningitis, biliary-tract infections, peritonitis, and

The Uses of Cefaclor

radioopaque agent

The Uses of Cefaclor

Cefaclor is used to study urinary tract, intra-abdominal, and?Haemophilus influenzae?infections. It is used to study the mechanism of human renal organic anion and peptide transporters such as hOAT1, hPEPT1, and hPEPT2 and to study the effects of inhibition of penicillin-binding proteins on bacterial cell wall mucopeptide synthesis.

Indications

For the treatment of certain infections caused by bacteria such as pneumonia and ear, lung, skin, throat, and urinary tract infections.

What are the applications of Application

Cefaclor is an antibiotic that inhibits cell wall synthesis

Background

Semisynthetic, broad-spectrum antibiotic derivative of cephalexin.

Definition

ChEBI: A cephalosporin bearing chloro and (R)-2-amino-2-phenylacetamido groups at positions 3 and 7, respectively, of the cephem skeleton.

Manufacturing Process

Preparation of 7-amino-3-chloro-3-cephem-4-carboxylic acid: To a solution of 750 mg (185 mmol) of p-nitrobenzyl 7amino-3-chloro-3cephem-4-carboxylate hydrochloride in 20 ml of tetrahydrofuran and 40 ml of methanol was added a suspension of 750 mg of prereduced 5% palladium on carbon catalyst in 20 ml of ethanol and the suspension was hydrogenated under 50 psi of hydrogen at room temperature for 45 minutes. The catalyst was filtered and washed with THF and water. The filtrate and catalyst washes were combined and evaporated to dryness, The residue was dissolved in a water-ethyl acetate mixture and the pH adjusted to pH 3. The insoluble product was filtered and triturated with acetone. The product was then dried to yield 115 mg of 7- amino-3-chloro-3-cephem-4-carboxylic acid.
Preparation of 7-(D-α-phenylglycylamido)-3-chloro-3-cephem-4-carboxylic acid: To a suspension of 280 mg (1.2 mmol) of 7-amino-3-chloro-3-cephem- 4-carboxylic acid in 14 ml of acetonitrile was added with stirring at room temperature 0.5 ml of N,O-bis-(trimethylsilyl)acetamide to form the soluble disilylmethyl derivative thereof. The solution was cooled to 0 C and was slowly added to a solution of the mixed anhydride formed by reacting 408 mg (1.5 mmol) of methyl-3-α-carboxybenzylaminocrotonate sodium salt with 161 mg (1.7 mmol) of methyl chloroformate in the presence to 2 drops of N,N-dimethylbenzyl amine in 7 ml of acetonitrile.
The mixture was stirred at ice bath temperature for 2 hours, 1 ml of methanol was added and the mixture was filtered to remove insoluble impurities. Two milliliters of water were added to the filtrate and the pH was adjusted momentarily to pH 1.5, to effect removal of the enamine block, and then to pH 4.5 with triethylamine. After stirring for an additional hour at ice bath temperature the reaction product, 7-(D-α-phenylglycylamido)-3-chloro-3- cephem-4-carboxylic acid (zwitterion) precipitated from the reaction mixture as a crystalline solid. The product was filtered, washed with acetonitrile and dried in vacuo to yield 200 mg.

brand name

Ceclor (Lilly); Raniclor (Ranbaxy).

Therapeutic Function

Antibiotic

Antimicrobial activity

It is less resistant than other group 2 cephalosporins to staphylococcal β-lactamase. It is active against N. gonorrhoeae and H. influenzae and against most enterobacteria, but it is susceptible to common enterobacterial β-lactamases. Pr. vulgaris and Providencia, Acinetobacter and Serratia spp. are resistant. B. fragilis and clostridia are resistant but other anaerobes are commonly susceptible.

Pharmacokinetics

Cefaclor is a second generation cephalosporin antibiotic with a spectrum resembling first-generation cephalosporins. In vitro tests demonstrate that the bactericidal action of the cephalosporins results from inhibition of cell-wall synthesis. As indicated by in vitro and in vivo clinical studies, cefaclor was shown to be effective against most strains of Gram positive aerobes - Staphylococci (including coagulase-positive, coagulase-negative, and penicillinase-producing strains), Streptococcus pneumoniae, Streptococcus pyogenes (group A ?-hemolytic streptococci), as well as Gram-negative aerobes - Escherichia coli, Haemophilus influenzae (including ?-lactamase-producing ampicillin-resistant strains), Klebsiella sp, and Proteus mirabilis.

Pharmacokinetics

Oral absorption: c. 90%
C_max 250 mg oral: c. 6–7 mg/L after 50 min
Plasma half-life: 0.5–1 h
Volume of distribution: 0.37 L
Plasma protein binding: 25%
Absorption
Food intake increases the time taken to reach peak plasma levels and reduces the peak by 25–50%. The actual amount absorbed is unaffected. In children receiving 15 mg/kg per day (maximum daily dose 1 g) the mean peak serum level was 16.8 mg/L at 0.5–1 h. There is no accumulation of the drug during repeated administration.
Distribution
In patients receiving 500 mg every 8 h for 10 days, concentrations were 0–1.7 (mean 0.5) mg/L in mucoid sputum and 0–2.8 (mean 1.0) mg/L in purulent sputum. In children with chronic serous otitis media receiving 15 mg/kg per day, the mean peak concentration in middle ear secretion was 3.8 mg/L within 30 min of the dose when the mean simultaneous serum concentration was 12.8 mg/L.
Metabolism and excretion No metabolites have been identified, but the drug probably chemically degrades in serum. About half of the dose is recovered from the urine in the first 6 h and 70% in 24 h. Probenecid prolongs the plasma levels but in renal insufficiency the plasma half-life is only moderately increased. In patients with creatinine clearance values of 5–15 mL/min the mean plasma elimination half-life rose to 2.3 h and the 24 h urinary excretion fell to less than 10%. In patients requiring intermittent hemodialysis and receiving 500 mg every 8 h for 10 days, the half-life rose to 2.9 h. Dialysis removed 34% of the dose

Clinical Use

Uses are similar to those of other group 2 cephalosporins. It is among the few suitable for use in respiratory infections because of its activity against H. influenzae.

Clinical Use

Cefaclor (Ceclor) is an orally active semisyntheticcephalosporin that was introduced in the American market in1979. It differs structurally from cephalexin in that the 3-methyl group has been replaced by a chlorine atom. It issynthesized from the corresponding 3-methylenecepham sulfoxideester by ozonolysis, followed by halogenation of theresulting β-ketoester. The 3-methylenecepham sulfoxideesters are prepared by rearrangement of the corresponding 6-acylaminopenicillanic acid derivative. Cefaclor is moderatelystable in acid and achieves enough oral absorption to provideeffective plasma levels (equal to about two-thirds of thoseobtained with cephalexin). The compound is apparentlyunstable in solution, since about 50% of its antimicrobial activityis lost in 2 hours in serum at 37°C. The antibacterialspectrum of activity is similar to that of cephalexin, but it isclaimed to be more potent against some species sensitiveto both agents. Currently, the drug is recommended for thetreatment of non–life-threatening infections caused by H.influenzae, particularly strains resistant to ampicillin.

Side Effects

Apart from mild gastrointestinal disturbance, the drug is well tolerated. Transiently increased transaminase levels and symptomatic vaginal candidosis have been noted. Clusters of a serum sickness-like illness have been described in children.

Safety Profile

Moderately toxic by intraperitoneal route. Human systemic effects by ingestion: joints, dermatitis, increased body temperature. An experimental teratogen. Experimental reproductive effects. When heated to decomposition it emits toxic fumes of Clí, SOx, an

Synthesis

Cefaclor, (6R,7R)-7-[(R)-2-amino-2-phenylacetamido]-3-chloro-8-oxo-5-thia- 1-azabicyclo[4.2.0]oct-2-en-2-carboxylic acid (32.1.2.48), is synthesized from the most accessible antibiotic of this series, cefalotin (32.1.2.1), in which the carboxyl group is protected by esterification by a reaction with 4-nitrobenzylbromide in triethylamine, giving the 4-nitrobenzyl ester of 7-(2-thienylacetamido)-cephalosporanic acid (32.1.2.40). Reacting this with potassium ethyl xantogenate replaces the acetoxy group in the third position of the cephalosporin system, giving the corresponding S-derivative (32.1.2.41). Upon reducing this compound using zinc in formic acid, the product is desulfurized, giving the 4-nitrobenzyl ester of 3-exo-methylen-7-(2-thienylacetamido)-cefem-4-carboxylic acid (32.1.2.42). The exomethylene group is oxidized by ozone and the resulting dicarbonyl derivative tautomerizes to the enol form (32.1.2.43) upon reaction with sulfur anhydride. Then, the hydroxyl group is replaced with a chlorine atom upon reaction with thionyl chloride, giving the 4-nitrobenzyl ester of 3-chloro-7-(2-thienylacetamido)-3-cefem-4-carboxylic acid (32.1.2.44). The resulting product undergoes deacylation upon reaction with a mixture of pyridine with phosphorous pentachloride in isobutanol, forming the hydrochloride of 4-nitrobenzyl ester of 7-amino-3-chloro-3-cefem-4-carboxylic acid (32.1.2.45). This is acylated with an N-protected derivative of phenylglycine, (N-tert-butoxycarbonyl)-D-|á-phenylglycine in the presence of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline in tetrahydrofuran, giving the product (32.1.2.46). The tert-butoxycarbonyl protection in this molecule is removed by heating in acetonitrile in the presence of p-toluenesulfonic acid. Finally, upon hydrogen reduction using zinc and hydrochloric acid in dimethylformamide, the 4-nitrobenzyl protecting group is removed from the resulting tosylate (32.1.2.47) giving cefaclor (32.1.2.48).

Veterinary Drugs and Treatments

Cefaclor may potentially be useful when an oral cephalosporin is desired to treat infections that are susceptible to it but resistant to first generation cephalosporins such as cephalexin or cefadroxil. Little information is available with regard to its clinical use in small animals, however.

Drug interactions

Potentially hazardous interactions with other drugs
Anticoagulants: effects of coumarins may be enhanced.

Metabolism

No appreciable biotransformation in liver (approximately 60% to 85% of the drug is excreted unchanged in the urine within 8 hours).

Metabolism

Cefaclor is rapidly excreted by the kidneys; up to 85% of a dose appears unchanged in the urine within 8 hours, the greater part within 2 hours. Probenecid delays excretion